Thrombocytopenia in malaria--correlation with type and severity of malaria

Malaria is a major health problem in the tropics with increased morbidity and mortality. Thrombocytopenia is a common finding in malaria. Although a reliable diagnostic marker, prognostic implications could vary in the two types of malaria. This study was undertaken to correlate the presence and severity of thrombocytopenia with the type of malaria.

A total of 1565 subjects were included in the study and identified positive for malaria parasites on peripheral smear examination with conventional microscopy. Platelet count was done on a fully automated, quantitative, hematology Coulter analyser.

Normal platelet count was noted in 21.6% cases. The mean platelet count in vivax malaria (n=973) was 1,15,390/microl (SD 64,580) with a range of 8000-5,73,000/microl, as against falciparum malaria (n=590) where the mean platelet count was 100,900/microl (SD 75,437) with a range of 2000-497,000/microl (Pearson coefficient 8.825, p < 0.0001). Platelet count < 20,000/microl was noted in only 1.5% cases in vivax malaria as against 8.5% cases of falciparum malaria, and none of the subjects with vivax malaria had a platelet count less than 5000/microl.

Although absence of thrombocytopenia is uncommon in malaria, its presence is not a distinguishing feature between the two types. Thrombocytopenia less than 20,000/microl can occur in P. vivax malaria although statistically more common with P. falciparum malaria. The above findings can have therapeutic implications in context of avoiding unnecessary platelet infusions with the relatively more benign course in P. vivax malaria.