From the Guidelines
The best test for microscopic hematuria, apart from cystoscopy, is microscopic urinalysis that demonstrates 3 or more erythrocytes per high-powered field 1.
Key Points
- Microscopic urinalysis is the recommended initial test for confirming microscopic hematuria, as dipstick testing has limited specificity (65 percent to 99 percent for two to five red blood cells per high-power microscopic field) 1.
- The definition of microscopic hematuria is three or more red blood cells per high-power field on microscopic evaluation of urinary sediment from two of three properly collected urinalysis specimens 1.
- High-risk patients, such as those with a history of urologic disease, smoking, or occupational exposure to chemicals, should be considered for full urologic evaluation after one properly performed urinalysis documenting the presence of at least three red blood cells per high-power field 1.
- Patients with microscopically confirmed hematuria in the absence of a demonstrable benign cause should be considered for urology referral for cystoscopy and imaging 1.
- The evaluation of hematuria should be pursued even if the patient is receiving antiplatelet or anticoagulant therapy 1.
Testing Approach
- Initial determination of microscopic hematuria should be based on microscopic examination of urinary sediment from a freshly voided, clean-catch, midstream urine specimen 1.
- Hematuria can be measured quantitatively by determination of the number of red blood cells per milliliter of urine excreted, direct examination of the centrifuged urinary sediment, or indirect examination of the urine by dipstick 1.
From the Research
Diagnostic Tests for Microscopic Hematuria
The best test for microscopic hematuria, apart from cystoscopy, is a topic of ongoing research and debate.
- According to 2, a combination of renal ultrasound (US) and urinalysis, including urine culture and cytology, is a good initial evaluation in patients with microhematuria.
- For patients with persistent microhematuria after 3 months without a definite etiology, intravenous urography (IVU) may be beneficial 2.
- Automated urinalysis machines, which use flow cytometry to identify red blood cells, are also being used to evaluate microscopic hematuria, but their use and definition of normal range vary 3.
- The American Urological Association definition of microscopic hematuria may not correlate with the definitions used by automated urinalysis machines, highlighting the need for further investigation into the role of these devices 3.
Patient Selection for Diagnostic Tests
The selection of patients for diagnostic tests, such as cystoscopy, depends on various factors, including age and the presence of symptoms.
- Cystoscopy is recommended as an initial diagnostic modality in older patients with asymptomatic microscopic hematuria to rule out bladder cancer 4, 5.
- For patients younger than 40 years with a single microscopic hematuria, cystoscopy may not be necessary 5.
- Further studies are needed to justify the implementation of cystoscopy as an initial diagnostic modality in younger patients with asymptomatic microscopic hematuria 4.