Usefulness of an automated urinary flow cytometer in mass screening for nephritis

We aimed to assess the utility of a newly developed automated urinary flow cytometer (UFCM) in differentiating the origin of hematuria in the mass screening system for renal diseases in school children. In total, 4,620 children aged 6-14 years with abnormal urinary findings by the screening program in Tokyo were enrolled. Tentative diagnoses were made based on the criteria for this screening program: nephritis in 11, suspected nephritis in 104, hematuria in 771, minimal hematuria in 1,506, proteinuria in 477, urinary tract infection in 83, and healthy in 1,668. Glomerular hematuria, assessed by UFCM, was found in 81.8% of nephritis, 58.7% of suspected nephritis, 59.7% of hematuria, 57.4% of minimal hematuria, 13.4% of proteinuria, and 21.5% of the healthy group. The presence of glomerular hematuria assessed by UFCM had a sensitivity of 61.0%, specificity of 78.5%, positive predictive value of 16.3%, and negative predictive value of 96.7% for the diagnosis of nephritis and suspected nephritis. Thus, our results imply that the absence of glomerular hematuria as assessed by UFCM is highly predictive of the absence of nephritis. If "healthy" children with non-glomerular hematuria by UFCM could be excluded, the total annual cost saving would be approximately 147.4 million JPY, which is equivalent to 5.2% of the current system. In conclusion, a simple, automated and rapid test for glomerular hematuria using UFCM is useful for mass screening. It can precisely predict children with only transient hematuria who do not have any serious illness, and therefore can exclude further unnecessary examinations, resulting in the improvement of cost-effectiveness of the current program.