The accuracy of the first response histidine-rich protein2 rapid diagnostic test compared with malaria microscopy for guiding field treatment in an outbreak of falciparum malaria

Evaluation of rapid PfHRP-2/pLDH-based tests in diagnosing microscopy-confirmed falciparum malaria in Hodeidah governorate, Yemen

Along with the determination of malaria infection rate among suspected patients attending hospitals in Hodeidah governorate, the present study evaluated the accuracy of Plasmodium falciparum histidine-rich protein-2 (PfHRP-2)/parasite-specific lactate dehydrogenase (pLDH)-based rapid diagnostic test (RDT) for the diagnosis of microscopy-confirmed falciparum malaria. An overall malaria infection rate of 19.3% (57/295) among suspected patients attending hospitals was microscopically confirmed. The sensitivity of thin blood films for the detection of malaria parasites was 79.0% compared to thick films and was greatly affected by the parasite density, being 65.0% or less at parasite densities of ≤1000 parasites/μl of blood. Compared to light microscopy, the present study revealed sensitivity levels of 100.0% (95% CI: 92.0-100.0) vs. 94.7% (95% CI: 84.2-98.6), specificity levels of 97.3% (95% CI: 89.8-99.5) vs. 100.0% (95% CI: 93.9-100.0), positive predictive values of 89.9% (95% CI: 88.3-99.0) vs. 100.0 (95% CI: 91.6-100.0) and negative predictive values of 100.0% (95% CI: 93.9-100.0) vs. 98.7% (95% CI: 89.3-98.7) for the PfHRP-2 and pLDH components of SD BIOLINE^® RDT, respectively, for falciparum malaria diagnosis. Therefore, the overall accuracy levels of the PfHRP-2 and pLDH components of the investigated RDT for the diagnosis of microscopy-confirmed falciparum malaria are 98.5% (95% CI: 94.6-99.6) and 97.7% (95% CI: 93.5-99.2), respectively.

Low prevalence of laboratory-confirmed malaria in clinically diagnosed adult women from the Wakiso district of Uganda

Background

The malaria burden in sub-Saharan Africa (SSA) has fallen substantially. Nevertheless, malaria remains a serious health concern, and Uganda ranks third in SSA in total malaria burden. Epidemiological studies of adult malaria in Uganda are scarce and little is known about rates of malaria in non-pregnant adult women. This pilot study assessed malaria prevalence among adult women from Wakiso district, historically a highly malaria endemic region.

Methods

Adult women using public health services were screened for malaria, HIV and pregnancy. A physician-selected subset of women presenting to the Outpatient Department of Entebbe General Hospital (EGH) with current fever (axillary temperature ≥37.5 °C) or self-reporting fever during the previous 24 h, and a positive thick smear for malaria in the EGH laboratory were enrolled (n = 86). Women who self-identified as pregnant or HIV-positive were excluded from screening. Malaria infection was then assessed using HRP2/pLDH rapid diagnostic tests (RDTs) in all participants. Repeat microscopy and PCR were performed at a research laboratory for a subset of participants. In addition, 104 women without a history of fever were assessed for asymptomatic parasitaemia using RDT, and a subset of these women screened for parasitaemia using microscopy (40 women) and PCR (40 women).

Results

Of 86 women diagnosed with malaria by EGH, only two (2.3%) had malaria confirmed using RDT, subsequently identified as a Plasmodium falciparum infection by research microscopy and PCR. Subset analysis of hospital diagnosed RDT-negative participants detected one sub-microscopic infection with Plasmodium ovale. Compared to RDT, sensitivity, specificity and PPV of hospital microscopy were 100% (CI 19.8–100), 0% (CI 0–5.32) and 2.33% (CI 0.403–8.94) respectively. Compared to PCR, sensitivity, specificity and PPV of hospital microscopy were 100% (CI 31.0–100), 0% (CI 0–34.5) and 23.1% (CI 6.16–54.0), respectively. No malaria was detected among asymptomatic women using RDT, research microscopy or PCR.

Conclusions

Malaria prevalence among adult women appears to be low in Wakiso, but is masked by high rates of malaria overdiagnosis. More accurate malaria testing is urgently needed in public hospitals in this region to identify true causes of febrile illness and reduce unnecessary provision of anti-malarial therapy.

