I85PREP
⌘ K
NHPC BMLT study materials
NHPC BMLT study resources

NHPC BMLT practice questions

One question at a time. Build your NHPC BMLT understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Clinical Biochemistry

Which plasma protein is the principal carrier of free fatty acids in the fasting state?

  1. Ceruloplasmin
  2. Albumin Correct answer.
  3. Transferrin
  4. Haptoglobin

Explanation

Free fatty acids are poorly water soluble and circulate bound non-covalently to albumin, which has multiple hydrophobic binding sites. This binding also limits their cellular uptake until dissociation occurs at the capillary bed. The other proteins shown transport hemoglobin, iron, and copper respectively.

Question 2Clinical Biochemistry

A patient with severe vomiting has an arterial blood gas showing pH 7.52, PaCO2 48 mmHg, and HCO3- 38 mmol/L. Which acid-base disturbance is present?

  1. Metabolic alkalosis with respiratory compensation Correct answer.
  2. Respiratory acidosis with metabolic compensation
  3. Respiratory alkalosis with metabolic compensation
  4. Metabolic acidosis with respiratory compensation

Explanation

The primary abnormality is a raised bicarbonate with alkalinemia, indicating metabolic alkalosis. The elevated PaCO2 represents hypoventilation, the expected respiratory compensation that retains carbon dioxide. In respiratory acidosis the bicarbonate rise would be secondary and pH would be acidemic.

Question 3Clinical Biochemistry

In the urea cycle, which enzyme catalyzes the condensation of ammonia with bicarbonate to form carbamoyl phosphate?

  1. Argininosuccinate lyase
  2. Arginase
  3. Ornithine transcarbamoylase
  4. Carbamoyl phosphate synthetase I Correct answer.

Explanation

Carbamoyl phosphate synthetase I is the mitochondrial, ammonia-dependent, rate-limiting enzyme of ureagenesis and requires N-acetylglutamate as an activator. Ornithine transcarbamoylase then transfers the carbamoyl group to ornithine. The other enzymes act later in the cycle.

Question 4Clinical Biochemistry

Which laboratory finding is most characteristic of nephrotic syndrome?

  1. Selective proteinuria above 3.5 g per day with hypoalbuminemia Correct answer.
  2. Isolated glucosuria with normal plasma glucose
  3. Hyperkalemia with metabolic acidosis and normal urine output
  4. Persistent microscopic hematuria with normal protein excretion

Explanation

Nephrotic syndrome reflects glomerular filtration barrier injury that permits heavy loss of protein, conventionally above 3.5 g/day, producing hypoalbuminemia, edema, and hyperlipidemia. Hematuria and hypertension are more typical of nephritic presentations. Tubular disorders instead cause glucosuria with normal glycemia.

Question 5Clinical Biochemistry

A 54-year-old man with acute pancreatitis has a serum calcium of 7.4 mg/dL and an albumin of 2.0 g/dL. Using the albumin-corrected calcium formula, what is the corrected total calcium?

  1. 6.2 mg/dL
  2. 7.4 mg/dL
  3. 9.8 mg/dL
  4. 8.6 mg/dL Correct answer.

Explanation

The correction adds 0.8 mg/dL to measured total calcium for every 1.0 g/dL that albumin falls below 4.0 g/dL. Here the albumin deficit is 2.0 g/dL, so 7.4 plus 1.6 gives 8.6 mg/dL. This adjusted value better reflects the physiologically active fraction than the raw measurement.

Question 6Clinical Biochemistry

Which enzyme is regarded as the most specific marker of acute pancreatic acinar injury?

  1. Creatine kinase
  2. Pancreatic amylase
  3. Alkaline phosphatase
  4. Lipase Correct answer.

Explanation

Lipase is more pancreas-specific than amylase because amylase also arises from salivary glands and other tissues. Lipase also remains elevated longer, aiding delayed presentation. Alkaline phosphatase and creatine kinase reflect hepatobiliary and muscle sources respectively.

Question 7Clinical Biochemistry

In the fasting state, which process predominantly maintains blood glucose after hepatic glycogen stores become depleted?

