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.

[Serological study of toxoplasmosis in Vietnam in a population of drug users (Ho Chi Minh city) and pregnant women (Nha Trang)]. / Etude sérologique de la toxoplasmose au Vietnam dans une population de toxicomanes (Ho Chi Minh ville) et de femmes enceintes (Nha Trang).

Toxoplasmosis is a neglected disease in Vietnam particularly in populations with a high risk of developing complications. The seroprevalence of Toxoplasma gondii was calculated by testing blood samples for Toxoplasma specifically immunoglobulin G and immunoglobulin M on 300 intravascular drug users and on 300 pregnant women. Among intravascular drug users, the seroprevalence of IgG and IgM was 7.7% and 0.08%, respectively. In pregnant women the prevalence of anti-toxoplasmosis IgG and IgM was respectively 11.2% and 0%. 0.28% of all estimated pregnancies in Vietnam are affected with toxoplasmosis, i.e. around 4800 pregnancies per year. In conclusion, a screening of Toxoplasma infections should be recommended in HIV/AIDS patients.

[Incidence of HIV infection in consultants reviewed after a first negative test in an anonymous and free screening center at the Institut Pasteur of Cambodia, 1996-1999]. / Incidence de l'infection VIH parmi les consultants revus après un premier test négatif au centre de dépistage anonyme et gratuit de l'Institut Pasteur du Cambodge, 1996-1999.

A retrospective study was performed to determine the incidence of HIV seroconversion among repeat consultants attending the voluntary testing and counselling centre of the Institut Pasteur of Cambodia as well as factors associated with HIV seroconversion. From 1996 to 1999, 5541 repeat consultants were selected for the study. Exclusion criteria included being aged under 15 years, having initially tested positive or inconclusive and a time span of fewer than 30 days since the last test. In all, 276 persons had seroconverted to HIV, giving an incidence rate of 5.56 per 100 person-years. The seroconversion rate declined from 8.46% in 1996, to 3.06% in 1999 (chi 2 test for trend, p = 10(-5)). Among the risk factors analysed, 3 were significantly associated with lack of seroconversion: being a student (RR = 0.53, p = 0.032) or a civil servant (RR = 0.63, p = 0.012) and systematic condom use with causal partners (RR = 0.37, p = 10(-5)). The decline of HIV seroconversion among repeat consultants attending the VCT centre over the study period may reflect changes in risk behaviour and the beneficial impact of counselling.