Urinary tract cancer screening through analysis of urinary red blood cell volume distribution

Background: Hematuria is differentiated between glomerular and urinary tract origins on the basis of urinary red cell morphology. We used this distinction in a program of mass screening for urinary tract cancer to achieve cost-effective and safe hematuria screening. Methods: Of a total of 21 372 adults (mean age 52.3 years; range 20-79 years) participating in a health screening, 912 (4.3%) had a positive dipstick for hematuria and were enrolled in the present study. Urinary red cell volume distribution curves (RDC), the simplest method of assessing urinary red cell morphology, were calculated and subjects were divided into two groups based on their RDC patterns. Group I subjects had a normocytic or mixed pattern and they were immediately investigated for urinary tract malignancy because of the associated risk for urological disease. Group II subjects had a microcytic pattern and, therefore, were judged to be at a low risk of urologic malignancy and were followed up 3 years later without urologic investigations. Results: Among the 38 subjects in group I (4% of all dipstick-positive subjects), one case of bladder cancer was detected. In the remaining 37 patients, 15 cases of benign diseases were discovered. Group II was composed of 869 subjects (96%). The inquiry into their health status conducted 3 years later revealed that 831 (95.6%) were healthy and, of these, 13 had experienced gross hematuria during the period but urological malignancies were ruled out by their urologists, two (0.2%) had died of diseases other than urological cancer and 36 (4.1%) were lost to follow-up. With our method, total costs have been reduced by 93.8% against a conventional setting of a full evaluation for all cases of hematuria. Conclusions: Microcytic hematuria, accounting for 96% of asymptomatic microhematuria cases in the present study, was not associated with a risk for urinary tract malignancy. Compared with conventional hematuria screening with a complete work-up of all cases of hematuria, investigating only subjects with mixed or normocytic RDC patterns was safe and cost effective.