Field evaluation of a PfHRP-2/pLDH rapid diagnostic test and light microscopy for diagnosis and screening of falciparum malaria during the peak seasonal transmission in an endemic area in Yemen

BACKGROUND

Malaria is a public health threat in Yemen, with 149,451 cases being reported in 2013. Of these, Plasmodium falciparum represents 99%. Prompt diagnosis by light microscopy (LM) and rapid diagnostic tests (RTDs) is a key element in the national strategy of malaria control. The heterogeneous epidemiology of malaria in the country necessitates the field evaluation of the current diagnostic strategies, especially RDTs. Thus, the present study aimed to evaluate LM and an RDT, combining both P. falciparum histidine-rich protein-2 (PfHRP-2) and Plasmodium lactate dehydrogenase (pLDH), for falciparum malaria diagnosis and survey in a malaria-endemic area during the transmission season against nested polymerase chain reaction (PCR) as the reference method.

METHODS

A household-based, cross-sectional malaria survey was conducted in Mawza District, a malaria-endemic area in Taiz governorate. A total of 488 participants were screened using LM and PfHRP-2/pLDH RDT. Positive samples (160) and randomly selected negative samples (52) by both RDT and LM were further analysed using 18S rRNA-based nested PCR.

RESULTS

The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the RDT were 96.0% (95% confidence interval (CI): 90.9-98.3), 56.0% (95% CI: 44.7-66.8), 76.3% (95% CI: 69.0-82.3), and 90.4% (95% CI: 78.8-96.8), respectively. On the other hand, LM showed sensitivity of 37.6% (95% CI: 29.6-46.3), specificity of 97.6% (95% CI: 91.7-99.7), PPV of 95.9% (95% CI: 86.3-98.9), and NPV of 51.3% (95% CI: 43.2-59.2). The sensitivity of LM dropped to 8.5% for detecting asymptomatic malaria. Malaria prevalence was 32.8% (32.1 and 37.5% for ≥10 and <10 years, respectively) with the RDT compared with 10.7% (10.8 and 9.4% for age groups of ≥10 and <10 years, respectively) with LM. Among asymptomatic malaria individuals, LM and RDT-based prevalence rates were 1.6 and 25.6%, respectively. However, rates of 88.2 and 94.1% of infection with P. falciparum were found among patients who reported fever in the 48 h prior to the survey by LM and PfHRP-2/pLDH RDT, respectively.

CONCLUSIONS

The PfHRP-2/pLDH RDT shows high sensitivity for the survey of falciparum malaria even for asymptomatic malaria cases. Although the RDT had high sensitivity, its high false-positivity rate limits its utility as a single diagnostic tool for clinical diagnosis of malaria. On the other hand, low sensitivity of LM indicates that a high proportion of malaria cases is missed, underestimating the true prevalence of malaria in the community. Higher NPV of PfHRP-2/pLDH RDT than LM can give a straightforward exclusion of malaria among febrile patients, helping to avoid unnecessary presumptive treatments.

Status of the use and compliance with malaria rapid diagnostic tests in formal private health facilities in Nigeria

Background

Nigeria has the largest number of malaria-related deaths, accounting for a third of global malaria deaths. It is important that the country attains universal coverage of key malaria interventions, one of which is the policy of universal testing before treatment, which the country has recently adopted. However, there is a dearth of data on its implementation in formal private health facilities, where close to a third of the population seek health care. This study identified the level of use of malaria rapid diagnostic testing (RDT), compliance with test results and associated challenges in the formal private health facilities in Nigeria.

Methods

A cross-sectional study that involved a multi-stage, random sampling of 240 formal private health facilities from the country’s six geo-political zones was conducted from July to August 2014. Data were collected using health facility records, healthcare workers’ interviews and an exit survey of febrile patients seen at the facilities, in order to determine fever prevalence, level of testing of febrile patience, compliance with test results, and health workers’ perceptions to RDT use.

Results

Data from the 201 health facilities analysed indicated a fever prevalence of 38.5 % (112,521/292,430). Of the 2077 exit interviews for febrile patients, malaria testing was ordered in 73.8 % (95 % CI 71.7–75.7 %). Among the 1270 tested, 61.8 % (719/1270) were tested with microscopy and 38.2 % (445/1270) with RDT. Compliance to malaria test result [administering arteminisin-based combination therapy (ACT) to positive patients and withholding ACT from negative patients] was 80.9 % (95 % CI 78.7–83 %). Compliance was not influenced by the age of patients or type of malaria test. The health facilities have various cadres of the health workers knowledgeable on RDT with 70 % knowing the meaning, while 84.5 % knew what it assesses. However, there was clearly a preference for microscopy as only 20 % reported performing only RDT.

