Reference: Urology. 2020 Jul
Microscopic hematuria (defined as ≥ 3 RBCs per high-power field [HPF]) accounts for more than 20% of urology referrals with a detection rate of urologic cancer ranging from 1% to 10% (Tan et al. 2020). A new guideline from the American Urologic Association addresses risk stratification for microscopic hematuria. Previous guidelines considered CT urography with cystoscopy to be the preferred method for evaluating microscopic hematuria. In hopes of reducing the need for invasive and costly evaluation, investigators set out to externally validate a previously published risk stratification tool, the Hematuria Risk Index (HRI). This index stratifies individuals into low risk (0-4 points), moderate risk (5-8 points), and high risk (9-11 points) using four factors: gross hematuria (4 points), age ≥ 50 years (4 points), tobacco history (1 point), male sex (1 point), and > 25 RBC per HPF (1 point).
Investigators analyzed retrospective data from a suburban cohort of 1,049 patients referred to urology for microscopic hematuria at a single institution. Participants had an average age of 57 years, 40% identified as male, and 27% had a history of smoking (Samson et al. 2018). The investigators excluded 55 participants who were not evaluated, but these 55 participants were included in the denominator of reported lesion detection rates. The HRI was calculated for each patient, although since this cohort excluded those with gross hematuria, the maximum possible score was 7. Only 10 participants had a score of 7 (moderate risk) while 643 had a score of 4 or lower (low risk). The rate of combined cystoscopy and any upper tract imaging (defined as CT, MRI, or ultrasound) was similar in both the low-risk (57%) and moderate-risk (59%) groups. The detection rate of genitourinary malignancy was 0% in the low-risk group and 2.96% (12/406) in the moderate-risk group. There was no difference in the rates of malignancy detection for ultrasound versus CT in the moderate-risk group (1.63% vs. 1.31%, p = 0.728).
The Hematuria Risk Index is a risk stratification tool that can potentially reduce overtesting and overspending. It tested well in the inception cohort, but the current study serves only as a narrow external validation. This study is limited by a homogenous suburban population, an unclear intention to treat analysis, and most importantly, the absence of patients in the highest risk group. These shortfalls make it impossible to fully evaluate the HRI for intended use. Additionally, not all participants had ‘gold standard’ diagnostic testing of both cystoscopy and CT urography, which raises the possibility of missed diagnoses. This study suggests that the HRI is useful for risk stratification in low- to moderate-risk patients, but a broader external validation is definitely indicated.
For more information, see the topic Microhematuria - Approach to the Adult in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Carina Brown, MD, Assistant Professor at Cone Health Family Medicine Residency. Edited by Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School, Dan Randall, MD, Deputy Editor for Internal Medicine at DynaMed, and Katharine DeGeorge, MD, MS, Associate Professor of Family Medicine at the University of Virginia and Clinical Editor at DynaMed.