Paracheck Pf Research Articles

No evidence of false-negative Plasmodium falciparum rapid diagnostic results in Monrovia, Liberia

BackgroundMalaria diagnosis in many malaria-endemic countries relies mainly on the use of rapid diagnostic tests (RDTs). The majority of commercial RDTs used in Africa detect the Plasmodium falciparum histidine-rich protein 2 (PfHRP2). pfhrp2/3 gene deletions can therefore lead to false-negative RDT results. This study aimed to evaluate the frequency of PCR-confirmed, false-negative P. falciparum RDT results in Monrovia, Liberia.MethodsPfHRP2-based RDT (Paracheck Pf®) and microscopy results from 1038 individuals with fever or history of fever (n = 951) and pregnant women at first antenatal care (ANC) visit (n = 87) enrolled in the Saint Joseph’s Catholic Hospital (Monrovia) from March to July 2019 were used to assess the frequency of false-negative RDT results. True–false negatives were confirmed by detecting the presence of P. falciparum DNA by quantitative PCR in samples from individuals with discrepant RDT and microscopy results. Samples that were positive by 18S rRNA qPCR but negative by PfHRP2-RDT were subjected to multiplex qPCR assay for detection of pfhrp2 and pfhrp3.ResultsOne-hundred and eighty-six (19.6%) and 200 (21.0%) of the 951 febrile participants had a P. falciparum-positive result by RDT and microscopy, respectively. Positivity rate increased with age and the reporting of joint pain, chills and shivers, vomiting and weakness, and decreased with the presence of coughs and nausea. The positivity rate at first ANC visit was 5.7% (n = 5) and 8% (n = 7) by RDT and microscopy, respectively. Out of 207 Plasmodium infections detected by microscopy, 22 (11%) were negative by RDT. qPCR confirmed absence of P. falciparum DNA in the 16 RDT-negative but microscopy-positive samples which were available for molecular testing. Among the 14 samples that were positive by qPCR but negative by RDT and microscopy, 3 only amplified pfldh, and among these 3 all were positive for pfhrp2 and pfhrp3.ConclusionThere is no qPCR-confirmed evidence of false-negative RDT results due to pfhrp2/pfhrp3 deletions in this study conducted in Monrovia (Liberia). This indicates that these deletions are not expected to affect the performance of PfHRP2-based RDTs for the diagnosis of malaria in Liberia. Nevertheless, active surveillance for the emergence of PfHRP2 deletions is required.

Detecting Plasmodium falciparum in community surveys: a comparison of Paracheck Pf\xae Test and ICT Malaria Pf\xae Cassette Test to polymerase chain reaction in Mutasa District, Zimbabwe

BackgroundMicroscopy and rapid diagnostic tests (RDTs) are the main techniques used to diagnose malaria. While microscopy is considered the gold standard, RDTs have established popularity as they allow for rapid diagnosis with minimal technical skills. This study aimed to compare the diagnostic performance of two Plasmodium falciparum histidine-rich protein 2 (PfHRP2)-based RDTs (Paracheck Pf® Test (Paracheck) and Malaria Pf™ ICT (ICT)) to polymerase chain reaction (PCR) in a community survey.MethodsA cross-sectional study was conducted between October 2012 and December 2014 in Mutasa District, Manicaland Province, eastern Zimbabwe. Households were randomly selected using satellite imagery, and 224 households were visited. Residents present in the household on the date of the visit were recruited for the study. Participants of all age groups from the selected households were screened with Paracheck and ICT RDTs in parallel. Dried blood spots (DBS) and thin and thick smears were collected. Parasite DNA extracted from the DBS was subjected to nested PCR targeting the Plasmodium cytochrome b mitochondrial gene. Data analysis was performed using the Cohen’s Kappa test to determine the interrater agreement and the sensitivity and specificity of the diagnostic test were reported.ResultsResults from a total of 702 participants were analysed. Most were females, 397 (57%), and the median age of participants was 21 years with an interquartile range of 9–39 years. Of those who were screened, 8 (1.1%), 35 (5.0%), and 21 (2.9%) were malaria parasite positive by microscopy, RDT and PCR, respectively. Paracheck and ICT RDTs had a 100% agreement. Comparing RDT and PCR results, 34 participants (4.8%) had discordant results. Most of the discordant cases were RDT positive but PCR negative (n = 24). Half of those RDT positive, but PCR negative individuals reported anti-malarials to use in the past month, which is significantly higher than reported anti-malarial drug use in the population (p < 0.001). The participant was febrile on the day of the visit, but relying on PfHRP2-based RDT would miss this case. Among the diagnostic methods evaluated, with reference to PCR, the sensitivity was higher with the RDT (52.4%) while specificity was higher with the microscopy (99.9%). The positive predictive value (PPV) was higher with the microscopy (87.5%), while the negative predictive values were similar for both microscopy and RDTs (98%). Overall, a strong correlated agreement with PCR was observed for the microscopy (97.9%) and the RDTs (95.2%).ConclusionsParacheck and ICT RDTs showed 100% agreement and can be used interchangeably. As malaria transmission declines and Zimbabwe aims to reach malaria elimination, management of infected individuals with low parasitaemia as well as non-P. falciparum infection can be critical.

