The characteristics of preoperative blood tests and
their costs at Dr George Mukhari Hospital
By
KELETSO ADRINAH NTHWANE
STUDENT NO: 19622497
RESEARCH DISSERTATION
Submitted in fulfillment of the requirements for the degree of
MASTER OF MEDICINE
In
ANAESTHESIOLOGY
in the
FACULTY OF MEDICINE
at the
UNIVERSITY OF LIMPOPO
SUPERVISOR: Dr M.C John
CO-SUPERVISOR: Dr B.C Gumbo
2010
TABLE OF CONTENTS
TABLE OF CONTENTS ............................................................................................................................... 2
AUTHOR'S DECLARATION ........................................................................................................................ 4
ACKNOWLEDGEMENTS............................................................................................................................. 5
DEDICATION ................................................................................................................................................ 6
LIST OF FIGURES ....................................................................................................................................... 7
LIST OF TABLES ......................................................................................................................................... 8
LIST OF ABBREVIATIONS/ ACRONYMS .................................................................................................. 9
ABSTRACT................................................................................................................................................. 10
CHAPTER 1: INTRODUCTION .................................................................................................................. 11
1.1.
1.2.
1.3.
1.4.
1.5.
INTRODUCTION AND PROBLEM STATEMENT ..................................................................................... 11
PURPOSE OF THE STUDY ................................................................................................................ 11
OBJECTIVES OF THE STUDY ............................................................................................................ 11
JUSTIFICATION OF THE STUDY ........................................................................................................ 12
COMPONENTS OF THE REPORT ....................................................................................................... 12
CHAPTER 2: LITERATURE REVIEW ....................................................................................................... 13
2.1. INTRODUCTION ................................................................................................................................... 13
2.2. CONCEPTUAL FRAMEWORK ................................................................................................................. 13
2.3. USEFULNESS OF PREOPERATIVE TESTS ............................................................................................... 13
2.4. PREVIOUS STUDIES ON THE PREOPERATIVE TESTS................................................................................ 13
2.5. REPORTS ON SPECIFIC LABORATORY TESTS STUDIES ............................................................................ 14
2.6. CONCLUDING REMARKS....................................................................................................................... 17
CHAPTER 3: METHODS............................................................................................................................ 18
3.1. STUDY DESIGN ................................................................................................................................... 18
3.2. STUDY SITE AND POPULATION .............................................................................................................. 18
3.3. SAMPLING AND SAMPLE SIZE ............................................................................................................... 18
3.4 DATA COLLECTION AND ANALYSIS ......................................................................................................... 18
3.5. ETHICAL ISSUES.................................................................................................................................. 20
CHAPTER 4: RESULTS ............................................................................................................................. 21
4.1. INTRODUCTION ................................................................................................................................... 21
4.2. DEMOGRAPHIC CHARACTERISTICS OF THE SAMPLE ............................................................................... 21
4.3. SURGERIES CONTEMPLATED ............................................................................................................... 23
4.4. LABORATORY TESTS PERFORMED ........................................................................................................ 26
4.5. IMPACT OF TESTS RESULTS ON THE SURGERIES CONTEMPLATED ........................................................... 30
CHAPTER 5: DISCUSSION OF RESULTS AND LIMITATIONS OF STUDY ........................................... 35
5.1. INTRODUCTION ................................................................................................................................... 35
5.2. PREVALENCE AND COSTS OF TESTS PERFORMED .................................................................................. 35
5.2. DEMOGRAPHIC PROFILE AND RESULTS OF TESTS PERFORMED............................................................... 36
5.3. IMPACT OF THE RESULTS OF TESTS ON THE CLINICAL MANAGEMENT ....................................................... 37
5.4. LIMITATIONS OF THE STUDY ................................................................................................................. 37
CHAPTER 6: CONCLUSIONS AND RECOMMENDATIONS ................................................................... 38
6.1. INTRODUCTION ................................................................................................................................... 38
6.2. CONCLUSIONS .................................................................................................................................... 38
2
6.2. RECOMMENDATIONS ........................................................................................................................... 38
REFERENCES ............................................................................................................................................ 39
APPENDIX .................................................................................................................................................. 43
APPENDIX 1: DATA COLLECTION FORM ....................................................................................................... 43
3
AUTHOR'S DECLARATION
I declare that the dissertation hereby submitted to the University of Limpopo, for the degree of
Masters in Medicine in Anaesthesiology has not been previously submitted by me for a degree
at this or any other university, that is my work in design and in execution and that all material
contained herein has been duly acknowledged. The clearance certificate number is
MREC/M/103/2009:PG.
