Prevalence of subclinical pulmonary tuberculosis in adults in community settings: an individual participant data meta-analysis

BACKGROUND

Subclinical pulmonary tuberculosis, which presents without recognisable symptoms, is frequently detected in community screening. However, the disease category is poorly clinically defined. We explored the prevalence of subclinical pulmonary tuberculosis according to different case definitions.

METHODS

We did a one-stage individual participant data meta-analysis of nationally representative surveys that were conducted in countries with high incidence of tuberculosis between 2007 and 2020, that reported the prevalence of pulmonary tuberculosis based on chest x-ray and symptom screening in participants aged 15 years and older. Screening and diagnostic criteria were standardised across the surveys, and tuberculosis was defined by positive Mycobacterium tuberculosis sputum culture. We estimated proportions of subclinical tuberculosis for three case definitions: no persistent cough (ie, duration ≥2 weeks), no cough at all, and no symptoms (ie, absence of cough, fever, chest pain, night sweats, and weight loss), both unadjusted and adjusted for false-negative chest x-rays and uninterpretable culture results.

FINDINGS

We identified 34 surveys, of which 31 were eligible. Individual participant data were obtained and included for 12 surveys (620 682 participants) across eight countries in Africa and four in Asia. Data on 602 863 participants were analysed, of whom 1944 had tuberculosis. The unadjusted proportion of subclinical tuberculosis was 59·1% (n=1149/1944; 95% CI 55·8-62·3) for no persistent cough and 39·8% (773/1944; 36·6-43·0) for no cough of any duration. The adjusted proportions were 82·8% (95% CI 78·6-86·6) for no persistent cough and 62·5% (56·6-68·7) for no cough at all. In a subset of four surveys, the proportion of participants with tuberculosis but without any symptoms was 20·3% (n=111/547; 95% CI 15·5-25·1) before adjustment and 27·7% (95% CI 21·0-36·4) after adjustment. Tuberculosis without cough, irrespective of its duration, was more frequent among women (no persistent cough: adjusted odds ratio 0·79, 95% CI 0·63-0·97; no cough: adjusted odds ratio 0·76, 95% CI 0·62-0·93). Among participants with tuberculosis, 29·1% (95% CI 25·2-33·3) of those without persistent cough and 23·1% (18·8-27·4) of those without any cough had positive smear examinations.

INTERPRETATION

The majority of people in the community who have pulmonary tuberculosis do not report cough, a quarter report no tuberculosis-suggestive symptoms at all, and a quarter of those not reporting any cough have positive sputum smears, suggesting infectiousness. In high-incidence settings, subclinical tuberculosis could contribute considerably to the tuberculosis burden and to Mycobacterium tuberculosis transmission.

FUNDING

Mr Willem Bakhuys Roozeboom Foundation.

Antituberculosis Drug Resistance Survey in Lesotho, 2008-2009: Lessons Learned

SETTING

Drug resistance is an increasing threat to tuberculosis (TB) control worldwide. The World Health Organization advises monitoring for drug resistance, with either ongoing surveillance or periodic surveys.

METHODS

The antituberculosis drug resistance survey was conducted in Lesotho in 2008-2009. Basic demographic and TB history information was collected from individuals with positive sputum smear results at 17 diagnostic facilities. Additional sputum sample was sent to the national TB reference laboratory for culture and drug susceptibility testing.

RESULTS

Among 3441 eligible smear-positive persons, 1121 (32.6%) were not requested to submit sputum for culture. Among 2320 persons submitted sputum, 1164 (50.2%) were not asked for clinical information or did not have valid sputum samples for testing. In addition, 445/2320 (19.2%) were excluded from analysis because of other laboratory or data management reasons. Among 984/3441 (28.6%) persons who had data available for analysis, MDR-TB was present in 24/773 (3.1%) of new and 25/195 (12.8%) of retreatment TB cases. Logistical, operational and data management challenges affected survey results.

CONCLUSION

MDR-TB is prevalent in Lesotho, but limitations reduced the reliability of our findings. Multiple lessons learned during this survey can be applied to improve the next drug resistance survey in Lesotho and other resource constrained countries may learn how to avoid these bottlenecks.