  1. Muscle glycogenolysis releasing free glucose into blood
  2. Adipose lipolysis releasing glucose
  3. Hepatic gluconeogenesis from lactate, glycerol, and amino acids Correct answer.
  4. Renal filtration of filtered glucose

Explanation

After glycogen depletion, the liver synthesizes glucose de novo from lactate, glycerol, and glucogenic amino acids under glucagon and cortisol drive. Muscle lacks glucose-6-phosphatase, so its glycogen cannot directly raise blood glucose. Lipolysis yields glycerol as a gluconeogenic substrate but not glucose itself.

Question 8Clinical Biochemistry

A patient with type 1 diabetes has marked hyperglycemia, ketonemia, and a calculated serum osmolality of 300 mOsm/kg. Which finding best supports diabetic ketoacidosis over hyperosmolar hyperglycemic state?

  1. Serum osmolality above 320 mOsm/kg
  2. Absence of ketones with mild acidosis
  3. Bicarbonate above 30 mmol/L
  4. Elevated beta-hydroxybutyrate with high anion gap Correct answer.

Explanation

Diabetic ketoacidosis is defined by ketone accumulation, and beta-hydroxybutyrate is the dominant ketone body, producing a high anion gap metabolic acidosis. Hyperosmolar hyperglycemic state typically shows greater osmolality with minimal ketosis. A high bicarbonate or absent ketones argues against ketoacidosis.

Question 9Clinical Biochemistry

Which lipoprotein fraction is richest in triglycerides and is normally cleared most rapidly after a fatty meal?

  1. Lipoprotein(a)
  2. Chylomicrons Correct answer.
  3. Low-density lipoprotein
  4. High-density lipoprotein

Explanation

Chylomicrons are assembled in enterocytes to transport dietary triglyceride and are the largest, least dense lipoproteins. Lipoprotein lipase rapidly hydrolyzes their triglyceride core, so they are normally absent after a 12-hour fast. LDL and HDL are cholesterol-enriched and far longer lived.

Question 10Clinical Biochemistry

Which apolipoprotein is the essential structural component and receptor ligand of LDL?

  1. ApoE
  2. ApoC-II
  3. ApoA-I
  4. ApoB-100 Correct answer.

Explanation

ApoB-100 is the sole apolipoprotein of LDL and is recognized by the LDL receptor, so it mediates clearance. ApoA-I is the major HDL protein, ApoC-II activates lipoprotein lipase, and ApoE mediates remnant clearance. Each has a distinct role in lipoprotein handling.

Question 11Clinical Biochemistry

A 30-year-old woman has fasting glucose 118 mg/dL on two occasions and HbA1c 6.2%. What is the most appropriate interpretation?

  1. Established diabetes mellitus
  2. Prediabetes Correct answer.
  3. Normal glucose tolerance
  4. Gestational diabetes

Explanation

Fasting glucose of 100 to 125 mg/dL and HbA1c of 5.7% to 6.4% both fall in the prediabetes range. Diabetes requires fasting glucose of 126 mg/dL or more or HbA1c of 6.5% or more. Gestational diabetes requires pregnancy context and separate criteria.

Question 12Clinical Biochemistry

Which isoenzyme pattern of alkaline phosphatase suggests a hepatic rather than skeletal origin?

  1. Elevated liver isoenzyme with gamma-glutamyl transferase also raised Correct answer.
  2. Elevated intestinal isoenzyme after a fatty meal
  3. Elevated bone isoenzyme with normal liver fraction
  4. Elevated placental isoenzyme in a nonpregnant adult

Explanation

Alkaline phosphatase is raised in both cholestasis and bone disease, so gamma-glutamyl transferase is used to localize the source. A concurrent rise in gamma-glutamyl transferase points to hepatobiliary induction. The bone isoenzyme is heat-labile and is not accompanied by a raised gamma-glutamyl transferase.

Question 13Clinical Biochemistry

Which pattern of liver function tests most suggests hepatocellular injury rather than cholestasis?

  1. Isolated conjugated hyperbilirubinemia with normal enzymes
  2. Low albumin with normal transaminases
  3. Disproportionate alkaline phosphatase and gamma-glutamyl transferase elevation
  4. Disproportionate ALT and AST elevation with modest alkaline phosphatase rise Correct answer.

Explanation

Hepatocellular damage releases transaminases, so ALT and AST rise disproportionately while alkaline phosphatase changes little. Cholestasis instead produces a predominant rise in alkaline phosphatase and gamma-glutamyl transferase. Isolated hyperbilirubinemia suggests a conjugation or transport defect.

