Relationship between Two-hour Oral Glucose Tolerance Test Plasma Glucose and Urinalysis as
Screening Method for Diabetes in Hypertensive Patients
A. N. Adamu*, A. E. Ohwovoriole†, J. K. Olarinoye*, O. A. Fasanmade†, C. O. Ekpebegh†.
*Endocrinology and Metabolism Unit, Department of Medicine, University of Ilorin Teaching Hospital, Nigeria.
† Endocrinology and Metabolism Unit, Department of Medicine, University of Lagos, Nigeria.
Address for correspondence to Abdullahi N. Adamu, Department of Medicine, University of Ilorin, Ilorin, Kwara
State, Nigeria.
Abstract
Objective- To evaluate random urine samples as a screening test for type 2 diabetes mellitus
among people with systemic hypertension.
Methodology- Between January and March 2004, screening for type 2 diabetes was conducted
among people known to have systemic hypertension and who were regular attendees of medical
out-patient clinic of the Lagos University Teaching Hospital. Screening was done using random
urine sample. Oral glucose tolerance test was carried out on all the subjects as the standard for the
diagnosis of diabetes. Subjects were classified as screen positive if the urinalysis result is positive.
World Health Organization criteria are used to interpret the oral glucose tolerance test result.
Results- We recruited 206 persons to give room for attrition, out of which 131 (participation rate
of 63.41%) of them had OGTT and urinalysis done; 87 were females constituting 65.64% while
males were 44 in number constituting 34.35%. A sensitivity of 25%, specificity of 97.19%,
positive predictive value of 66.66%, negative predictive value of 85.24% was reported. The
correlation of random urinalysis to two-hour plasma glucose of OGTT was 0.55 (P=0.00) and the
r2 was 0.30.
Conclusion- Urinalysis is a poor screening tool for type 2 diabetes mellitus among people with
systemic hypertension.
Key words- screening- Type 2 diabetes-Urinalysis-Oral glucose tolerance test- 2-hour plasma
glucose.
Introduction
Type 2 diabetes is a common and serious condition that is associated with reduced life
expectancy and considerable morbidity and mortality. It may remain undetected for a number of
years; a significant number of newly diagnosed type 2 diabetes has established complications (1).
The role of screening of undiagnosed type 2 diabetes in asymptomatic subjects as a strategy to
reduce the personal, public and economic cost of type 2 diabetes has being extensively reviewed
(2). Some evidence show that earlier detection is associated with improved outcomes (3). The
prevalence is higher among the high risk group. There is clear evidence that the screening yield
of diabetes is low in community studies and high if targeted towards high risk individuals (4-6).
Screening for diabetes using biochemical tests (random blood sugar, fasting blood) is the
common practice in many developed countries. This may be a difficult task in poor-resource
nations because of its cost, technicality and invasiveness. Safety issues in dealing with blood
specimens also need to be considered.
Oral glucose tolerance test (OGTT) is still favoured by World Health Organization (WHO) as a
gold standard for diagnosing diabetes despites its cumbersome nature (7). Glycosuria testing as
screening test for type 2 diabetes could be used as it is inexpensive, feasible, safe and reliable
test for detecting asymptomatic patients.
The available studies using urinalysis as screening tests were done at community level and
included those with known diabetes and not known to have diabetes (8, 9). Some did not include
those known to have diabetes (10-12). All of them were prospective diagnostic studies; some
used clinistest® and fasting blood sugar as diagnostic test.
No study to our understanding used combined clinistix® which is specific for glucose, OGTT as
a diagnostic test in a high risk group subjects. Our objective in this study was to assess the
relationship between 2-hour plasma glucose value of OGTT with urinalysis using clinistix® in
high risk people with systemic hypertension.
Methodology
Study Design and Location
The design was a cross sectional one. This study was carried out in the
Department of Medicine of the Lagos University Teaching Hospital (LUTH) and
the Endocrine Unit Laboratory of the Department of Medicine of the College of
Medicine, University of Lagos over a period of three months, spanning from
January to March 2004. The Lagos University Teaching Hospital is located in IdiAraba on the mainland and functions as a tertiary health care centre.
Subjects
The subjects were people with known history of systemic hypertension on life-style modification
and/ or drug(s) for the control of the hypertension, attending the Medical out Patients’
Department of the hospital were recruited for the screening exercise for type 2 diabetes. Those
patients with established secondary form of hypertension, chronic renal failure and chronic liver
disease were excluded from the study.
