The first national tuberculosis prevalence survey of Lao PDR (2010-2011)

Objective: The objective of the study was to measure the prevalence of bacteriologically confirmed pulmonary tuberculosis (TB) in Lao PDR in 2010-2011. Method: A nationwide, multistage cluster-sampled cross-sectional survey was undertaken in 2010-2011. All consenting participants ≥15 years were screened for pulmonary TB with chest X-ray and symptom questionnaire. Two sputum specimens for bacteriological examination by microscopy and culture were collected from those who screened positive. Prevalence was estimated using multiple imputation and inverse probability weighting methods. Results: Of 39 212 eligible participants from 50 clusters, 6290 participants provided at least one sputum sample for smear and culture. There were 237 bacteriologically confirmed pulmonary TB cases, 107 of which were smear-positive. Chest X-ray screening alone identified 230 (97.0%) cases compared with 118 (49.8%) by symptom screening alone. The estimated prevalence of smear-positive and bacteriologically confirmed TB in those ≥15 years was 278 per 100 000 (95%C.I. 199-356) and 595 per 100 000 (95%C.I. 457-733), respectively. Prevalence significantly increased with age and was higher in men than women. Conclusions: The prevalence of TB in Lao PDR is almost twice as high than previous estimates, with the greatest burden in the older population. Case detection efforts remain the primary goal of the national TB programme with case notifications being very low in comparison with the estimated number of prevalent cases. The survey observed major limitations with the diagnostic strategy of passive (symptom based) case finding that uses only direct smear microscopy for confirmation.