Lowering the cough threshold to one week reduces tuberculosis diagnostic delay: A real-world implementation study...

Passive case finding in low TB incidence areas, using a cough threshold of 2 weeks or more, can miss early or subclinical cases, resulting in diagnostic delays. Our study explored whether setting the cough threshold to at least one week could minimize diagnostic delays and boost TB detection rates in Shenzhen, a highly mobile, low-incidence city in China.

A quasi-experimental study was conducted in the general hospital's respiratory clinics from June 2021 to September 2025. It used historical and concurrent control groups with coughs lasting 2 weeks or more. The intervention group included patients with coughs of at least 1 week. Key outcomes measured were total diagnostic delay, patient delay, health system delay, and bacteriological positivity. Propensity score matching (1:1) adjusted for variables like age, sex, birthplace, residence, occupation, and hospital level. Analyses involved conditional logistic regression and Wilcoxon signed-rank tests.

Out of 56,695 screened individuals, 5742 were diagnosed with pulmonary TB. After matching, 191 intervention patients were compared with 191 historical and 191 concurrent controls. The intervention significantly reduced median total diagnostic delay (16.1 vs. 27.4 and 27.7 days; P < 0.001) and health system delay (3.0 vs. 6.4 and 9.4 days; P < 0.001), but not patient delay (13.0 vs. 15.0 days; P = 0.694 and 0.849). It decreased the odds of bacteriological positivity compared to historical (adjusted OR: 0.41; P < 0.001) and concurrent controls (adjusted OR: 0.28; P < 0.001), increased the odds of prolonged patient delay (>30 days) (adjusted OR: 5.11-5.56; P < 0.001), and reduced prolonged health system delay (>14 days) (adjusted OR: 0.10-0.14; P < 0.001).

Reducing the cough screening threshold from ≥2 weeks to ≥1 week in a low-incidence, high-mobility urban area significantly decreased diagnostic delays, especially within the health system, and identified earlier-stage disease without extra resources. This cost-free policy can be easily implemented in similar regions to help achieve End TB goals.