Sample Size
We recruited 206 persons to give room for attrition, out of which 131 (participation rate of
63.41%) of them had OGTT and urinalysis done; 87 were females constituting 65.64% while
males were 44 in number constituting 34.35%.
Approval was obtained from the Ethical Committee of the Lagos University Teaching Hospital.
An informed consent was obtained from the patients/ subjects before commencing the studies.
The patients on usual medical follow-up were approached and given a brief health talk on the
importance of screening for diabetes among people with systemic hypertension. A questionnaire
containing biodata and anthropometric parameters of the subjects were taken. The information
taken included: name, age, gender, hospital number, height (m) with measurement taken to the
closest centimeter, weight (kg) to the closest mg, and body mass index (BMI) calculated as the
ratio of weight to the square of height in metres. Waist circumference was taken at umbilical
level, to the closest centimeter, while the hip circumference was measured at maximal dimension
of the buttocks, to closest centimeters. Waist to hip ratio was calculated by finding the ratio of
the waist to that of hip. The 2-hours venous plasma glucose post standard 75g of OGTT and
urinalysis results were documented.
Performance of OGTT
At 7.30 a.m, all had their fasting venous blood sample taken and were given 75g of dissolved
anhydrous glucose in chilled water to drink at once and another sample was taken at 9.30 a.m.
Preservation and analysis of Blood Specimen
Immediately, after the venous blood was drawn, all samples were centrifuged, and aliquots were
prepared within 30 min of collection. Plasma aliquots were frozen at -80oC until conduction of
the analyses in the same laboratory. Plasma glucose was analyzed according to the method of
Trinder (13) using glucose oxidase enzyme buffered in phenoxylate and dissolved in colour
reagent. The coefficient of variation for intra-assay was 3.5% and inter-assay was 9%. Diabetes
was diagnosed based on 2-hour post OGTT venous plasma glucose of ≥11.1mmol-1.
Performance of urinalysis
The urinalysis was carried out in the clinic after the administration of the questionnaire. Plain
bottles were given to the patients to pass 3-5 ml of non-fasting urine. The urine was mixed
thoroughly and tested by dipping the reagent area of the Clinistix® strip directly into the urine
and removed immediately. The edge of the strip was run against the rim of the container to
remove excess urine during removal. The colour change was read within 5- 10sec by matching
and comparing it with the colours on the strip container.
Statistics
The data were entered into a Microsoft Excel database. Analysis of data was with SPSS version
11. The Means±SDs were assessed for continuous variables, and frequencies and proportions
were assessed for categorical variables. Differences among groups were assessed using t- test
and p ≤ 0.05 is considered significant. Sensitivity, specificity, predictive values and efficiency
were assessed from 2x2 table made between mean 2hour plasma glucose and urinalysis.
Sensitivity is the proportion of a diseased population that is identified by the screening test as
positive-the true positives. Specificity is the proportion of the healthy population that is
identified as healthy by the screening test- the true negatives. Positive predictive result is the
proportion of positive results in a mixed population of sick and healthy people. Negative
predictive value is the proportion of negative results in a mixed population of sick and healthy
people while efficiency is the percentage that the sum of the true positives and the true negatives
is of the grand total population.
A plot of correlation was made using a linear regression model where regression coefficient (r)
and correlation equation of 2-hour plasma glucose to urinalysis (y) were estimated.
Results
One hundred and thirty one of the 207 subjects completed the study. These consisted of 87
females and 44 males. One hundred and twenty-two of the subjects had negative screening result.
This is made up of 81 females and 41 males. Nine were screened positive for diabetes making 6
female and 3 males. The mean age of the subjects was 53.11±8.69 years and ranged from 31 to
78 years and median of 52. All the anthropometric measurements were not statistically
significant, however, mean 2-hour plasma glucose between the categories was found to be
markedly significant.
The BMI across the age ranges was particularly higher among those who had positive screen test
in the age range of 60-69 years old as shown in Figure 1. The overall waist to hip ratio was
higher among those who had positive screen test as shown in Figure 2.