K.A NTHWANE
Initials & Surname(Title)
2010/12/05
Student Number: 19622497
Date
4
ACKNOWLEDGEMENTS
I am sincerely grateful to my supervisors, Dr John and Dr Gumbo, for their guidance,
constructive criticism and encouragement throughout the period of this research.
I would also like to express my gratitude to all my mentors, colleagues and professor in the
department of anaesthesiology for their valuable contribution in shaping my career.
I extend my gratitude to the management of DGMH for giving me the opportunity to conduct this
study.
Most of all, I would like to thank my dear husband, my son, sister and mother for their untiring
and unconditional love and support in all my educational endevours.
5
DEDICATION
I dedicate this dissertation to my family and the department of anaesthesiology University of
Limpopo for all the years of support and encouragement.
6
LIST OF FIGURES
Figures
Page No
Figure 1: Age parameters
21
Figure 2: Gender distribution
22
Figure 3: Age and Gender distribution
22
Figure 4: Parameters of laboratory tests
27
Figure 5: Parameters describing the costs of tests performed
28
Figure 6: Results of the tests performed
29
Figure 7: Abnormal results of the tests performed
30
Figure 8: Changes of surgeries contemplated
31
Figure 9: Demographic characteristics and postponement of surgery
32
Figure 10: Laboratory tests associated with postponement of surgery
33
7
LIST OF TABLES
Table
Page No
Table 1: Types of surgeries
23
Table 2: Surgeries by age category
24
Table 3: Surgeries by gender
25
Table 4: Percentage of tests performed
26
Table 5: Logistics regression of factors associated with
postponement
34
8
LIST OF ABBREVIATIONS/ ACRONYMS
Term
Meaning
AST
Aspartate aminotransferase
ALT
Alanine aminotransferase
BT
Bleeding Time
CABG
Coronary Artery Bypass Grafting
DGMH
Dr George Mukhari Hospital
ENT
Ear, Nose and Throat
FBC
Full Blood Count
HB
Hemoglobin
MCREC
Medunsa Campus Research and Ethics Committee
O&G
Obstetrics and Gynaecology
PT
Prothrombin Time
PTT
Partial Prothrombin Time
UA
Urinalysis
UTI
Urinary Tract Infection
ZAR
South African Rands
9
ABSTRACT
In surgical practice, preoperative testing involves a certain number of routine tests, among them
chest X-rays, electrocardiography, urine analysis and blood tests. This study sought to
characterize routine preoperative blood tests performed at DGMH.
This was a descriptive cross-sectional prospective study of preoperative blood tests conducted
at the Medical Laboratory of DGMH. Patient files and their laboratory reports of tests performed
during a 2-month period were examined for the extraction and collation of data.
Of the 246 patients’ records included in the analysis, there were 130 male and 116 female
patients but the distribution differed based on the age, since in female patients, the majority of
them were older than 40 years.
The main findings were that the most commonly done tests at DGMH are hemoglobin, FBC
electrolytes, creatinine, glucose and partial prothrombin test. The average number of tests per
patient was 3 and their cost on average was R224 per patient. The results of these tests
impacted on the management of patients in that 11.4% of elective surgeries were postponed.
The tests that were associated with postponement were low values of HB.
In conclusion, hemoglobin was the common laboratory test and the only one that had significant
impact as it led to the postponement of planned surgical procedures. This test may be
recommended for routine testing before surgical operations.
10
Chapter 1: INTRODUCTION
1.1. Introduction and Problem statement
In surgical practice, preoperative testing involves a certain number of routine tests, among them
chest X-rays, electrocardiography, urine analysis and blood tests. The last group includes tests
aimed to uncover latent or undiagnosed conditions that may interfere with anaesthesia and
surgery. To date, little is known about the range of tests, their costs and how their results are
used for clinical management at Dr George Mukhari Hospital (DGMH).
Therefore, this study aimed to answer the following questions:

What preoperative blood tests are commonly performed at this hospital?

Is clinical management of patients changed based on the results of these tests?

How many tests are performed per patient and type of surgeries?

How much do they cost? How much of the hospital budget do they consume?
