Background

Rapid diagnostic tests (RDTs) for Plasmodium falciparum malaria use antibodies to detect either HRP-2 antigen or pLDH antigen, and can improve access to diagnostics in developing countries.

Objectives

To assess the diagnostic accuracy of RDTs for detecting P. falciparum parasitaemia in persons living in endemic areas who present to ambulatory healthcare facilities with symptoms suggestive of malaria by type and brand.

Search strategy

We undertook a comprehensive search of the following databases:Cochrane Infectious Diseases Group Specialized Register; MEDLINE; EMBASE; MEDION; Science Citation Index; Web of Knowledge; African Index Medicus; LILACS; IndMED; to January 14, 2010.

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 P. falciparum endemic areas.

Data collection and analysis

For each study, a standard set of data was extracted independently by two authors, using a tailored data extraction form. Comparisons were grouped hierarchically by target antigen, and type and brand of RDT, and combined in meta-analysis where appropriate.

Main results

We identified 74 unique studies as eligible for this review and categorized them according to the antigens they detected. Types 1 to 3 include HRP-2 (from P. falciparum) either by itself or with other antigens. Types 4 and 5 included pLDH (from P. falciparum) either by itself or with other antigens. In comparisons with microscopy, we identified 71 evaluations of Type 1 tests, eight evaluations of Type 2 tests and five evaluations of Type 3 tests. In meta-analyses, average sensitivities and specificities (95% CI) were 94.8% (93.1% to 96.1%) and 95.2% (93.2% to 96.7%) for Type 1 tests, 96.0% (94.0% to 97.3%) and 95.3% (87.3% to 98.3%) for Type 2 tests, and
99.5% (71.0% to 100.0%) and 90.6% (80.5% to 95.7%) for Type 3 tests, respectively.

Overall for HRP-2, the meta-analytical average sensitivity and specificity (95% CI) were 95.0% (93.5% to 96.2%) and 95.2% (93.4% to 99.4%), respectively.

For pLDH antibody-based RDTs verified with microscopy, we identified 17 evaluations of Type 4 RDTs and three evaluations of Type 5 RDTs. In meta-analyses, average sensitivity for Type 4 tests was 91.5% (84.7% to 95.3%) and average specificity was 98.7% (96.9% to 99.5%). For Type 5 tests, average sensitivity was 98.4% (95.1% to 99.5%) and average specificity was 97.5% (93.5% to 99.1%).

Overall for pLDH, the meta-analytical average sensitivity and specificity (95% CI) were 93.2% (88.0% to 96.2%) and 98.5% (96.7% to 99.4%), respectively.

For both categories of test, there was substantial heterogeneity in study results. Quality of the microscopy reference standard could only be assessed in 40% of studies due to inadequate reporting, but results did not seem to be influenced by the reporting quality.

Overall, HRP-2 antibody-based tests (such as the Type 1 tests) tended to be more sensitive and were significantly less specific than pLDH-based tests (such as the Type 4 tests). If the point estimates for Type 1 and Type 4 tests are applied to a hypothetical cohort of 1000 patients where 30% of those presenting with symptoms have P. falciparum, Type 1 tests will miss 16 cases, and Type 4 tests will miss 26 cases. The number of people wrongly diagnosed with P. falciparum would be 34 with Type 1 tests, and nine with Type 4 tests.

Authors’ conclusions

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.

Rapid diagnostic tests for diagnosing uncomplicated P. falciparum 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' parasitaemia

Eleven 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 parasitaemia

Eight 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.

