Active tuberculosis case finding using portable radiography reveals high undetected burden in rural Himachal Pradesh

Active Case Finding (ACF) in tuberculosis (TB) is a provider-initiated, systematic, community-based screening process that targets high-risk populations and is deployed across India, including Himachal Pradesh, as a strategy to eliminate TB. Himachal Pradesh reports a disproportionately high proportion of extra-pulmonary TB (EP-TB) compared with the national average. An implementation study deploying portable digital X-ray devices in Kangra district identified structural barriers to case detection following which a barrier decomposition framework was applied to quantify each barrier’s contribution to the observed yield gap. One hundred and forty-six villages of Block Dadasibha (population 1,15,766) in Kangra district were covered through preliminary screening of 20,207 high-risk individuals by Accredited Social Health Activists (ASHAs), followed by screening camps using handheld X-ray devices and sputum smear examination. Camps were conducted on weekdays using a fixed-facility and outreach approach. All X-rays were read by a single pulmonologist. NIKSHAY portal data for Kangra District (Year 2024, N = 2,921 notified cases) were used to benchmark expected prevalence and disease-type distribution. A notification rate of 193 per 100,000 (2011 Census denominator) was applied to the screened population to derive expected cases. The barrier decomposition framework attributed the expected-vs.-detected deficit to four pre-specified structural barriers using NIKSHAY age, sex, and site distributions as denominators. 7,464 people (770 chest-symptomatic and 6,694 high-risk individuals) attended TB screening camps. Of these, 7,409 (99%) underwent X-ray screening with handheld devices; 704 (9.5%) were flagged as X-ray suggestive. Sputum testing was completed for 650 individuals (91.4% of those flagged as X-ray suggestive or chest-symptomatic), and 2 were confirmed TB-positive. Using the district notification rate (193 per 100,000) as a conservative lower-bound denominator yielded 14.3 expected cases. Applying a higher prevalence estimate of 500 per 100,000 (appropriate for high-risk cohorts) yields an upper-bound of 37.0 expected cases. Barrier decomposition (base case: 14.3 expected) attributed the 12.3-case deficit to EP-TB invisible to sputum screening (5.3 cases; 37%), weekday camp timing excluding working-age adults (4.3 cases; 30%), mobility constraints among the elderly (2.4 cases; 17%), and residual factors (0.3 cases; 2%). Under the higher-bound scenario (37.0 expected), the total deficit rises to 35.0 cases, with barrier attributions scaled proportionally. Effective TB screening in this hill-district setting requires a multilayered, context-adapted strategy. Each structural barrier maps onto a distinct screening layer; clinical (EP-TB), temporal (weekday timing), spatial (elderly mobility), and diagnostic (sputum smear sensitivity) that a single-modality programme is not expected to address simultaneously.