1.2. Purpose of the study
To characterize routine preoperative blood tests performed at DGMH.
1.3. Objectives of the study

To determine the prevalence of common preoperative blood tests performed at the
hospital

To determine the proportion of patients whose clinical management was changed due to
the tests’ results

To describe the demographic profile of patients tested and the findings of the tests

To calculate the costs incurred for these preoperative tests (total and average) and their
impact on the hospital budget.
11
1.4. Justification of the study
Preoperative investigations represent a line item of hospital costs, it is important to determine
their share. Additionally, the findings of this study may be used to provide data that could be
used to develop or revise the policy on routine preoperative testing at this institution and to train
both medical and laboratory staff on preoperative testing.
1.5. Components of the report
In the following pages, a literature review of these factors will be done in Chapter 2, while the
methods and results will be presented respectively in Chapter 3 and 4. The remainder of the
dissertation comprises the discussion of results and the concluding remarks in Chapter 5 and 6.
12
Chapter 2: LITERATURE REVIEW
2.1. Introduction
In this chapter, the conceptual framework is presented first. This is followed by a review of
previous studies on the topic. A concluding statement ends this chapter.
2.2. Conceptual framework
In medical and surgical practices, it is important to ensure that one intervention does not
aggravate a pre-existing condition. Hence, when contemplating a surgical operation, laboratory
tests are performed in order to get a picture of the patient’s state with respect to their
electrolytes’ content, renal function, blood count , hemoglobin level and the liver condition. Other
tests are also performed depending on the types of surgery, demographic and clinical
presentation of the patient. However, as discussed below, it seems that the range of tests
conducted and their usefulness are subject to different opinions.
2.3. Usefulness of preoperative tests
In a landmark systematic review conducted by Munro, Booth and Nicholl (1), abnormal findings
in preoperative blood tests were reported in up to 15.6% patients. These abnormal findings lead
to a change in the management of 0.1 to 5.2% patients. There is a view held by some authors
that the tests are useless , implying that the costs incurred to do them is wasteful (2).
2.4. Previous studies on the preoperative tests
Few studies have been conducted to assess the true costs of routine blood tests. A paper by
Zwack and Derkay(3) reported that costs for full blood count (FBC) was 25 American dollars,
and that 81 dollars were required to perform a panel of tests including prothrombin time (PT),
partial prothrombin time (PTT) and bleeding time (BT). No other studies were identified on the
costs of tests particularly in the South African context. However, Smetana and Macpherson(4)
13
reported that they are neither expensive nor risky, but clinicians should consider the affordability
and costs when ordering these tests.
A review of 416 surgeries by Asaf and co-workers (5) found that 29.1% of patients had
prolonged PT, but only 3.3% of them experienced bleeding episodes following operations. In
trying to establish the predictive value of preoperative tests, Dzankic et al.(6), reported that
although abnormal findings on haemoglobin, creatinine and glucose were common, they were
not predictive of the postoperative outcomes in geriatric patients. Similarly, Burk and
colleagues(7) evaluated the usefulness of preoperative coagulation in children; they found that
only 2% of the 1603 patients had initial abnormalities, mainly prolonged PTT. They also
concluded that laboratory screening had high specificity but low predictive value due to the low
prevalence as reported above.
The above arguments justify why Narr and colleagues (8) advocated the elimination of all
preoperative tests for healthy patients undergoing surgery. Although this point of view may be
held by others, a cost-effectiveness study cannot be considered at this moment since basic
descriptive data in the African contexts are still not available.
2.5. Reports on specific laboratory tests studies
2.5.1. Full blood count (FBC)
Several studies have reported a wide range of hemoglobin abnormalities in surgery patients,
based on different study populations. In healthy individuals undergoing elective surgery, the
variation is estimated to be less than 1%. A mild hemoglobin abnormality was not associated
with an increased incidence of perioperative morbidity or mortality. Some authors recommend
preoperative hemoglobin testing if the history is suggestive of underlying anemia or if a
significant blood loss is anticipated during the operation. In one study, even mild degrees of
preoperative anemia or polycythemia were associated with an increased risk of 30-day
postoperative mortality and cardiac events in older patients (9). Moreover, no studies were
found discussing the cost implications of the above test.