/pdf/rapid-diagnostic-tests-for-diagnosing-uncomplicated-non-2ao8rxpm00.pdf

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

Malaria is a leading cause of mortality in southern Benin. The main causative agent, Plasmodium falciparum, poses a threat on critical transfusions in pregnant women and children. This study’s objective was to compare the performance of different malaria screening methods in blood donors in southern Benin, a malaria-endemic country. Blood from 2,515 voluntary blood donors in Benin was collected over a period of 10 months in ethylenediaminetetraacetic acid (EDTA) tubes, which were then classified according to extraction time: long rainy season, short dry season, short rainy season, and long dry season. Microscopic examination was used to count parasites. Parasite density (PD) was expressed as the number of parasites per μL of blood. Pan Plasmodium pLDH detection was assessed by an ELISA-malaria antigen test. Using crude soluble P. falciparum antigens, an ELISA-malaria antibody test detected anti-Plasmodium antibodies. Among the 2,515 blood donors (2,025 males and 488 females) screened, the rate of asymptomatic Plasmodium carriage was 295/2,515 (11.72%, 95% CI: 10.5-13.1%). Males had a higher infection rate (12.4%) than did females (8.8%). Parasite density was very low: between seven and100 parasites per μL of blood was reported in 80% of donors with parasitaemia. Three Plasmodium species were diagnosed: P. falciparum in 280/295 patients (95.0%), Plasmodium malariae in 14/295 (5.0%), and Plasmodium ovale in 1/295 (0.34%). Malaria prevalence in donors was higher during the rainy seasons (13.7%) compared with the dry seasons (9.9%). The use of a highly sensitive assay enabled pan Plasmodium pLDH detection in 966/2,515 (38.4%, 95% CI: 36.5%-40.3%). Malaria antibody prevalence was 1,859/2,515 (73.9%, 95% CI: 72.16-75.6%). Donors’ antigenaemia and antibody levels varied significantly (P <0.05) over the course of the four seasons. The highest antigenaemia rate 323/630 (51.3%), was observed during the short rainy season, while the highest antibody prevalence, 751/886 (84.7%), was recorded during the long dry season. Blood donations infected with Plasmodium can transmit malaria to donation recipients. Malaria diagnostic methods are currently available, but the feasibility criteria for mass screening in endemic areas become preponderant. Detection of the pLDH antigen seems to be an adequate screening tool in endemic areas, for this antigen indicates parasite presence. Routine screening of all donated blood would prevent infected blood donations and reduce P. falciparum transmission in critical patients, such as children and pregnant women. This tool would also decrease medical prophylaxis in donation recipients and contribute to lower Plasmodium resistance.

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Is a Plasmodium lactate dehydrogenase (pLDH) enzyme-linked immunosorbent (ELISA)-based assay a valid tool for detecting risky malaria blood donations in Africa?

Background
In 2006, the Senegalese National Malaria Control Programme (NMCP) has recommended artemisinin-based combination therapy (ACT) as the first-line treatment for uncomplicated malaria and, in 2007, mandated testing for all suspected cases of malaria with a Plasmodium falciparum HRP-2-based rapid diagnostic test for malaria (RDT(Paracheck®). Given the higher cost of ACT compared to earlier anti-malarials, the objectives of the present study were i) to study the accuracy of Paracheck® compared to the thick blood smear (TBS) in two areas with different levels of malaria endemicity and ii) analyse the cost-effectiveness of the strategy of the parasitological confirmation of clinically suspected malaria cases management recommended by the NMCP.

/pdf/use-of-hrp-2-based-rapid-diagnostic-test-for-plasmodium-375bk24ayx.pdf

Use of HRP-2-based rapid diagnostic test for Plasmodium falciparum malaria: assessing accuracy and cost-effectiveness in the villages of Dielmo and Ndiop, Senegal

