Haematological parameters of Plasmodium falciparum infection in immunocompetent adults at a tertiary care centre in Douala

Background The haematological profile of children and at-risk groups of malaria patients in endemic areas has been extensively studied, but those parameters have not been thoroughly evaluated in immunocompetent adults with malaria. Method This was a cross-sectional study at Marie O Polyclinic which included all patients over 15 years who were symptomatic and had Plasmodium falciparum infection confirmed on microscopy. Consenting patients received complete clinical examinations, then venous blood samples were collected and analysed for Complete Blood Counts and C-Reactive Protein (CRP). Results Samples of 349 adults were retained. 147/349 had anaemia, 221/349 had thrombocytopaenia and 261/349 had at least one alteration of their leukogram profile. The most frequent alteration of the white blood cells was lymphopenia (240/349). All but three patients with malaria had positive CRP values, that is, CRP > 5mg/L. Parasitaemia (in trophozoites of Plasmodium falciparum /µl -TPF/µl) ranged from 5,020 to 84,040. Multivariable logistic regression showed that the presence of moderate thrombocytopenia, moderate leukopenia and CRP levels above 100 mg/L were the best predictors of severe malaria. A scoring system was developed using these variables, in which scores less than 5 (level 1) were associated with a low probability for severe malaria, scores of 6–9 (level 2) with an intermediate probability, and scores of 10 or more (level 3) with a high probability for severe malaria. A predictor graph based on the patient sample in which 43% of patients had severe malaria and a Receiver Operating Characteristic (ROC) curve were constructed. The Area under the ROC curve (AUROC) with this prediction model was 94%. Using a cut-point between level 2 and 3 on the predictor graph gave sensitivity of 66%, specificity of 99%, a positive predictive value of 0.98, and a negative predictive value of 0.79 for severe malaria. Conclusion Complete blood counts and CRP values can predict severe malaria accurately independently of currently established clinical and paraclinical criteria. Clinical trial number: not applicable.