A comparison of thick-film microscopy, rapid diagnostic test, and polymerase chain reaction for accurate diagnosis of Plasmodium falciparum malaria

Kenji O Mfuh,Livo F Esemu,Obase N Bekindaka,Krupa Gandhi,Vivek R Nerurkar,Diane W Taylor,Olivia A Achonduh-Atijegbe,Rose G F Leke,Calixt D Mbakop

doi:10.1186/s12936-019-2711-4

Kenji O Mfuh, Livo F Esemu + Show 7 more

Open Access

https://doi.org/10.1186/s12936-019-2711-4

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Abstract

BackgroundAccurate diagnosis of malaria is important for effective disease management and control. In Cameroon, presumptive clinical diagnosis, thick-film microscopy (TFM), and rapid diagnostic tests (RDT) are commonly used to diagnose cases of Plasmodium falciparum malaria. However, these methods lack sensitivity to detect low parasitaemia. Polymerase chain reaction (PCR), on the other hand, enhances the detection of sub-microscopic parasitaemia making it a much-needed tool for epidemiological surveys, mass screening, and the assessment of interventions for malaria elimination. Therefore, this study sought to determine the frequency of cases missed by traditional methods that are detected by PCR.MethodsBlood samples, collected from 551 febrile Cameroonian patients between February 2014 and February 2015, were tested for P. falciparum by microscopy, RDT and PCR. The hospital records of participants were reviewed to obtain data on the clinical diagnosis made by the health care worker.ResultsThe prevalence of malaria by microscopy, RDT and PCR was 31%, 45%, and 54%, respectively. However, of the 92% of participants diagnosed as having clinical cases of malaria by the health care worker, 38% were malaria-negative by PCR. PCR detected 23% and 12% more malaria infections than microscopy and RDT, respectively. A total of 128 (23%) individuals had sub-microscopic infections in the study population. The sensitivity of microscopy, RDT, and clinical diagnosis was 57%, 78% and 100%; the specificity was 99%, 94%, and 17%; the positive predictive values were 99%, 94%, and 59%; the negative predictive values were 66%, 78%, and 100%, respectively. Thus, 41% of the participants clinically diagnosed as having malaria had fever caused by other pathogens.ConclusionsMalaria diagnostic methods, such as TFM and RDT missed 12–23% of malaria cases detected by PCR. Therefore, traditional diagnostic approaches (TFM, RDT and clinical diagnosis) are not adequate when accurate epidemiological data are needed for monitoring malaria control and elimination interventions.

Highlights

Accurate diagnosis of malaria is important for effective disease management and control
Proportion of diagnosed malaria cases by various diagnostic methods The overall proportion of participants diagnosed with malaria by thick-film microscopy (TFM), rapid diagnostic tests (RDT), and Polymerase chain reaction (PCR) in the cohort was 31%, 45%, and 54%, respectively
92% (507/551) of the participants were diagnosed with clinical malaria, of which 41% (209/551) were negative for malaria by PCR (Table 2)

Summary

Introduction

Accurate diagnosis of malaria is important for effective disease management and control. In Came‐ roon, presumptive clinical diagnosis, thick-film microscopy (TFM), and rapid diagnostic tests (RDT) are commonly used to diagnose cases of Plasmodium falciparum malaria. These methods lack sensitivity to detect low parasitae‐ mia. In most malaria-endemic countries, malaria is usually diagnosed by microscopy or rapid diagnostic tests (RDT) and clinical evidence. The traditional practice by health care workers (HCW) in malaria-endemic countries has been to diagnose malaria based on a history of fever (clinical diagnosis) [3,4,5,6]. The specificity of the commonly used RDT that detects histidine rich protein–II (HRP-II) of P. falciparum, is limited when the parasite is cleared and antigens remain in circulation for about 28 days (false positive) [2]

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