14
2.5.2. Electrolytes
Some studies have reported that unanticipated electrolyte abnormalities (sodium, potassium,
bicarbonate, chloride) range from 0.2% to 8.0% among surgery patients. One systemic literature
review reported that unsuspected electrolyte abnormality is 1.4% among healthy elective
surgery patients. Although hypokalemia is considered a minor risk factor for perioperative
cardiac complications based on the Goldman risk index, no study showed a relation between
hypokalemia and perioperative morbidity and mortality. Similarly , although post-operative
hyponatremia is common in certain types of surgeries, such as transurethral resection of the
prostate and neurosurgical procedures, there is still no clarity on how baseline electrolyte
abnormality may affect surgeons' decisions in postoperative management. Accordingly, the
same authors suggested that electrolyte determination should not be routinely done for elective
surgery in healthy individuals (10).
2.5.3. Creatinine
The prevalence of elevated creatinine levels in asymptomatic patients ranges from 0.2% to
2.4% and increases with age. Approximately 9.8% of patients aged 46-60 years have elevated
creatinine levels (11). Patients with mild to moderate renal insufficiency are usually
asymptomatic but have an increased risk of perioperative morbidity and mortality (12).
Accordingly, most authors have recommended that the renal function with a serum creatinine
level test should be done in all patients older than 40 years, especially if hypotension or the use
of nephrotoxic medications is anticipated.
2.5.4. Blood sugar (blood glucose)
It has been reported that the frequency of abnormal glucose laboratory results in asymptomatic
patients ranges from 1.8% to 5.5%. This frequency increases with age, so that nearly 25% of
patients older than 60 years have a fasting blood sugar level above 120 mg/dL. Some studies
indicated that
in certain operations, such as vascular surgery and coronary artery bypass
grafting (CABG), diabetes was associated with higher perioperative risks. There is conflicting
findings about the routine blood sugar determination, but it seems there is consensus in the
15
case of patients with a high risk for diabetes, such as those who are obese, those taking
steroids, or those with a strong family history of diabetes, or patients that are candidates for
vascular or bypass surgery (13).
2.5.5. Liver enzymes
The frequency of a hepatic aminotransferase enzyme , aspartate aminotransferase [AST] and
alanine aminotransferase [ALT]) abnormalities, are estimated to be approximately 0.3%.
Although Rizvon MK et al (14) showed that severe liver test abnormalities may lead to an
increase in surgical morbidity and mortality risk, no evidence confirms that mild elevation in liver
enzymes is associated with such an increased risk. Routine preoperative testing (preoperative
screening) is not recommended for healthy individuals because most patients with severe
aminotransferase enzyme elevation are likely to be symptomatic i.e. jaundice may be detected
by physical examination.
2.5.6. Hemostasis
In the absence of a history of bleeding diathesis in elective surgery patients, abnormal bleeding
time, prothrombin time (PT) and activated partial thromboplastin time (aPTT) results are
estimated to be less than 1%. Suchman and Mushlin (15) showed that in low-risk patients, per
history and physical examination, aPTT does not predict the risk of perioperative bleeding.
Similarly, the bleeding time has no predictive value on the incidence of perioperative bleeding in
healthy elective surgery patients. Accordingly, PT, PTT and bleeding time are not recommended
for routine preoperative testing.
2.5.7. Urinalysis (UA)
The primary rationale for ordering a UA preoperatively is to detect either asymptomatic renal
disease or an underlying urinary tract infection (UTI). To detect unsuspected renal insufficiency,
serum creatinine measurement is recommended for any elective surgery patient older than 40
years, although it is unclear if any correlation exists between asymptomatic UTI and surgical
wound infection. One study that included 200 patients undergoing orthopedic procedures
16
showed that physicians addressed only 5 of 27 abnormal urine test results (16). A further
economic analysis showed that in order to prevent a single wound infection, approximately $1.5
million must be spent on UAs (17) , therefore UAs are not recommended routinely for
asymptomatic patients.
2.5.8. Fecal occult blood
The prevalence of positive fecal occult blood findings among healthy individuals undergoing
elective surgery is unknown. In addition, the benefits of routine screening are unclear. A
decision-analysis study showed no benefit of routine screening (18) , therefore insufficient
evidence exists to support routine screening for fecal occult blood.
2.6. Concluding remarks
No studies from South Africa were found on this topic; the review indicated two things, firstly
that there is a paucity of data in this area and secondly there are some controversies about the
routine preoperative blood tests. The findings from this study will contribute positively to this
topic.
