Routine TB Surveillance as a Diagnostic Tool: Subnational Care Cascade Gaps in East Nusa Tenggara, Indonesia.

BACKGROUND: Tuberculosis (TB) control remains challenging in decentralised health systems, where subnational variation may be obscured by aggregate programme indicators. OBJECTIVES: To assess district-level variation in the TB care cascade using routine TB surveillance data in East Nusa Tenggara, Indonesia, and develop a composite TB Programme Performance Index (TPPI) for subnational benchmarking. METHODS: We conducted a cross-sectional analysis of aggregated 2025 TB surveillance data (SITB) covering all 22 districts. The cascade comprised presumptive TB identification, diagnostic evaluation, notification and treatment enrolment. A TPPI was constructed using four equally weighted indicators. Sensitivity analyses assessed ranking stability under alternative weighting schemes. RESULTS: Among 87,547 presumptive TB cases, 82,281 (94.0%) completed diagnostic evaluation, yielding 10,318 notified cases. Treatment enrolment among notified cases was 93.2% (9622/10,318). Substantial district-level variation was observed: diagnostic evaluation completion ranged from 76.7% in West Sumba to 98.7% in Central Sumba; notification yield ranged from 4.7% in East Flores to 34.1% in West Sumba; and treatment enrolment ranged from 82.0% in Belu to 98.6% in Malaka. TPPI scores ranged from 42.8 in South Central Timor to 80.6 in Malaka. Rankings remained stable across weighting schemes (Spearman's ρ = 0.93-0.96). CONCLUSIONS: Routine TB surveillance revealed substantial subnational variation, particularly in diagnostic and notification indicators, while treatment enrolment among notified cases was high. Early cascade differences may reflect both underlying TB burden and health-system performance. District-level cascade analysis can inform targeted TB programme planning.