Asymptomatic microscopic hematuria is a clinical challenge fraught with uncertainty, risk, and expense. With an estimated hematuria prevalence of 9%-18% and a threshold of at least 3 red blood cells per high-power field (RBC/HPF) as a cutoff for evaluation, we are all dealing with this problem – a lot. CT urograms, urine cytologies, and cystoscopies commonly compose the evaluation algorithm for this relatively low-prevalence disease.
What we need is a reliable and predictable way to place patients into different risk categories.
Dr. Ronald K. Loo of the Southern California Permanente Medical Group, Los Angeles, and his colleagues tried to answer this need by evaluating the performance of the Hematuria Risk Index (Mayo Clin. Proc. 2013;88:129-38).
The investigators assembled a prospective cohort of patients who were in the Kaiser Permanente system and had been referred to a urologist to undergo a full evaluation for asymptomatic microscopic hematuria. They derived the risk index from a "test cohort" composed of 2,630 patients, among whom 2.1% had a cancer detected and 1.9% had a pathologically confirmed urinary tract cancer.
The Hematuria Risk Index they developed is scored as follows: 4 points for gross hematuria and/or age at least 50 years and 1 point for a history of smoking, male gender, and/or greater than 25 RBC/HPF on recent urinalysis. The range is from 0 to 11 points, with patients stratified as low risk (0-4 points), moderate risk (5-8 points), or high risk (9-11 points).
Applying this risk index to a validation cohort, cancer was detected in 10.7% of the high-risk patients, 2.5% of the moderate-risk patients, and 0% of the low-risk patients.
Importantly, Dr. Loo and his associates concluded that microscopic hematuria is an unreliable indicator of urothelial malignancy. They further concluded that the risk of identifying a urinary tract cancer in anyone younger than 50 years without a history of gross hematuria is close to zero. Non-neoplastic findings included urinary stones, prostatic bleeding, urinary tract infection, and glomerular disease
This is a fantastically helpful study. Now, getting this Hematuria Risk Index as an app on my smartphone will make my year.
Dr. Ebbert is professor of medicine and a primary care clinician at the Mayo Clinic in Rochester, Minn. He reported having no relevant financial conflicts. The opinions expressed are those of the author. Reply via e-mail at imnews@frontlinemedcom.com.