17
Chapter 3: METHODS
3.1. Study design
This was a descriptive cross-sectional prospective study of preoperative blood tests conducted
at the Medical Laboratory of DGMH. Patient files and their laboratory reports of tests performed
during a 2-month period were examined for the extraction and collation of data.
This
prospective design was chosen because it was possible to get most of the necessary
information and thus minimize the possibility of missing files.
3.2. Study site and population
The study was conducted at the Medical Laboratory of DGMH. The study population comprised
patients screened for preoperative blood tests during the study period. The study period was
from August to September 2009.
3.3. Sampling and sample size
There will be no sampling as all files of patients meeting the inclusion criteria will be included in
the study. The only inclusion criterion is that the patient had a preoperative blood test defined as
hemoglobin measurement, blood counts, tests for hemostasis (BT, PT, PTT), serum
biochemistry (sodium and potassium, creatinine and glucose).
With regard to sample size, it was expected that at least 240 patients’ files would be included in
the analysis. This minimum sample size was calculated based on the following assumptions: a
prevalence of 15%, a tolerance of 0.2, an alpha error of 0.05(19). Indeed, the final sample size
was 246.
3.4 Data collection and analysis
3.4.1 Data collection procedures
18
A designed data collection form was used. It was constituted on the basis of the information
from the literature as cited above. In an effort to minimize bias, in case of illegible handwriting,
medical doctors were contacted for clarity; only two instances of this were encountered. In order
to minimize measurement errors, the same data collection were used to collect all data. In
addition, the two data collectors were trained in the completion of the data collection form. All
completed forms were checked for completeness at the end of the day by the investigator. All
records were retrieved for the study period.
The following information were recorded: date of test, the surgical procedure contemplated, the
name of tests and findings, in particular the abnormalities found, cost of the tests as per hospital
tariff; as well as the age (years) and gender of the patient.
The date was recorded in order to ensure that the patient data included fitted in the study
period. The name of the surgical procedure was written and later on classified in one of the nine
categories of surgery, namely, general, obstetric, orthopedic, urology, neurological, cardiothoracic, ophthalmological, ENT and plastic surgery. The results of the tests were assessed as
normal, when the readings actually were in the expected normal range based on the age of the
patient; or it was assessed and recorded as low or high if the readings were lower or higher than
the expected normal range. Hence, abnormalities were results that were either high or low. The
number of tests performed per patient were collated. From this, the average number of tests
was calculated as the arithmetic mean of individual costs of tests for each patient; while the total
number of tests was calculated as the sum of the individual number of tests per patient.
Similarly, the costs of tests were taken from the laboratory tests tariff schedule. The average
cost was calculated as the arithmetic mean of individual costs of tests for each patient; while the
total cost was the sum of individual costs per patient.
3.4.2 Data analysis
Two data capturers were employed to capture data into the MS-Excel sheet. They were chosen
on the basis of their experience with data handling. Hence, data capturing was double entered
19
and checked by a third person by means of a printout for every set of 20 records captured. The
final data sheet was entirely cleaned before analysis.
In consultation with a statistician, Epi-info was used for analysis. The datasheet constituted in
MS-Excel sheet was double-checked for correctness using frequency distributions; there was no
incorrectly captured data requiring any correction. The final dataset was saved and imported in
the software for analysis.
Descriptive statistics were calculated such as the percentages of groups per gender, laboratory
tests and types of surgery. For discrete data, the mean and other parameters were determined.
As inferential statistics, a logistic regression model was built to assess the factors associated
with the postponement of surgery. The p-value was set at p<0.05 for statistical significance.
3.5. Ethical issues
This study was submitted and the approval was obtained from the Medunsa Campus Research
and Ethics Committee (MCREC). The permission was sought and obtained from the Chief
Executive Officer of DGMH before accessing patients’ records. No personal identifiers such the
name, or address of patients or doctors were recorded in order to ensure the confidentiality and
anonymity of study subjects.
20
Chapter 4: RESULTS
4.1. Introduction
This chapter presents the findings of the study; it starts by describing the findings related to the
demographic variables, types of surgery performed and the laboratory tests. It ends with a
description of the impact of the tests on the surgery and patients’ management.
4.2. Demographic characteristics of the sample
4.2.1. Age of the patients
Figure 1: Age parameters
This figure shows that the distribution of the sample with regard to age was approximately
normal, as the mean and the median were respectively 42.0±19.6 and 42.7 years.
