Quantify registry effects before citing prevalence

National prevalence reports should routinely publish a standardized, quantitative decomposition of observed trend changes into components: diagnostic‑criteria shifts, registry coverage changes (inpatient→outpatient), and residual (possible incidence) change. The approach uses time‑dependent covariates on population cohorts to estimate attributable fractions, so reported prevalence numbers come with an auditable attribution. — Requiring a transparent attribution statement with every prevalence release would prevent misleading headlines, focus policy on service needs driven by true incidence, and improve public trust in health statistics.