Conclusion

In formal private health facilities in Nigeria there is a high rate of malaria testing for febrile patients, high level of compliance with test results but relatively low level of RDT utilization. This calls for improved engagement of the formal private health sector with a view to achieving universal coverage targets on malaria testing.

Genetic variation of pfhrp2 in Plasmodium falciparum isolates from Yemen and the performance of HRP2-based malaria rapid diagnostic test

Background

The genetic variation in the Plasmodium falciparum histidine-rich protein 2 (pfhrp2) gene that may compromise the use of pfhrp2-based rapid diagnostic tests (RDTs) for the diagnosis of malaria was assessed in P. falciparum isolates from Yemen.

Methods

This study was conducted in Hodeidah and Al-Mahwit governorates, Yemen. A total of 622 individuals with fever were examined for malaria by CareStart™ malaria HRP2-RDT and Giemsa-stained thin and thick blood films. The Pfhrp2 gene was amplified and sequenced from 180 isolates, and subjected to amino acid repeat types analysis.

Results

A total of 188 (30.2 %) participants were found positive for P. falciparum by the RDT. Overall, 12 different amino acid repeat types were identified in Yemeni isolates. Six repeat types were detected in all the isolates (100 %) namely types 1, 2, 6, 7, 10 and 12 while types 9 and 11 were not detected in any of the isolates. Moreover, the sensitivity and specificity of the used PfHRP2-based RDTs were high (90.5 % and 96.1 %, respectively).

Conclusion

The present study provides data on the genetic variation within the pfhrp2 gene, and its potential impact on the PfHRP2-based RDTs commonly used in Yemen. CareStart™ Malaria HRP2-based RDT showed high sensitivity and specificity in endemic areas of Yemen.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1008-x) contains supplementary material, which is available to authorized users.

Rapid diagnostic tests for diagnosing uncomplicated non-falciparum or Plasmodium vivax malaria in endemic countries

BACKGROUND

In settings where both Plasmodium vivax and Plasmodium falciparum infection cause malaria, rapid diagnostic tests (RDTs) need to distinguish which species is causing the patients' symptoms, as different treatments are required. Older RDTs incorporated two test lines to distinguish malaria due to P. falciparum, from malaria due to any other Plasmodium species (non-falciparum). These RDTs can be classified according to which antibodies they use: Type 2 RDTs use HRP-2 (for P. falciparum) and aldolase (all species); Type 3 RDTs use HRP-2 (for P. falciparum) and pLDH (all species); Type 4 use pLDH (fromP. falciparum) and pLDH (all species).More recently, RDTs have been developed to distinguish P. vivax parasitaemia by utilizing a pLDH antibody specific to P. vivax.

OBJECTIVES

To assess the diagnostic accuracy of RDTs for detecting non-falciparum or P. vivax parasitaemia in people living in malaria-endemic areas who present to ambulatory healthcare facilities with symptoms suggestive of malaria, and to identify which types and brands of commercial test best detect non-falciparum and P. vivax malaria.

SEARCH METHODS

We undertook a comprehensive search of the following databases up to 31 December 2013: Cochrane Infectious Diseases Group Specialized Register; MEDLINE; EMBASE; MEDION; Science Citation Index; Web of Knowledge; African Index Medicus; LILACS; and IndMED.

SELECTION CRITERIA

Studies comparing RDTs with a reference standard (microscopy or polymerase chain reaction) in blood samples from a random or consecutive series of patients attending ambulatory health facilities with symptoms suggestive of malaria in non-falciparum endemic areas.

DATA COLLECTION AND ANALYSIS

For each study, two review authors independently extracted a standard set of data using a tailored data extraction form. We grouped comparisons by type of RDT (defined by the combinations of antibodies used), and combined in meta-analysis where appropriate. Average sensitivities and specificities are presented alongside 95% confidence intervals (95% CI).

