Mock OSCE
Debriefing
Station No 1
Glucose estimation
 Principle
 Requirements
Semi-automatic analyser
Adjustable pipette
GOD-PAP reagents
Working literature
Glucose Standard
Two levels of QC material
Value sheets of QC
Station No 2
Levy Jennings’s Plot
Calculation of basic statistics
Plotting of Levy Jennings’s (LJ ) charts
Application of Westgard`s Rules
Station No 3
External Quality Assurance
Method means
`Z` value for bias (accuracy)
Allowable bias
Plots for precision (Bio-rad)
Station No 5
Method Evaluation
 Any step involved in method evaluation can be asked
 Requirements include:
Semi-automatic analyser
Adjustable pipette
GOD-PAP reagents
Working literature
Glucose Standard
 Glucose solution (25%)
Station No 6
First scenarios
 A female patient has very angrily complained you about a
beta-HCG report from your lab. Your result is 1500 IU/L while
she got reports of < 1.0 IU/L from other two labs within 24 h
of the first test. You repeated the test with another sample
and found that it is < 01.0 IU/L from your lab, too. This gross
variation is a matter of concern for you, so after apologising
the patient you obtain the raw data of the test from the
autoanalyser which shows following results of the batch.
Raw data of autoanalyser
Sr No
Beta HCG result
112
<1.0
113
2.0
115
3.2
116
110,000
117
1500
118
<1.0
119
4.1
Most Probable Cause: Sample carry over.
Station No 6
Second scenarios
 You have just started an Arterial Blood Gasses (ABG) system
which also incorporates electrolyte analysis. During the first
day of analyses of patients` sample the result of Sodium
worries you, some of them are like following:
 Most Probable Cause: Use of Sodium Heparin as an
anticoagulant.
Station No 6
Third scenarios
 You have received a call from the Intensive Care Unit about
Calcium and Electrolyte reports of two patients with gross
Hypocalcaemia and Hyperkalaemia which are otherwise
apparently normal.
 Most Probable Cause: EDTA Contamination
EDTA Contamination
 EDTA binds Calcium
 False Hypocalcaemia
 False Hyperkalaemia
“Spurious hyperkalaemia due to
kEDTA contamination is common “
Michael P Cornes1, Clare Ford and Rousseau Gama; Spurious hyperkalaemia due to EDTA
contamination: common and not always easy to identify Ann Clin Biochem 2008;45:601-603
doi:10.1258/acb.2008.007241
© 2008
Correct Filling Order
Always fill Plain tube and
Lithium Heparin tube first
Followed by EDTA tubes
(Glucose and CP tubes)
Right Order
Serum and Lithium
Heparin First
CP and
Glucose last
Station No 7
Derived Tests
Creatinine Clearance
 Urinary Creatinine: 8.5 mmol/L
 Serum Creatinine : 98 µmol/L
 Urinary Volume: 1440 ml
 Creatinine Clearance : 86.73 ml /min
Station No 7
Derived Tests
HOMA –IR
 Plasma Glucose Fasting: 6.8 mmol/L
 Serum Insulin:
18.3 IU/L
 HOMA –IR :
5.53
Station No 7
Derived Tests
Delta Ratio
pH :
7.57 (7.35 – 7.45)
Base Excess:
7.0 (+3 to -3)
PCO2 :
2.8 (4.7 – 6.0 kPa)
PO2:
19.2 (10.7 – 13.3 kPa)
HCO3:
21
(22 – 28 mmol/L)
Chloride:
80
(94-111 mmol/L)
Anion Gap:
33
(7-17 mmol/L)
Delta Ratio:
7
DELTA RATIO
The delta ratio is used for the determination
of a mixed acid base disorder in an elevated
anion gap metabolic acidosis
Measured anion gap – Normal anion gap
Normal [HCO3-] – Measured [HCO3-]
or
(anion gap – 12)
(24 - [HCO3-])
Station No 9
Data Interpretation
a. A patient having following arterial blood gas analyses
results:
 pH :
7.40
(7.35 – 7.45)
 Base Excess:
21.8
(<+3 - >-3)
 PCO2 :
10.7
(4.7 – 6.0 kPa)
 PO2
10.9
(10.7 – 13.3 kPa)
 HCO3
51.1
(23 – 33 mmol/L)
 Oxygen Sat
95.1
(95-98%)
What is the most probable biochemical diagnosis:
Correct Answer: Mixed Respiratory Acidosis and Metabolic
Alkalosis
Station No 9
Data Interpretation
b. A 60 year old female presented with polyuria and
nocturia:
Serum
 Ca :
3.21 mmol/L (2.15–2.55)
 PO4 :
2.5 mmol/L (0.60 – 1.25)
 Albumin : 43 g/L
(37-52)
 ALP :
114
U/L
(30 –120)
 Urea :
6.2 mmol/L
(3.3 – 6.6)
What is the most probable diagnosis?
Correct Answer: Vitamin D Intoxication
Station No 9
Data Interpretation
c. A boy of 15 years presented with oedema all over the
body:
Serum
 Total Proteins:
55 g/L
(65-80)
 Albumin:
25 g/L
(35-50)
 Serum Cholesterol :
8.5 mmol/L (<5.1)
 Serum Triglycerides:
1.8 mmol/L (<2.83)
What is the most likely diagnosis ?
Correct Answer: Nephrotic Syndrome
Station No 9
Data Interpretation
d. A 22 year old female complained of hair growth on face
and limbs with regular menstrual cycles:
Serum
 FSH
:
 LH
:
 Testosterone:
6
20
5.8
mIU/L
mIU/L
nmol/L
(2-10)
(3-14)
(2.2-4.1)
What is the most probable diagnosis?
Correct Answer: PCOS
Station No 9
Data Interpretation
e. An infant with ambiguous genitalia and failure to thrive:

Karyotype:
XX
What is the most probable diagnosis?
What investigations you will like to carry out?
Correct Answer: CAH
17 OH Progesterone