Question 14Clinical Biochemistry

Which analyte is most useful for detecting alcohol-related chronic liver disease when transaminases are only mildly abnormal?

  1. Prostate-specific antigen
  2. Mean corpuscular volume and gamma-glutamyl transferase Correct answer.
  3. D-dimer
  4. Troponin I

Explanation

Chronic alcohol use induces gamma-glutamyl transferase and commonly produces macrocytosis, so both are supportive markers when transaminases are near normal. The AST to ALT ratio above 2 is also characteristic. Troponin, prostate-specific antigen, and D-dimer reflect cardiac, prostatic, and thrombotic processes.

Question 15Clinical Biochemistry

Which cardiac biomarker remains elevated longest after an acute myocardial infarction?

  1. Aspartate aminotransferase
  2. Myoglobin
  3. Troponin I Correct answer.
  4. Creatine kinase MB

Explanation

Cardiac troponin I and T rise within hours and remain elevated for roughly 7 to 14 days because of slow cytoskeletal degradation. Creatine kinase MB normalizes within about 2 to 3 days, and myoglobin is the earliest to rise and clear. This persistence makes troponin useful for late presentation.

Question 16Clinical Biochemistry

Serum from a patient with a suspected myocardial infarction is analyzed for the MB fraction of creatine kinase. Which property underlies the use of the MB fraction rather than total activity?

  1. The MB isoenzyme is found only in skeletal muscle
  2. The MB isoenzyme is identical to the brain isoenzyme
  3. The MB isoenzyme is absent from all human tissue
  4. The MB isoenzyme is relatively enriched in myocardium Correct answer.

Explanation

Creatine kinase has MM, MB, and BB isoenzymes, and myocardium contains a substantial MB fraction whereas skeletal muscle is mostly MM. Measuring the MB fraction therefore improves cardiac specificity over total activity. Brain tissue expresses BB, not MB.

Question 17Clinical Biochemistry

Which protein is the most sensitive marker of iron deficiency before anemia develops?

  1. Hemoglobin
  2. Mean corpuscular volume
  3. Total iron-binding capacity
  4. Ferritin Correct answer.

Explanation

Ferritin reflects body iron stores and falls early in depletion, before hemoglobin or red cell indices change. However, ferritin is an acute-phase reactant and can be falsely normal during inflammation. Hemoglobin and mean corpuscular volume fall only once deficiency is advanced.

Question 18Clinical Biochemistry

A patient with chronic inflammation has a serum ferritin of 250 ng/mL and a transferrin saturation of 12%. Which condition best explains this pattern?

  1. Anemia of chronic disease Correct answer.
  2. Vitamin B12 deficiency
  3. Iron overload hemochromatosis
  4. Thalassemia trait

Explanation

Inflammation raises ferritin as an acute-phase reactant while hepcidin reduces iron release, lowering transferrin saturation and producing functional iron restriction. This combination of high ferritin with low saturation is typical of anemia of chronic disease. Hemochromatosis instead shows high saturation with high ferritin.

Question 19Clinical Biochemistry

Which finding is most consistent with intravascular hemolysis rather than extravascular hemolysis?

  1. Elevated lactate dehydrogenase with low haptoglobin and hemoglobinuria Correct answer.
  2. High haptoglobin with normal lactate dehydrogenase
  3. Elevated conjugated bilirubin with normal reticulocyte count
  4. Isolated unconjugated hyperbilirubinemia with normal haptoglobin

Explanation

Intravascular hemolysis releases free hemoglobin that binds and depletes haptoglobin, and hemoglobin spills into urine once binding capacity is exceeded. Lactate dehydrogenase rises from red cell destruction. Extravascular hemolysis usually preserves haptoglobin and does not cause hemoglobinuria.

Question 20Clinical Biochemistry

Which laboratory pattern is expected in untreated vitamin B12 deficiency?

  1. Macrocytic anemia with elevated methylmalonic acid and homocysteine Correct answer.
  2. Macrocytic anemia with normal homocysteine and normal methylmalonic acid
  3. Normocytic anemia with normal methylmalonic acid
  4. Microcytic anemia with low ferritin and normal homocysteine

Explanation

Vitamin B12 is required for methionine synthase and methylmalonyl-CoA mutase, so deficiency raises both homocysteine and methylmalonic acid. Impaired DNA synthesis produces macrocytic anemia with hypersegmented neutrophils. Folate deficiency raises homocysteine but not methylmalonic acid.

