What is the proper procedure for performing a urine dipstick test?

How to Perform Urine Dipstick Testing

Use a first morning void urine sample collected via clean-catch midstream technique, immerse the dipstick completely in fresh urine for the manufacturer-specified time (typically 1-2 seconds), remove and tap off excess urine, then read results at the exact timing intervals specified on the bottle (usually 30-120 seconds depending on the parameter). 1, 2

Specimen Collection

• Collect a first morning void sample whenever possible to minimize variability and maximize accuracy, as this provides the most concentrated specimen with adequate bladder dwell time for bacterial conversion of nitrates to nitrites 1

• For patients who cannot provide a first morning sample, ensure all collections occur at the same time of day, with the patient well-hydrated and having not eaten for at least 2 hours prior 1

• Use midstream clean-catch technique in cooperative adults: have the patient begin voiding, then collect the middle portion of the stream in a sterile container 2, 3

• For women unable to provide clean specimens (high epithelial cell contamination), perform in-and-out catheterization to obtain an uncontaminated sample 2

• For infants and young children, catheterization or suprapubic aspiration is required for definitive diagnosis; bag-collected specimens have only 15% positive predictive value and require confirmation if positive 3

Timing and Processing

• Process urine within 1 hour at room temperature or within 4 hours if refrigerated at 4°C to prevent bacterial overgrowth and degradation of cellular elements 2, 3

• If urine has been refrigerated, allow it to warm to room temperature for 5 minutes before testing, as cold temperatures can cause uromodulin polymer formation that may trap cellular elements 1

• Ensure the urine sample is well-mixed before testing to distribute cellular elements evenly 1, 4

Dipstick Technique

• Remove one dipstick from the container and immediately recap the bottle to prevent moisture exposure, which causes rapid degradation of reagents, particularly nitrite (specificity drops to 28% after 2 weeks of open storage) 5

• Completely immerse all reagent pads in the urine sample for 1-2 seconds, ensuring no air bubbles are trapped under the pads 6, 4

• Remove the dipstick and tap the edge against the container or blot on clean absorbent paper to remove excess urine, preventing reagent mixing between adjacent pads 6, 4

• Hold the dipstick horizontally to prevent urine from running between pads 4

Reading Results

• Read each parameter at its specific timing interval as indicated on the bottle label (typically 30 seconds for glucose/blood, 60 seconds for leukocyte esterase, 60-120 seconds for nitrite) 1, 4

• Compare the color of each reagent pad to the corresponding color chart on the bottle under good lighting conditions, holding the dipstick close to the chart 6, 4

• For visual interpretation, ensure adequate lighting and avoid reading in dim conditions or under colored lights that may distort color perception 7

• Automated readers eliminate human color vision variability and provide standardized lighting, showing almost perfect agreement (κ = 0.82-0.88) with visual interpretation for clinically relevant parameters 7

Quality Control Measures

• Use dipsticks as rapid quality control to measure pH, leukocytes, erythrocytes, protein, glucose, nitrate, ketones, blood, bilirubin, and urobilinogen 1

• Check the expiration date on the dipstick bottle before use 5

• Discard dipsticks that have been exposed to moisture, extreme temperatures, or direct sunlight 5

• If results seem inconsistent with clinical presentation, repeat testing with a fresh specimen and new dipstick 1

Interpretation for UTI Diagnosis

• A positive dipstick is defined as ≥1+ leukocyte esterase OR positive nitrite, which achieves 93% sensitivity and 72% specificity for UTI 2, 3

• The combination of negative leukocyte esterase AND negative nitrite effectively rules out UTI with 90.5% negative predictive value 2

• Leukocyte esterase alone has 83% sensitivity and 78% specificity, while nitrite has only 53% sensitivity but 98% specificity 3

• Never diagnose UTI based on dipstick alone—positive results require clinical correlation with symptoms (dysuria, frequency, urgency, fever, gross hematuria) and confirmation with urine culture showing ≥50,000 CFU/mL 2, 3

Common Pitfalls to Avoid

• Do not leave dipstick bottles uncapped, as the nitrite reagent loses specificity rapidly (one-third false positives after 1 week, three-quarters after 2 weeks) 5

• Do not read results too early or too late, as timing significantly affects accuracy—leukocyte esterase read before 60 seconds may be falsely negative 4

• Do not use contaminated specimens with high epithelial cells (>5-10 per HPF), as these cause false-positive leukocyte esterase results 2

• Avoid testing urine that has been sitting at room temperature for >1 hour, as bacterial overgrowth can cause false-positive nitrite results 2

• Do not interpret positive results in asymptomatic patients as requiring treatment—asymptomatic bacteriuria with pyuria should not be treated 2

• Remember that negative nitrite does not rule out UTI, particularly in patients who void frequently (short bladder dwell time prevents nitrate conversion) or with non-nitrate-reducing organisms 3