Objective To determine the frequency of Plasmodium (P.) vivax and P. falciparum in cases of acute febrile illness, and the haematological parameters in patients suffering with acute malaria. Study design An observational study. Place and duration of study Baqai Medical University, Fatima Hospital Laboratory, Karachi, from January 2006 to December 2007. Methodology Patients with acute febrile illness were evaluated. Complete blood count and malarial parasite were performed. Descriptive statistics of haematological parameters was computed. Mean and standard deviations (SD) were calculated; p-value was determined using test of proportions on SPSS. Results Out of 3344 patients, 392 (11.72%) were proved as suffering from malaria with male to female ratio of 1.36. The age ranged from 1 month to 94 years. One hundred and seventy six (42.6%) had P. falciparum, 204 (52%) had P. vivax, and 21 (5.4%) had mixed infection. Haemoglobin varied from 1.10 g/dl -17.10 g/dl, (mean 9.83 + 3.09 g/dl). TLC ranged from 1.30 x 103/ul - 48.50 x 103/ul, (mean 6.80 + 5.15 x 103/ul. The platelet counts ranged from 10.0 x 103/ul - 850 x 103/ul, (mean 106 + 90.98 x 103/ul). Thrombocytopenia was observed in 70%, platelet count was significantly lower in patients with mixed infection as compared to patients with P. falciparum and P. vivax (p=.017). Conclusion The frequency of malaria was 11.72%. Thrombocytopenia was the most common finding. In none of the patients platelet counts dropped below the critical levels of 10 x 103/microl.

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Haematological findings and endemicity of malaria in Gadap region.

Objective: To evaluate the sensitivity and specificity of immunochromatographic test (ICT) malaria p.f/p.v using microscopy as the gold standard diagnosis. Methods: Five hundred and sixty patients of both sexes and all age groups with clinical suspicion of malaria were studied. Venous blood was collected for microscopy and ICT. Thick and thin films prepared and stained with Leishman's stain were examined. ICT malaria test was performed and interpreted according to manufacturer's instructions. Data was analyzed using Epi-6. Results: A total of 560 cases were studied, 339 males and 221 females with age ranges between 2 to 73 years. Seventy two (12.85%) cases had parasitaemia (with or without sexual forms). On microscopy 65 (11.6%) cases had asexual-stage parasitaemia and 7 (1.25%) cases had P. falciparum gametocytes only. Thirty two cases were infected with P. falciparum, 29 with P. vivax and 4 had mixed infection. For P. falciparum the ICT was 97.0% sensitive, 98.3% specific, with positive predictive value (PPV) of 78.0% and a negative predictive value (NPV) of 99.8%. For P. vivax the sensitivity was only 89.7%, specificity 97.9%, PPV was 70.3% and NPV 99.4%. Conclusion: Our results are in concordance with previous studies. Rapid tests though expensive are simple to perform and effective diagnostic tools of malaria. They can be used selectively, though microscopy remains the gold standard diagnosis, economical and accurate if performed by skilled technologists (JPMA 56:167;2006).

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Role of ICT malaria immunochromatographic test for rapid diagnosis of malaria.

Results: A total of 56 patients were enrolled, 4 were excluded due to inadequate cytogenetic analysis and the remaining patients entered the study protocol. There were 32 males and 20 females with mean age of 31.3 years (range 9 months to 73 years). Thirty-five (67.3%) patients had normal karyotype while 17 (32.7%) were found to have cytogenetic abnormalities. Eleven patients did not receive treatment at our hospital. Half of the (51.2%) patients out of remaining 41 achieved complete remission on bone marrow examination after receiving induction chemotherapy. In favourable risk group 3/3 (100%) achieved complete remission (CR) while 15/32 (46.9%) in intermediate risk group and 3/6 (50%) in unfavourable risk group. There was low CR rate in patients with high white cell counts. Conclusion: The frequency of cytogenetic abnormalities in AML and response to induction chemotherapy was low when compared with international data possibly due to the small sample size. However, there was a clear difference in CR rates between favourable and unfavourable risk groups (JPMA 56:9;2006).

/pdf/significance-of-cytogenetic-abnormalities-in-acute-myeloid-4j0p0erin1.pdf

Significance of cytogenetic abnormalities in acute myeloid leukaemia.

/pdf/supplementation-of-probiotic-and-fibrolytic-enzymes-on-2wjvc1r5.pdf

Mahadev S. Harani

Papers

Role of ICT malaria immunochromatographic test for rapid diagnosis of malaria.

Significance of cytogenetic abnormalities in acute myeloid leukaemia.

"Supplementation of Probiotic and Fibrolytic Enzymes on Growth Performance and Nutrient Utilization in Crossbred Calves"