Question 21Clinical Biochemistry

Which enzyme deficiency is the most common cause of hereditary hemolytic anemia due to impaired glutathione regeneration?

  1. Glucose-6-phosphatase
  2. Glucose-6-phosphate dehydrogenase Correct answer.
  3. Pyruvate kinase
  4. Hexokinase

Explanation

Glucose-6-phosphate dehydrogenase generates NADPH that keeps glutathione reduced, protecting red cells from oxidative stress. Deficiency causes episodic hemolysis after oxidant exposure or infection. Pyruvate kinase deficiency causes hemolysis by impaired ATP generation, not glutathione loss.

Question 22Clinical Biochemistry

A patient with chronic kidney disease has a plasma creatinine of 4.0 mg/dL. Which additional measurement best estimates glomerular filtration rate without relying on muscle mass?

  1. Urine specific gravity
  2. Blood urea nitrogen
  3. Cystatin C Correct answer.
  4. Serum uric acid

Explanation

Cystatin C is produced at a constant rate by nucleated cells and is freely filtered, so it is less dependent on muscle mass than creatinine. This makes it useful in patients with reduced muscle bulk. Blood urea nitrogen, specific gravity, and uric acid are affected by many non-renal factors.

Question 23Clinical Biochemistry

Which statement correctly describes the relationship between plasma osmolality and effective osmolality (tonicity)?

  1. Tonicity and measured osmolality are always numerically identical
  2. Tonicity is determined mainly by urea because urea is impermeant
  3. Tonicity depends on solutes that cannot cross membranes, such as sodium Correct answer.
  4. Tonicity falls whenever measured osmolality rises

Explanation

Tonicity reflects only osmotically active solutes that cannot freely cross cell membranes, principally sodium salts and glucose. Urea crosses membranes readily and contributes to measured osmolality but not to tonicity. Thus measured osmolality and tonicity can diverge in uremia.

Question 24Clinical Biochemistry

Which cerebrospinal fluid finding best supports bacterial meningitis?

  1. Neutrophilic pleocytosis with low glucose and high protein Correct answer.
  2. Normal cell count with high glucose
  3. Lymphocytic pleocytosis with normal glucose and normal protein
  4. Xanthochromia with elevated red cell count

Explanation

Bacterial meningitis typically produces a neutrophil-predominant pleocytosis, low CSF glucose relative to serum, and elevated protein. Viral meningitis more often shows lymphocytic pleocytosis with normal glucose. Xanthochromia indicates prior subarachnoid hemorrhage.

Question 25Clinical Biochemistry

A 62-year-old woman has a serum sodium of 124 mmol/L, serum osmolality of 262 mOsm/kg, urine osmolality of 520 mOsm/kg, and clinically euvolemic status. Which cause is most likely?

  1. Primary polydipsia
  2. Hyperglycemic hyperosmolar state
  3. Diabetes insipidus
  4. Syndrome of inappropriate antidiuretic hormone secretion Correct answer.

Explanation

Hypotonic hyponatremia with inappropriately concentrated urine and euvolemia fits SIADH, where ADH secretion persists despite low osmolality. Primary polydipsia dilutes urine rather than concentrating it. Diabetes insipidus produces dilute urine and hypernatremia.

Question 26Clinical Biochemistry

In a healthy adult, which laboratory finding best fits a fasting plasma glucose result used to diagnose diabetes mellitus under standard WHO criteria?

  1. A random plasma glucose of 140 mg/dL in an asymptomatic person
  2. A fasting plasma glucose of 126 mg/dL or more confirmed on a separate occasion Correct answer.
  3. A glycated hemoglobin of 5.9% with a normal fasting plasma glucose
  4. A fasting plasma glucose of 100 mg/dL with a normal oral glucose tolerance test

Explanation

WHO and ADA criteria accept a fasting plasma glucose of 126 mg/dL (7.0 mmol/L) or higher as diagnostic of diabetes, and in an asymptomatic patient the result should be confirmed by repeat testing on another day. The fasting sample must follow at least 8 hours without caloric intake. Values between 100 and 125 mg/dL define impaired fasting glucose rather than diabetes.

Question 27Clinical Biochemistry

A 55-year-old man with crushing chest pain has a serum troponin I that is normal at 2 hours after symptom onset. What is the most appropriate interpretation and next step?

