MLPAO Urinalysis and Body Fluids Fundamentals 1 — Questions and Answers
Question 1: What is the preferred urine specimen for routine urinalysis?
- Random collection
- First morning midstream clean-catch specimen (Correct answer)
- 24-hour collection
- Post-prandial specimen
Correct answer: First morning midstream clean-catch specimen
The first morning midstream clean-catch specimen is preferred for routine urinalysis because it is the most concentrated, maximizing the detection of chemical constituents and formed elements. Midstream collection reduces contamination from urethral flora and epithelial cells. Proper patient instruction is essential for specimen quality.
Question 2: What are the three components of a complete urinalysis?
- Color, clarity, and specific gravity only
- Physical examination (colour, clarity, specific gravity), chemical examination (dipstick), and microscopic examination (sediment) (Correct answer)
- Dipstick and culture only
- Microscopic examination only
Correct answer: Physical examination (colour, clarity, specific gravity), chemical examination (dipstick), and microscopic examination (sediment)
A complete urinalysis includes: 1) Physical examination (colour, clarity/turbidity, specific gravity, odour), 2) Chemical examination (reagent strip/dipstick testing for pH, protein, glucose, ketones, blood, bilirubin, urobilinogen, nitrite, leukocyte esterase, and specific gravity), and 3) Microscopic examination (centrifuged sediment for cells, casts, crystals, and organisms).
Question 3: What does a positive nitrite test on a urine dipstick indicate?
- Normal finding
- Presence of bacteria (particularly gram-negative) that reduce dietary nitrate to nitrite (Correct answer)
- Kidney stones
- Dehydration
Correct answer: Presence of bacteria (particularly gram-negative) that reduce dietary nitrate to nitrite
A positive nitrite indicates the presence of bacteria (mainly gram-negative Enterobacterales like E. coli) that convert dietary nitrate to nitrite via bacterial nitrate reductase. The test requires the urine to have been in the bladder for at least 4 hours. Not all bacteria produce nitrite (e.g., enterococci, staphylococci), so a negative nitrite does not rule out UTI.
Question 4: What is the principle of the leukocyte esterase test on the dipstick?
- It detects intact white blood cells by size
- It detects an enzyme released from lysed granulocytes (neutrophils), indicating pyuria (Correct answer)
- It measures white blood cell count directly
- It detects bacteria in the urine
Correct answer: It detects an enzyme released from lysed granulocytes (neutrophils), indicating pyuria
The leukocyte esterase test detects esterase enzyme released from lysed neutrophils. It indicates pyuria (white blood cells in urine) and suggests inflammation or infection. It can be positive even when intact WBCs are not seen microscopically because it detects enzyme from lysed cells. Combined with nitrite, it has good negative predictive value for UTI.
Question 5: Which urine cast is most indicative of glomerulonephritis?
- Hyaline cast
- Red blood cell cast (Correct answer)
- Granular cast
- Waxy cast
Correct answer: Red blood cell cast
Red blood cell (RBC) casts are virtually pathognomonic for glomerulonephritis because they indicate bleeding within the nephron. RBCs trapped in Tamm-Horsfall protein within the tubular lumen form these casts. Their presence localizes hematuria to the kidney (glomerular origin) rather than the lower urinary tract.
Question 6: What does the urine specific gravity measure?
- Urine volume
- The concentration of dissolved solutes in urine relative to water (Correct answer)
- Urine pH
- The number of cells in urine
Correct answer: The concentration of dissolved solutes in urine relative to water
Specific gravity measures the density of urine compared to pure water (1.000), reflecting the kidney's ability to concentrate or dilute urine. Normal range is 1.005-1.030. High specific gravity (>1.030) indicates concentrated urine (dehydration), while low specific gravity (1.001-1.005) indicates dilute urine. Fixed specific gravity (1.010) suggests renal tubular dysfunction.
MLPAO Urinalysis and Body Fluids Fundamentals 1
What is the preferred urine specimen for routine urinalysis?