• Evaluation of three parasite lactate dehydrogenase-based rapid diagnostic tests for the diagnosis of falciparum and vivax malaria

      Ashley, Elizabeth A; Touabi, Malek; Ahrer, Margareta; Hutagalung, Robert; Htun, Khayae; Luchavez, Jennifer; Dureza, Christine; Proux, Stephane; Leimanis, Mara; Lwin, Myo Min; Koscalova, Alena; Comte, Eric; Hamade, Prudence; Page, Anne-Laure; Nosten, François; Guerin, Philippe J; Epicentre, Paris, France; Department of Microbiology, Hammersmith Hospital, Imperial College NHS Trust, London, UK; Médecins sans Frontières, Switzerland; Médecins sans Frontières, Myanmar; Research Institute for Tropical Medicine, Alabang, Muntinlupa City, Philippines; Shoklo Malaria Research Unit, Mae Sot, Thailand; Mahidol-Oxford Tropical Medicine Research Unit (MORU), Mahidol University, Bangkok, Thailand; Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, UK; Médecins sans Frontières Malaria Working Group, UK; Malaria Consortium, London, UK (2009-10-27)
      BACKGROUND: In areas where non-falciparum malaria is common rapid diagnostic tests (RDTs) capable of distinguishing malaria species reliably are needed. Such tests are often based on the detection of parasite lactate dehydrogenase (pLDH). METHODS: In Dawei, southern Myanmar, three pLDH based RDTs (CareStart Malaria pLDH (Pan), CareStart Malaria pLDH (Pan, Pf) and OptiMAL-IT)were evaluated in patients presenting with clinically suspected malaria. Each RDT was read independently by two readers. A subset of patients with microscopically confirmed malaria had their RDTs repeated on days 2, 7 and then weekly until negative. At the end of the study, samples of study batches were sent for heat stability testing. RESULTS: Between August and November 2007, 1004 patients aged between 1 and 93 years were enrolled in the study. Slide microscopy (the reference standard) diagnosed 213 Plasmodium vivax (Pv) monoinfections, 98 Plasmodium falciparum (Pf) mono-infections and no malaria in 650 cases. The sensitivities (sens) and specificities (spec), of the RDTs for the detection of malaria were- CareStart Malaria pLDH (Pan) test: sens 89.1% [CI95 84.2-92.6], spec 97.6% [CI95 96.5-98.4]. OptiMal-IT: Pf+/- other species detection: sens 95.2% [CI95 87.5-98.2], spec 94.7% [CI95 93.3-95.8]; non-Pf detection alone: sens 89.6% [CI95 83.6-93.6], spec 96.5% [CI95 94.8-97.7]. CareStart Malaria pLDH (Pan, Pf): Pf+/- other species: sens 93.5% [CI95 85.4-97.3], spec 97.4% [95.9-98.3]; non-Pf: sens 78.5% [CI95 71.1-84.4], spec 97.8% [CI95 96.3-98.7]. Inter-observer agreement was excellent for all tests (kappa > 0.9). The median time for the RDTs to become negative was two days for the CareStart Malaria tests and seven days for OptiMAL-IT. Tests were heat stable up to 90 days except for OptiMAL-IT (Pf specific pLDH stable to day 20 at 35 degrees C). CONCLUSION: None of the pLDH-based RDTs evaluated was able to detect non-falciparum malaria with high sensitivity, particularly at low parasitaemias. OptiMAL-IT performed best overall and would perform best in an area of high malaria prevalence among screened fever cases. However, heat stability was unacceptable and the number of steps to perform this test is a significant drawback in the field. A reliable, heat-stable, highly sensitive RDT, capable of diagnosing all Plasmodium species has yet to be identified.
    • Evaluation of Three Rapid Tests for Diagnosis of P. Falciparum and P. Vivax Malaria in Colombia.

