MLPAO Urinalysis and Body Fluids Advanced Practice

Question 1

What is the clinical significance of Bence Jones protein in urine?

Accepted Answer

It indicates the presence of monoclonal immunoglobulin light chains (kappa or lambda), strongly suggestive of multiple myeloma or other plasma cell dyscrasias

Answer

Bence Jones protein consists of monoclonal immunoglobulin free light chains (kappa or lambda) that are small enough to be filtered by the glomerulus. They are associated with multiple myeloma, Waldenstrom macroglobulinemia, and amyloidosis. Importantly, Bence Jones protein is NOT detected by routine dipstick (which primarily detects albumin) and requires urine protein electrophoresis or immunofixation.

Question 2

How is a body fluid cell count performed and what counting chamber is used?

Accepted Answer

Manual count using a hemocytometer (Neubauer counting chamber); automated methods are increasingly used for high-volume laboratories

Answer

Body fluid cell counts are traditionally performed manually using a hemocytometer (Neubauer counting chamber) that holds a precise volume of fluid. WBCs are counted in the four corner squares (1 mm²), and the count is converted to cells/µL. Automated analyzers (Sysmex XN-BF, BeckmanCoulter) are increasingly used but must be validated for body fluids.

Question 3

What is the albumin-to-creatinine ratio (ACR) and what does an elevated value indicate?

Accepted Answer

A spot urine test that normalizes albumin excretion for urine concentration; elevated values indicate early diabetic nephropathy or other glomerular disease

Answer

The urine ACR uses a random (spot) urine specimen to estimate 24-hour albumin excretion by correcting for urine concentration. Normal: <2.0 mg/mmol (males) or <2.8 mg/mmol (females). Microalbuminuria (3-30 mg/mmol) is the earliest marker of diabetic nephropathy. It is recommended for annual screening in diabetic patients by Canadian Diabetes Association guidelines.

Question 4

What is the difference between a transudate and an exudate in serous body fluids?

Accepted Answer

Transudates result from hydrostatic/oncotic pressure imbalance (low protein, low LDH, low cells); exudates result from inflammation/infection (high protein, high LDH, high cells)

Answer

Transudates are ultrafiltrates resulting from systemic factors (congestive heart failure, cirrhosis, nephrotic syndrome) with low protein (<30 g/L), low LDH, and few cells. Exudates result from local disease processes (infection, malignancy, inflammation) with high protein (>30 g/L), high LDH, and elevated cells. Light's criteria provide the definitive classification.

Question 5

What is the corrected WBC count in CSF when a traumatic tap introduces blood into the specimen?

Accepted Answer

The corrected WBC = CSF WBC - (CSF RBC × blood WBC/blood RBC), accounting for WBCs introduced with the traumatic blood

Answer

When a traumatic tap introduces blood, WBCs from the blood contaminate the CSF cell count. The correction formula subtracts the expected number of blood-derived WBCs: Corrected WBC = CSF WBC - (CSF RBC × peripheral blood WBC ÷ peripheral blood RBC). This helps determine if there is a true pleocytosis or if the WBCs are simply from the traumatic blood.

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO Urinalysis and Body Fluids Advanced Practice