Abstract
Simple SummaryAlteration of platelet count is frequently seen in patients with malaria. However, the platelet biology under severe pathological conditions like severe malaria remains unclear. The present systematic review collated literatures and synthesized the evidence regarding the risks of severe and profound thrombocytopenia in patients with severe non-Plasmodium falciparum malaria. We found that the high prevalence of severe and profound thrombocytopenia in patients with severe non-P. falciparum malaria at 47% and 20%, respectively. Moreover, deaths were seen in patients with severe and profound thrombocytopenia at 11%. Therefore, the present systematic review provided the new insight into the clinical relevance of severe and profound thrombocytopenia in diagnosing and managing non-P. falciparum malaria. Severe thrombocytopenia should serve as a warning sign of increased chances of complications. Meanwhile, profound thrombocytopenia should serve as a marker of mortality among patients with non-P. falciparum malaria.The understanding of platelet biology under physiological and pathological conditions like malaria infection is critical importance in the context of the disease outcome or model systems used. The importance of severe thrombocytopenia (platelet count < 50,000 cells (µL) and profound thrombocytopenia (platelet count < 20,000 cells/µL) in malaria patients remains unclear. This study aimed to synthesize evidence regarding the risks of severe and profound thrombocytopenia in patients with severe non-Plasmodium falciparum malaria. Our overall aim was to identify potential indicators of severe non-P. falciparum malaria and the Plasmodium species that cause severe outcomes. This systematic review was registered at the International Prospective Register of Systematic Reviews (PROSPERO) under registration ID CRD42020196541. Studies were identified from previous systematic reviews (n = 5) and the MEDLINE, Scopus, and Web of Science databases from 9 June 2019 to 9 June 2020. Studies were included if they reported the outcome of severe non-Plasmodium species infection, as defined by the World Health Organization (WHO) criteria, in patients with known platelet counts and/or severe and profound thrombocytopenia. The risk of bias was assessed using the Newcastle–Ottawa Scale (NOS). Data were pooled, and pooled prevalence (PP) and pooled odds ratios (ORs) were calculated using random effects models. Of the 118 studies identified from previous meta-nalyses, 21 met the inclusion criteria. Of the 4807 studies identified from the databases, three met the inclusion criteria. Nine studies identified from reference lists and other sources also met the inclusion criteria. The results of 33 studies reporting the outcomes of patients with severe P. vivax and P. knowlesi infection were pooled for meta-analysis. The PP of severe thrombocytopenia (reported in 21 studies) was estimated at 47% (95% confidence interval (CI): 33–61%, I2: 96.5%), while that of profound thrombocytopenia (reported in 13 studies) was estimated at 20% (95% CI: 14–27%, 85.2%). The pooled weighted mean difference (WMD) in platelet counts between severe uncomplicated Plasmodium infections (reported in 11 studies) was estimated at −28.51% (95% CI: −40.35–61%, I2: 97.7%), while the pooled WMD in platelet counts between severe non-Plasmodium and severe P. falciparum infections (reported in eight studies) was estimated at −3.83% (95% CI: −13.90–6.25%, I2: 85.2%). The pooled OR for severe/profound thrombocytopenia comparing severe to uncomplicated Plasmodium infection was 2.92 (95% CI: 2.24–3.81, I2: 39.9%). The PP of death from severe and profound thrombocytopenia was estimated at 11% (95% CI: 0–22%). These results suggest that individuals with severe non-P. falciparum infection (particularly P. vivax and P. knowlesi) who exhibit severe or profound thrombocytopenia should be regarded as high risk, and should be treated for severe malaria according to current WHO guidelines. In addition, severe or profound thrombocytopenia coupled with other clinical and microscopic parameters can significantly improve malaria diagnosis, enhance the timely treatment of malaria infections, and reduce the morbidity and mortality of severe non-P. falciparum malaria.
Highlights
An understanding of platelet biology under physiological and pathological conditions like malaria infection is of critical importance in the context of the disease outcome or model systems used
Twenty-one studies reporting the outcomes of severe non-P. falciparum malaria were retrieved from previous systematic reviews and meta-analyses [18,19,20,21,22]
The results showed that the odds of severe or proBiology 2021, 10, x FOR PEER REVIEWfound thrombocytopenia were comparable in patients with severe P. knowlesi and1s2eovfer2e0 P. falciparum malaria (OR: 1.09, 95% confidence interval (CI): 0.42–2.83)
Summary
An understanding of platelet biology under physiological and pathological conditions like malaria infection is of critical importance in the context of the disease outcome or model systems used. Thrombocytopenia (platelet count < 100,000 cells/μL) is common in patients with malaria [2,3,4]. In patients with Plasmodium falciparum and Plasmodium vivax infections, thrombocytopenia is associated with increased mortality [5,6]. The proposed pathogenic mechanisms during P. falciparum malaria are increased platelet activation and consumption by factors such as the cytoadherence of infected erythrocytes and subsequent endothelial damage [7], platelet accumulation in the microvasculature [8], bone marrow alterations, and antibody-mediated platelet destruction [9]. Severe thrombocytopenia is defined as a platelet count of
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