  1. A single early normal troponin does not exclude infarction, so serial sampling 3 to 6 hours later is required Correct answer.
  2. Acute myocardial infarction is excluded and no further sampling is needed
  3. The result indicates skeletal muscle injury rather than cardiac injury
  4. Troponin should be replaced by myoglobin as the sole confirmatory marker

Explanation

Cardiac troponin rises 3 to 6 hours after myocardial necrosis begins, so a single sample drawn very early can be falsely negative. Guidelines require a serial strategy with a second sample (or a high-sensitivity 0/1-hour algorithm) to look for a rise and fall. Myoglobin is an early but nonspecific marker and is not used alone.

Question 28Clinical Biochemistry

Which statement correctly describes the renal handling of creatinine that limits its value as a glomerular filtration marker?

  1. Creatinine is freely filtered and also actively secreted by the proximal tubule, so it slightly overestimates GFR Correct answer.
  2. Creatinine is freely filtered but completely reabsorbed by the proximal tubule, so it underestimates GFR
  3. Creatinine is largely bound to plasma proteins and therefore poorly filtered
  4. Creatinine is filtered only at the distal tubule and is not affected by tubular secretion

Explanation

Creatinine is filtered freely at the glomerulus and is additionally secreted by proximal tubular cells via organic cation transporters. This tubular secretion adds creatinine to the filtrate, so creatinine clearance exceeds true GFR by roughly 10 to 20%. The effect becomes more pronounced at low GFR, which is why cystatin C or measured clearance is preferred when accuracy matters.

Question 29Clinical Biochemistry

A 24-year-old woman has a serum calcium of 11.8 mg/dL, serum phosphate of 2.1 mg/dL, and a parathyroid hormone level that is inappropriately normal. Which diagnosis best fits this pattern?

  1. Primary hyperparathyroidism Correct answer.
  2. Vitamin D deficiency osteomalacia
  3. Chronic kidney disease with secondary hyperparathyroidism
  4. Primary hypoparathyroidism

Explanation

Hypercalcemia with hypophosphatemia and a PTH that is not suppressed indicates inappropriate PTH secretion, the hallmark of primary hyperparathyroidism. PTH raises serum calcium by bone resorption and renal reabsorption while increasing phosphate excretion, which explains the low phosphate. In secondary hyperparathyroidism the calcium is low or normal, not elevated.

Question 30Clinical Biochemistry

Which laboratory finding is characteristic of nephrotic syndrome rather than nephritic syndrome?

  1. Hematuria with red cell casts in the urine sediment
  2. A rising serum creatinine with oliguria
  3. Low serum complement with active urinary sediment
  4. Urine protein excretion above 3.5 g per day with hypoalbuminemia Correct answer.

Explanation

Nephrotic syndrome reflects increased glomerular permeability to protein, producing heavy proteinuria (over 3.5 g/day), hypoalbuminemia, edema, and hyperlipidemia. The sediment is typically bland, without significant hematuria or red cell casts. Nephritic syndrome, by contrast, is an inflammatory glomerular lesion with hematuria, casts, and often reduced complement.

Question 31Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A blood culture isolate from a febrile patient grows a Gram-negative bacillus that is oxidase-positive and non-fermentative. Which organism is most consistent with these findings?

  1. Klebsiella pneumoniae
  2. Escherichia coli
  3. Salmonella Typhi
  4. Pseudomonas aeruginosa Correct answer.

Explanation

Pseudomonas aeruginosa is a non-fermentative Gram-negative bacillus that is oxidase-positive, a combination that distinguishes it from the Enterobacterales. The oxidase test is the key discriminator here, since all the other listed organisms are oxidase-negative glucose fermenters.

Question 32Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

Which laboratory finding best supports a diagnosis of acute hepatitis B infection rather than past resolved infection?

  1. HBsAg with IgM anti-HBc Correct answer.
  2. IgG anti-HBs alone
  3. IgG anti-HBc alone
  4. Anti-HBe with anti-HBs

Explanation

The presence of hepatitis B surface antigen together with IgM-class antibody to the core antigen is the classic serological signature of acute hepatitis B. IgM anti-HBc indicates recent infection, whereas IgG anti-HBc persists for life after resolution.

Question 33Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A stool sample from a patient with bloody diarrhoea grows a lactose-negative organism on MacConkey agar. Which additional test would most strongly support Shigella over Salmonella?

