Malaria over-diagnosis in Cameroon: diagnostic accuracy of Fluorescence and Staining Technologies (FAST) Malaria Stain and LED microscopy versus Giemsa and bright field microscopy validated by polymerase chain reaction

Abstract

BackgroundMalaria is a major world health issue and its continued burden is due, in part, to difficulties in the diagnosis of the illness. The World Health Organization recommends confirmatory testing using microscopy-based techniques or rapid diagnostic tests (RDT) for all cases of suspected malaria. In regions where Plasmodium species are indigenous, there are multiple etiologies of fever leading to misdiagnoses, especially in populations where HIV is prevalent and children. To determine the frequency of malaria infection in febrile patients over an 8-month period at the Regional Hospital in Bamenda, Cameroon, we evaluated the clinical efficacy of the Flourescence and Staining Technology (FAST) Malaria stain and ParaLens AdvanceTM microscopy system (FM) and compared it with conventional bright field microscopy and Giemsa stain (GS).MethodsPeripheral blood samples from 522 patients with a clinical diagnosis of “suspected malaria” were evaluated using GS and FM methods. A nested PCR assay was the gold standard to compare the two methods. PCR positivity, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were determined.ResultsFour hundred ninety nine samples were included in the final analysis. Of these, 30 were positive via PCR (6.01%) with a mean PPV of 19.62% and 27.99% for GS and FM, respectively. The mean NPV was 95.01% and 95.28% for GS and FM, respectively. Sensitivity was 26.67% in both groups and specificity was 92.78% and 96.21% for GS and FM, respectively. An increased level of diagnostic discrepancy was observed between technicians based upon skill level using GS, which was not seen with FM.ConclusionsThe frequency of malarial infections confirmed via PCR among patients presenting with fever and other symptoms of malaria was dramatically lower than that anticipated based upon physicians’ clinical suspicions. A correlation between technician skill and accuracy of malaria diagnosis using GS was observed that was less pronounced using FM. Additionally, FM increased the specificity and improved the PPV, suggesting this relatively low cost approach could be useful in resource-limited environments. Anecdotally, physicians were reluctant to not treat all patients symptomatically before results were known and in spite of a negative microscopic diagnosis, highlighting the need for further physician education to avoid this practice of overtreatment. A larger study in an area with a known high prevalence is being planned to compare the two microscopy methods against available RDTs.Electronic supplementary materialThe online version of this article (doi:10.1186/s40249-017-0251-0) contains supplementary material, which is available to authorized users.

Diagnostic Performance of Blood Film Microscopy and PfHRP2-based RDT in a Routine Clinical Setting of a Secondary Health Facility in Ghana

“…Firstly, the importance of parasite based testing before treatment is highlighted as more than half of patients presenting with malaria-like symptoms and signs including fever were malaria free. This observation is consistent with several studies in malaria endermic regions [2,3,5]. Thus, presumptive diagnosis and treatment of malaria without prior parasite-based testing is likely to lead to over -diagnosis of malaria and subsequent less attention to other conditions that present with signs and symptoms that are akin to malaria.…”

“…These challenges and possibly other factors like poor confidence in laboratory systems might have led to presumptive treatment of suspected malaria cases without laboratory evidence of malaria parasitaemia. In a study carried out at a regional hospital in Bamenda, Cameroon, out of 469 patients who were presumptively treated for malaria, only 30 actually had malaria parasitaemia [2]. Similarly, a study conducted in Ghana reported that of 605 feverish children who sought medical care at a hospital in Accra, only 11% were found positive for malaria by microscopy after 80% had been diagnosed presumptively with malaria and treated with anti-malarial medication [3].…”

Image analysis and machine learning for detecting malaria

“…We also briefly discuss the other options for malaria diagnosis, although they are arguably less suited for the conditions in remote malaria regions. For more information about malaria diagnosis, we refer readers to the surveys in Ref 7 and 9 and the following references: 8,13,14 .…”

Prevalence of Asymptomatic Malaria among Children in the Tamale Metropolis: How Does the PfHRP2 CareStart™ RDT Perform against Microscopy?

“…Malaria continues to remain a global burden and a threat to world health despite increasing awareness and public heath efforts aimed at improving vector control and therapeutics and diagnostics, which in recent times have reduced the incidence of the infection worldwide [1][2][3]. In 2018, the World Health Organization (WHO) reported an estimated 219 million malaria cases globally with 435,000 deaths, 93% of which occurred in sub-Saharan Africa, where it is the second leading cause of death related to infectious diseases [4,5], with pregnant women and children being the significantly affected.…”