Reference values for neonates and children for the UF-100 urine flow cytometer.

The UF-100 fully automated urine flow cytometer classifies urinary particles on the basis of their light scattering, fluorescence, and impedance properties. The UF-100 counts erythrocytes, leukocytes, bacteria, epithelial cells, and casts. The operating principles of the UF-100 and its precision, accuracy, and analytical sensitivity have been published previously (1–4). The high sensitivity of the flow cytometer leads to different reference values. In a recent report, Gyory et al. (5 ) presented reference values for children; for newborns, however, reference values have not as yet been published. In this report, we present preliminary reference values for neonates and children. To establish these reference ranges, samples from two groups of children were analyzed. The pediatricians considered the infants in the first group to have no afflictions of the urinary tract after studying the case history, laboratory values (e.g., creatinine and urea), and the urine test strip results (n 5 114). These infants were admitted to the neonatal clinic and remained there for .5 days. Admission automatically included urine examination in daily routine programs without additional consent of the parents. The long admission periods were attributable to other factors: maternal problems, such as cesarean section (n 5 57); or neonatal problems, such as atresia of the esophagus (n 5 3), inguinal hernia (n 5 5), atrio-ventricular canal (n 5 3), or preterm birth at more than 34 weeks of gestation without respiratory complications (n 5 46). Urine was collected using perineal stick-on plastic containers that were inspected every hour. Urine was also collected from preoperative children without evidence of hematuria, urinary tract infection (UTI), or renal disease (n 5 141) as evaluated by the case history, laboratory values (e.g., creatinine and urea), and test strip results from the laboratory. In each case, a pediatrician was the person evaluating the child. The surgical procedures were adenotomy (n 5 57), tonsillectomy (n 5 54), otocleisis (n 5 7), and correction of various forms of cheilognathouranoschisis (n 5 23). Three children were excluded because of UTI from unknown causes in the case history. Both groups that constituted the reference population were regarded as free of any afflictions of the kidney and the urinary tract. Both groups of samples were analyzed using the test strip analyzer Clinitek Atlas (Bayer Diagnostics) and the UF-100 urine flow cytometer (Sysmex). Results for flow cytometry were given in cells per microliter of urine. Pathological values were rechecked using not only the above mentioned analyzers but also in several cases by examination of the urinary sediment after centrifugation. This result was reported as cells/HPF (high-power field). The children were again clinically examined, and those with previously undetected UTIs or other diseases affecting the urogenital system were not included in the reference set. Because the values did not exhibit a gaussian distribution, the 5th and 95th percentiles were used as reference limits. The provisional reference values for healthy neonates (n 5 114) are shown in the upper portion of Table 1. For comparison, the results for erythrocytes and leukocytes obtained after centrifugation and microscopic analysis of the urinary sediment (0–2 cells/HPF and 0–3 cells/ HPF, respectively) are shown. The UF-100 measurements clearly gave higher cell counts for erythrocytes (;5 cells/mL) and leukocytes (;12 cells/mL). Epithelial cells were also counted by the UF-100, yielding a numerical value of ;4 cells/mL. When sediment microscopy was used, only the presence of epithelial cells was reported. Casts were not usually present. Practically all urine samples examined exhibited the presence of bacteria. Thus, a relatively high cell count (;83 cells/mL) was obtained. Preanalytical factors such as storage time before analysis certainly affect this result. The reference values obtained for children (n 5 141) are also shown in the lower portion of Table 1. Slightly higher values for erythrocytes and leukocytes were obtained with the UF-100 (; 4 cells/mL for both eryth-