Evaluation of IRIS Automated Urine Chemistry and Sediment Analyzers for Total Urinalysis in Prediction of UTI

Automated IRIS instruments for urine chemistry and urine sediment were integrated as total urinalysis system recently. The advantages of shortening turnaround time and cross-checking results are expected between tandem iChem Velocity for chemistry and iQ200 ELITE for sediment, but the performance of this system has not yet been examined. In this study, the total IRIS urinalysis system was evaluated in routine testing for a purpose to predict urinary tract infection (UTI) and correlate with characterizations of UTI etiology. In National Cheng Kung University Hospital, 315 suspected UTI patients including 132 males and 183 females (mean age: 54.3 yr) were recruited consecutively and a retrospective survey of urinalysis data warehouse and urine culture was conducted. The urine culture yielded 98 (31.1%) positive and 217 (68.9%) negative for UTI, with the positive rate for female over that for male by ~3 folds (p＜0.0001). The comparisons of the results by iChem and iQ200 revealed significant correlations for leukocyte esterase vs. white blood cell count (Spearman's rank correlation coefficient R=0.854, p＜0.001), nitrite vs. bacteria count (R=0.537, p＜0.001) and hemoglobin vs. red blood cell count (R=0.548, p＜0.001). Combined items of iChem leukocyte esterase and iQ200 bacteria count served as the best rule-out criteria of UTI (negative likelihood ratio=0.06), with a negative predictive value of 0.98, false negative rate of 3.1% and diagnostic odds ratio of 39.2. The most frequently isolate was E. coli (59.4%), followed by K. pneumonia (9.4%) and Enterococcus (9.4%). Furthermore, the Gram-negative isolates exhibited higher iQ200 WBC count (p=0.012) and bacteria count (p=0.023) than did Gram-positive isolates, whereas the extended-spectrum beta-lactamase phenotype exhibited a higher bacteria count than did those without this antibiotics resistance phenotype (p=0.047). In conclusion, the performance of IRIS total urinalysis system was satisfactory which might provide additional values in predictive of UTI and causative etiology.