We prospectively compared the performance of the new flow cytometer UF-5000 with UF-1000i and Gram stain in predicting the bacterial patterns in urine samples obtained from community women with uncomplicated urinary tract infection (uUTI)

From July, 2016 to June, 2019, women aged 20-80 years who visited urological clinics with symptoms suggestive of uUTI were invited to fill the questionnaire of Urinary Tract Symptoms Assessment questionnaire (UTISA). Patients with UTISA score 4 or more were invited to join the study, and those with urolithiasis, pregnancy, recent antibiotics use, neurogenic bladder or with urinary catheter were excluded. After signed informed consent and completion of a questionnaire for baseline characteristics, mid-stream urine sample was collected for gram staining, urine analysis and urine culture. Urine analyses were performed with the both models of laser flow cytometry (UF1000i and UF- 5000 Sysmex, Kobe, Japan). Trough the diagrams generated from laser flow cytometry, specimen was classified as none, cocci bacteria or rods/mixed growth in UF1000i. For UF- 5000 and gram staining, specimen was classified as none, cocci, rods or mixed growth. Standard urine cultures were performed, and  the agreement between cultures and the UF1000i/UF5000/Gram staining interpretations was analyzed.

Finally, 102 samples from 102 women (age: 49.6 ± 16.6 years) with UTISA score of 10.7 ± 3.8 met the criteria for analysis. Among these samples, there were 10 gram-positive cocci, 2 gram-positive bacilli, 66 gram-negative rods, and 24 specimens with two bacteria species or more that were regarded as mixed growth. The sensitivity/specificity of UF-1000i was 81.8/91.1% for gram-negative rods and 23.5/96.9% for cocci/mixed. The sensitivity/specificity of UF-5000 was 80.0%/88.2% for gram negative rods and 70.0/86.5% for gram-positive cocci.

The results showed that the UF5000 keep a good sensitivity (80.0%) in identifying gram negative bacteria with acceptable specificity (88.2%). With regard to gram positive bacteria, UF5000 outperformed UF1000i in detecting gram positive cocci (sensitivity: 70 % and specificity: 86.5%) with good specificity which was comparable to gram staining (sensitivity: 60 % and specificity: 100%). However, the sensitivity of UF5000 for identifying mixed growth is poor. Gram staining is associated with a sensitivity rate of 88%, a specificity rate of 95%, a negative predictive value of 96%, and a positive predictive value of 84% for identifying bacteriuria.

UF-5000 demonstrated potential utility for the rapid screening of bacterial morphology, which inherited the good sensitivity and specificity of UF1000i for GNB bacteria and improve the sensitivity for detecting the Gram-positive cocci.