Rapid Malaria Diagnostic Test Evaluated in Asia

Rapid diagnostic tests (RDT) for malaria have been brought into field operations to supplement and in some cases replace the gold standard of light microscopy.

Although attempts have been made to augment or even replace microscopic diagnosis of malaria with enzyme-linked immunosorbent assays (ELISA), real time, and conventional polymerase chain reactions (PCR), these are not feasible in the field.

Scientists at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B; Dhaka, Bangladesh) collected whole blood samples from 372 febrile patients referred for malaria diagnosis by clinicians from May 2009 to December 2010. The samples were assayed by a newly available RDT and were compared to microscopy adjusted with nested PCR as the gold standard. DNA extraction for the PCR was prepared using QiaAmp blood mini-kit (Qiagen; Hilden, Germany) from preserved whole blood. Other PCR reagents were obtained from New England BioLabs Inc.; Ipswich, MA, USA).

The RDT device evaluated was the Onsite (Pf/Pan) RDT produced by CTK Biotech Inc. (San Diego, CA, USA) which has the ability to detect Pan-specific lactate dehydrogenase (pLDH) and Plasmodium falciparum specific histidine-rich protein 2 (HRP-2). Of these 372 patients, 229 (61.6%) tested positive for malaria infection detected by microscopy and nested PCR. The OnSite (Pf/Pan) RDT was 94.2% sensitive and 99.5% specific for P. falciparum diagnosis and 97.3% sensitive and 98.7% specific for P. vivax diagnosis. Sensitivity varied with differential parasite count for both malaria species. The highest sensitivity was observed in febrile patients with parasitemias that ranged from 501 to 1,000 parasites/µL regardless of the Plasmodium species.

The authors concluded that the OnSite (Pf/Pan) RDT, a lateral flow chromatographic immunoassay, performed satisfactorily in standard laboratory conditions. It can be utilized for diagnosis of symptomatic malaria as well as to discriminate falciparum malaria infection from vivax malaria in endemic areas and during outbreaks. However, a field evaluation is required to assess its applicability for routine diagnosis in resource-limited settings where the practicability of microscopy is limited. The study was published on December 12, 2012, in the Malaria Journal.

Related Links:
International Centre for Diarrheal Disease Research Bangladesh
Qiagen
New England BioLabs Inc.