Estimation of serum immunoglobulin M as a screening technique for trypanosomiasis. A field trial in the Democratic Republic of the Congo.

Field trials in West Africa have shown the value of the estimation of serum immunoglobulin M (IgM) levels as a screening test in endemic trypanosomiasis areas. A further field trial carried out in the Democratic Republic of the Congo is described. The technique used, based on double diffusion on an agar plate, gave consistent results in skilled hands, but the standard required is probably too high for the wide application of the method under normal field conditions. The diameter of the precipitation zones for 200 sera from new patients from a survey population of nearly 10 000 was generally between 8.3 mm and 9.7 mm, while the mean diameter for 210 sera from healthy persons was 6.2 mm. The results for 115 sera from previously treated patients were generally intermediate between these two levels.Duplicate IgM estimations made in the laboratory on dried blood samples collected on filter-paper in the field gave agreement with the serum IgM test in 96% of the cases. The greater simplicity of the filter-paper method might make it suitable for wide-scale IgM estimations.