From tuberculin to prevalence survey in Cambodia

Abstract

Objectives: To assess the annual risk of tuberculosis infection (ARTI) in urban and rural areas of Cambodia in 1995, and to document the decreasing trend since 1955. To compare tuberculosis (TB) estimates based on ARTI with active case finding activities and tuberculosis notification data.

Methods: Two national representative samples of 3524 and 4407 schoolchildren were tested with 1 TU of tuberculin, PPD RT23/Tween 80. Estimates based on ARTI were compared with the results of both active TB case finding and case notification, using WHO/IUATLD-recommended quarterly reports available country-wide since 1994.

Findings: ARTI was estimated to be 0.75% (0.56-0.96%) in Cambodia in 1995 using a 10 mm induration cut-off point. The average ARTI annual decrease was 4.2% per year in Phnom Penh and 4.9% per year in the provincial areas from 1955 to 1995. The estimated TB incidence based on urban ARTI is 2.4 times lower than the TB notification rate in 1995, and 4.3 times lower than the incidence estimated from the screening survey.

Conclusion: The ARTI has regularly declined over time. Predicting the TB incidence from ARTI should be complemented in Cambodia by ongoing prevalence surveys. More accurate estimates are needed to maintain political support for the National Tuberculosis Programme.