Test | Normal Values | Sensitivity | Comments |
---|---|---|---|
Specific gravity | 1.001–1.035 | 1.000–1.030b | Highly buffered alkaline urine may cause low specific gravity readings. Moderate proteinuria (100–750 mg/dL) may cause high readings. Loss of concentrating or diluting capacity indicates renal dysfunction. If the specific gravity of a random urine specimen is ≥ 1.023, the concentrating ability of the kidneys can be considered normal. |
pH | 4.6–8.0 | 5.0–8.5 (visually)b | Excessive urine on strip may cause protein reagent to run over onto pH area, yielding falsely low pH reading. Bacterial growth by certain organisms (eg, Proteus ) in a specimen may cause a marked alkaline shift (urine pH > 8), usually because of urea conversion to ammonia. |
Protein | Negative <15 mg/dL | 15–30 mg/dL albumin | Test is based on protein-error-of-indicators principle. False-positive readings can be caused by highly buffered alkaline urine. Reagent is more sensitive to albumin than other proteins. A negative result does not rule out the presence of globulins, hemoglobin, light chains (Bence Jones) proteins, or mucoprotein. 1+ = 30 mg/dL 3+ = 300 mg/dL 2+ = 100 mg/dL 4+ = ≥ 2000 mg/dL |
Glucose | Negative (<15 mg/dL or <50 mg/day) | 75–125 mg/dL | Test is based on a double sequential enzyme reaction (glucose oxidase and peroxidase), and is specific for glucose. False-negative results occur with urinary ascorbic acid concentrations ≥ 30 mg/dL and with ketone body levels ≥ 40 mg/dL. Test reagent reactivity also varies with specific gravity and temperature. Trace = 100 mg/dL 1 = 1000 mg/dL ¼ = 250 mg/dL 2 = ≥ 2000 mg/dL ½ = 500 mg/dL |
Ketone | Negative | 5–10 mg/dL acetoacetate | Test does not react with acetone or β-hydroxybutyric acid. False-positive (trace) results may occur with highly pigmented urines or those containing levodopa metabolites or sulfhydryl-containing compounds (eg, Mesna). Trace results may occur during physiological stress conditions (fasting, pregnancy, strenuous exercise). Trace = 5 mg/dL Moderate = 40 mg/dL Small = 15 mg/dL Large = 80–160 mg/dL |
Bilirubin | Negative (≤ 0.02 mg/dL) | 0.4–0.8 mg/dL | Positive (conjugated) bilirubin indicates hepatitis. False-negative readings can be caused by ascorbic acid concentrations ≥ 25 mg/dL. False-positive readings can be caused by metabolites of lodine (etodolac). Test is based on the coupling of bilirubin with diazotized dichloroaniline in an acidic medium. Test is less sensitive and specific than Ictotest Reagent Tablets. A positive test may be confirmed by Ictotest Reagent Tablets. To detect very small amounts of bilirubin in urine (eg, in the earliest phase of viral hepatitis), Ictotest Reagent Tablets should be used. |
Blood | Negative (<0.010 mg/dL hemoglobin or <3 RBC/mcL)c | 0.015–0.062 mg/dL hemoglobin or 5–20 RBC/mcL | Test is equally sensitive to myoglobin and hemoglobin (including both intact RBC and free hemoglobin). Test is based on the peroxidase-like activity of hemoglobin. False-positive results can be caused by oxidizing contaminants (hypochlorite) and microbial peroxidase (urinary tract infection). Test sensitivity is reduced in urines with high specific gravity, captopril, or heavy proteinuria. |
Nitrite | Negative | 0.06–0.10 mg/dL nitrite ion | Test depends on the conversion of nitrate (derived from the diet) to nitrite by gram-negative bacteria in urine when their number is >105 /mL (≥ 0.075 mg/dL nitrite ion). Test is specific for nitrite. False-negative readings may occur with shortened urine time in the bladder (<4 hr) and can also be caused by ascorbic acid. Test sensitivity is reduced in urines with high specific gravity. A negative result does not rule out significant bacteriuria. |
Leukocytes (esterase) | Negatived | 5–15 WBCs/hpf | Indicator of urinary tract infection. Test detects esterases contained in granulocytic leukocytes. Test sensitivity is reduced in urines with elevated glucose concentrations ≥3 g/dL), or presence of cephalexin, cephalothin, tetracycline, or high concentrations of oxalate. False-positive results may occur with specimen contamination by vaginal discharge. |
See Table 2–3 for a guide to interpretation of urinalysis, and Figure 2–1 for a guide to microscopic findings in urine.
NOTE: Fully automated urinalysis systems (either image- or flow cytometry-based) are now available in many clinical laboratories, so manual microscopy examination may not be performed routinely in a central laboratory.
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