Laboratory diagnosis of malaria -- overview.

Abstract

Features of the laboratory diagnosis of malaria are described. Microscope equipment is absolutely essential. Clinical symptoms are inadequate for the proper diagnosis of malaria. Screening for malaria involves identification of all cases where high fever is present in endemic areas. Diagnosis is complicated because many people take antimalarial drugs which reduce the chances of detecting malarial parasites. Confirmation should be made before treatment is administered. A thick blood slide can be quickly and cheaply taken without much training of health personnel. The disadvantage of thick stains is the difficulty in identifying "plasmodium" strains. When a thin smear with Giemsa and Leishmanin stain is used, a light infection may be missed. Thin smears require trained personnel and time, which in peak seasons may be impractical. Urinary tract and viral infections may be confused with malaria. Evidence of parasites can be discerned from thick stains. Modern assay techniques are also available. There are enzyme linked immunosorbent assays (ELISA) and immunofluorescent assay techniques (IFAT), which are frequently used in large scale seroepidemiological studies. DNA probes have the limitation of radioisotope handling problems. Acridine orange fluorescent microscopy with capillary centrifuged blood is a technique which improves the viability of Giemsa stain procedures. This technique is desirable because of the sensitivity and speed of diagnosis. The quantitative buddy coat (GBC) technique is superior to Giemsa stained thick blood film in identifying malaria, but it is not reliable with mixed infections. Advanced techniques are not readily available in local settings. The recommendation is to continue use of thick or thin blood film and trained health personnel. Laboratory results must be interpreted in the context of when the flood film was prepared, prior drug administration, and clinical manifestations.