The correlation between malaria RDT (Paracheck pf.\xae) faint test bands and microscopy in the diagnosis of malaria in Malawi

BackgroundFaint test bands of Paracheck Pf.® are interpreted as malaria positive according to world health organization (WHO) guideline. However if there are conspicuous number of faint test bands, a performance of Paracheck Pf.® could be influenced depending on whether interpreting faint test bands as malaria positive or negative. Finding out the frequency and accurate interpretation of faint test bands are important to prevent the overdiagnosis and drug resistance.MethodsA cross-sectional, descriptive study was conducted to find out the frequency of faint test bands and evaluate the performance of Paracheck Pf.® by sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of diagnosis of Paracheck Pf.® using microscopy as the gold standard. 388 suspected patients with malaria in Malawi were recruited in this study. Malaria rapid diagnostic tests (RDTs) and microscopy were used and patients’ information which includes age, sex, body temperature and signs or symptoms of malaria were recorded.ResultsAmong all patients involved in the study, 29.1% (113/388) were found malaria positive by RDT. Overall 5.4% (21/388) of all Paracheck Pf.® tests resulted in a “faint test band” and 85.7% (18/21) corresponded with malaria negative by microscopy. Faint test bands which corresponded with malaria positive by microscopy were lower parasite density and there are no patients who showed definitive symptom of malaria, such as fever. When Paracheck Pf.® “faint test bands” were classified as positive, accuracy of diagnosis was 76.5% (95% CI 72%–80.7%) as compared to 80.4% (95% CI 76.1%–84.2%) when Paracheck Pf.® “faint test bands” were classified as negative.ConclusionsThis study shows that frequency of faint test bands is 5.4% in all malaria RDTs. The accuracy of diagnosis was improved when faint test bands were interpreted as malaria negative. However information and data obtained in this study may not be enough and more intensive research including a frequency and property of faint test bands is needed for significant interpretation of faint test bands.

Frequency and correlates of malaria overdiagnosis and treatment in western Kenya

Abstract Background Despite decreasing malaria burden in sub-Saharan Africa, fever in children is frequently attributed to malaria and empirically treated with antimalarial drugs. The 2010 WHO guidelines recommend laboratory confirmation of malaria before initiating therapy, but the uptake of these guidelines is slow. We determined frequency and predictors of malaria overtreatment in febrile children at two western Kenya rural hospitals in regions with varied malaria endemicity. Methods We enrolled consecutive febrile children aged 6 months to 15 years presenting to Kisii Provincial (malaria endemicity: hypoendemic) or Homa Bay District (malaria endemicity: holoendemic) hospitals between March, 2012, and November, 2013. Detailed demographic, clinical, and laboratory data were collected, including physician diagnosis at admission and corresponding treatments. All children were screened for HIV with antibody or PCR testing, for malaria using smear microscopy and Paracheck Pf rapid diagnostic tests, and for invasive bacterial infections using blood culture. We determined the frequency of clinician-prescribed antimalarial treatment among those with negative smear and rapid diagnostic test results and evaluated independent predictors of overtreatment using multivariate logistic regression. Because the sites had marked differences in underlying malaria endemicities that might impact clinician suspicion of parasitaemia, analyses were stratified and compared by site. Findings Among the 1362 children enrolled (685 in Kisii and 677 in Homa Bay), 46 (6·7%) and 310 (45·8%) had laboratory-confirmed malaria in Kisii and Homa Bay, respectively (p vs gold-standard laboratory-based diagnosis) was lower in Kisii than in Homa Bay (73·0% vs 95·3%, p vs 33·7%, p Interpretation Malaria was treated, despite negative laboratory testing, more frequently in Homa Bay than in Kisii, probably owing to underlying higher malaria prevalence. Despite availability of diagnostic testing, malaria prevalence appears to influence the clinical management of children in Kenya and may result in missed opportunities to accurately diagnose alternative causes of fever. Strengthening health system use and adherence to existing treatment guidelines appears necessary, particularly in areas of high malaria endemicity. Funding US National Institutes of Health.

