Three case definitions of malaria and their effect on diagnosis, treatmentand surveillance in Cox's Bazar district, Bangladesh

In countries where malaria is endemic, routine blood slide examinations rem ain the major source of data for the public health surveillance system. Thi s approach has become inadequate, however, as the public health emphasis ha s changed from surveillance of laboratory-confirmed malaria infections to t he early detection and treatment of the disease. As a result, it has been a dvocated that the information collected about malaria be changed radically and should include the monitoring of morbidity and mortality, clinical prac tice and quality of care. To improve the early diagnosis and prompt treatme nt (EDPT) of malaria patients, three malaria case definitions (MCDs) were d eveloped, with treatment and reporting guidelines, and used in all static h ealth facilities of Cox's Bazar district, Bangladesh (population 1.5 millio n). The three MCDs were: uncomplicated malaria (UM); treatment failure mala ria (TFM); and severe malaria (SM). The number of malaria deaths was also r eported. This paper reviews the rationale and need for MCDs in malaria cont rol programmes and presents an analysis of the integrated surveillance info rmation collected during the three-year period, 1995-97. The combined analy sis of slide-based and clinical data and their related indicators shows tha t blood slide analysis is no longer used to document fever episodes but to support EDPT, with priority given to SM and TFM patients. Data indicate a d ecrease in the overall positive predictive value of the three MCDs as malar ia prevalence decreases. Hence the data quantify the extent to which the ma inly clinical diagnosis of UM leads to over-diagnosis and over-treatment in changing epidemiological conditions. Also the new surveillance data show: a halving in the case fatality rate among SM cases (from 6% to 3.1%) attrib utable to improved quality of care, and a stable proportion of TFM cases (a round 7%) against a defined population denominator. Changes implemented in the EDPT of malaria patients and in the surveillance system were based on e xisting staff capacity and routine reporting structures.