Abstract:

Objective: To evaluate the screening workload and yield for different community-based active case-finding (ACF) strategies for pulmonary tuberculosis (TB) in the elderly. Methods: A retrospective study was conducted. Data from three consecutive years (2013—2015) of active TB screening among individuals aged ≥65 years were re-analyzed. The screening, implemented by the China CDC across 27 townships/communities in 10 counties/districts spanning eastern, central, and western China, collected data on risk factors, presumptive TB symptoms, and chest radiography (CXR). Eight ACF strategies for the elderly were simulated: symptom screening (Strategies 1-3), high-risk group screening (Strategies 4-7), and universal screening (Strategy 8). Analyses focused on screening participation, TB screening outcomes, detection of individuals with presumptive TB symptoms, screening workload, and case detection yield for each strategy. Results: From 2013 to 2015, the eligible elderly populations (≥65 years) were 38888, 40909, and 43006 individuals, respectively. The numbers undergoing symptom screening were 37989 (97.69%), 37219 (90.98%), and 37771 (87.83%), and those receiving CXR were 33717 (86.70%), 33686 (82.34%), and 33268 (77.36%), showing a significant declining trend year-on-year (Z=-51.651 and -34.802, respectively; P<0.001 for both). During the 2013 initial symptom screening, Strategy 3 (using the WHO-recommended 4-symptom screen) identified significantly more individuals with presumptive TB symptoms (3.75%, 1424/37989) compared to Strategy 1 (national guideline symptoms: 1.92%, 731/37989) and Strategy 2 (study-defined symptoms: 2.10%, 798/37989), and detected 5 more active TB cases than Strategy 1. Strategies 1, 2, and 3 required CXR for 1.79% (696/38888), 1.96% (762/38888), and 3.39% (1317/38888) of the elderly, respectively. These strategies detected 25.00% (14/56), 26.79% (15/56), and 28.57% (16/56) of bacteriologically confirmed pulmonary TB cases, and 18.39% (32/174), 18.97% (33/174), and 21.26% (37/174) of active TB cases. The number needed to screen (NNS) to detect one bacteriologically confirmed TB case was 50, 51, and 83, respectively, and to detect one active TB case was 22, 24, and 36, respectively. Compared to symptom screening, high-risk group strategies (4-7) required CXR for a larger proportion of participants, ranging from 9.07% (Strategy 4, 3527/38888) to 36.81% (Strategy 7, 14314/38888). The detection proportions for bacteriologically confirmed TB and active TB increased from Strategy 4 (37.50% (21/56); 30.46% (53/174)) to Strategy 7 (64.29% (36/56); 66.09% (115/174)). Correspondingly, the NNS increased from 168 and 67 (Strategy 4) to 398 and 125 (Strategy 7). Universal screening (Strategy 8) detected all cases (100.00%; 56/56 bacteriologically confirmed, 174/174 active TB). Screening efficiency in the second year for high-risk strategies was comparable to the first year, but declined significantly in the third year. Conclusion: Community-based ACF for pulmonary TB in the elderly should employ a more sensitive symptom definition to improve case detection. Incorporating high-risk factors enhances screening efficiency. Continuous ACF implementation should not exceed two consecutive rounds; strategies require timely evaluation and adjustment.

Key words: Tuberculosis, pulmonary, Elderly, Community health services, Public health surveillance, Cohort studies