What is the first line test for hematuria (blood in the urine)?

First-Line Testing for Hematuria

The first-line test for hematuria is microscopic examination of urinary sediment from a freshly voided, clean-catch, midstream urine specimen to confirm the presence of ≥3 red blood cells per high-power field (RBC/HPF). 1, 2

Initial Evaluation Algorithm

• Dipstick testing alone is insufficient and requires microscopic confirmation, as dipstick has limited specificity (65-99%) and can produce false positives due to hemoglobinuria, myoglobinuria, or certain medications 1, 2
• Microscopic hematuria is defined as three or more red blood cells per high-power field on microscopic evaluation of a properly collected urine specimen 2
• For proper diagnosis, microscopic hematuria should be present in at least one properly performed urinalysis documenting ≥3 RBCs/HPF 3
• If a benign cause is suspected (menstruation, vigorous exercise, sexual activity, trauma), repeat urinalysis 48 hours after cessation of the activity 3, 1

Distinguishing Glomerular vs. Non-Glomerular Sources

• Examine urinary sediment for dysmorphic red blood cells and red cell casts which indicate glomerular origin 1, 4
• Assess for proteinuria and measure serum creatinine to help determine the source 1, 4
• Glomerular source indicators include significant proteinuria (>500 mg/24 hours), dysmorphic RBCs (>80%), red cell casts, and elevated serum creatinine 1, 4
• Non-glomerular (urologic) source is likely with normal-shaped RBCs, minimal or no proteinuria, and normal serum creatinine 4

Risk Stratification

• Gross hematuria requires urgent evaluation due to high association with malignancy (30-40%) 3, 4
• Risk factors for significant urologic disease include:
  • Age >35-40 years 3, 1
  • Smoking history 1, 4
  • Occupational exposure to chemicals or dyes (benzenes or aromatic amines) 1, 4
  • History of gross hematuria 1, 2
  • Irritative voiding symptoms 1
  • History of urinary tract infection 1
  • Analgesic abuse 1
  • History of pelvic irradiation 1

Further Evaluation Based on Initial Results

• For patients with urinary tract infection, treat appropriately and repeat urinalysis 6 weeks after treatment to confirm resolution 1
• For patients with microscopic hematuria without a benign cause, complete urologic evaluation is indicated 3, 1
• Urine cytology is recommended in patients with risk factors for transitional cell carcinoma 3
• Nephrology referral is indicated if there is evidence of glomerular disease (proteinuria >500 mg/24 hours, red cell casts, or predominantly dysmorphic RBCs) 1, 4

Common Pitfalls to Avoid

• Relying solely on dipstick results without microscopic confirmation 1, 2
• Attributing hematuria solely to antiplatelet or anticoagulant therapy without further investigation 1, 4
• Neglecting to evaluate women with hematuria as thoroughly as men 2
• Failing to repeat urinalysis after treatment of presumed benign causes 2
• Assuming that a single negative urinalysis excludes significant pathology, as hematuria can be intermittent 3

Follow-up Recommendations

• For patients with persistent hematuria after negative initial evaluation, repeat urinalysis at 6,12,24, and 36 months 1, 4
• Monitor blood pressure and consider nephrology referral if hematuria persists with development of hypertension, proteinuria, or evidence of glomerular bleeding 1, 4