BERKELEY, CA (UroToday.com) - While there is no question that patients with gross hematuria deserve further evaluation to find a root cause, there is still considerable debate as to the value of extensively evaluating asymptomatic microhematuria found on screening urinalysis. The prevalence of microhematuria is reported to be anywhere from < 0.2% - 33%, based on population studied and method of detection. Furthermore, it has been reported that up to 21% of men over age 50 with microhematuria may harbor a cancer. Feldstein and colleagues, in this study, sought to determine the value of upper tract imaging in the evaluation of microhematuria as a means of detecting occult upper tract tumors.

In this retrospective case controlled study out of Mayo Clinic Scottsdale, 278 patients with untreated upper tract neoplasms with urinalysis data were compared to controls that did not have upper tract neoplasms, matched for age and sex. Using 13 definitions of microscopic hematuria (≥1, ≥2, ≥3, ≥4, ≥5, ≥6, ≥7, ≥8, ≥9, ≥10 ≥15, ≥20 RBC/HPF, or dipstick positive), the authors calculated odds ratios (ORs) for each of the microhematuria definitions based on their case-control study population. The found that a urinalysis considered positive with ≥4 RBC's/HPF was associated with a statistically significant OR of having an upper tract tumor (2-fold increased risk), but at issue was whether this difference was significant enough to warrant upper tract imaging on all patients with asymptomatic microhematuria with 4 or more RBC's on their urinalysis. To examine this, the authors used the calculated OR's from their study to determine the likelihood of detecting a renal neoplasm in a hypothetical population of 10,000 patients with a "positive" urinalysis. The findings are listed in the table below.

With increasing number of RBC's in the screening urinalysis, the likelihood of a positive upper tract evaluation significantly increased. The authors concluded that urinalyses with ≥4 or 5 RBC/HPF were twice as common in the patients with upper tract neoplasms as compared to matched controls and that urinalyses with less RBC's than this were not associated with significant OR's and may not warrant further evaluation.

Of note, the authors report that the current AUA recommendations for considering an evaluation of microscopic hematuria are ≥3 RBC/HPF in two out of three urine specimens.

BJU International 96: 612-617, 2005