Validating Dental Sampling Frames in Rapidly Expanding Cities: Riyadh Case

OBJECTIVES: Rapid urbanization and the privatization of health markets frequently render administrative registries obsolete, threatening the validity of epidemiological research. Riyadh exemplifies this challenge, where expansion of dental services under Vision 2030 necessitates spatially verified sampling frames. Using Riyadh as a case study, this study aimed to develop and validate a spatially explicit sampling framework to support rigorous, representative facility-based research in fast-changing urban environments. METHODS: We conducted a comprehensive cross-sectional field census (August 2023-October 2025) across 168 districts in Riyadh. Commercial streets (n = 2,669 segments) were identified using satellite imagery and municipal data. Seven 2-person teams, calibrated via a 2-phase pilot study, surveyed these segments to geolocate private health facilities. Specialized nondental centers (e.g., dialysis, labs) were excluded. To estimate coverage, a quality control team resurveyed a stratified random sample of 10% of street segments by district. After fieldwork, we contacted a random sample of 100 facilities to validate operational status, dental service provision, and coordinates and calculated accuracy, sensitivity, and specificity. True counts were estimated using the Rogan-Gladen estimator to correct for misclassification bias. Spatial analyses mapped facility density (per 10,000 population using the 2022 census) and regional differences. RESULTS: Field enumeration identified 876 eligible private facilities, with data collector coverage estimated at 92.2%. Validation confirmed 98% inclusion accuracy. Sensitivity for dental service provision was 96.2%, and specificity was 61.1%. Spatial precision was high, with 97.9% of coordinates validated within 100 meters. Spatial analysis revealed marked clustering of clinics in central and eastern districts, with lower density in southern and western regions. CONCLUSION: This study established a rigorously validated, comprehensive sampling frame that overcomes limitations of administrative data. It supports representative facility-based research, which reaches only those who attend and complements population-based designs, and documents marked geographic differences in dental care availability that persist when public facilities are included.Knowledge Transfer Statement:This validated spatial framework shows policymakers and planners where private dental facilities are, and are not, located relative to the resident population. That is a measure of horizontal equity in geographic availability only, and the gaps it reveals persist when public facilities are included. Closing them is necessary but not sufficient: improving oral health also depends on affordability, perceived need, and the acceptability of care and on allocating resources according to need.