Comparison of HRP2- and pLDH-based rapid diagnostic tests for malaria with longitudinal follow-up in Kampala, Uganda. The usefulness of a new rapid diagnostic test, the First Response Malaria Combo (pLDH/HRP2) card test, for malaria diagnosis in the forested belt of central India. Determinants of the accuracy of rapid diagnostic tests in malaria case management: evidence from low and moderate transmission settings in the East African highlands. Rapid diagnostic tests for malaria at sites of varying transmission intensity in Uganda. Relative utility of dipsticks for diagnosis of malaria in mesoendemic area for Plasmodium falciparum and P. vivax in northeastern India. Evaluation of two new immunochromatographic assays for diagnosis of malaria. Clinical trials of a new immunochromatographic test for diagnosis of Plasmodium falciparum malaria in Goa. Diagnostic performance of two antigen capture tests for the diagnosis of Plasmodium falciparum malaria in Zimbabwe. Field evaluation of the ICT malaria P.f/P.v immunochromatographic test for detection of Plasmodium falciparum and Plasmodium vivax in patients with a presumptive clinical diagnosis of malaria in eastern Indonesia.
Presumptive treatment of malaria results in significant overuse of antimalarials. Malaria rapid diagnostic tests (RDTs) may offer a reliable alternative for case management, but the optimal RDT strategy is uncertain. We compared the diagnostic accuracy of histidine-rich protein 2 (HRP2)- and plasmodium lactate dehydrogenase (pLDH)-based RDTs, using expert microscopy as the gold standard, in a longitudinal study of 918 fever episodes over an 8-month period in a cohort of children in Kampala, Uganda. Sensitivity was 92% for HRP2 and 85% for pLDH, with differences primarily due to better detection with HRP2 at low parasite densities. Specificity was 93% for HRP2 and 100% for pLDH, with differences primarily due to rapid clearance of pLDH antigenemia after treatment of a previous malaria episode. RDTs may provide an effective strategy for improving rational delivery of antimalarial therapy; in Kampala, either test could dramatically decrease inappropriate presumptive treatments. Malaria presents a diagnostic challenge in tribal belt of central India where two Plasmodium species, Plasmodium falciparum and Plasmodium vivax, are prevalent. In these areas, rapid detection of the malaria parasites and early treatment of infection remain the most important goals of disease management. Therefore, the usefulness of a new rapid diagnostic (RDT), the First Response(R) Combo Malaria Ag (pLDH/HRP2) card test was assessed for differential diagnosis between P. falciparum with other Plasmodium species in remote villages of Jabalpur district.
                A finger prick blood sample was collected to prepare blood smear and for testing with the RDT after taking informed consent. The figures for sensitivity, specificity, accuracy and predictive values were calculated using microscopy as gold standard.
                Analysis revealed that overall, the RDT was 93% sensitive, 85% specific with a positive predictive value (PPV) of 79%, and a negative predictive value (NPV) of 95%. The accuracy 88% and J-index was 0.74. For P. falciparum, the sensitivity and specificity of the test were 96% and 95% respectively, with a PPV of 85% and a NPV of 99%. The RDT accuracy 95% and J-index was 0.84. For non-falciparum malaria, the sensitivity, specificity and accuracy were 83%, 94% and 92% respectively with a PPV of 69% and a NPV of 97%.
                The RDTs are easy to use, reliable and simple to interpret. RDTs are more suited to health workers in situations where health services are deficient or absent. Therefore, the test can be used as an epidemiological tool for the rapid screening of malaria. The accuracy of malaria diagnosis has received renewed interest in recent years due to changes in treatment policies in favour of relatively high-cost artemisinin-based combination therapies. The use of rapid diagnostic tests (RDTs) based on histidine-rich protein 2 (HRP2) synthesized by Plasmodium falciparum has been widely advocated to save costs and to minimize inappropriate treatment of non-malarial febrile illnesses. HRP2-based RDTs are highly sensitive and stable; however, their specificity is a cause for concern, particularly in areas of intense malaria transmission due to persistence of HRP2 antigens from previous infections.
                In this study, 78,454 clinically diagnosed malaria patients were tested using HRP2-based RDTs over a period of approximately four years in four highland sites in Kenya and Uganda representing hypoendemic to mesoendemic settings. In addition, the utility of the tests was evaluated in comparison with expert microscopy for disease management in 2,241 subjects in two sites with different endemicity levels over four months.
