Evaluation of the thick smear in a field condition in a malaria endemic area in the Middle Region of Rio Negro, Amazon

In order to assess the reliability of the thick smear in a Plasmodium infection area, 322 thick smears were examined by a trained microscopist in field conditions. Later, the same smears were examined by an experience microscopist in ideal laboratory conditions. Reliability was measured by the Kappa index. In symptomatic malaria patients the Kappa index was 0.91 (IC 95% 0.57-0.98 p<0.05) while in asymptomatic Plasmodium infection the Kappa index was as low as 0.42 (IC 95% 0.15-0.68 p<0.05). In areas of asymptomatic infection, improvement in the sensibility of thick smears by increasing the number of microscopic fields read or using other more accurate diagnostic malaria techniques alone or in combination is fundamental.