The laboratory aspects of proteinuria

Introduction. The existence of proteinuria may be overlooked by applying the test strips. The aim of this study has been to determine the discrepancy between the findings of proteinuria detected by test strips when compared to the results of its testing with the sulfosalicylic acid. Material and Methods. The study sample consisted of 1106 subjects, who were divided into the proteinuria positive (test strips showed the presence of isolated proteinuria), and proteinuria negative group (microscopic examination revealed the presence of >10 fresh red blood cells/μL, and/or >1 dysmorphic erythrocyte/μL, and/or >10 leukocytes/μL, and/or> 1 cylinder, and/or >1 nonsquamous epithelial cells/μL, and/or >100 bacteria/μL). Both groups had the urine tested with sulfosalicylic acid. The chemical and microscopic examination of the urine was done by the analyzer LabUMat-UriSed. Results. Proteinuria was confirmed with the sulfosalicylic acid test in 96.5% of subjects from group 1 and in 85.3% of subjects from group 2. Among the patients with the negative finding of proteinuria on the test strip and with the positive sulfosalicylic acid test there was a significantly higher number of those with pathological findings of erythrocytes, leukocytes, bacteria and cylinders in the urine when compared to those of the same group with negative sulfosalicylic acid test. Conclusion. Sulfosalicylic acid test should be performed in cases of pathological microscopic findings in the urine in case of the presence of >10 fresh erythrocytes/μL and/or >1 dysmorphic eryth­rocyte/μL and/or >10 leukocytes/μL and/or >1 cylinder (except hya­line) and/or >1 nonsquamous epithelial cells/μL and/or >100 bacteria/μL even if the test strip examination is negative for proteinuria.