Rational case management of malaria with a rapid diagnostic test, Paracheck Pf®, in antenatal health care in Bangui, Central African Republic

BackgroundBoth treatment and prevention strategies are recommended by the World Health Organization for the control of malaria during pregnancy in tropical areas. The aim of this study was to assess use of a rapid diagnostic test for prompt management of malaria in pregnancy in Bangui, Central African Republic.MethodsA cohort of 76 pregnant women was screened systematically for malaria with ParacheckPf® at each antenatal visit. The usefulness of the method was analysed by comparing the number of malaria episodes requiring treatment in the cohort with the number of prescriptions received by another group of pregnant women followed-up in routine antenatal care.ResultsIn the cohort group, the proportion of positive ParacheckPf® episodes during antenatal clinics visits was 13.8%, while episodes of antimalarial prescriptions in the group which was followed-up routinely by antenatal personnel was estimated at 26.3%. Hence, the relative risk of the cohort for being prescribed an antimalarial drug was 0.53. Therefore, the attributable fraction of presumptive treatment avoided by systematic screening with ParacheckPf® was 47%.ConclusionsUse of a rapid diagnostic test is useful, affordable and easy for adequate treatment of malaria in pregnant women. More powerful studies of the usefulness of introducing the test into antenatal care are needed in all heath centres in the country and in other tropical areas.

Reliability of rapid diagnostic tests in diagnosing pregnancy-associated malaria in north-eastern Tanzania

BackgroundAccurate diagnosis and prompt treatment of pregnancy-associated malaria (PAM) are key aspects in averting adverse pregnancy outcomes. Microscopy is the gold standard in malaria diagnosis, but it has limited detection and availability. When used appropriately, rapid diagnostic tests (RDTs) could be an ideal diagnostic complement to microscopy, due to their ease of use and adequate sensitivity in detecting even sub-microscopic infections. Polymerase chain reaction (PCR) is even more sensitive, but it is mainly used for research purposes. The accuracy and reliability of RDTs in diagnosing PAM was evaluated using microscopy and PCR.MethodsA cohort of pregnant women in north-eastern Tanzania was followed throughout pregnancy for detection of plasmodial infection using venous and placental blood samples evaluated by histidine rich protein 2 (HRP-2) and parasite lactate dehydrogenase (pLDH) based RDTs (Parascreen™) or HRP-2 only (Paracheck Pf® and ParaHIT®f), microscopy and nested Plasmodium species diagnostic PCR.ResultsFrom a cohort of 924 pregnant women who completed the follow up, complete RDT and microscopy data was available for 5,555 blood samples and of these 442 samples were analysed by PCR. Of the 5,555 blood samples, 49 ((proportion and 95% confidence interval) 0.9% [0.7 -1.1]) samples were positive by microscopy and 91 (1.6% [1.3-2.0]) by RDT. Forty-six (50.5% [40.5 - 60.6]) and 45 (49.5% [39.4 – 59.5]) of the RDT positive samples were positive and negative by microscopy, respectively, whereas nineteen (42.2% [29.0 - 56.7]) of the microscopy negative, but RDT positive, samples were positive by PCR. Three (0.05% [0.02 - 0.2]) samples were positive by microscopy but negative by RDT. 351 of the 5,461 samples negative by both RDT and microscopy were tested by PCR and found negative. There was no statistically significant difference between the performances of the different RDTs.ConclusionsMicroscopy underestimated the real burden of malaria during pregnancy and RDTs performed better than microscopy in diagnosing PAM. In areas where intermittent preventive treatment during pregnancy may be abandoned due to low and decreasing malaria risk and instead replaced with active case management, screening with RDT is likely to identify most infections in pregnant women and out-performs microscopy as a diagnostic tool.