21
4.1.2. Gender distribution
Figure 2: Distribution of patients per gender (as percentage)
The sample had slightly more male than female patients. But the distribution differed based on
the age.
4.1.3. Age and gender distribution
Figure 3: Distribution of patients by gender and age category
22
In female patients , the majority of them were older than 40 years contrary to the situation in
males.
4.3. Surgeries contemplated
4.3.1. Types of surgeries
Table 1: Types of surgeries
Types of surgery
Percentage
General surgery
44.3
Obstetrics and Gynaecology (O & G)
18.7
Orthopedics
6.5
Urological surgery
11.8
Neurological surgery
5.7
Plastic surgery
4.9
Cardiothoracic surgery
4.1
ENT (Ear, Nose, and Throat) surgery
2.4
Ophthalmological surgery
1.6
The majority of patients underwent general surgery; the other most commonly performed
surgeries were obstetrics , gynaecology and urology.
23
4.3.2. Distribution of types of surgery based on age category
Table 2: Surgeries by age category
Types of surgery
Percentage
<40years
40 and older
General surgery
49.6
40.0
Obstetrics and Gynaecology (O & G)
15.3
21.5
Orthopedics
5.4
7.4
Urology surgery
7.2
15.6
Neurological surgery
9.0
3.0
Plastic surgery
5.4
4.4
Cardiothoracic surgery
4.5
3.7
ENT (Ear, Nose, and Throat) surgery
2.7
2.2
Ophthalmological surgery
0.9
2.2
100.0
100.0
Total
There are substantial differences based on age: General, ENT, cardiothoracic, neurological and
plastic surgeries were more common in patients younger than 40 years; while obstetrics &
gynaecology, orthopedic, urology, and ophthalmological surgery were performed more in those
40 years and above.
24
4.3.3. Distribution of types of surgery based on gender
Table 2: Surgeries by gender
Types of surgery
Percentage
Female
Male
General surgery
39.3
47.7
Obstetrics & Gynaecology
38.2
0
6.3
7.0
0
24.2
Neurological surgery
3.6
7.8
Plastic surgery
5.4
4.7
Cardiothoracic surgery
4.5
3.9
ENT (Ear, Nose, and Throat) surgery
0.9
3.1
Ophthalmological surgery
1.8
1.6
Total
100
100
Orthopedics
Urology surgery
There are substantial differences based on gender: ENT, general, neurological and orthopedic
surgeries were more common in male patients; while ophthalmological, cardio-thoracic, and
plastic surgeries were performed more on females.
25
4.4. Laboratory tests performed
4.4.1. Frequencies of tests performed
Table 4: Percentage of tests performed
Laboratory tests
Percentage
HB
92.7
Sodium
90.2
Potassium
90.2
Creatinine
86.6
Glucose
52.4
PPT
10.2
BT
3.7
PT
0.4
The test most commonly performed was the determination of hemoglobin level (HB), followed
by electrolytes (sodium and potassium) and creatinine level.
26
4.4.2. Parameters of tests performed
Figure 4: Parameters of laboratory tests
On average, three tests were performed per patients, while the minimum and the maximum
number of tests were respectively 1 and 9.
27
4.4.3. Cost parameters of tests performed
Figure 5: Parameters describing the costs of tests performed
The cost of tests in South African Rands (ZAR) ranged from ZAR48.8 to ZAR713.00. On
average, it costs ZAR227.3 per patient. The total costs for all patients included in the sample
were ZAR 55228.60 .
28
4.4.4. Description of the results of the tests performed
Figure 6: Results of the tests performed
The majority of tests performed yielded results that were in the normal ranges based on
reference values except for hemoglobin (HB) and bleeding time (BT) where the majority of
results were below the reference values. In addition, results of creatinine, PTT, BT, sodium and
potassium showed value’s that were higher than the reference values. The low and high values
constituted abnormalities.
29
4.4.5. Description of the abnormal results of the tests performed
Figure 7: Abnormal results of the tests performed
The mean abnormalities per tests performed was 1.7±1.3; ranging from zero to a maximum of
six abnormalities.
4.5. Impact of test results on the surgeries contemplated
4.5.1. Impact on medical management
Patients who had results that were grossly abnormal were treated.
