scholarly journals Collider bias and the apparent protective effect of glucose-6-phosphate dehydrogenase deficiency on cerebral malaria

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
James A Watson ◽  
Stije J Leopold ◽  
Julie A Simpson ◽  
Nicholas PJ Day ◽  
Arjen M Dondorp ◽  
...  

Case fatality rates in severe falciparum malaria depend on the pattern and degree of vital organ dysfunction. Recent large-scale case-control analyses of pooled severe malaria data reported that glucose-6-phosphate dehydrogenase deficiency (G6PDd) was protective against cerebral malaria but increased the risk of severe malarial anaemia. A novel formulation of the balancing selection hypothesis was proposed as an explanation for these findings, whereby the selective advantage is driven by the competing risks of death from cerebral malaria and death from severe malarial anaemia. We re-analysed these claims using causal diagrams and showed that they are subject to collider bias. A simulation based sensitivity analysis, varying the strength of the known effect of G6PDd on anaemia, showed that this bias is sufficient to explain all of the observed association. Future genetic epidemiology studies in severe malaria would benefit from the use of causal reasoning.

2014 ◽  
Vol 19 (4) ◽  
pp. 325-334
Author(s):  
Heather N. Damhoff ◽  
Robert J. Kuhn ◽  
Laura P. Stadler

Approximately 1,500 cases of malaria are diagnosed in the United States each year. Most cases are travelers and immigrants returning from parts of the world where malaria transmission occurs. Malaria is the most frequent cause of systemic febrile illness without localizing symptoms in travelers returning from the developing world, so vigilance by providers is needed when evaluating patients returning from areas in which malaria is endemic. Despite the availability of effective treatment, malaria still accounts for more than 1 million deaths per year worldwide, with rates being disproportionately high in young children under the age of 5. We present the case of a 4-year-old refugee who emigrated from Tanzania with severe malaria due to dual infections of Plasmodium falciparum and P. ovale, whose treatment course was complicated by quinidine gluconate cardiotoxicity and glucose-6-phosphate dehydrogenase deficiency.


eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Geraldine M Clarke ◽  
Kirk Rockett ◽  
Katja Kivinen ◽  
Christina Hubbart ◽  
Anna E Jeffreys ◽  
...  

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is believed to confer protection against Plasmodium falciparum malaria, but the precise nature of the protective effect has proved difficult to define as G6PD deficiency has multiple allelic variants with different effects in males and females, and it has heterogeneous effects on the clinical outcome of P. falciparum infection. Here we report an analysis of multiple allelic forms of G6PD deficiency in a large multi-centre case-control study of severe malaria, using the WHO classification of G6PD mutations to estimate each individual’s level of enzyme activity from their genotype. Aggregated across all genotypes, we find that increasing levels of G6PD deficiency are associated with decreasing risk of cerebral malaria, but with increased risk of severe malarial anaemia. Models of balancing selection based on these findings indicate that an evolutionary trade-off between different clinical outcomes of P. falciparum infection could have been a major cause of the high levels of G6PD polymorphism seen in human populations.


2016 ◽  
Vol 15 (1) ◽  
Author(s):  
Christian N. Nguetse ◽  
Christian G. Meyer ◽  
Ayola Akim Adegnika ◽  
Tsiri Agbenyega ◽  
Bernhards R. Ogutu ◽  
...  

The Lancet ◽  
1979 ◽  
Vol 313 (8115) ◽  
pp. 524-526 ◽  
Author(s):  
S.K Martin ◽  
L.H Miller ◽  
D Alling ◽  
V.C Okoye ◽  
G.J.F Esan ◽  
...  

Author(s):  
Briantais Antoine ◽  
Froidefond Margaux ◽  
Seguier Julie ◽  
Swiader Laure ◽  
Durand Jean Marc

BMC Medicine ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Andrea L. Conroy ◽  
Robert O. Opoka ◽  
Paul Bangirana ◽  
Ruth Namazzi ◽  
Allen E. Okullo ◽  
...  

Abstract Background In 2011, the World Health Organization recommended injectable artesunate as the first-line therapy for severe malaria (SM) due to its superiority in reducing mortality compared to quinine. There are limited data on long-term clinical and neurobehavioral outcomes after artemisinin use for treatment of SM. Methods From 2008 to 2013, 502 Ugandan children with two common forms of SM, cerebral malaria and severe malarial anemia, were enrolled in a prospective observational study assessing long-term neurobehavioral and cognitive outcomes following SM. Children were evaluated a week after hospital discharge, and 6, 12, and 24 months of follow-up, and returned to hospital for any illness. In this study, we evaluated the impact of artemisinin derivatives on survival, post-discharge hospital readmission or death, and neurocognitive and behavioral outcomes over 2 years of follow-up. Results 346 children received quinine and 156 received parenteral artemisinin therapy (artemether or artesunate). After adjustment for disease severity, artemisinin derivatives were associated with a 78% reduction in in-hospital mortality (adjusted odds ratio, 0.22; 95% CI, 0.07–0.67). Among cerebral malaria survivors, children treated with artemisinin derivatives also had reduced neurologic deficits at discharge (quinine, 41.7%; artemisinin derivatives, 23.7%, p=0.007). Over a 2-year follow-up, artemisinin derivatives as compared to quinine were associated with better adjusted scores (negative scores better) in internalizing behavior and executive function in children irrespective of the age at severe malaria episode. After adjusting for multiple comparisons, artemisinin derivatives were associated with better adjusted scores in behavior and executive function in children <6 years of age at severe malaria exposure following adjustment for child age, sex, socioeconomic status, enrichment in the home environment, and the incidence of hospitalizations over follow-up. Children receiving artesunate had the greatest reduction in mortality and benefit in behavioral outcomes and had reduced inflammation at 1-month follow-up compared to children treated with quinine. Conclusions Treatment of severe malaria with artemisinin derivatives, particularly artesunate, results in reduced in-hospital mortality and neurologic deficits in children of all ages, reduced inflammation following recovery, and better long-term behavioral outcomes. These findings suggest artesunate has long-term beneficial effects in children surviving severe malaria.


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