The sensitivity of this screening test is 25%, specificity is 97.19%, positive predictive value is
66.66%, negative predictive value is 85.24% while efficiency is 83.96% as shown in the crosstabulation of mean 2-hour plasma glucose and urinalysis in table 2. The logistic model of the
performance of urinalysis to 2-hour plasma glucose of OGTT is shown in Figure 3. The
correlation coefficient is 0.55 Pvalue of 0.00. The equation relating the relationship between
urinalysis and mean 2-hour plasma glucose is shown in equation 1.
Table 1. The features of those that had Urinalysis test for Glucose
Urine Negative
122(93%)
Age in years
Urine Positive
9(7%)
53.02±8.66
54.44±9.46
0.63
Height in meters
1.63±0.08
1.66±0.07
0.25
Weight in kilogram
81±18.15
85.39±11.71
0.48
Body Mass Index in kg/m2
30.39±6.68
31.06±6.60
0.77
Waist in meters
97.94±11.86
101.89±7.80
Hip in meters
107.73±11.69
Waist to hip ratio
110.56±8.56
0.91±0.09
Mean 2-hour plasma glucose in mg/dl
0.93±0.7
155.47±65.38
359.36±187.86
34
33
32
31
30
29
Mean BMI
P value
Uri neCat
28
Negative
27
Positive
Less than 40yrs
40 - 49yrs
50 - 59yrs
70yrs and above
60 - 69yrs
Age in category
Figure 1. The body mass index of the screened subjects against age
0.33
0.48
0.54
0.00
1.1
Mean WHRATIO
1.0
.9
Uri neCat
Negative
.8
Positive
Less than 40yrs
50 - 59yrs
40 - 49yrs
70yrs and above
60 - 69yrs
Age in category
Figure 2. The waist to hip ratio of the screened subjects against age
Table 2. 2x2 cross tabulation of mean 2-hour plasma glucose of OGTT to urinalysis.
Urine category
OGTT category
Negative
Positive
Total
Mean 2-hour <200mg/dl 104
3
107
Mean 2-hour ≥200mg/dl
18
6
24
Total
122
9
131
800
700
600
500
400
Mean2hrspp
300
200
100
0
-.2
0.0
.2
.4
.6
.8
1.0
1.2
Uri neCat
Equation 1 y=155.47 + 203.90 urinalysis r=0.55, r square=0.304 p=0.00
Figure 3. Relationship 2-hour plasma glucose estimation and urinalysis.
Discussion
Urine glucose testing reagents were developed in the presumption that urine glucose
concentration was an effective indicator of prevailing plasma glucose. Consequently, it was
discovered that the amount of glucose found in urine is a function of the amount of blood level of
glucose and the renal threshold of the individual. The renal status can be affected by several
pathologies like procedural errors such as improper timing, collection, reading of colour
development, advanced age, systemic hypertension, sex, pregnancy and a lot of other primary
and secondary renal diseases. The correlation of random urine sample to 2-hour plasma glucose
of OGTT was 0.55 and the r2=0.30 with a significant P value. The importance of r2 is that it is a
measure of the odds of urinalysis to positive diabetes screening test.
Comparison of our finding to the previous studies, a sensitivity of 67% and specificity of 94.4%
was reported in a prospective diagnostic study (8). There is a much disparity between this result
compared to our study because the studied population also included subjects with known
diabetes and the diagnostic blood glucose was lower than current WHO criteria. Similarly,
sensitivity of 20.80% and specificity of 99.14% was reported in another prospective diagnostic
study (12). The result of this study is close to ours because diabetes subjects were not included.
The importance of this study lies in the fact that this the first time r2 will be reported in studies
that used urinalysis as a screening test for diabetes. The reported correlation and r2 of the study is
moderate as a screening test. The sensitivity and specificity result of this study suggests that
hypertension though a risk factor for type 2 diabetes does not necessarily increase the screening
yield of the study. Hypertension can lead to renal damage, which may increase the renal
threshold to glucose. The prevalence of hypertension among dipstick-positive and dipsticknegative diabetes did not differ (14). This thus suggests that hypertension may not necessarily
contribute to the screening yield of diabetes using urinalysis as a screening tool.
Conclusion
This study supports the previous studies showing that urinalysis is a poor screening tool for type
2 diabetes. The yield is not increased by the presence of systemic hypertension as a risk factor
for type 2 diabetes mellitus.
Limitations
Limited numbers of subjects were used and it was a hospital based study. We advise that a larger
sample of people with systemic hypertension should be used in further studies to substantiate the
result we got in this study.
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