Improvement of a direct agglutination test for field studies of visceral leishmaniasis

Abstract

To increase the potential for the wide-scale application of our direct agglutination test for visceral leishmaniasis, modifications in the components and procedures were introduced. Supplementation with 0.056 M citrate of the suspension medium stabilized the antigen for 9 weeks at 3rC. To circumvent the need for cooling systems in the field, 0.2% (wt/vol) gelatin was added to the serum diluent instead of fetal bovine serum, with reliable results. Specificity and sensitivity were improved by the incorporation of 0.1 M 2-mercaptoethanol in samples with borderline titers. The test could be performed on samples of whole blood; thus the difficulties of preparation and storage of serum, plasma, or filter paper blood are avoided. For mass screening programs, a single serum dilution of 1:6,400 could be employed, contributing to a further reduction in test expenses. Sera from different geographical areas showed equal reactivities in this direct agglutination test despite the nonhomologous Leishmania donovani antigens used.

Post-kala-azar dermal leishmaniasis in the Sudan: clinical presentation and differential diagnosis

“…A medical history was taken from, and a physical examination was conducted on, all individuals in the village; the spleen size was measured in centimetres from the costal margin in the anterior axillary line to the tip of the spleen. A drop of fingerprick blood was collected on filter paper for the direct agglutination test (DAT), which was performed as described by Harith et al 6 A leishmanin skin test (LST) was carried out by injecting 0´1 mL of L. infantum antigen (Istituto Superiore di Sanita Á, Rome) into the volar surface of the left arm; a reaction $ 5 mm as measured by the ballpoint pen method was considered positive. 7 In addition, individuals from surrounding villages who presented during the surveys and who were suspected as having kala-azar or PKDL were examined in a similar way.…”

Subpopulations of T Lymphocytes in the Peripheral Blood, Dermal Lesions and Lymph Nodes of Post Kala‐azar Dermal Leishmaniasis Patients

“…Serological tests. Antileishmanial antibody titres in the patients' sera were determined by direct agglutination test [20].…”

PCR and direct agglutination as Leishmania infection markers among healthy Nepalese subjects living in areas endemic for Kala‐Azar

“…Direct agglutination test was performed as described elsewhere (Jacquet et al 2006) using freeze dried antigen suspension of trypsin-treated Leishmania promastigotes (purchased from ITG-Belgium), as described by Harith et al (1988). A 5-mm filter paper disc fully covered with blood was punched out (which corresponds to 5 ll blood, thus in average 2.5 ll serum) and eluted in 1000 lL DAT buffer (PBS-PH 7.2 supplemented with protein) in a sealable tube, to obtain a 1:400 dilution.…”

“…The comparisons were made by the survey logistic regression model and did not show the evidence of a relation between the PCR and DAT positivity (when not controlling for age and sex) and the corresponding incidence rate in different clusters in the HNK population. (Figure 3a (PCR) and b (DAT) shows the observed prevalences and incidence rates for the Table 1 for definition) and (ii) VL patients [data from Harith et al (1988)] from the VL endemic region of Terai, Nepal. The error bars show the 95% confidence intervals (CI) for the prevalence of each test.…”