Biochemistry and Clinical Pathology Questions and Answers

Answer: C

The answer is Both Salah's Klima and Jamshidi's marrow aspiration needle.

Bone marrow aspiration needs a strong needle with a stylet and an adjustable guard that stops it going too deep. The Salah and Klima needles are the classic sternal and iliac aspiration needles of this kind, and the Jamshidi needle, with its tapered tip, is widely used today for both aspiration and trephine biopsy.

Since both kinds are used, options naming only one are incomplete. A vacuum syringe can be attached to draw the marrow, but it is not a needle that can penetrate bone.

Answer: D

The site not used for bone marrow in adults is the tibia.

In adults, active red marrow is confined mainly to flat bones and the axial skeleton. Marrow is therefore taken from the posterior or anterior iliac crest, the sternum (aspiration only), and the vertebral spinous processes.

The tibia is used only in infants, usually under about two years old, while the long bones still hold active marrow. In adults the tibial marrow has turned to fatty yellow marrow, so a sample from it would not be representative.

Answer: B

The correct matching is 1-a, 2-d, 3-b, 4-c.

• Dark urine: concentrated urine from excessive sweating or dehydration.
• Light coloured urine: dilute urine from a high fluid intake, or from kidneys that cannot concentrate urine.
• Bright yellow: vitamin B supplements, whose riboflavin is excreted with a fluorescent yellow colour.
• Red: blood in the urine (haematuria).

The first code wrongly pairs pale urine with vitamin B and bright yellow with blood. The others fail on dark urine, which reflects concentration, not vitamins or blood.

Answer: B

Fresh frozen plasma can be stored at −30°C for 1 year.

Under the standards followed by Indian blood banks, FFP separated and frozen within hours of collection keeps its labile clotting factors (V and VIII) when stored at −30°C or colder for up to one year.

The other periods belong to other components: 5 days is the shelf life of platelet concentrates stored at 20-24°C with agitation, and 42 days is that of red cells in SAGM additive solution at 2-6°C. Six months is shorter than the permitted storage at this temperature.

Answer: A

The missing step is fibrin monomer.

Thrombin cleaves the small fibrinopeptides A and B from the central part of the fibrinogen molecule. What remains is a fibrin monomer. The monomers then join end to end and side to side by themselves into a loose fibrin polymer, and factor XIIIa cross-links it into the stable fibrin clot.

Dimers, hexamers or octamers are not formed as fixed stages. Polymerization of monomers is a continuous process that builds long strands of many units, so none of the numbered multimers is the product of the thrombin step.

Answer: B

A raised AST to ALT ratio is associated with alcoholic hepatitis.

In alcoholic liver disease the AST:ALT ratio is usually above 1 and often above 2. Alcohol damages mitochondria, which hold much of the cell's AST, and chronic drinkers are short of pyridoxal phosphate (vitamin B6), which ALT needs more than AST does, so ALT stays relatively low.

In acute viral hepatitis and in non-alcoholic fatty liver disease, ALT is typically higher than AST, so the ratio is below 1. Jaundice is a clinical sign of raised bilirubin from many causes and has no characteristic enzyme ratio.

Answer: B

In tuberculous meningitis the CSF protein is increased.

The typical CSF picture of tuberculous meningitis is a markedly raised protein, often well above 100 mg/dL, a moderately raised cell count made up mostly of lymphocytes, and a low glucose. A cobweb clot may form when the fluid stands.

Glucose is decreased, not increased, because the bacilli and inflammatory cells consume it. Chloride is classically low in tuberculous meningitis. Sodium is not a parameter that rises in the CSF in this disease.

Answer: B

The enzyme used to evaluate pancreatic function is amylase.

Serum amylase rises within hours of the onset of acute pancreatitis, and a level above three times the upper limit of normal supports the diagnosis. Serum lipase is the other pancreatic enzyme used, and is more specific.

Alkaline phosphatase is a marker of liver (biliary) and bone disease. Aspartate transaminase reflects damage to the liver, heart or muscle. Lactate dehydrogenase is present in almost every tissue and rises in haemolysis, tissue damage and many tumours, so none of them points to the pancreas.

Answer: A

Fibrinogen is Factor I.

The clotting factors are numbered in Roman numerals in the order they were discovered. Factor I is fibrinogen, the soluble plasma protein that thrombin converts into insoluble fibrin at the end of the coagulation cascade.

Factor II is prothrombin, the precursor of thrombin. Factor IV is calcium ions, needed at several steps of the cascade. Factor VIII is the antihaemophilic factor, whose deficiency causes haemophilia A.

Answer: A

Whipple's triad is used to diagnose hypoglycaemia.

The triad confirms that a patient's symptoms are really due to low blood sugar:

1. symptoms consistent with hypoglycaemia,
2. a low plasma glucose measured at the time of the symptoms, and
3. relief of the symptoms when the glucose is raised.

It is classically used in the work-up of an insulinoma. It has no role in diagnosing hypotension, cancer in general or tuberculosis, which have their own criteria and tests.