Comparison of Paracheck Pf® test with conventional light microscopy for the diagnosis of malaria in Ethiopia

Objective To assess the accuracy of Paracheck Pf® in reference to the conventional light microscopy. Methods A total of 400 patients visiting Awash, Methara and Ziway malaria centers were simultaneously screened with both light microscopy and Paracheck Pf® for the presence of Plasmodium falciparum ( P. falciparum) malaria. Results Of the 190 samples that were negative by light microscope, the Paracheck Pf® showed 11 false positive and 179 true negative results, and from a total of 210 samples positive by light microscope, Paracheck Pf® accurately diagnosed 200 true malaria cases. Taking the light microscopy as a standard test for malaria, the sensitivity, specificity, positive predictive value and negative predictive value of Paracheck Pf® is 95.2% [cofidence interval (CI)=92.4–97.1], 94.2% (CI=91.1–96.3), 94.8% (CI=92.0–96.7) and 94.7% (CI=91.6–96.8), respectively. Conclusions Paracheck Pf® showed good sensitivity and specificity for the diagnosis of P. falciparum malaria, and fulfill the world health organization (WHO) recommendation that requires the sensitivity of rapid diagnostic tests (RDTs) to be greater than 95%. Therefore, Paracheck Pf® can be used as an alternative to the Giemsa stain light microscopy in resource poor set ups.

Performance of a Histidine-Rich Protein 2 Rapid Diagnostic Test, Paracheck Pf®, for Detection of Malaria Infections in Ugandan Pregnant Women

Improved laboratory diagnosis is critical to reduce the burden of malaria in pregnancy. Peripheral blood smears appear less sensitive than Plasmodium falciparum histidine-rich protein 2-based rapid diagnostic tests (RDTs) for placental malaria infections in studies conducted at delivery. In this study, 81 women in Uganda in the second or third trimester of pregnancy were followed-up until delivery. At each visit, peripheral blood was tested by blood smear, RDT, and nested species-specific polymerase chain reaction (PCR). Sensitivity and specificity of the tests was calculated with PCR, which detected 22 infections of P. falciparum, as the gold standard. The sensitivity and specificity of blood smears were 36.4% (95% confidence interval [CI] = 18.0-59.2%) and 99.6% (95% CI = 97.7-100%), respectively. The corresponding values for RDT were 31.8% (95% CI = 14.7-54.9%) and 100% (95% CI = 98.3-100%). The RDTs could replace blood smears for diagnosis of malaria in pregnancy by virtue of their relative ease of use. Field-based sensitive tests for malaria in pregnancy are urgently needed.

Reducing malaria misdiagnosis: the importance of correctly interpreting Paracheck Pf®"faint test bands" in a low transmission area of Tanzania

BackgroundAlthough malaria rapid diagnostic tests (RDTs) have been extensively evaluated since their introduction in the early 1990's, sensitivity and specificity vary widely limiting successful integration into clinical practice. This paper reviews specific issues surrounding RDT use in field settings and presents results of research investigating how to interpret "faint test bands" on ParaCheck Pf® in areas of low transmission in order to reduce malaria misdiagnosis.MethodsA multi-phase cross-sectional study was conducted at a remote hospital in the northern Tanzanian highlands. Capillary blood samples were taken from consenting participants (n = 319) for blood smear and ParaCheck Pf® testing. Primary outcome variables were sensitivity, specificity and proportion misdiagnosed by ParaCheck Pf® and local microscopy. ParaCheck Pf® "faint bands" were classified as both true positives or true negatives during evaluation to determine appropriate clinical interpretation. Multivariate logistic regression adjusted for age and gender was conducted to determine odds of misdiagnosis for local microscopy and ParaCheck Pf®.ResultsOverall, 23.71% of all ParaCheck Pf® tests resulted in a "faint band" and 94.20% corresponded with true negatives. When ParaCheck Pf® "faint bands" were classified as positive, specificity was 75.5% (95% CI = 70.3% - 80.6%) as compared to 98.9% (95% CI = 97.0% - 99.8%) when classified as negative. The odds of misdiagnosis by local microscopy for those > 5 years as compared to those ≤ 5 years are 0.370 (95% CI = 0.1733 - 0.7915, p = 0.010). In contrast, even when ParaCheck Pf® faint bands are considered positive, the odds of misdiagnosis by ParaCheck Pf® for those > 5 years as compared to those ≤ 5 years are 0.837 (95% CI = 0.459 - 1.547, p = 0.5383).ConclusionsWe provide compelling evidence that in areas of low transmission, "faint bands" should be considered a negative test when used to inform clinical decision-making. Correct interpretation of RDT test bands in a clinical setting plays a central role in successful malaria surveillance, appropriate patient management and most importantly reducing misdiagnosis.

