Mircohematuria a poor predictor of urinary tract cancer

February 2, 2013

Asymptomatic microhematuria rarely represented a manifestation of urinary tract cancer in a prospective study involving more than 4,000 patients.

Downey, CA-Asymptomatic microhematuria rarely represented a manifestation of urinary tract cancer in a prospective study involving more than 4,000 patients.

Overall, workups based on asymptomatic microhematuria led to diagnosis of bladder cancer in 2.3% of patients and renal cancer in 0.3%, reported researchers from Kaiser Permanente Downey Medical Center in Downey, CA. Stones, prostatic bleeding, and urinary tract infection (UTI) were more often the cause of microhematuria.

“The best indicators of urinary tract cancer were a history of gross hematuria in the past 6 months and age greater than or equal to 50,” said first author Ronald Loo, MD, a urologist at Kaiser Permanente Downey Medical Center.

“Microhematuria was the least sensitive predictor, even though we considered a much higher level of hematuria than currently recommended to initiate a workup for cancer,” said Dr. Loo of the findings, which were presented at the 2012 AUA annual meeting in Atlanta and recently published in the February issue of Mayo Clinic Proceedings.

On the basis of their findings, the authors developed a five-item hematuria risk index that demonstrated accuracy for categorizing patients as having a low, intermediate, or high risk of urinary tract cancer.

Management of asymptomatic microhematuria has represented a clinical conundrum: Screening urinalysis is not recommended for asymptomatic patients, but microscopic hematuria is a common clinical finding.

In 2001, the AUA published a best practice statement on asymptomatic microhematuria that set the threshold for a workup as a finding of ≥3 RBC/HPF on two of three urinalyses. The AUA recommended cystoscopy followed by intravenous pyelogram (IVP).

The recommendation is impractical in the current clinical practice environment, said Dr. Loo. Busy primary care physicians do not have time for serial urinalyses for every patient with asymptomatic hematuria. Moreover, abdominal computed tomography has become the preferred imaging modality, which is more accurate than IVP but exposes asymptomatic patients to radiation risks.

An updated guideline, announced at the 2012 AUA annual meeting in Atlanta and recently published (J Urol 2012; 188[6 suppl]:2473-81), retains the ≥3 RBC/HPF threshold, but eliminates the requirement for multiple urinalyses. After exclusion of potential benign causes of microscopic hematuria, every patient ≥35 years of age should have cystoscopy, followed by abdominal multiphasic CT. Patients who have contraindications to CT should undergo magnetic resonance urography.

Nevertheless, the new recommendation may expose more young asymptomatic patients to potentially hazardous radiation than did the 2001 guideline, Dr. Loo said.

To examine the value of asymptomatic hematuria as a marker of urinary tract cancer, Dr. Loo and colleagues prospectively evaluated data provided by 151 urologists in four regions of the Kaiser Permanente network. The analysis included 4,414 patients: 2,630 in a test cohort from Southern California and the Pacific Northwest and 1,784 in a validation cohort from Northern California and Hawaii.

Overall, women accounted for 54.6% of the patients, 43.8% of whom had a positive smoking history and 19.8% a history of gross hematuria.

Dr. Loo reported that 36.4% of the patients were <50 years of age, 48.4% were 50 to 69 years of age, and 21.6% were ≥70 years of age.

Ultimately, 103 patients (2.3%) were found to have bladder cancer and 13 (0.3%) had renal cancer. The most common finding was stones (7.3%), followed by prostatic bleeding (4.6%) and UTI (2.7%).

Microhematuria least predictive factor

Multivariate analysis identified five predictors of a cancer diagnosis based on asymptomatic microhematuria: history of gross hematuria, age ≥50 years, male sex, positive smoking history, and microhematuria defined as ≥25 RBC/HPF on a single urinalysis. Asymptomatic microhematuria was the least predictive factor.

From those five factors, the authors constructed a hematuria risk index that assigned a score of 4 to history of gross hematuria in the past 6 months and age ≥50 years and a score of 1 to the remaining three factors.

Applying the index to their study population, they found that a low score of 0-4 conferred a low cancer risk (0.3% in the test cohort and no cancers in the validation cohort); 5-8 conferred an intermediate risk (1.1% in the test cohort and 2.5% in the validation cohort); and 9-11 a high risk (11.6% in the test group and 10.7% in the validation group).

“The risk of radiation exposure may not justify the use of CT in this group,” said Dr. Loo. “A workup may be unnecessary for patients who are younger than 50 and have no history of gross hematuria.

“A more effective means of screening for bladder cancer in asymptomatic patients may be to convince our primary care colleagues to stop ordering urinalysis and start asking about gross hematuria.”UT