[Reference limits for urine sediments performed on Sysmex UF-50]

The Sysmex UF-50 is an automated flow cytometer for urine sediments analysis. Interpretation of the results needs establishment of reference limits for the different constituents measured. First of all, we checked precision of measurements and stability of urines during transportation. Then, urine samples from 4 to 95 year old subjects were examined with the UF-50, by visual microscopy and test strips. Distributions of results for erythrocytes, leukocytes, epithelial cells, casts, bacteria and conductivity were described in a sample of 680 subjects (364 men and 316 women), with creatininemia below 140 micromol/L, consuming no drugs and for women without intra uterine device and apart from menstruation period. Then, the results were compared with those obtained in groups selected on microscopic analysis and test strip results. UF-50 sensitivity and specificity were 77.5% and 88% for 15 erythrocytes/microL in reference to microscopic urinalysis, they were 91.3% and 87.3% for 15 leucocytes/microL. The reference sample was defined with negative microscopic results. The upper reference limits (centile 97.5) were 16 red blood cells/microL for men 14.5 for women, 13.5 and 33 leucocytes/microL, 8 and 19 epithelial cells/microL, 1,3 and 0,4 casts/microL, 5 500 et 7 700 bacteria/microL, 36,2 et 34,6 conductivity mS/cm. The Sysmex UF-50 is a suitable analyser for urinary sediments. Reference limits may be different from usual reference limits due to variability in performances of other methods.