Detection of malaria in relation to fever and grade of malnutrition among malnourished children in Ethiopia.

Forty-eight nutritional rehabilitation centres in southern Ethiopia. To determine 1) the frequency of temperature recording under programme conditions, 2) the proportion of malnourished children with and without fever who had falciparum malaria and 3) the association between malaria and grade of malnutrition. This was a retrospective analysis of routine programme data. Of 19 200 malnourished children, 16 716 (mean age 4.4 years, 7412 males) underwent a rapid malaria diagnostic test (Paracheck Pf (®)). Malnutrition was graded as severe (38%), moderate (35%) and mild (27%). Temperature was not recorded in 15 248 (91%) children. Malaria was diagnosed in 57 (28%) children with fever (n = 206) and 122 (10%) children with no fever (n = 1262). The prevalence of falciparum malaria was 9%. Malaria prevalence was significantly associated with grade of malnutrition: Paracheck Pf was positive in respectively 5%, 8% and 10% of children with mild, moderate and severe malnutrition (χ(2) for trend 78, P < 0.001). This study shows the value of routine malaria screening in malnourished children, especially those with more severe grades of malnutrition, irrespective of fever. Operational shortcomings are highlighted and ways forward to address these problems are discussed.

Diagnosis of malaria parasitemia in children using a rapid diagnostic test

This cross-sectional study was conducted to evaluate the diagnostic performance of a new rapid immunochromatographic test named "Paracheck pf" in the diagnosis of malaria in Nigerian children. A total of 380 Nigerian children aged between 6 and 59 months who presented at the University of Nigeria Teaching Hospital (UNTH) Enugu with fever and no obvious focus of any other infection were consecutively recruited. Malaria parasitemia was determined using simple microscopy and "Paracheck pf". "Paracheck pf" has the following diagnostic performance characteristics: Sensitivity of 82%, specificity of 91.5%, negative predictive value of 91.5%, positive predictive value of 82%, a strong positive correlation between parasite density and test sensitivity, and a detection limit of 397 parasites/μl. The test is, therefore, recommended for the use in Nigerian children aged between 6 and 59 months in Enugu for the diagnosis of malaria, but negative results should be cautiously interpreted in infants because symptomatic malaria may occur in these children at parasite densities as low as 100/μl.

Cost-effectiveness of three malaria treatment strategies in rural Tigray, Ethiopia where both Plasmodium falciparum and Plasmodium vivax co-dominate

BackgroundMalaria transmission in Ethiopia is unstable and the disease is a major public health problem. Both, p.falciparum (60%) and p.vivax (40%) co-dominantly exist. The national guideline recommends three different diagnosis and treatment strategies at health post level: i) the use of a p.falciparum/vivax specific RDT as diagnosis tool and to treat with artemether-lumefantrine (AL), chloroquine (CQ) or referral if the patient was diagnosed with p.falciparum, p.vivax or no malaria, respectively (parascreen pan/pf based strategy); ii) the use of a p.falciparum specific RDT and AL for p.falciparum cases and CQ for the rest (paracheck pf based strategy); and iii) the use of AL for all cases diagnosed presumptively as malaria (presumptive based strategy). This study aimed to assess the cost-effectiveness of the recommended three diagnosis and treatment strategies in the Tigray region of Ethiopia.MethodsThe study was conducted under a routine health service delivery following the national malaria diagnosis and treatment guideline. Every suspected malaria case, who presented to a health extension worker either at a village or health post, was included. Costing, from the provider's perspective, only included diagnosis and antimalarial drugs. Effectiveness was measured by the number of correctly treated cases (CTC) and average and incremental cost-effectiveness calculated. One-way and two-way sensitivity analyses were conducted for selected parameters.ResultsIn total 2,422 subjects and 35 health posts were enrolled in the study. The average cost-effectiveness ratio showed that the parascreen pan/pf based strategy was more cost-effective (US$1.69/CTC) than both the paracheck pf (US$4.66/CTC) and the presumptive (US$11.08/CTC) based strategies. The incremental cost for the parascreen pan/pf based strategy was US$0.59/CTC to manage 65% more cases. The sensitivity analysis also confirmed parascreen pan/pf based strategy as the most cost-effective.ConclusionThis study showed that the parascreen pan/pf based strategy should be the preferred option to be used at health post level in rural Tigray. This finding is relevant nationwide as the entire country's malaria epidemiology is similar to the study area.

