MLPAO Urinalysis and Body Fluids Advanced Practice 1 — Questions and Answers
Question 1: What is the clinical significance of Bence Jones protein in urine?
- It is a normal urinary protein
- It indicates the presence of monoclonal immunoglobulin light chains (kappa or lambda), strongly suggestive of multiple myeloma or other plasma cell dyscrasias (Correct answer)
- It indicates nephrotic syndrome
- It is detected by routine urine dipstick
Correct answer: It indicates the presence of monoclonal immunoglobulin light chains (kappa or lambda), strongly suggestive of multiple myeloma or other plasma cell dyscrasias
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?
- Automated hematology analyzer only
- Manual count using a hemocytometer (Neubauer counting chamber); automated methods are increasingly used for high-volume laboratories (Correct answer)
- Manual count on a glass slide
- Flow cytometry only
Correct answer: Manual count using a hemocytometer (Neubauer counting chamber); automated methods are increasingly used for high-volume laboratories
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?
- A test for liver disease
- A spot urine test that normalizes albumin excretion for urine concentration; elevated values indicate early diabetic nephropathy or other glomerular disease (Correct answer)
- A blood test for kidney function
- A test for urinary tract infection
Correct answer: A spot urine test that normalizes albumin excretion for urine concentration; elevated values indicate early diabetic nephropathy or other glomerular disease
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?
- They are identical in composition
- Transudates result from hydrostatic/oncotic pressure imbalance (low protein, low LDH, low cells); exudates result from inflammation/infection (high protein, high LDH, high cells) (Correct answer)
- Transudates have high protein; exudates have low protein
- Both require culture for differentiation
Correct 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)
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?
- The raw WBC count is reported without correction
- The corrected WBC = CSF WBC - (CSF RBC × blood WBC/blood RBC), accounting for WBCs introduced with the traumatic blood (Correct answer)
- WBCs cannot be counted in traumatic taps
- The correction is only applied if RBC count exceeds 1 million
Correct answer: The corrected WBC = CSF WBC - (CSF RBC × blood WBC/blood RBC), accounting for WBCs introduced with the traumatic blood
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.
Question 6: What is the mucin clot test (Ropes test) used for in synovial fluid analysis?
- Detecting crystals
- Assessing the quality of hyaluronic acid in synovial fluid; a poor clot suggests inflammatory degradation of hyaluronic acid (Correct answer)
- Testing for bacterial infection
- Measuring glucose levels
Correct answer: Assessing the quality of hyaluronic acid in synovial fluid; a poor clot suggests inflammatory degradation of hyaluronic acid
The mucin clot test assesses hyaluronic acid integrity by adding acetic acid to synovial fluid. Normal synovial fluid forms a firm, cohesive clot (good mucin clot). Inflammatory conditions (rheumatoid arthritis, septic arthritis) degrade hyaluronic acid through enzymatic action, producing a poor or friable clot. This test has largely been replaced by more specific analyses.
MLPAO Urinalysis and Body Fluids Advanced Practice 1
What is the clinical significance of Bence Jones protein in urine?