Mock OSCEDebriefing
Station No 1Glucose estimation Principle Requirements
Semi-automatic analyserAdjustable pipetteGOD-PAP reagentsWorking literatureGlucose StandardTwo levels of QC materialValue sheets of QC
Station No 2Levy Jennings’s PlotCalculation of basic statisticsPlotting of Levy Jennings’s (LJ ) chartsApplication of Westgard`s Rules
Station No 3External Quality Assurance Method means`Z` value for bias (accuracy)Allowable bias Plots for precision (Bio-rad)
Station No 5Method Evaluation Any step involved in method evaluation can be asked Requirements include:
Semi-automatic analyserAdjustable pipetteGOD-PAP reagentsWorking literatureGlucose Standard Glucose solution (25%)
Station No 6First 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 autoanalyserSr 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 6Second 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 6Third 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 firstFollowed by EDTA tubes (Glucose and CP tubes)
Right Order
Serum and Lithium Heparin First
CP and Glucose last
Station No 7Derived TestsCreatinine Clearance
Urinary Creatinine: 8.5 mmol/L Serum Creatinine : 98 µmol/L Urinary Volume: 1440 ml
Creatinine Clearance : 86.73 ml /min
Station No 7Derived TestsHOMA –IR
Plasma Glucose Fasting: 6.8 mmol/L Serum Insulin: 18.3 IU/L
HOMA –IR : 5.53
Station No 7Derived TestsDelta 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 9Data 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 9Data 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 9Data 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 9Data Interpretation
d. A 22 year old female complained of hair growth on face and limbs with regular menstrual cycles:
Serum FSH : 6 mIU/L (2-10) LH : 20 mIU/L (3-14) Testosterone: 5.8 nmol/L (2.2-4.1)
What is the most probable diagnosis?
Correct Answer: PCOS
Station No 9Data 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
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