National HIV prevalence surveillance among TB patients through periodic surveys: experience in Cambodia.

SETTING: The National Tuberculosis Programme (NTP) in Cambodia, one of the countries most affected by tuberculosis (TB) and human immunodeficiency virus (HIV) infection in Asia. OBJECTIVE: To conduct national HIV prevalence surveillance among TB patients, to estimate HIV prevalence among TB patients and to determine the potential of the NTP as a source for antiretroviral treatment (ART) scale-up. DESIGN: Anonymous unlinked cross-sectional seroprevalence surveys including all TB patients registered by the NTP in January 2003 and January 2005. RESULTS: HIV prevalence among all TB patients fell from 11.8% in 2003 to 9.9% in 2005 (P < 0.05). In 2003 and 2005, respectively 265 and 261 TB patients were identified as HIV-positive in a given month. Among new smear-positive pulmonary TB patients, the prevalence dropped from 8.2% to 5.2% (P < 0.01). CONCLUSION: The two periodic surveys demonstrated a high prevalence of HIV among TB patients in Cambodia. However, the declining incidence of HIV from the late 1990s might now be reflected in the HIV prevalence among new smear-positive TB patients. The NTP is a potential source of ART if HIV counselling and testing are made more widely available to TB patients.

Tuberculosis prevalence surveys: rationale and cost.

This article is the first of the educational series 'Assessing tuberculosis (TB) prevalence through population-based surveys'. The series will give overall guidance in conducting cross-sectional surveys of pulmonary TB (PTB) disease. TB prevalence surveys are most valuable in areas where notification data obtained through routine surveillance are of unproven accuracy or incomplete, and in areas with an estimated prevalence of bacteriologically confirmed TB of more than 100 per 100,000 population. To embark on a TB prevalence survey requires commitment from the national TB programme, compliance in the study population, plus availability of trained staff and financial resources. The primary objective of TB prevalence surveys is to determine the prevalence of PTB in the general population aged >or=15 years. Limitations of TB prevalence surveys are their inability to assess regional or geographic differences in prevalence of TB, estimate the burden of childhood TB or estimate the prevalence of extra-pulmonary TB. The cost of a prevalence survey is typically US$ 4-15 per person surveyed, and up to US$ 25 per person with radiographic screening. A survey of 50,000 people, of limited precision, would typically cost US$ 200,000-1,250,000.

Trend in the annual risk of tuberculous infection in Egypt, 1950-1996.

OBJECTIVE: To determine the trend in the risk of tuberculous infection in non-BCG vaccinated children in Egypt in the period 1950-1996. METHODS: In 1949-1952, a tuberculin survey was carried out in Egypt by the World Health Organization (WHO) covering 103 districts. In 1995-1997 a tuberculin survey was carried in 73 620 primary school children in grade one in the same districts, using international guidelines. The trend in tuberculous infection was determined by comparing the prevalence of Mantoux reactions of > or =6 mm in the two surveys in subjects without apparent BCG scar aged 6-7 years. For an estimate of current risk of infection the 17 mm cut-off point (number with 17 mm plus twice the number with greater than 17 mm) was used. RESULTS: In 1995-1997, 76% of children had a BCG scar. Infection prevalence estimates in 14 766 non-BCG-vaccinated children with a mean age of 6.7 years were 11.9%, 4.1%, and 2.1% for the cut-off points 6 mm, 10 mm, and 17 mm, respectively. Decline in the risk of infection was estimated to be in the order of 50% over 45 years, or 1.5% per year. The geometric mean annual risk of infection in the 6.7 years before the survey was estimated at 0.32% (95% confidence interval 0.27-0.40%). For Egypt, the incidence of smear-positive tuberculosis was estimated at 16 per 100000 population, giving a case detection rate of 85% (range 56-100%). CONCLUSION: This survey has shown that the size of the tuberculosis problem in Egypt is considerably smaller now than it was 45 years ago.