  1. Absence of gas from glucose fermentation Correct answer.
  2. Motility in semi-solid medium
  3. Positive urease reaction
  4. Hydrogen sulphide production on TSI

Explanation

Shigella ferments glucose without producing gas and is non-motile, whereas most Salmonella produce gas from glucose and are motile. The absence of gas helps separate Shigella from Salmonella in stool culture workup.

Question 34Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

Which microscopic feature is characteristic of Plasmodium falciparum trophozoites on a thick blood film?

  1. Banana-shaped gametocytes
  2. Multiple ring forms in a single red cell Correct answer.
  3. Schüffner's dots in enlarged red cells
  4. Large amoeboid trophozoites

Explanation

Plasmodium falciparum often shows multiple delicate ring forms within one erythrocyte and high parasitaemia because infected cells are not selectively sequestered in peripheral blood. Banana-shaped gametocytes are also typical of P. falciparum but are not trophozoites.

Question 35Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A fungal culture from a bronchial wash grows a mould that produces septate hyphae with dichotomous branching at 45 degrees. Which organism is most likely?

  1. Rhizopus species
  2. Aspergillus fumigatus Correct answer.
  3. Cryptococcus neoformans
  4. Candida albicans

Explanation

Aspergillus species characteristically show narrow, septate hyphae with regular dichotomous branching at approximately 45 degrees. This morphology in respiratory specimens strongly suggests Aspergillus rather than the other listed fungi.

Question 36Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A sputum Gram stain from a patient with lobar pneumonia shows Gram-positive lancet-shaped diplococci. Which organism should be suspected?

  1. Staphylococcus aureus
  2. Streptococcus pneumoniae Correct answer.
  3. Moraxella catarrhalis
  4. Haemophilus influenzae

Explanation

Streptococcus pneumoniae appears as Gram-positive, lancet-shaped diplococci and is a leading cause of lobar pneumonia. The distinctive paired coccus morphology with pointed ends supports this identification.

Question 37Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

Which culture medium is selective for Vibrio cholerae because of its alkaline pH and ability to suppress most enteric organisms?

  1. MacConkey agar
  2. Thiosulphate citrate bile salts sucrose agar Correct answer.
  3. Blood agar
  4. Selenite F broth

Explanation

Thiosulphate citrate bile salts sucrose agar is designed for Vibrio species, using alkaline pH and bile salts to inhibit much of the competing enteric flora. Vibrio cholerae grows as sucrose-fermenting yellow colonies on this medium.

Question 38Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A wound swab from a patient with a deep puncture injury grows an anaerobic Gram-positive bacillus. Which organism is most consistent with this finding?

  1. Fusobacterium nucleatum
  2. Bacteroides fragilis
  3. Peptostreptococcus species
  4. Clostridium perfringens Correct answer.

Explanation

Clostridium perfringens is a Gram-positive anaerobic bacillus associated with deep wound and gas gangrene infections. The other listed anaerobes are either Gram-negative bacilli or Gram-positive cocci.

Question 39Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

An HIV antibody screening test is reactive, but the follow-up confirmatory assay is negative. What is the most appropriate interpretation?

  1. The patient is confirmed HIV-positive
  2. The patient has acute HIV infection
  3. The screening result is likely a false positive Correct answer.
  4. The sample should be reported as indeterminate permanently

Explanation

A reactive screening test followed by a negative confirmatory assay usually indicates a false-positive screen, so the result should not be reported as HIV-positive. Confirmatory testing is required because screening assays have limited positive predictive value in low-prevalence populations.

Question 40Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

Which parasite is diagnosed by finding barrel-shaped eggs with bipolar plugs in a stool sample?

  1. Enterobius vermicularis
  2. Ascaris lumbricoides
  3. Trichuris trichiura Correct answer.
  4. Taenia solium

Explanation

Trichuris trichiura eggs are characteristically barrel-shaped with mucoid plugs at both poles. This morphology is distinctive among common intestinal helminths.

Question 41Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A newborn develops meningitis, and a cerebrospinal fluid culture grows a Gram-negative bacillus. Which organism is most likely in this age group?

  1. Escherichia coli Correct answer.
  2. Streptococcus agalactiae
  3. Listeria monocytogenes
  4. Neisseria meningitidis

Explanation

Escherichia coli is a leading Gram-negative cause of neonatal meningitis, often acquired from the maternal genital tract during delivery. Neisseria meningitidis is Gram-negative but is more typical in older children and adolescents.