Performance of HRP-2 based rapid diagnostic test for malaria and its variation with age in an area of intense malaria transmission in southern tanzania

BackgroundThe use of malaria rapid diagnostic tests (RDTs) has been widely advocated to improve Plasmodium falciparum diagnosis, especially in settings where quality microscopy is not available. RDTs based on the detection of histidine-rich protein 2 (HRP-2) can remain positive for several weeks after an infection is cured, due to the persistence of HRP-2 antigens. As a result, test specificity may vary between age groups with different prevalence of P. falciparum infection.MethodsA community-based cross-sectional survey, carried out in southern Tanzania in July and August 2004, evaluated the performance of the Paracheck Pf in comparison with microscopy (number of P. falciparum parasites/200 leucocytes). A sample of 598 individuals living in an area of intense malaria transmission had demographic data collected before an RDT was performed. HRP-2 test sensitivity, specificity, positive and negative predictive values were calculated and compared between distinct age groups, using microscopy as "gold standard".ResultsThe overall malaria prevalence was 34.3% according to microscopy and 57.2% according to the HRP-2 test. The HRP-2 test had a sensitivity of 96.1%, a specificity of 63.1%, a positive predictive value of 57.6% and a negative predictive value of 96.9%. The test sensitivity was higher (ranging from 98% to 100%) amongst people less than 25 years of age, but decreased to 81.3% in older adults. The HRP-2 test specificity varied between age groups, ranging from 25% among children of five to nine years of age, to 73% among adults aged 25 or more. The test positive predictive value increased with malaria prevalence, while the negative predictive value was consistently high across age groups.ConclusionsThese results suggest that the performance of HRP-2 tests in areas of intense malaria transmission varies by age and the prevalence of P. falciparum infection. The particularly low specificity among children will lead to the over-estimation of malaria infection prevalence in this group.

Comparison of Parascreen Pan/Pf, Paracheck Pf and light microscopy for detection of malaria among febrile patients, Northwest Ethiopia

Two malaria rapid diagnostic tests (RDT), Parascreen Pan/Pf ® and Paracheck Pf ®, were tested in rural health centres in Ethiopia against independent expert microscopy (the gold standard). Participants ( n =1997) presented with presumptive malaria to ten health centers in Amhara Regional State during the 2007 peak malaria season (October to December). By microscopy, 475 (23.8%) suspected malaria cases were positive, of which 57.7% were P. falciparum; 24.6% P. vivax and 17.7% mixed infections. Parascreen and Paracheck were positive for 442 (22.1%) and 277 (13.9%) febrile patients, respectively. For Parascreen, P. falciparum sensitivity was 79.6%, specificity 97.4%, positive predictive value (PPV) 86.9%, and negative predictive value (NPV) 95.6%. For Parascreen, P. vivax sensitivity was 74.4%, specificity 98.6%, PPV 76.3% and NPV 98.4%. For Paracheck, P. falciparum sensitivity was 73.7%, specificity 99.2%, PPV 95.3%, NPV 94.5%. Sensitivity was significantly higher for both tests ( P < 0.05) when parasite density was >100/μl of blood; in these cases Parascreen was 90.7% and 91.5% sensitive for P. falciparum and P. vivax, respectively, while Paracheck was 87.9% sensitive for P. falciparum. Parascreen thus performed adequately for both P. falciparum and P. vivax compared to expert microscopy and is more useful than Paracheck where microscopy is unavailable.

Evaluation of the performance of CareStart™ Malaria Pf/ Pv Combo and Paracheck Pf ® tests for the diagnosis of malaria in Wondo Genet, southern Ethiopia

