Medical Laboratory Technician Exam Medical Laboratory Technician Urinalysis and Body Fluids 1

Question 1

A urine specimen turns dark brown-black upon standing and tests positive for reducing substances but negative for glucose by the glucose oxidase method. Which substance is most likely present?

Accepted Answer

Homogentisic acid

Answer

Homogentisic acid, excreted in alkaptonuria, oxidizes upon exposure to air and turns the urine dark brown-black. It is a reducing substance but is not detected by the glucose oxidase method, distinguishing it from glucosuria.

Question 2

Which urine sediment finding is most consistent with acute tubular necrosis (ATN)?

Accepted Answer

Muddy brown granular casts

Answer

Muddy brown coarsely granular casts are the hallmark of acute tubular necrosis. They form from degenerating renal tubular epithelial cells and pigmented material, reflecting direct tubular injury.

Question 3

A pleural fluid specimen has a protein concentration of 4.8 g/dL and a pleural fluid-to-serum LDH ratio of 0.7. How would this effusion be classified?

Accepted Answer

Exudate, suggesting infection or malignancy

Answer

By Light's criteria, a pleural fluid protein >3.0 g/dL or a pleural/serum LDH ratio >0.6 classifies the effusion as an exudate, which is associated with inflammatory, infectious, or malignant processes rather than hydrostatic imbalances.

Question 4

A urine dipstick is strongly positive for blood, but microscopic examination reveals no red blood cells. Which of the following conditions best explains this discrepancy?

Accepted Answer

Myoglobinuria from rhabdomyolysis

Answer

The dipstick blood reaction detects heme, so it is positive for both hemoglobin and myoglobin. In rhabdomyolysis, myoglobin released from damaged muscle is excreted in urine and gives a positive dipstick reaction without intact red blood cells being present.

Question 5

During a peritoneal fluid analysis, a milky white appearance is noted. Which analyte should be measured first to investigate this finding?

Accepted Answer

Triglycerides

Answer

A milky white (chylous) peritoneal effusion strongly suggests the presence of chyle from disrupted lymphatic vessels. Triglyceride measurement is the primary test; a level above 110 mg/dL confirms a chylous effusion.

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Exam Medical Laboratory Technician Urinalysis and Body Fluids 1