MAIN RESULTS

We included 47 studies enrolling 22,862 participants. Patient characteristics, sampling methods and reference standard methods were poorly reported in most studies. RDTs detecting 'non-falciparum' parasitaemiaEleven studies evaluated Type 2 tests compared with microscopy, 25 evaluated Type 3 tests, and 11 evaluated Type 4 tests. In meta-analyses, average sensitivities and specificities were 78% (95% CI 73% to 82%) and 99% (95% CI 97% to 99%) for Type 2 tests, 78% (95% CI 69% to 84%) and 99% (95% CI 98% to 99%) for Type 3 tests, and 89% (95% CI 79% to 95%) and 98% (95% CI 97% to 99%) for Type 4 tests, respectively. Type 4 tests were more sensitive than both Type 2 (P = 0.01) and Type 3 tests (P = 0.03).Five studies compared Type 3 tests with PCR; in meta-analysis, the average sensitivity and specificity were 81% (95% CI 72% to 88%) and 99% (95% CI 97% to 99%) respectively. RDTs detecting P.vivax parasitaemiaEight studies compared pLDH tests to microscopy; the average sensitivity and specificity were 95% (95% CI 86% to 99%) and 99% (95% CI 99% to 100%), respectively.

AUTHORS' CONCLUSIONS

RDTs designed to detect P. vivax specifically, whether alone or as part of a mixed infection, appear to be more accurate than older tests designed to distinguish P. falciparum malaria from non-falciparum malaria. Compared to microscopy, these tests fail to detect around 5% ofP. vivax cases. This Cochrane Review, in combination with other published information about in vitro test performance and stability in the field, can assist policy-makers to choose between the available RDTs.

Early phase clinical trials with human immunodeficiency virus-1 and malaria vectored vaccines in The Gambia: frontline challenges in study design and implementation

Human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) and malaria are among the most important infectious diseases in developing countries. Existing control strategies are unlikely to curtail these diseases in the absence of efficacious vaccines. Testing of HIV and malaria vaccines candidates start with early phase trials that are increasingly being conducted in developing countries where the burden of the diseases is high. Unique challenges, which affect planning and implementation of vaccine trials according to internationally accepted standards have thus been identified. In this review, we highlight specific challenges encountered during two early phase trials of novel HIV-1 and malaria vectored vaccine candidates conducted in The Gambia and how some of these issues were pragmatically addressed. We hope our experience will be useful for key study personnel involved in day-to-day running of similar clinical trials. It may also guide future design and implementation of vaccine trials in resource-constrained settings.

Use of a three-band HRP2/pLDH combination rapid diagnostic test increases diagnostic specificity for falciparum malaria in Ugandan children

BACKGROUND

Rapid diagnostic tests (RDTs) for malaria provide a practical alternative to light microscopy for malaria diagnosis in resource-limited settings. Three-band RDTs incorporating two parasite antigens may have enhanced diagnostic specificity, relative to two-band RDTs with a single parasite antigen (typically histidine-rich protein 2 [HRP2]).

METHODS

Phase 1: 2,000 children, two months to five years of age, admitted to a referral hospital in Jinja, Uganda, with acute febrile illness were enrolled. A WHO highly rated three-band RDT was compared to light microscopy of thick peripheral blood films read by local expert microscopists.Phase 2: the three-band RDT was used as a screening tool for inclusion of patients in a clinical trial, and subjects with three positive RDT bands were tested by microscopy using blood samples drawn in parallel. Discordant results were adjudicated by PCR.

RESULTS

Phase 1: 1,648 children had both a RDT and peripheral blood smear performed. The specificity of a RDT with all three bands positive was 82% (95% CI: 79-85%) compared to 62% (95% CI: 59-66%) for HRP2 alone. The sensitivity was 88% (95% CI: 85-89%) and 94% (95% CI: 92-95%) for three-band positive RDT and HRP2 antigen, respectively. 119 patients (7.2%) had a positive HRP2 band, but negative parasite lactate dehydrogenase (pLHD) band and negative peripheral smear, and 72 (61%) of these had received pre-treatment with anti-malarials, suggesting a false positive HRP2 result (p = 0.002).Phase 2: the positive predictive value (PPV) of the three-band RDT was 94% (95% CI 89%-97%) using microscopy as the reference standard. However, microscopy-discordant results were shown to be positive for P. falciparum by PCR in all cases, suggesting that the PPV was in fact higher.

CONCLUSION

The pLDH antigen on three-band RDTs, used in combination with HRP2, provides added diagnostic specificity for malaria parasitaemia and may be useful to distinguish acute infection from recently treated infection. In situations where diagnostic specificity is desirable (e.g., for selection of malaria-infected participants in clinical trials), a three-band RDT should be considered in a sub-Saharan African setting.