Testing for antibody to human immunodeficiency virus type 1 in a population in which mycobacterial diseases are endemic.

During a large epidemiologic study in the Karonga District of northern Malawi, serum samples from 139 patients with incident leprosy, 124 with newly diagnosed leprosy, 277 patients with incident tuberculosis, and 2296 controls were tested for antibodies to human immunodeficiency virus. Sera were tested according to a four-test protocol using two ELISAs and two particle agglutination assays. Overall, 188 samples were considered positive, 2634 were considered negative, and 14 were indeterminate. All 18 available positive specimens from leprosy patients, a random sample of 14 positive specimens from tuberculosis patients, and 15 positive specimens from controls were tested by Western blot. There was no evidence of substantial numbers of ELISA false-positives in any patient group or among controls.

Is HIV infection a risk factor for leprosy?

A case control study was undertaken during 1988 and 1989 within the framework of the LEPRA Evaluation Project (LEP)/Karonga Prevention Trail (KPT) in Karonga District, northern Malawi, to investigate whether HIV infection is a risk factor for clinical leprosy. Cases were newly ascertained, biopsy-confirmed, incident leprosy patients older than 14 years of age. Controls were selected from the computer data base on over 170,000 people who form the basis of LEP/KPT. They were matched for sex, age, and area of residence. HIV seropositivity rates were 1.8% (2/112) for incident leprosy cases and 2.4% (24/1011) for controls. The Mantel Haenszel odds ratio is 0.6 (95% confidence interval 0.1-3.3). Thus, no evidence for an association between HIV infection and leprosy incidence has been observed in this population. In a parallel investigation, an odds ratio of 7.4% (95% confidence interval 3.3-16.7) was found for 102 microscopy- and/or culture-confirmed, incident pulmonary tuberculosis cases in the same population during 1989, a result similar to those obtained elsewhere in Africa. Among leprosy relapses, 16.7% (2/12) were HIV positive.

Setting up HIV serology for the Karonga leprosy vaccine trial in Malawi.

As part of the leprosy vaccine trial taking place in Karonga District, Northern Malawi, it is essential to establish whether the presence of HIV infection in the population is affecting the incidence rate or clinical presentation of leprosy or the effectiveness of the trial vaccines. To obtain the appropriate information, a rapid and economical HIV testing protocol, which could be performed in a rural laboratory and would be robust under variable environmental conditions, had to be developed. This paper reports on the development/evaluation phase of a multitest protocol based on commercially available particle agglutination and ELISA anti-HIV antibody detection kits. The protocol was devised by first evaluating a range of kits in London using a battery of African and non-African sera and then field testing 1455 sera in Malawi, which included 184 sera from leprosy patients and 60 sera from syphilis patients to check for cross-reactivity. According to the protocol developed, all sera are screened initially both by indirect ELISA (Organon) and using a rapid and economical modification of the Serodia particle agglutination test. Positives are retested using both a competitive ELISA (Wellcome or Behring) and the standard Serodia particle agglutination test. The validity of this multitest protocol was confirmed by Western blotting a large sample of the positive and negative Malawian sera in London. Factors affecting kit selection, and problems associated with individual kits, are discussed. While the specific multitest protocol developed for Malawi might not be suitable for every project, the principle of developing economical alternatives to Western blotting is an important consideration for any field investigation of HIV.