Question 42Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

Which test is used to detect latent tuberculosis infection by measuring interferon-gamma release from sensitised T cells?

  1. Interferon-gamma release assay Correct answer.
  2. Mycobacterial culture on Lowenstein-Jensen medium
  3. Mantoux tuberculin skin test
  4. Acid-fast bacilli smear

Explanation

Interferon-gamma release assays measure cell-mediated immune response to Mycobacterium tuberculosis antigens in vitro and are used for latent infection screening. They are not affected by prior BCG vaccination in the same way as the tuberculin skin test.

Question 43Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A patient returns from a tropical area with fever, and a blood film shows trypanosomes. Which vector is responsible for transmission of African trypanosomiasis?

  1. Anopheles mosquito
  2. Sandfly
  3. Triatomine bug
  4. Tsetse fly Correct answer.

Explanation

African trypanosomiasis is transmitted by the tsetse fly of the genus Glossina. The vector differs from those of malaria, leishmaniasis, and Chagas disease.

Question 44Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

Which organism is a common cause of antibiotic-associated pseudomembranous colitis and is detected by testing for toxin in stool?

  1. Campylobacter jejuni
  2. Clostridioides difficile Correct answer.
  3. Vibrio parahaemolyticus
  4. Yersinia enterocolitica

Explanation

Clostridioides difficile causes antibiotic-associated pseudomembranous colitis, and diagnosis commonly relies on stool toxin or nucleic acid detection. Its association with prior antibiotic use is a key clinical clue.

Question 45Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A Gram stain of urethral discharge shows Gram-negative intracellular diplococci. Which organism is most likely?

  1. Neisseria gonorrhoeae Correct answer.
  2. Mycoplasma genitalium
  3. Chlamydia trachomatis
  4. Treponema pallidum

Explanation

Neisseria gonorrhoeae appears as Gram-negative diplococci within polymorphonuclear cells in urethral discharge, a finding strongly suggestive of gonorrhoea. The other agents listed are not reliably seen as intracellular Gram-negative diplococci.

Question 46Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

Which feature distinguishes Cryptococcus neoformans from other yeasts on India ink preparation?

  1. Formation of arthroconidia
  2. Production of pseudohyphae
  3. A prominent polysaccharide capsule Correct answer.
  4. Positive germ tube test

Explanation

Cryptococcus neoformans has a thick polysaccharide capsule that appears as a clear halo around the yeast cell in India ink preparations. This capsule is the key distinguishing feature.

Question 47Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A patient with neutropenia develops a pulmonary infection, and culture grows a mould with broad, non-septate hyphae with right-angle branching. Which genus is most likely?

  1. Fusarium
  2. Mucor Correct answer.
  3. Aspergillus
  4. Penicillium

Explanation

Mucorales such as Mucor show broad, ribbon-like, non-septate hyphae with right-angle branching, unlike the narrow septate hyphae of Aspergillus. This morphology is important because it guides antifungal choice.

Question 48Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

Which serological marker indicates past infection with hepatitis A virus?

  1. IgM anti-HAV
  2. IgM anti-HBc
  3. HBsAg
  4. IgG anti-HAV Correct answer.

Explanation

IgG antibody to hepatitis A virus appears after infection and persists, indicating past infection or immunity. IgM anti-HAV instead indicates acute or recent infection.

Question 49Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

A stool examination reveals cysts with four nuclei and a smooth wall. Which parasite is most likely?

  1. Cryptosporidium parvum
  2. Balantidium coli
  3. Entamoeba histolytica Correct answer.
  4. Giardia lamblia

Explanation

Entamoeba histolytica cysts typically contain up to four nuclei and have a smooth refractile wall. This morphology helps distinguish them from other protozoan cysts in stool.

Question 50Clinical Microbiology (Bacteriology, Virology, Mycology, Parasitology)

Which antibiotic susceptibility method determines the minimum inhibitory concentration by diluting antibiotic in broth?

  1. Kirby-Bauer disc diffusion
  2. Beta-lactamase chromogenic test
  3. E-test strip method
  4. Broth microdilution Correct answer.

Explanation

Broth microdilution determines the minimum inhibitory concentration by exposing organisms to serial dilutions of antibiotic in broth. It provides a quantitative MIC rather than a zone diameter.