                RDT positivity rates varied by season and year, indicating temporal changes in accuracy of clinical diagnosis. Compared to expert microscopy, the sensitivity, specificity, positive predictive value and negative predictive value of the RDTs in a hypoendemic site were 90.0%, 99.9%, 90.0% and 99.9%, respectively. Corresponding measures at a mesoendemic site were 91.0%, 65.0%, 71.6% and 88.1%. Although sensitivities at the two sites were broadly comparable, levels of specificity varied considerably between the sites as well as according to month of test, age of patient, and presence or absence of fever during consultation. Specificity was relatively high in older age groups and increased towards the end of the transmission season, indicating the role played by anti-HRP2 antibodies. Patients with high parasite densities were more likely to test positive with RDTs than those with low density infections.
                RDTs may be effective when used in low endemicity situations, but high false positive error rates may occur in areas with moderately high transmission. Reports on specificity of RDTs and cost-effectiveness analyses on their use should be interpreted with caution as there may be wide variations in these measurements depending upon endemicity, season and the age group of patients studied. In Africa, fever is often treated presumptively as malaria, resulting in misdiagnosis and the overuse of antimalarial drugs. Rapid diagnostic tests (RDTs) for malaria may allow improved fever management.
                We compared RDTs based on histidine-rich protein 2 (HRP2) and RDTs based on Plasmodium lactate dehydrogenase (pLDH) with expert microscopy and PCR-corrected microscopy for 7000 patients at sites of varying malaria transmission intensity across Uganda.
                When all sites were considered, the sensitivity of the HRP2-based test was 97% when compared with microscopy and 98% when corrected by PCR; the sensitivity of the pLDH-based test was 88% when compared with microscopy and 77% when corrected by PCR. The specificity of the HRP2-based test was 71% when compared with microscopy and 88% when corrected by PCR; the specificity of the pLDH-based test was 92% when compared with microscopy and >98% when corrected by PCR. Based on Plasmodium falciparum PCR-corrected microscopy, the positive predictive value (PPV) of the HRP2-based test was high (93%) at all but the site with the lowest transmission rate; the pLDH-based test and expert microscopy offered excellent PPVs (98%) for all sites. The negative predictive value (NPV) of the HRP2-based test was consistently high (>97%); in contrast, the NPV for the pLDH-based test dropped significantly (from 98% to 66%) as transmission intensity increased, and the NPV for expert microscopy decreased significantly (99% to 54%) because of increasing failure to detect subpatent parasitemia.
                Based on the high PPV and NPV, HRP2-based RDTs are likely to be the best diagnostic choice for areas with medium-to-high malaria transmission rates in Africa. For diagnosis of malaria, popular brands of rapid test kits collectively termed as "dipsticks" were subject to field evaluation in northeastern India for their comparative sensitivity and specificity vis-à-vis conventional microscopic results. Dipsticks based on Plasmodium falciparum-specific histidine-rich protein (Pf HRP-2) antigen capture assay revealed 100% sensitivity and high specificity (94-100%); thus, they were concluded to be reliable tools for confirmed diagnosis of malarial infection. However, an advanced version of the same kit, having incorporated additional pan-malarial monoclonal antibody, was found to be less sensitive (71%) for non-falciparum infections. Besides, Pf HRP-2-based kits continued to show positive results up to day 7, even after clearance of parasitemia on account of persistent antigenemia. This very limitation seemed to have been overcome by parasite-specific lactate dehydrogenase (pLDH) enzyme-based kit. This kit was observed to have high sensitivity (81-89%) and specificity (100%) for both falciparum and non-falciparum malaria, but cannot distinguish mono-infection from mixed infections. It is concluded that the rational use of these kits would accord health benefits in terms of early detection and prompt treatment, reduce drug pressure, and possibly delay the emergence and spread of multi-drug-resistant strains of malarial parasites. We assessed the performance of two new commercially available rapid diagnostic tests (RDTs) for malaria (SD Bioline Malaria Ag Pf test and Ag Pf/Pan test) in 200 patients with uncomplicated malaria between August and October 2007 in Madagascar. Results of the two RDTs were compared with those obtained by microscopy and real-time polymerase chain reaction. The sensitivity and specificity for detection of Plasmodium falciparum were 93% and 98.9%, respectively, for the SD Bioline Malaria Ag Pf test and 92.9% and 98.9% for the SD Bioline Malaria Ag Pf/Pan test. The sensitivity of the SD Bioline Malaria Ag Pf/Pan test was much lower for detection of other species (63.6%). The sensitivity of the two new assays decreased to 77.3% at parasitemia levels < 100 parasites/microL for detection of P. falciparum. Plasmodium falciparum histidine rich protein-2 (PfHRP-2) based immunochromatographic test kit (ICT Malaria Pf) for the rapid diagnosis of P. falciparum malaria was evaluated at the clinic of Malaria Research Centre (Field Station), Goa. Of the 98 febrile patients screened, 22 were ICT positive for P. falciparum. Simultaneous microscopic examination of the blood smears of these ICT positive patients showed that 20 were positive for P. falciparum alone, whereas one had mix infection of both P. vivax and P. falciparum suggesting 100% sensitivity. Only one slide negative patient who had taken 600 mg chloroquine the previous day was positive in the ICT. Out of the remaining 76 blood smears, 41 showed P. vivax infection and none cross-reacted with P. falciparum HRP-2 antigen and were ICT negative except one mix infection case in which P. vivax and P. falciparum infections occurred concomitantly suggesting species specificity of 98.7%. The positive predictive value, negative predictive value and efficacy of the ICT were 95.4, 100 and 98.9% respectively. The band intensity of the ICT positive cases significantly correlated with P. falciparum parasitaemia (p < 0.01). The usefulness and the disadvantages of this diagnostic kit have been discussed in context of prevailing malaria situation in the country. The objective was to compare the diagnostic performance of two antigen capture tests, ParaSight-F test and Immunochromatographic test (ICT), for the diagnosis of Plasmodium falciparum malaria.
