Lab Medicine

lab medicine questions

3 members0 open

Jul 20
A patient with chronic liver disease has AST 180 and ALT 70 U/L (AST:ALT ≈ 2.6), a raised GGT, and macrocytosis. Which aetiology does this pattern most suggest?
Closed
Jul 19
An oliguric patient with acute kidney injury has a urine sodium of 10 mmol/L and a fractional excretion of sodium (FENa) of 0.5%, and has not received diuretics. What does this suggest?
Closed
Jul 18
A patient had a severe thunderclap headache 12 hours ago; the CT head is normal. Lumbar puncture CSF is centrifuged and the supernatant is yellow (xanthochromia positive) on spectrophotometry. What does this indicate, and why does timing matter?
Closed
Jul 17
A febrile patient's CSF shows: high opening pressure, > 1000 white cells/µL (neutrophil-predominant), protein 2.5 g/L (high), and a CSF:serum glucose ratio of 0.2 (low). Which pattern is this, and why is the glucose low?
Closed
Jul 16
A child with encephalopathy has a markedly elevated venous ammonia, but the result is questioned because of sample handling. Which preanalytical practice is essential for a reliable ammonia measurement?
Closed
Jul 15
A patient with a platelet count of 900 × 10⁹/L has a serum potassium of 6.2 mmol/L, but a simultaneously drawn heparinised plasma (or blood gas) potassium is 4.4 mmol/L, with a normal ECG. What explains the discrepancy?
Closed
Jul 14
A well, asymptomatic woman with regular menses and no galactorrhoea has a persistently 'raised' prolactin. After polyethylene glycol (PEG) precipitation the recovered prolactin is < 40% and now within range. What was the cause?
Closed
Jul 13
In screening for Cushing's syndrome, a patient takes 1 mg dexamethasone at 11 p.m. and the 8 a.m. serum cortisol fails to suppress below 50 nmol/L. How is this interpreted, and what can cause a false-positive?
Closed
Jul 12
A patient with resistant hypertension and unprovoked hypokalaemia has an elevated aldosterone:renin ratio (ARR) with suppressed plasma renin. Which condition does this suggest, and which preanalytical factors most affect the result?
Closed
Jul 11
A hyponatraemic, hyperkalaemic patient with hypotension and fatigue has a low 9 a.m. cortisol. A 250 µg Synacthen (cosyntropin) test shows the cortisol fails to rise above ~450 nmol/L at 30 minutes. What does this indicate, and which test localises the lesion?
Closed
Jul 4
To investigate a suspected phaeochromocytoma, which test offers the highest sensitivity, and which preanalytical factor most affects its reliability?
Closed
Jul 3
A man develops acute haemolysis after an infection. A quantitative G6PD assay drawn DURING the acute episode is reported as normal, yet G6PD deficiency is still strongly suspected. Why can the assay be falsely normal, and when should it be repeated?
Closed
Jul 2
A patient with metabolic acidosis has HCO3- 12 mmol/L and a measured pCO2 of 40 mmHg. Applying Winter's formula, what is the acid–base interpretation?
Closed
Jul 1
In a critically ill patient with diabetic ketoacidosis, creatinine measured by the kinetic Jaffe method reads higher than by an enzymatic assay. Which interferent classically causes positive (falsely high) interference with the Jaffe reaction?
Closed
Jun 30
A patient with known haemolytic anaemia has an HbA1c that seems implausibly low despite documented hyperglycaemia. Why is HbA1c unreliable here, and what is a better measure of medium-term control?
Closed
Jun 29
A euvolaemic patient with hyponatraemia (Na 122) has low serum osmolality (260), inappropriately high urine osmolality (450), urine sodium 60 mmol/L, and normal thyroid and cortisol. What is the diagnosis?
Closed
Jun 28
Two patients have hypercalcaemia. Patient A: high Ca, low phosphate, HIGH PTH. Patient B: high Ca, low phosphate, SUPPRESSED PTH, with known squamous lung carcinoma. What distinguishes their mechanisms?
Closed
Jun 27
An older patient with bone pain has anaemia, a high total protein with a narrow-based spike in the gamma region on serum protein electrophoresis, calcium 2.9 mmol/L, raised creatinine, and rouleaux on the film. Which test best types and quantifies the abnormal protein and adds prognostic information?
Closed
Jun 26
A patient with a pulmonary–renal syndrome has a cytoplasmic (c-ANCA) immunofluorescence pattern and antibodies to proteinase-3 (PR3) on antigen-specific ELISA. Which condition is most associated?
Closed
Jun 25
Seven days after starting unfractionated heparin, a patient's platelet count falls by 60% and a new DVT appears. Which laboratory pattern supports heparin-induced thrombocytopenia (HIT)?
Closed