30
4.5.2. Impact on surgeries contemplated
Figure 8: Changes of surgeries contemplated
There was no cancellation of any contemplated surgery based on the results of the laboratory
tests performed. However, while patients were treated, the surgery was postponed in 11.4% of
patients.
31
4.5.3. Factors associated with postponement of surgery
Figure 9: Demographic characteristics and postponement of surgery
The majority of surgeries postponed were among male and patients younger than 40 years. The
decision for the postponement was based on the laboratory tests.
32
Figure 10: Laboratory tests associated with postponement of surgery
The two tests associated with postponement were low values of HB and creatinine. Of the two
tests the most significant test was HB level as shown in the above table.
33
Table 5: Logistic regression of factors associated with postponement
Odds
Predictor
Coef
StDev
Constant
4.468
1.775
2.52 0.012
Agecat
0.2187
0.4841
0.45 0.651
Gender
-0.1465
0.5383
-0.27 0.785
0.86
0.30
2.48
HBstatus
-1.4523
0.6890
-2.11 0.035
0.23
0.06
0.90
Creastat
-0.4116
0.4090
-1.01 0.314
0.66
0.30
1.48
Nrtests
0.0292
Nrabnorm
0.2440
0.1815
0.2992
Z
95% CI
P
Ratio
Lower
1.24
0.16 0.872
1.03
0.82 0.415
1.28
Upper
0.48
0.72
0.71
3.21
1.47
2.29
Log-Likelihood = -61.034
Test that all slopes are zero: G = 7.366, DF = 6, P-Value = 0.288
Out of the 6 factors in the model, three factors positively associated with postponement, but
none of them was statistically significant; the other three factors were negatively associated with
postponement of surgery, but only the abnormal level of HB was statistically significant.
34
Chapter 5: DISCUSSION OF RESULTS AND LIMITATIONS OF STUDY
5.1. Introduction
This chapter discusses the findings shown in the preceding chapter. It starts with a discussion
on the prevalence of laboratory tests and their costs; and ends with the description of the
limitations of this study.
5.2. Prevalence and costs of tests performed
A preoperative assessment is useful to identify factors associated with increased risks of
specific complications and to recommend a management plan that minimizes the risks. Each
person should be assessed individually and judgments should be based on an individual's
problem and physiologic status, not on age alone. The findings of this study have shown that
pre-operative tests were conducted in 100% of patients as a routine activity before surgery.
Because of the need for electrolytes assessment due to the fact that patients under general
anesthesia have a decrease in renal blood flow and a similar reduction in glomerular filtration
rate, electrolytes, namely sodium and potassium levels were assessed in the majority of
patients together with HB and creatinine. Though patients with liver disease are at particularly
high risk for morbidity and mortality in the postoperative period due to both the stress of surgery
and the effects of general anesthesia (20) in this study few pre-operative tests for liver function
were reported. It is also well established that patients with acute hepatitis have been associated
with an increased risk of surgical morbidity and mortality (21). Therefore, it is prudent to
postpone surgery, especially elective surgery, in the patients with acute and/or chronic liver
disease.
With regard to the costs, there were no studies found that could be used to compare this study
with but the impact of the costs of pre-operative tests is enormous and efforts should be made
to minimize these costs.
35
5.2. Demographic profile and results of tests performed
With regard to age, this study has shown that there was a substantial difference based on age
with regard to the types of surgery. There were substantial differences based on age: General,
ENT, cardiothoracic, neurological and plastic surgeries were more common in patients younger
than 40 years; while O&G, orthopedic, urology and ophthalmological surgeries were performed
more in those 40 years and above. This finding is consistent with the age-related morbidity
profile in these individuals. It is reported that older persons often have multiple comorbid
conditions including eye conditions such glaucoma and cataracts that may require surgery. With
regard to gender, gynecologic patients are at high risk of ureteral injury, hence baseline
information on their electrolytes may be used for post-operative follow-up, but this is not
considered too important. However, in case of vomiting, diarrhea and the use of diuretics,
electrolyte disturbances and intravascular volume depletion have been reported in gynecologic
patients (22,23). Patients with severe vomiting deplete their sodium and potassium secondary to
the loss of these ions in the vomitus and resultant hypochloremic metabolic alkalosis, which is
associated with renal sodium and potassium loss. Women with severe diarrhea also loose
sodium and potassium and present with hypochloremic acidosis. These electrolyte
abnormalities, especially potassium, must be corrected before surgery because hypokalemia
potentiates neuromuscular blocking agents creates cardiac arrhythmia and leads to acid-base
imbalance. This explains why, in this study patients with abnormal results were treated before
surgery.
