Development and external validation of a pragmatic nomogram for point-of-care urolithiasis screening in resource-limited settings of Laos: a multicenter retrospective cohort study

Background The rising burden of urolithiasis in Southeast Asia and the lack of efficient risk-screening tools for low-resource primary care, such as those in Laos, motivated the development and external validation of a pragmatic nomogram integrating accessible environmental, behavioral, and clinical factors for in-hospital urolithiasis risk stratification, with long-term goal of application in grassroots screening. Methods A retrospective study was conducted with 665 consecutive inpatients (≥18 years, local residence ≥6 months) at a Lao Military Hospital (March 2024–February 2025). Data were collected using standardized questionnaires and electronic medical records. Least Absolute Shrinkage and Selection Operator (LASSO) regression selected predictors; nomogram performance was assessed by discrimination (area under the curve (AUC)), calibration (Brier score and Hosmer–Lemeshow test), and clinical utility (decision curve analysis (DCA)). Results Urolithiasis prevalence was 23.0% (153/665). Independent predictors included age (30–59 years, OR = 1.54; ≥60 years, OR = 1.13), sex (OR = 0.59), rural residence (OR = 0.52), high water intake (>1,500 mL/day, OR = 0.02), high sodium consumption (>10 g/day, OR = 21.90), and elevated blood calcium (OR = 9.12). The nomogram presented stable predictive performance, with an AUC of 0.882–0.907, Brier score of 0.086–0.111 (acceptable calibration, Hosmer–Lemeshow p = 0.198–0.892), and optimal clinical threshold at 0.20. Conclusions This externally validated nomogram uses six accessible environmental, behavioral, and clinical factors to stratify urolithiasis risk in Laos. At present, it helps guide targeted referral and optimize s resource allocation for hospitalized patients in resource—limited settings, while its application in primary care and among broader Southeast Asian populations remains to be prospectively evaluated.