Objective To evaluate the diagnostic performance of CareStart™ Malaria Pf/Pv Combo test relative to microscopy for the diagnosis of falciparum and vivax malaria in Ethiopia. Methods 668 febrile patients visiting two health centers in Wondo Genet, southern Ethiopia, involved in this study in 2008. Giemsa-stained thin and thick blood smears were prepared and microscopically examined under a 100× oil immersion microscope objective for Plasmodium species identification and determination of parasitaemia, respectively. CareStart™ Malaria Pf/Pv Combo test and Paracheck Pf ® test were performed as per the manufacturers’ instruction. Findings The diagnostic validity of CareStart™ Malaria Pf/Pv Combo test for the diagnosis of Plasmodium falciparum were very good with sensitivity of 99.4%, specificity of 98%, positive predictive value of 94.4% and negative predictive value of 99.8%. Sensitivity, specificity, positive predictive value and negative predictive value of the test for the diagnosis of P. vivax were 99.4%, 98.2%, 94.5% and 99.8%, respectively. The diagnostic performance of CareStart™ Malaria Pf/Pv Combo test is comparable to that of Paracheck Pf ® test for the diagnosis of P. falciparum (sensitivity 99.4%, specificity 98.2%). Conclusion Although CareStart™ Malaria Pf/Pv Combo test and Paracheck Pf ® test have comparable diagnostic performance for the diagnosis of P. falciparum, CareStart™ Malaria Pf/Pv Combo test has the added advantage of diagnosing P. vivax. Hence, it is preferable to use CareStart™ Malaria Pf/Pv Combo test for the diagnosis of malaria in areas where microscopy is not accessible and where malaria due to P. falciparum and P. vivax are co-endemic as in Ethiopia.

Highly Sensitive Amperometric Immunosensor for Detection of Plasmodium falciparum Histidine-Rich Protein 2 in Serum of Humans with Malaria: Comparison with a Commercial Kit

A disposable amperometric immunosensor was developed for the detection of Plasmodium falciparum histidine-rich protein 2 (PfHRP-2) in the sera of humans with P. falciparum malaria. For this purpose, disposable screen-printed electrodes (SPEs) were modified with multiwall carbon nanotubes (MWCNTs) and Au nanoparticles. The electrodes were characterized by cyclic voltammetry, scanning electron microscopy, and Raman spectroscopy. In order to study the immunosensing performances of modified electrodes, a rabbit anti-PfHRP-2 antibody (as the capturing antibody) was first immobilized on an electrode. Further, the electrode was exposed to a mouse anti-PfHRP-2 antibody from a serum sample (as the revealing antibody), followed by a rabbit anti-mouse immunoglobulin G-alkaline phosphatase conjugate. The immunosensing experiments were performed on bare SPEs, MWCNT-modified SPEs, and Au nanoparticle- and MWCNT-modified SPEs (Nano-Au/MWCNT/SPEs) for the amperometric detection of PfHRP-2 in a solution of 0.1 M diethanolamine buffer, pH 9.8, by applying a potential of 450 mV at the working electrode. Nano-Au/MWCNT/SPEs yielded the highest-level immunosensing performance among the electrodes, with a detection limit of 8 ng/ml. The analytical results of immunosensing experiments with human serum samples were compared with the results of a commercial Paracheck Pf test, as well as the results of microscopy. The specificities, sensitivities, and positive and negative predictive values of the Paracheck Pf and amperometric immunosensors were calculated by taking the microscopy results as the "gold standard." The Paracheck Pf kit exhibited a sensitivity of 79% (detecting 34 of 43 positive samples; 95% confidence interval [CI], 75 to 86%) and a specificity of 81% (correctly identifying 57 of 70 negative samples; 95% CI, 76 to 92%), whereas the developed amperometric immunosensor showed a sensitivity of 96% (detecting 41 of 43 positive samples; 95% CI, 93 to 98%) and a specificity of 94% (correctly identifying 66 of 70 negative samples; 95% CI, 92 to 99%). The developed method is more sensitive and specific than the Paracheck Pf kit.

Paracheck Pf® compared with microscopy for diagnosis of &lt;i&gt;Plasmodium falciparum&lt;/i&gt; malaria among children in Tanga City, north-eastern Tanzania

Malaria is a major public health problem particularly in rural Sub-Saharan Africa. In most urban areas, malaria transmission intensity is low thus monitoring trends using reliable tools is crucial to provide vital information for future management of the disease. Rapid diagnostic tests (RDT) such as Paracheck Pf are now increasingly adopted for Plasmodium falciparum malaria diagnosis and are advantageous and cost effective alternative to microscopy. This cross sectional survey was carried out during June 2005 to determine the prevalence of malaria in an urban setting and compare microscopy diagnosis versus Paracheck Pf for detecting Plasmodium falciparum. Blood samples from a total of 301 children (< 10 years) attending outpatient clinic at Makorora Health Centre, in Tanga, Tanzania were examined for the presence of malaria. Twenty-nine (9.6%) of the children were positive to malaria by microscopy while 30 (10.0%) were positive by Paracheck test. Three out of 30 positive cases detected by Paracheck were negative by microscopy; thus considered to be false positive results. For the 271 Paracheck Pf negative cases, 2 were positive by microscopy; yielding 2 false negative results. Paracheck Pf sensitivity and specificity were 93.1% and 98.9%, respectively. P. falciparum was the only malarial species observed among the 29 microscopy positive cases. The prevalence of anaemia among the children was 53.16%. These findings indicate a low prevalence of malaria in Tanga City and that Paracheck Pf can be an effective tool for malaria diagnosis.

