Monday, August 17, 2020

Microscopic hematuria: to refer, or not to refer?

 - Jennifer Middleton, MD, MPH

The American Urological Association (AUA) updated its guideline last month for evaluating microscopic hematuria. The AUA defines microscopic hematuria, or "microhematuria," as "greater than 3 red cells per high powered field," and the Choosing Wisely campaign advocates against diagnosing microscopic hematuria based solely on urine dipstick testing. While the AUA's 2012 guideline advised computed tomography (CT) imaging and cystoscopy for all persons over the age of 35 years with microscopic hematuria, the 2020 guideline tailors the diagnostic approach by risk factors, and a study published last month further validates one of these risk assessment tools.

The 2020 AUA guideline on microhematuria includes guidance on diagnosis and evaluation with a new emphasis on risk stratification. Patients with microscopic hematuria that the authors considered to be at low risk of bladder malignancy include women under the age of 50, men under the age of 40, a less than 10-pack-year tobacco smoking history, a single abnormal UA with no more than 10 red cells per high powered field, and no risk factors for urothelial cancer (family history, occupational exposures, history of pelvic radiation). The authors acknowledge that, while there is data linking various risk factors with a cancer diagnosis, little data exists regarding morbidity and mortality outcomes. Additionally:

While there are similarities between the current risk categories outlined in the Guideline and published risk score should be acknowledged that these risk categories are not based on meta-analyses or original studies, and instead represent the Panel’s consensus based on a review of available data on risk factors for urinary tract malignancy.

One of the those risk score models, the Hematuria Risk Index (HRI), was developed in 2013 and was  further validated by a retrospective case study published just one month after this updated AUA guideline. The researchers performed a retrospective analysis of just over 1000 patients with asymptomatic microscopic hematuria and applied the HRI; they then performed a cost benefit analysis. Almost all of the patients had cystoscopy and CT imaging, and none with a score less than 5 were found to have cancer. The potential cost savings from avoiding these evaluations in the low-risk group were sizable:

[T]he cost to find one high-grade clinically significant lesion/cancer was $136,125.3 for the overall group. When the low-risk group was removed, the cost to find a high-grade clinically significant lesion/cancer decreased to $55,417.3 without missing any significant lesions. 

Family physicians, who typically care for a broad population, should think carefully about the adoption of subspecialty guidelines. Some, such as the American College of Cardiology/American Heart Association hypertension and cholesterol guidelines, have failed to receive endorsement by primary care groups such as the AAFP and the American College of Physicians. This new AUA guideline includes some statements that are, by its own admission, consensus-based, though the primary literature surrounding the HRI seems more robust. Avoiding unnecessary care is part of the inherent stewardship in primary care, and both the AUA guideline and this HRI study support de-escalating invasive testing for what is a benign symptom in many patients. Applying the HRI, and discussing with our urology colleagues which patients should undergo further testing, may be reasonable steps.