                A comparative study.
                Burma Valley, Mutare District, Manicaland in Zimbabwe.
                Patients attending the local clinic with clinical signs and symptoms associated with malaria infection. A blood film was collected from the patient and at the same time blood for the ParaSight-F test and the ICT was collected too. A total of 123 patients were diagnosed using the ICT test, the ParaSight-F test and microscopy which was used as a "gold" standard.
                True positives and negatives, false positives and negatives with reference to microscopy.
                The results indicate that ICT had a higher sensitivity (100%) than the ParaSight-F test (93.94%) but showing a lower specificity. The specificity for ICT (75%) is lower than the ParaSight-F test (81.2%) because of the presence of circulating P. falciparum histidine-rich protein-2 (PfHRP-2) in blood even after two weeks post treatment. Two slides that were negative for ParaSight-F tests showed positive on microscopy. However, 21 and 12 slides which were negative on microscopy, showed positive with ICT and ParaSight-F respectively. The fact that ICT detects very low quantities of PfHRP-2 puts it at a comparative advantage because it detects positives even at very low parasite rates.
                The availability of these two antigen capture tests, which are easy to perform, will reduce the number of severe cases by providing early diagnosis. The tests will also reduce the number of unnecessary treatments and irrational use of antimalarials. In areas such as eastern Indonesia where both Plasmodium falciparum and Plasmodium vivax occur, rapid antigen detection tests for malaria need to be able to detect both species. We evaluated the new combined P. falciparum-P. vivax immunochromatographic test (ICT Malaria P.f/P.v.) in Radamata Primary Health Centre, Sumba, Indonesia, from February to May 1998 with 560 symptomatic adults and children with a presumptive clinical diagnosis of malaria. Blinded microscopy was used as the "gold standard," with all discordant and 20% of concordant results cross-checked blindly. Only 50% of those with a presumptive clinical diagnosis of malaria were parasitemic. The ICT Malaria P.f/P.v immunochromatographic test was sensitive (95. 5%) and specific (89.8%) for the diagnosis of falciparum malaria, with a positive predictive value (PPV) and a negative predictive value (NPV) of 88.1 and 96.2%, respectively. HRP2 and panmalarial antigen line intensities were associated with parasitemia density for both species. Although the specificity and NPV for the diagnosis of vivax malaria were 94.8 and 98.2%, respectively, the overall sensitivity (75%) and PPV (50%) for the diagnosis of vivax malaria were less than the desirable levels. The sensitivity for the diagnosis of P. vivax malaria was 96% with parasitemias of >500/microl but only 29% with parasitemias of <500/microl. Nevertheless, compared with the test with HRP2 alone, use of the combined antigen detection test would reduce the rate of undertreatment from 14.7 to 3.6% for microscopy-positive patients, and this would be at the expense of only a modest increase in the rate of overtreatment of microscopy-negative patients from 7.1 to 15. 4%. Cost remains a major obstacle to widespread use in areas of endemicity.
The sensitivity and specificity of all RDTs is such that they can replace or extend the access of diagnostic services for uncomplicated P. falciparum malaria. HRP-2 antibody types may be more sensitive but are less specific than pLDH antibody-based tests, but the differences are small. The HRP-2 antigen persists even after effective treatment and so is not useful for detecting treatment failures.