Parasitology

LADEZA, Angela C.

MT-311

CASE STUDY

1. Discuss about the new trends with regards the diagnosis of malaria

Standard Technique

Microscopy is the most widely used laboratory-based diagnostic test for malaria, and it likely will remain the test of choice for some time. In this technique, two drops of blood, typically obtained from a finger pricked by a metal lancet, are placed on a glass microscope slide. One drop is smeared to create a thin blood film, the other drop (the thick film) is left alone, and the slide is allowed to air-dry. The cells in the thin blood smear are chemically fixed to the slide, and the slide is stained with Giemsa or some other stain formulation to facilitate detection of parasites. The water in the staining solution lyses the unfixed red blood cells in the thick blood film, removing the hemoglobin, and white blood cells and any malaria parasites are fixed to the slide.

Quantitative Buffy Coat Technique

The quantitative buffy coat (QBC) technique is a commercially available test based on fluorescence microscopy (Wardlaw and Levine, 1983). The test uses a specially made glass capillary tube of precise internal diameter containing acridine orange as a vital stain. After the tube is filled with blood, it is capped and a small plastic float is inserted. The float displaces precisely 90 percent of the interior tube space along its length, and when centrifuged, settles at the plasma-red blood cell interface, physically expanding the length of the buffy coat layer 10-fold. White blood cell components appear as discrete bands and can be accurately quantified with a specially designed optical device.

QBC Versus Microscopy

QBC is a relatively new technique, and the limits of its sensitivity and specificity are still being explored. QBC is a quick and efficient method of processing batches of blood specimens. Its advantage in this regard is less apparent, however, when a microscopist who is an expert at interpreting blood smears for malaria...