Is seeing 5-10 red blood cells (RBCs) on urinalysis significant?

From the Guidelines

Finding 5-10 red blood cells (RBCs) per high-power field on urinalysis is generally considered mildly abnormal but not necessarily clinically significant in most cases. This level represents microscopic hematuria, which is blood in the urine that isn't visible to the naked eye. While this finding warrants acknowledgment, it often doesn't require immediate intervention unless accompanied by other concerning symptoms or risk factors. Transient microscopic hematuria can occur due to exercise, menstruation in women, sexual activity, certain foods (like beets), or minor trauma. If this is an isolated finding on a single urinalysis, your healthcare provider may recommend repeating the test in a few weeks to see if the RBCs persist. However, persistent microscopic hematuria (found on multiple occasions) should be evaluated further to rule out conditions such as urinary tract infections, kidney stones, kidney disease, or in rare cases, urinary tract cancers. The significance increases if you have risk factors like smoking, chemical exposure, family history of urologic disease, or if the hematuria is accompanied by symptoms like pain, frequent urination, or visible blood in urine. According to the American College of Physicians, clinicians should confirm heme-positive results of dipstick testing with microscopic urinalysis that demonstrates 3 or more erythrocytes per high-powered field before initiating further evaluation in all asymptomatic adults 1.

Some key points to consider:

• The presence of 5-10 RBCs per high-power field may not necessarily require immediate action, but it should be acknowledged and potentially monitored.
• Risk factors such as smoking, chemical exposure, and family history of urologic disease can increase the significance of microscopic hematuria.
• Persistent microscopic hematuria should be evaluated further to rule out underlying conditions.
• Clinicians should consider urology referral for cystoscopy and imaging in adults with microscopically confirmed hematuria in the absence of some demonstrable benign cause 1.

It's essential to follow the guidance of the American College of Physicians and consider the individual patient's risk factors and symptoms when evaluating the significance of microscopic hematuria. As stated in the guidelines, clinicians should not use screening urinalysis for cancer detection in asymptomatic adults 1, but rather use it as a tool to investigate symptoms or risk factors.

In terms of next steps, clinicians should refer for further urologic evaluation in all adults with gross hematuria, even if self-limited 1, and consider urology referral for cystoscopy and imaging in adults with microscopically confirmed hematuria in the absence of some demonstrable benign cause. Ultimately, the decision to pursue further evaluation should be based on the individual patient's presentation and risk factors.

From the Research

Significance of Seeing 5-10 RBCs on Urinalysis

• The presence of 5-10 red blood cells (RBCs) per high-power field (HPF) on urinalysis can be significant, as it may indicate underlying pathology 2.
• A study found that patients with <5 RBCs/HPF on three urinalyses are unlikely to have significant pathology and could possibly be followed up conservatively 2.
• However, another study suggested that three to eight RBCs per HPF would be accepted by most investigators as an acceptable dividing point between normal and abnormal hematuria 3.
• The American Urological Association criteria for radiologic evaluation define appropriate use of CT urography as more than 3 RBCs per high-power field in the absence of urinary tract infection 4.
• A study compared the test characteristics of urine dipstick and urinalysis at various test cutoff points, and found that if urinalysis results are defined as positive when WBCs are more than 3 per high-power field or RBCs are more than 5 per high-power field, the overtreatment rate is 44% and the undertreatment rate is 11% 5.

Diagnostic Utility of Urinalysis

• Urinalysis is a common diagnostic tool used to evaluate patients with hematuria, but its diagnostic accuracy can be limited 6, 5.
• The presence of pyuria (>5 WBCs/HPF) had a sensitivity between 82 and 89% and specificity of between only 53 and 55% in detecting urinary tract infection in hemodialysis patients 6.
• The diagnostic performance of urinalysis can vary depending on the cutoff values used, and the presence of RBCs or WBCs can have different implications for diagnosis and treatment 5.

Clinical Implications

• Patients with asymptomatic microscopic hematuria undergoing CT urography should meet the American Urological Association criteria for radiologic evaluation, which includes more than 3 RBCs per high-power field in the absence of urinary tract infection 4.
• The yield of CT urography for upper urinary tract malignancy is low, and its use should be guided by clinical judgment and adherence to established guidelines 4.
• Patients with 5-10 RBCs/HPF on urinalysis should be evaluated further to determine the underlying cause of hematuria, and treatment should be guided by clinical findings and diagnostic results 2, 3.