Prevalence of urinary tract infection in pregnancy and screening performance of the Sysmex UF-5000 in Bhutan

ABSTRACT Urinary tract infections (UTIs) are among the most common bacterial infections worldwide, representing a significant clinical and economic burden, and are particularly prevalent during pregnancy. Physiological changes in pregnancy increase susceptibility to UTIs, which are associated with serious maternal and neonatal complications, including pyelonephritis, preterm birth, and low birth weight. This burden is especially pronounced in low- and middle-income countries (LMICs), where screening and treatment capacities are often limited, yet data from Bhutan remain scarce. This study aimed to determine the prevalence of UTIs among pregnant women attending the Gyaltsuen Jetsun Pema Mother and Child Hospital (GJPMCH) under Jigme Dorji Wangchuck National Referral Hospital (JDWNRH) in Thimphu, Bhutan, and to evaluate the diagnostic performance of the Sysmex UF-5000, using urine culture as the gold standard. We conducted a cross-sectional study involving 2,000 pregnant women attending routine antenatal check-ups at the Community Health Department of GJPMCH-JDWNRH between June 30, 2025, and November 18, 2025. Midstream urine samples were collected and tested using dipstick, a semi-automated urine chemistry analyzer (UC-1000), and a fully automated urine particle analyzer (UF-5000). All the urine samples were subjected to culture. Culture-positive UTI was defined according to symptom status: bacterial growth of >10⁴ CFU/mL in symptomatic women and ≥10⁵ CFU/mL in asymptomatic women. Receiver operating characteristic (ROC) analysis was used to determine UF-5000 diagnostic performance. Of the 2,000 urine specimens screened, 570 complete samples were included in the final analysis after exclusion of contaminated and incomplete specimens; 139 samples were culture-positive, corresponding to a UTI prevalence of 24.4% among evaluable urine cultures. Among culture-positive cases, 82.7% were asymptomatic, and 17.3% were symptomatic. UTI prevalence was highest in the third trimester, followed by the second and first trimesters. Escherichia coli was the predominant pathogen, accounting for 87.8% of isolates. UF-5000 BACT showed good discriminatory performance for culture-positive UTI, with an AUC of 0.847 (95% CI: 0.806–0.887). At the optimal cut-off of 4,118/µL, sensitivity was 67.6%, specificity was 89.8%, positive predictive value was 68.1%, and negative predictive value was 89.6%. At a lower BACT threshold of 2075/µL, sensitivity increased to 78.4%, and specificity was 77.5%. UF-5000 WBC showed moderate performance (AUC 0.736, 95% CI: 0.693–0.779), while combining BACT and WBC yielded an AUC of 0.846 (95% CI: 0.805–0.884), indicating limited incremental benefit over BACT alone. Compared with dipstick parameters, UF-5000 BACT provided a more balanced sensitivity-specificity profile than nitrite or leukocyte esterase. UTI was common among pregnant women in this Bhutanese cohort and was predominantly asymptomatic, highlighting the importance of routine antenatal screening. The Sysmex UF-5000, particularly the BACT parameter, demonstrated good diagnostic utility and may serve as a practical rapid screening tool to prioritize urine cultures and support earlier detection of UTI during pregnancy. However, the high contamination rate observed in this study represents an important limitation that may reduce overall screening efficiency and affect the generalizability of the findings. Further studies are warranted to optimize urine collection procedures and to refine the implementation of automated urine flow cytometry for UTI screening in pregnant populations. IMPORTANCE Urinary tract infections during pregnancy can lead to serious complications for both mothers and babies if they are not detected and treated early. Many infections occur without symptoms, making routine screening essential. In this study, we found that nearly one in four pregnant women attending antenatal care in Bhutan had a urinary tract infection, and more than 80% of these infections were asymptomatic. We also demonstrated that the Sysmex UF-5000 automated urine analyzer can rapidly identify women at increased risk of infection with good diagnostic accuracy. Because urine culture requires additional time and laboratory resources, automated screening could help prioritize samples that need further testing and enable earlier clinical intervention. These findings provide the first comprehensive data on urinary tract infections among pregnant women in Bhutan and support the integration of rapid urine flow cytometry into antenatal screening programs, particularly in settings where laboratory capacity and turnaround time are limited.