MLT GlobeMOH exam preparation (UAE) – page 27
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
A total calcium is 10 mg/dL. Calcium has an atomic weight of 40 and a valence of 2. What is the result in mEq/L?
10 mg/dL = 100 mg/L; 100/40 = 2.5 mmol/L. mEq/L = mmol/L × valence = 2.5 × 2 = 5.0 mEq/L. 2.5 is the mmol/L value.
How many grams of H2SO4 (MW 98 g/mol) are required to prepare 1 L of a 1 N solution?
Equivalent weight = MW/valence = 98/2 = 49 g. For 1 N in 1 L, 49 g is needed. 98 g would make a 1 mol/L (2 N) solution.
A totally enclosed, gas-tight biosafety cabinet operated through attached rubber gloves is a:
Class III cabinets (glove boxes) are gas-tight with glove ports and give maximum protection, used for BSL-4 agents. Class I and II cabinets have an open front.
Under the Globally Harmonized System (GHS), a Safety Data Sheet contains how many standard sections?
GHS and OSHA HazCom 2012 require a 16-section SDS format, for example Section 2 hazard identification and Section 4 first-aid measures.
Sodium azide preservative should not be poured down drains in large volumes because it:
Sodium azide reacts with copper and lead plumbing to form shock-sensitive, explosive metal azides. Disposal follows the SDS and local rules, with copious water flushing if permitted.
A grossly hemolyzed serum sample would cause the greatest false increase in which analyte?
Red cells contain far more LD than plasma, so hemolysis releases it and falsely raises LD (along with potassium and AST). Sodium and chloride are higher in plasma than in red cells.
Immediately after a new reagent lot is placed in use, all control values abruptly move to a new level above the mean and stay there. This pattern is a:
A sudden, sustained change in the level of control values is a shift, typically from a new reagent lot, recalibration or instrument change. A trend changes gradually over time.
A patient's MCV is 72 fL today but was 95 fL two days ago, with no transfusion. The QA tool that flags this is the:
A delta check compares a result with the same patient's previous result; a large unexplained change (MCV is very stable) suggests a specimen mix-up or error. Westgard rules evaluate control data, not patient results.
Small oval yeasts, 2–4 µm, packed inside macrophages in a bone marrow smear from an HIV patient suggest:
Histoplasma capsulatum var. capsulatum appears as tiny intracellular yeasts within macrophages. Leishmania amastigotes look similar but have a kinetoplast.
Which dermatophyte genus produces many smooth, thin-walled, club-shaped macroconidia but rarely microconidia, and does NOT infect hair?
Epidermophyton floccosum forms smooth club-shaped macroconidia, often in clusters, with no microconidia, and infects skin and nails but not hair.
Microsporum canis is best recognized in culture by:
M. canis forms large spindle-shaped, rough, thick-walled macroconidia with six or more cells and a yellow colony reverse. Pencil-shaped smooth macroconidia suggest Trichophyton.
A corneal scraping from a contact-lens wearer grows a lavender-pink mold with sickle- or canoe-shaped multicelled macroconidia. The genus is:
Fusarium produces banana-shaped multiseptate macroconidia and often pink-purple colonies; it is a major cause of fungal keratitis. Acremonium has only single-celled conidia in slimy heads.
A fast-growing fluffy grey mold fills the Petri dish ('lid lifter') in 2 days. Sporangiophores arise directly above root-like rhizoids. The genus is:
Rhizopus has nodal rhizoids with sporangiophores arising opposite them. Mucor lacks rhizoids, and Lichtheimia has internodal rhizoids with pear-shaped sporangia.
Skin biopsy from a farm worker with chronic warty lesions of the leg shows brown, thick-walled, round cells with cross-walls ('copper pennies'). The diagnosis is:
Pigmented muriform (sclerotic) bodies in tissue define chromoblastomycosis, caused by agents such as Fonsecaea pedrosoi. Phaeohyphomycosis shows pigmented hyphae, and mycetoma shows grains.
A dematiaceous mold shows brown, club-shaped conidia with both transverse and longitudinal septa, formed in chains. The genus is:
Alternaria forms drumstick-shaped muriform conidia in chains. Curvularia conidia are curved with transverse septa only, and Cladosporium produces small shield-shaped conidia.
Which Candida species is intrinsically resistant to fluconazole and should be reported with this comment?
Pichia kudriavzevii (C. krusei) is intrinsically resistant to fluconazole. The other species are usually susceptible, although acquired resistance can occur.
Serum galactomannan testing is mainly used to support the diagnosis of:
Galactomannan is a cell wall antigen of Aspergillus, used in serum or bronchoalveolar lavage from high-risk haematology patients. Mucorales do not release galactomannan.
Which laboratory test is most useful for rapid diagnosis of disseminated histoplasmosis in an immunocompromised patient?
Histoplasma polysaccharide antigen in urine (and serum) is highly sensitive in disseminated disease. Galactomannan can cross-react but is not the test of choice.
After a needlestick from a source patient who is HBeAg-positive, which virus carries the HIGHEST transmission risk to a non-immune worker?
HBV from an HBeAg-positive source can transmit in up to about 30% of needlesticks in a non-immune person. Current CDC estimates are about 0.2% for HCV (older sources quoted 1.8%) and about 0.3% for HIV.
A 22-year-old with headache and neck stiffness has CSF: WBC 180/µL (85% lymphocytes), glucose 62 mg/dL (plasma 95 mg/dL), protein 70 mg/dL. The most likely diagnosis is:
Moderate lymphocytic pleocytosis, normal glucose ratio (about 0.65) and mildly raised protein fit viral meningitis. TB meningitis would show a low glucose and much higher protein.