Role of community-based active case finding in screening tuberculosis in Yunnan province of China

Abstract

Background: The barriers to access diagnosis and receive treatment, in addition to insufficient case identification and reporting, lead to tuberculosis (TB) spreads in communities, especially among hard-to-reach populations. This study evaluated a community-based active case finding (ACF) strategy for the detection of tuberculosis cases among high-risk groups and general population in China between 2013 and 2015.

Methods: This retrospective cohort study conducted an ACF in ten communities of Dongchuan County, located in northeast Yunnan Province between 2013 and 2015; and compared to 136 communities that had passive case finding (PCF). The algorithm for ACF was: 1) screen for TB symptoms among community enrolled residents by home visits, 2) those with positive symptoms along with defined high-risk groups underwent chest X-ray (CXR), followed by sputum microscopy confirmation. TB incidence proportion and the number needed to screen (NNS) to detect one case were calculated to evaluate the ACF strategy compared to PCF, chi-square test was applied to compare the incidence proportion of TB cases' demography and the characteristics for detected cases under different strategies. Thereafter, the incidence rate ratio (IRR) and multiple Fisher's exact test were applied to compare the incidence proportion between general population and high-risk groups. Patient and diagnostic delays for ACF and PCF were compared by Wilcoxon rank sum test.

Results: A total of 97 521 enrolled residents were visited with the ACF cumulatively, 12.3% were defined as high-risk groups or had TB symptoms. Sixty-six new TB patients were detected by ACF. There was no significant difference between the cumulative TB incidence proportion for ACF (67.7/100000 population) and the prevalence for PCF (62.6/100000 population) during 2013 to 2015, though the incidence proportion in ACF communities decreased after three rounds active screening, concurrent with the remained stable prevalence in PCF communities. The cumulative NNS were 34, 39 and 29 in HIV/AIDS infected individuals, people with positive TB symptoms and history of previous TB, respectively, compared to 1478 in the general population. The median patient delay under ACF was 1 day (Interquartile range, IQR: 0-27) compared to PCF with 30 days (IQR: 14-61).

Conclusions: This study confirmed that massive ACF was not effective in general population in a moderate TB prevalence setting. The priority should be the definition and targeting of high-risk groups in the community before the screening process is launched. The shorter time interval of ACF between TB symptoms onset and linkage to healthcare service may decrease the risk of TB community transmission. Furthermore, integrated ACF strategy in the National Project of Basic Public Health Service may have long term public health impact.

Keywords: Active case finding; Diagnosis; Passive case finding; Patient delay; Tuberculosis.

Fig. 1

Flow chart of active tuberculosis screening process among communities in Yunnan, 2013–2015 High-risk groups: Elderly, Diabetes mellitus, HIV/AIDS, close contact and history of previous tuberculosis case. CXR: chest X-ray

Fig. 2

Tuberculosis incidence proportion, 95% confidence intervals and pairwise comparison of new tuberculosis cases in high-risk groups of active case finding strategy in Yunnan, 2013–2015 High-risk groups: Elderly, Diabetes mellitus, HIV/AIDS, close contact and history of previous tuberculosis case. Pairwise χ² tests results were summarized as compact letter display, different letters represented statistically significant difference between groups. *Log transformed with Y-axis

Fig. 3

Number needed to screen, incidence rate ratios and 95% confidence intervals for high-risk populations in Yunnan, 2013–2015 NNS: Number needed to screen to detect one tuberculosis case. IRRs: Incidence rate ratio of high-risk population compared to general population in active case finding strategy; CI: confidence intervals. High-risk groups: Elderly, Diabetes mellitus, HIV/AIDS, close contact and history of previous tuberculosis case. *Log transformed with X-axis

Fig. 4

The patient, diagnostic and total delays stratified by case finding strategies and the year of tuberculosis diagnosis in Yunnan, 2013–2015 Days of patient delay: Date from the onset of tuberculosis symptoms to date of the patient’s first home visit for ACF or date to a healthcare facility for PCF. Days of diagnostic delay: Date of patient’s first visit to date of the confirmation of tuberculosis diagnosis by sputum smear or culture. Days of total delay: The sum of patient delay and diagnostic delay. * Wilcoxon rank sum test showed P-value < 0.05 between different case finding strategies between 2013 and 2015