Although bleeding abnormalities are discovered by using a combination of BT, PT and PTT; in
this study these tests were not frequently performed. The reasons for this are not well
established. However, a hemoglobin level of 10 g/dL is a widely accepted criterion that must be
met before anesthesia is induced for elective surgical procedures. Thus, if a patient has a
hemoglobin level of less than 10 g/dL, performing an evaluation and treating before surgery is
prudent. In gynecology, heavy menstrual flow is often the culprit causing a woman's anemia.
This study found that low HB was the most significant predictor of the postponement of surgery.
This finding suggests that as a pre-operative test, the HB level testing should be recommended.
36
Similarly younger women are more inclined to undergo plastic surgery for aesthetic reasons
than the older women. Since creatinine assist in establishing the renal function and that patients
with renal insufficiency are at increased risk of perioperative morbidity, the findings of this study
concur with previous recommendations that this testing should be done in all patients older than
40 years, especially if hypotension or the use of nephrotoxic medications is anticipated(24).
5.3. Impact of the results of tests on the clinical management
A complete history, physical examination, laboratory examinations and an assessment of the
surgical risks should be included for a preoperative evaluation of an elective surgery. Before
surgery, system deficits should be identified and attempts should be made to correct them. In
this study, the findings suggest that the laboratory tests performed helped in treating patients
when abnormalities were uncovered. This translated to a postponement of 11.4% of surgeries.
This finding lends support to the need to carry out some pre-operative tests provided clear
guidelines are developed to assist clinicians and surgeons in their decision-making (25). The
tests that were able to assist in predicting the postponement were HB and creatinine. However,
because creatinine is a non-specific test, it is not taken into consideration in surgical practice.
Our findings demonstrate that the only test that can be recommended for routine pre-operative
is HB. This is in agreement with Levy and co-authors and others (26, 27). However, the findings
of this study are in contrast with reports by other investigators who claimed that most perioperative tests are not useful (28, 29, 30)
5.4. Limitations of the study
The following are the limitations of this study:
1.
As a cross-sectional study, no causal relationships could be established
2.
The sampling was limited to two months; since there may be seasonal variations in the
uptake of surgical operations, studies covering a year will be needed to confirm these
preliminary findings
3.
The study was conducted at one facility in Gauteng, so the findings do not represent the
whole province or the situation of the whole country
37
Chapter 6: CONCLUSIONS AND RECOMMENDATIONS
6.1. Introduction
This short chapter presents the main conclusions and recommendations from this study.
6.2. Conclusions
The main findings are that the most commonly done tests at DGMH are hemoglobin,
electrolytes, creatinine, glucose and partial prothrombin test. The average number of tests per
patient was 3; these tests cost on average R224 per patient. The results of these tests impacted
on the management of patients in that 11.4% of surgeries contemplated were postponed. In
conclusion, hemoglobin was the common laboratory test and the only one that had significant
impact as it led to the postponement of planned surgical procedures. This test may be
recommended for routine testing before surgical operations.
6.2. Recommendations

HB is recommended as routine tests because of their value in predicting management of
patients.

In order to assist clinicians in deciding correctly when to use pre-operative tests, there is
a need for the design and implementation of clinical guidelines for the conduct of preoperative tests at DGMH. The implementation of guidelines will also assist in ensuring
cost-effectiveness of pre-operative costs.
38
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42
APPENDIX
Appendix 1: Data Collection Form
Section A: Patient Data
1. Age:
2. Gender:
3.Surgery Contemplated
4.Date:
Section B: Blood tests
Reference
values
Patients
Findings
Conclusions
Cost as per tariff
(Is it normal? Yes/No)
Name of tests:
1.Hb
2.BT
3.PT
4.PTT
5.Creatinine
6.Glucose
7.Sodium
8.Potassium
9. FBC
10. Other
Total
# of tests=
# abnormalities=
Costs=
Section C: Clinical management
What changed has been made based on the above results?
o
Was the surgery postponed?
1. Yes
2. No
o
Was the surgery cancelled?
1. Yes
2. No
o
Was the patient put on treatment 1. Yes 2. No
before or after surgery due to the
abnormalities uncovered?
---------------------------------------------------------Other changes (Specify)
--
o
43