      van den Broek, I; Hill, O; Gordillo, F; Angarita, B; Hamade, P; Counihan, H; Guthmann, J P; Médecins sans Frontières (MSF), London, UK. ingrid_vandenbroek@yahoo.com (2006-12)
      The diagnostic capacity of three malaria rapid diagnostic tests (RDTs), NOW-Malaria-ICT, OptiMAL-IT, and Paracheck-Pf, was evaluated against expert microscopy in Colombia. We tested 896 patients, of whom microscopy confirmed 139 P. falciparum, 279 P. vivax, and 13 mixed P.f/P.v infections and 465 negatives. Paracheck-Pf and NOW-malaria-ICT were more accurate in detecting P. falciparum (sensitivities 90.8% and 90.1%, respectively) in comparison with Optimal-IT (83.6%). NOW showed an acceptable Pf detection rate at low densities (< 500/microL), but resulted in a higher proportion of false positives. For P. vivax diagnosis, Optimal-IT had a higher sensitivity than NOW (91.0% and 81.4%, respectively). The choice between the two Pf/Pv detecting RDTs balances P. falciparum and P. vivax detection rates. Considering some degree of P. falciparum overtreatment and failure to detect all P. vivax cases as more acceptable than missing some cases of P. falciparum, we recommend careful implementation of NOW-malaria-ICT in areas where microscopy is lacking. The price is however still a constraint.
    • Plasmodium vivax resistance to chloroquine in Dawei, southern Myanmar.

      Guthmann, J P; Pittet, A; Lesage, A; Imwong, M; Lindegardh, N; Min Lwin, M; Zaw, T; Annerberg, A; de Radiguès, X; Nosten, F; Epicentre, Paris, France. (Wiley-Blackwell, 2008-01)
      OBJECTIVE: To assess the efficacy of chloroquine in the treatment of Plasmodium vivax malaria in in Dawei District, southern Myanmar. METHODS: Enrolled patients at Sonsinphya clinic >6 months of age were assessed clinically and parasitologically every week for 28 days. To differentiate new infections from recrudescence, we genotyped pre- and post-treatment parasitaemia. Blood chloroquine was measured to confirm resistant strains. RESULTS: Between December 2002 and April 2003, 2661 patients were screened, of whom 252 were included and 235 analysed. Thirty-four per cent (95% CI: 28.1-40.6) of patients had recurrent parasitaemia and were considered treatment failures. 59.4% of these recurrences were with a different parasite strain. Two (0.8%) patients with recurrences on day 14 had chloroquine concentrations above the threshold of 100 ng/ml and were considered infected with chloroquine resistant parasites. 21% of failures occurred during the first 3 weeks of follow-up: early recurrence and median levels of blood chloroquine comparable to those of controls suggested P. vivax resistance. CONCLUSIONS: Plasmodium vivax resistance to chloroquine seems to be emerging in Dawei, near the Thai-Burmese border. While chloroquine remains the first-line drug for P. vivax infections in this area of Myanmar, regular monitoring is needed to detect further development of parasite resistance.
    • Relapses of Plasmodium vivax infection usually result from activation of heterologous hypnozoites.

      Imwong, M; Snounou, G; Pukrittayakamee, S; Tanomsing, N; Kim, J R; Nandy, A; Guthmann, J P; Nosten, F; Carlton, J; Looareesuwan, S; Nair, S; Sudimack, D; Day, N P J; Anderson, T J C; White, N J; Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. (Infectious Diseases Society of America and University of Chicago Press, 2007-04-01)
      BACKGROUND: Relapses originating from hypnozoites are characteristic of Plasmodium vivax infections. Thus, reappearance of parasitemia after treatment can result from relapse, recrudescence, or reinfection. It has been assumed that parasites causing relapse would be a subset of the parasites that caused the primary infection. METHODS: Paired samples were collected before initiation of antimalarial treatment and at recurrence of parasitemia from 149 patients with vivax malaria in Thailand (n=36), where reinfection could be excluded, and during field studies in Myanmar (n=75) and India (n=38). RESULTS: Combined genetic data from 2 genotyping approaches showed that novel P. vivax populations were present in the majority of patients with recurrent infection (107 [72%] of 149 patients overall [78% of patients in Thailand, 75% of patients in Myanmar {Burma}, and 63% of patients in India]). In 61% of the Thai and Burmese patients and in 55% of the Indian patients, the recurrent infections contained none of the parasite genotypes that caused the acute infection. CONCLUSIONS: The P. vivax populations emerging from hypnozoites commonly differ from the populations that caused the acute episode. Activation of heterologous hypnozoite populations is the most common cause of first relapse in patients with vivax malaria.