Automation of urine sediment examination: A comparison of the sysmex UF-100 automated flow cytometer with routine manual diagnosis (microscopy, test strips, and bacterial culture)

Urine specimens from 438 patients were examined with the UF-100 flow cytometer (Sysmex TOA Medical Electronics (Europe) GmbH, Hamburg, Germany) and by manual microscopy and test strips. One hundred and forty-two of these were also examined bacteriologically. The measurements with the UF-100 were performed on native urine without prior centrifugation. Intraassay imprecision, CV of 1.3 % (547/mu l) to 8.5 % (24/mu l) for erythrocytes and CV of 2.4 % ( 218/mu l) to 5.6 % (10/mu l) for leukocytes, are similar to those usual in clinical chemistry, and are very much better than those seen in manual microscopy of sediment. In routine use, overloading the flow cytometer by an excessive concentration of particles was observed in 9 % of specimens. Such specimens should be checked visually. The UF-100 is distinctly more sensitive than manual microscopy for determining leukocytes, erythrocytes, epithelial cells and bacteria. Reference ranges were estimated from the results obtained. These enabled the UF-100 to replace routine manual diagnostic methods. Although the sensitivity is improved over manual microscopy of sediment, it is always necessary to perform parallel test strip examination when determining erythrocytes in order to detect haemolysis. In our opinion the Sysmex UF-100 is a suitable replacement for manual microscopy of urine sediment. In addition it offers an opportunity to improve standardization of basic urinalysis.