Paracheck-Pf® accuracy and recently treated Plasmodium falciparum infections: is there a risk of over-diagnosis?

BackgroundAn assessment of the accuracy of Paracheck Pf®, a malaria rapid diagnostic test (RDT) detecting histidine rich protein 2 was undertaken amongst children aged 6–59 months in eastern Democratic Republic of Congo.MethodsThis RDT assessment occurred in conjunction with an ACT efficacy trial. Febrile children were simultaneously screened with both RDT and high quality microscopy and those meeting inclusion criteria were followed for 35 days.Results358 febrile children were screened with 180 children recruited for five weeks follow-up. On screening, the RDT accurately diagnosed all 235 true malaria cases, indicating 100% RDT sensitivity. Of the 123 negative slides, the RDT gave 59 false-positive results, indicating 52.0% (64/123) RDT specificity. During follow-up after treatment with an artemisinin-based combination therapy, 98.2% (110/112), 94.6% (106/112), 92.0% (103/112) and 73.5% (50/68) of effectively treated children were still false-positive by RDT at days 14, 21, 28 and 35, respectively.ConclusionResults show that though the use of Paracheck-Pf® is as sensitive as microscopy in detecting true malaria cases, a low specificity did present a high frequency of false-positive RDT results. What's more, a duration of RDT false-positivity was found that significantly surpassed the 'fortnight' after effective treatment reported by its manufacturer. Though further research is needed in assessing RDT accuracy, study results showing the presence of frequent false positivity should be taken into consideration to avoid clinicians inappropriately focusing on malaria, not identifying the true cause of illness, and providing unnecessary treatment.

Malaria on the move: Ecological considerations for the armed forces

Background: Armed forces personnel deployed in the North Eastern states of India are vulnerable to falciparum malaria. This vulnerability increases during mobilization of troops. Methods: Epidemiological case sheet was used for recording individual movement, clinical features and laboratory investigations of each case of malaria. Immunochromotography test (ICT) or Paracheck Pf was used as a rapid test for falciparum malaria at the regimental aid post (RAP). Subsequently, a case control approach was used to ascertain whether the cases of malaria differed significantly from healthy controls in observing antimalaria measures such as the use of mosquito nets, repellants and chemoprophylaxis. Result: Nineteen out of 623 soldiers suffered from falciparum malaria during a short period of ten days during operational mobilization. Use of mosquito nets and repellants was significantly less among the cases as compared to healthy controls. There was no significant difference among the two groups regarding compliance with chemoprophylaxis. Conclusion: A paradigm of “malaria on the move” or “operational malaria” has been proposed.

EVALUATION OF DIFFERENT METHODS FOR DIAGNOSIS OF P. FALCIPARUM MALARIA

Rapid diagnosis is a prerequisite for institution of effective treatment and reducing the mortality and morbidity of falciparum malaria. This study was taken up to compare the efficacy of various rapid methods viz, acridine orange, Plasmodium falciparum histidine rich protein II antigen detection and Field’s stain with traditional microscopy i.e., Leishman stain for diagnosing falciparum malaria. Thick and thin blood films of 443 consecutive patients with history of fever with chills and rigors were examined by Leishman and Field’s method. Acridine orange stained wet mounts of blood were examined under fluorescence microscopy. All films were examined by two independent microbiologists. Plasmodium falciparum histidine rich protein II antigen was detected using commercially available kit, Paracheck Pf. Out of the 443 subjects examined for P.falciparum 18.28% were detected by Leishman stain, 6.32% by Field’s stain, 18.28% by acridine orange and 18.1% by antigen based technique. Field’s stain missed 53 (65.4%), while Paracheck Pf was negative in 6(7.4%) of the Leishman positive samples. All Field’s stain and acridine orange positives were positive by Leishman, but five Paracheck Pf positives were negative. Leishman stain is cost effective but if facilities are available one should use acridine orange for screening. The antigen detection kits are rapid, simple and are useful but to rule out false negatives in clinically suspected cases, Leishman stain is reliable.