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Questions and Answers
Which of the following can lead to a false negative result for the nitrite test on a urine reagent strip?
Which of the following can cause a false positive result for the leukocyte esterase test on a urine reagent strip?
Which of the following is the LEAST likely cause of a false positive nitrite test on a urine reagent strip?
Which of the following is the MOST likely cause of a false positive leukocyte esterase test on a urine reagent strip?
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Which of the following is the LEAST likely cause of a false negative nitrite test on a urine reagent strip?
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Which of the following can cause both a false positive nitrite test and a false positive leukocyte esterase test on a urine reagent strip?
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Which of the following is the LEAST likely cause of a false positive leukocyte esterase test on a urine reagent strip?
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Which of the following is the MOST likely cause of a false negative leukocyte esterase test on a urine reagent strip?
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Which of the following is the LEAST likely cause of a false positive result for the nitrite test on a urine reagent strip?
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Which of the following is the MOST likely cause of a false positive result for the leukocyte esterase test on a urine reagent strip?
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Study Notes
Leukocyte Esterase Reagent Strip
- Multistix: detects 5-15 WBC/hpf, Chemstrip: detects 10-25 WBC/hpf
- False positive results can occur due to high concentrations of protein, highly alkaline urines (pH > 6.5), and presence of nitrite
Specific Gravity Reagent Strip
- Based on the principle of change in pKa of polyelectrolytes in an alkaline medium
- Uses bromthymol blue as an indicator to measure pH changes
- Multistix and Chemstrip use different reagents, including poly (methyl vinyl ether/maleic diaminoethyl anhydride) and ethylene glycol ether, respectively
- False positive results can occur due to strong oxidizing agents, formalin, and highly pigmented urine, nitrofurantoin
- False negative results can occur due to high protein concentrations, oxalic acid, ascorbic acid, gentamicin, cephalosporins, and tetracyclines
- Correlation: as specific gravity increases, the indicator changes from blue to yellow (1.000 to 1.030)
Ascorbic Acid
- Principle: action of ascorbic acid to reduce a dye in the impregnated pad
- Can detect AA concentration as low as 7.0 mg/dl and consistently detect 20 mg/dl of AA in 90% urine tested
- High levels of AA cause false-negative results on glucose, blood, bilirubin, nitrite, and leukocyte esterase tests
Benedict's Test (Glucose and Reducing Sugars)
- Principle: copper reduction
- False-negative results can occur due to high levels of ascorbic acid (>25mg/dL)
- Reporting: grades of negative, trace, 1+, 2+, 3+, and 4+, with corresponding colors and characteristics
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Description
Test your knowledge on interpreting negative trace results on reagent strips for leukocyte esterase. Explore sensitivity, interference, and correlations related to reagent strips. Identify common reagents and their sensitivity to different concentrations.
