Overdiagnosis of Malaria Illness in an Endemic Setting: A Facility-Based Surveillance Study in Malawi

Abstract

In endemic settings where asymptomatic malaria infections are common, malaria infection can complicate fever diagnosis. Factors influencing fever misdiagnosis, including accuracy of malaria rapid diagnostic tests (mRDTs) and the malaria-attributable fraction of fevers (MAF), require further investigation. We conducted facility-based surveillance in Malawi, from January 2012 through December 2013 in settings of high perennial (Chikhwawa), high seasonal (Thoylo), and moderate seasonal (Ndirande) malaria transmission. Consecutive patients presenting to outpatient departments were screened; those with suspected malaria illness were tested by mRDT or routine thick-smear microscopy. Test positivity rates (TPRs), positive predictive value (PPVs) of mRDTs, and MAFs were calculated by site, age, and season. Of 41,471 patients, 10,052 (24.2%) tested positive for malaria. The TPR was significantly greater in Chikhwawa (29.9%; 95% CI, 28.6–30.0) compared with Thyolo (13.2%; 95% CI, 12.5–13.7) and Ndirande (13.1%; 95% CI, 12.2–14.4). The overall PPV was 77.8% (95% CI, 76.8–78.7); it was lowest among infants (69.9%; 95% CI, 65.5–74.2) and highest among school-age children (81.9%; 95% CI, 80.3–83.4). Malaria infection accounted for about 50% of fevers in children younger than 5 years old with microscopy-confirmed Plasmodium falciparum infection, and less than 20% of such fevers in school-age children. Outpatient settings in Malawi had a high burden of malaria illness, but also possible overdiagnosis of malaria illness. Interventions to reduce malaria transmission and rapid testing for other common febrile illness may improve diagnostic clarity among outpatients in malaria endemic settings.

High burden of malaria among Malawian adults on antiretroviral therapy after discontinuing prophylaxis

“…The high malaria prevalence in adults off TS prophylaxis is similar to in children <5 years of age in Malawi [20]. In Malawi, we and others have observed similar rates of malaria infection among young children and adults [29][30][31], although incidence of clinical disease decreases with age [32]. However, unlike young children who suffer from severe morbidity and mortality due to malaria, malaria disease in PWH remains generally uncomplicated and without long-term consequences.…”

Detection of acute dengue virus infection, with and without concurrent malaria infection, in a cohort of febrile children in Kenya, 2014–2019, by clinicians or machine learning algorithms

“…A similar study to ours uncovered a large burden of chikungunya virus infection among Kenyan children [ 29 ]. The high prevalence and force of infection of malaria, in combination with lack of routine surveillance for arboviruses such as DENV or chikungunya virus, contribute towards under-recognition of alternate or concomitant causes for AFI and over-diagnosis of malaria [ 30 ].…”

Serological and molecular evidence of chikungunya virus infection among febrile outpatients seeking healthcare in Northern Malawi

“…Although CHIKF has been reported in Malawi’s closest neighboring countries such as Tanzania, Mozambique and Zambia [ 26–28 ], Malawi remains the only country in Central Africa to lack such published data. In addition, a study conducted in Malawi reported that malaria is often over diagnosed in febrile patients [ 29 ]. This may be due to lack of epidemiological data and knowledge gap of other aetiologies of febrile illnesses other than malaria in Malawi.…”

“…Our study supports the results published elsewhere that malaria is no longer a huge public threat but other aetiologies of fevers have emerged that are responsible for high morbidity in Sub-Saharan countries [ 43 ]. The absence of the sero-epidemiological data of other aetiologies of fevers hampers the proper management of patients and is the main reason why many febrile illnesses are over diagnosed as malaria in Malawi [ 29 ]. The detection of CHIKV in this study as an aetiology of febrile illness supports the latter and the need for a continued surveillance of other aetiologies of febrile illnesses such as CHIKV in Malawi.…”