Validation of Prognostic Tools for Autosomal Dominant Polycystic Kidney Disease Progression in a Multiethnic South African Cohort .

BACKGROUND: Risk stratification in Autosomal Dominant Polycystic Kidney Disease (ADPKD) is essential for selecting candidates for disease-modifying therapies. However, established prognostic tools such as the Mayo Imaging Classification and Predicting Renal Outcome in Polycystic Kidney Disease (PROPKD) score rely on magnetic resonance imaging (MRI) and genotyping, which are often unavailable in resource-limited settings. Furthermore, these tools lack validation in African populations. We evaluated the utility of pragmatic, accessible prognostic markers in a multi-ethnic South African cohort. METHODS: In this retrospective cohort study of 276 adults with ADPKD, we assessed two prognostic tools: a Modified PROPKD score (range 0-5; derived solely from age, sex, hypertension, and urological events, excluding genotype) and ultrasound-measured kidney length. The primary outcome was progression to End-Stage Kidney Disease (ESKD). RESULTS: This was an ethnically diverse population (54% Black, 33% Indian/Asian, 8% White), mostly females. In multivariable Cox regression, the Modified Clinical PROPKD score strongly predicted ESKD (High-risk category: HR 4.34, 95% CI 2.88-6.71; p < 0.001), as did kidney length >16.5 cm (HR 1.87, 95% CI 1.32-2.64; p < 0.001). The Modified Clinical PROPKD score demonstrated moderate discriminative ability (AUC 0.66), numerically outperforming kidney length (AUC 0.61). The score's predictive performance was highest in Black patients (AUC 0.78) compared to White patients (AUC 0.51). CONCLUSIONS: A Modified PROPKD score was an independent predictor of ADPKD progression. Its superior performance in Black African patients supports that clinical phenotypes, particularly early-onset hypertension, are potent markers of disease severity in this demographic.