Rapid PCR Immunoassay Developed for Malaria Diagnosis

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The test, which combines PCR with a nucleic acid lateral flow immunoassay (PCR-NALFIA) for amplicon detection, was thoroughly evaluated for the analytical sensitivity and specificity in the laboratory, the robustness, and reproducibility in a ring trial and accuracy and predictive value in a field trial.

Investigators at the Royal Tropical Institute (Amsterdam, The Netherlands) developed a PCR-NALFIA and tested its validity by analyzing 241 malaria positive and negative samples from travelers returning from malaria-endemic areas and samples provided by the Dutch blood bank considered negative for malaria. Also tested was a blood sample from Sudanese patients with a confirmed P. falciparum infection. Accuracy was evaluated in Thailand and compared to expert microscopy and rapid diagnostic tests (RDTs). A nitrocellulose membrane of 120 mm (Millipore, Amsterdam, The Netherlands) was used for the preparation of the NALFIA.

The analytical sensitivity and specificity were very high, but were slightly less sensitive for the detection of P. vivax than for P. falciparum. The reproducibility tested in three laboratories was very good, though this evaluation showed that the PCR machine used could influence the results. In the field trial in Thailand, the overall and P. falciparum-specific sensitivity and specificity was good ranging from 0.86-1 and 0.95-0.98 respectively, compared to microscopy. P. vivax detection was better than the sensitivity of RDT, but slightly less than microscopy performed in this study.

The authors concluded that the assay in its current format, or slightly modified with more sensitive detection of P. vivax, could be an excellent tool for epidemiological studies on prevalence or distribution of parasites. In addition, it could be used as a screening tool at regional level for malaria control programs, especially in countries with declining transmission. Molecular tools have been shown to be especially valuable in areas where there is moderate to little transmission and PCR-NALFIA could be a usable simple method in these settings. The study was published on August 17, 2012, in the Malaria Journal.

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