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This paper describes changes in the circulating platelets of 25 patients with acute malaria within 2 to 6 days of onset of illness. Thrombocytopenia was observed in 10 out of 15 patients with Plasmodium falciparum infection, and in 4 out of 9 patients with P. vivax infection. One patient with a mixed infection of both species had a disseminated intravascular coagulation. Platelet antibody was detected in the sera of 8 out of 11 cases by the complement lysis inhibition technique and indirect immunofluorescence. The mean platelet antibody concentrations in the sera of 11 patients and 53 control subjects were 122.70 +/- 80.25 ng/10(7) platelets and 36.69 +/- 18.72 ng/10(7) platelets, respectively. An inverse relationship between the platelet count and platelet antibody levels in serum supported the view that thrombocytopenia in malaria may be partly immune-mediated. Platelet aggregation responses to agonists such as ADP, adrenaline, collagen and ristocetin revealed hyperactivity. Ultrastructural study of unstimulated platelets from patients revealed several changes such as centralization of dense granules, glycogen depletion, and formation of pseudopods and microaggregates, indicating in vivo activation of the platelets, which may also lead to thrombocytopenia.

Objective To develop and validate a novel decision tree-based clinical algorithm to differentiate Kawasaki disease (KD) from other pediatric febrile illnesses that share common clinical characteristics. Study design Using clinical and laboratory data from 801 subjects with acute KD (533 for development, and 268 for validation) and 479 febrile control subjects (318 for development, and 161 for validation), we developed a step-wise KD diagnostic algorithm combining our previously developed linear-discriminant-analysis (LDA)-based model with a newly developed, tree-based algorithm. Results The primary model (LDA) stratified the 1,280 subjects into FC (276), indeterminate (247), and KD (757) subgroups. The subsequent model (decision trees) further classified the indeterminate group into FC (103) and KD (58) subgroups, leaving only 29 of 801 (3.6%) KD and 57 of 479 (11.9%) FC subjects indeterminate. The 2-step algorithm had a sensitivity of 96.0% and a specificity of 78.5% and correctly classified all KD subjects who later developed coronary artery aneurysms. Conclusion The addition of a decision tree step increased sensitivity and specificity in KD/FC classification over our previously described LDA model. A multicenter trial is needed to prospectively determine its utility as a point of care diagnostic test for KD.

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