Definition of True Hematuria
No, it is not considered true hematuria if RBC/HPF are less than 3. The current standard definition requires >3 RBC/HPF on microscopic evaluation to diagnose microhematuria 1, 2.
Diagnostic Threshold
- Microhematuria is defined as >3 RBC/HPF (meaning 4 or more) on microscopic evaluation of urinary sediment from a single, properly collected urine specimen 1, 2
- This represents a strong recommendation from the 2020 AUA/SUFU guidelines based on systematic review of the literature 1
- Values of 1-3 RBC/HPF are considered within normal limits and do not meet the threshold for true hematuria 2, 3
Why Microscopic Confirmation is Essential
- Dipstick testing alone is insufficient for diagnosis and should never be used to define hematuria 1
- Dipstick has limited specificity (65-99%) and measures peroxidase activity, which can be confounded by povidone iodine, myoglobinuria, and dehydration 1, 2, 4
- A positive dipstick (trace blood or greater) should prompt formal microscopic evaluation, but the diagnosis depends on the microscopic count 1
- The sensitivity of detecting 1-3 RBC/HPF by the HPF method is only 63% for detecting ≥2,000 RBCs/ml, making it an inadequate screening threshold 5
Clinical Significance of the 3 RBC/HPF Threshold
- The >3 RBC/HPF cutoff was established based on literature review supporting this as the optimal balance between sensitivity and specificity 1
- Historical studies suggested 3-8 RBC/HPF as the dividing point between normal and abnormal, but the current consensus settled on >3 3
- Quantitative reporting of RBC/HPF is critical to determine whether further evaluation is warranted 1, 2
Important Caveats
- Even when hematuria is confirmed (>3 RBC/HPF), the degree of hematuria correlates with malignancy risk: 3-10 RBC/HPF carries 0%-0.4% risk, 11-25 RBC/HPF carries 0.2%-3.1% risk, and >25 RBC/HPF carries 1.3%-6.3% risk 2
- Hematuria can be intermittent, so the 2020 AUA guidelines now recommend proceeding with evaluation based on a single positive microscopic result (>3 RBC/HPF), departing from older recommendations requiring 2 of 3 positive specimens 1, 2
- Patients with findings <3 RBC/HPF should not undergo urologic evaluation for hematuria, though other clinical concerns may warrant investigation 2, 6