MLT GlobeQCHP exam preparation (Qatar) – page 9
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
A patient with diabetic ketoacidosis breathes deeply and rapidly (Kussmaul breathing). This breathing pattern represents:
Low pH stimulates the respiratory center, increasing ventilation to blow off CO2 and limit the fall in pH. It is a compensatory response, not a primary respiratory disorder.
In which form is glucose mainly stored in the liver and skeletal muscle?
Animals store glucose as glycogen, a branched glucose polymer, mainly in liver and muscle. Starch is the storage polysaccharide of plants.
For an accurate blood lactate result, which collection practice is correct?
Muscle activity and venous stasis raise lactate, and red cells keep producing lactate by glycolysis after collection. Cooling or fluoride and quick analysis prevent false increases.
Aldosterone acts on the renal collecting duct mainly to:
Aldosterone increases sodium channels and Na/K-ATPase activity in principal cells, so sodium is retained and potassium (and H+) is lost. Free-water reabsorption is the action of ADH.
Which test best reflects a person's vitamin D stores?
25-hydroxyvitamin D has a long half-life and reflects intake and skin production. 1,25-dihydroxyvitamin D is tightly regulated and may be normal or high in deficiency.
Enzymes speed up chemical reactions by:
Enzymes are catalysts: they lower activation energy so equilibrium is reached faster, but they do not change the equilibrium position and are not used up.
Which lipoprotein is the largest, least dense and richest in triglyceride?
Chylomicrons carry dietary triglyceride from the intestine; about 85–90% of their mass is triglyceride, making them the largest and lightest particles. VLDL carries mainly endogenous (liver-made) triglyceride.
A grossly lipemic serum must be tested for electrolytes and enzymes. What is the best way to reduce lipemic interference?
Ultracentrifugation or high-speed centrifugation floats the lipoproteins to the top so the clear lower layer can be tested. Heparin clears lipemia only in vivo by releasing lipoprotein lipase.
In diazo methods, bilirubin reacts with diazotized sulfanilic acid to form:
The diazo reaction splits bilirubin into two colored azobilirubin (azopigment) molecules, whose absorbance is measured. Glucuronidation happens in the liver, not in the assay.
In the liver, ammonia is detoxified mainly by conversion to:
The hepatic urea cycle converts ammonia to urea, which the kidneys excrete. Uric acid comes from purine breakdown and creatinine from creatine in muscle.
Which proteins make up most of the alpha-2 globulin band on serum protein electrophoresis?
Haptoglobin and alpha-2-macroglobulin (with ceruloplasmin) form the alpha-2 band. Transferrin and C3 are in the beta region; alpha-1 antitrypsin dominates alpha-1.
In intravascular hemolysis, serum haptoglobin is usually:
Haptoglobin binds free hemoglobin and the complex is quickly cleared by macrophages (CD163), so levels fall. Haptoglobin does rise in inflammation, which can mask mild hemolysis.
According to KDIGO, kidney damage or reduced GFR must be present for how long to diagnose chronic kidney disease?
CKD is defined as abnormal kidney structure or function present for more than 3 months with health effects. Shorter changes may represent acute kidney injury or acute kidney disease.
A 5-day-old baby who did not receive vitamin K at birth has umbilical bleeding. PT is prolonged; platelet count is normal. Which additional marker supports vitamin K deficiency?
Without vitamin K, factors II, VII, IX and X are not gamma-carboxylated, so non-functional forms like PIVKA-II circulate. Low fibrinogen and raised D-dimer suggest DIC.
A serum sample for vitamin A (retinol) should be handled by:
Retinol and carotenoids are destroyed by light, so samples are wrapped or kept in amber tubes. Fluoride prevents glycolysis and is used for glucose, not vitamins.
When counting cells in a hemacytometer square, cells that touch the boundary lines should be:
To avoid counting the same cell twice in neighboring squares, cells touching two chosen sides are included and those touching the opposite two are excluded. Counting all four sides gives falsely high results.
HbH disease results from deletion or inactivation of how many of the four alpha-globin genes?
HbH disease (--/-α) has only one working alpha gene, so excess beta chains form HbH (β4). Two deletions give alpha-thalassemia trait; four deletions cause Hb Bart's hydrops fetalis.
Unfractionated heparin acts as an anticoagulant mainly by:
A pentasaccharide sequence in heparin binds antithrombin, increasing its activity about 1000-fold. Longer chains are needed to bridge antithrombin to thrombin.
An elderly man with poor diet has perifollicular hemorrhages, corkscrew hairs and bleeding gums. PT, aPTT and platelets are normal. The likely cause is:
Scurvy weakens collagen in vessel walls, giving vascular bleeding with normal coagulation tests and platelet count. Vitamin K deficiency would prolong the PT.
A patient with thrombocytopenia has a warm autoimmune hemolytic anemia with a positive DAT, and no other cause is found. This combination is called:
Evans syndrome is autoimmune destruction of two or more cell lines, usually AIHA with ITP. Kasabach-Merritt is platelet trapping in a vascular tumor.