Overreliance on Plasmodium 18S rRNA gene for malaria molecular diagnosis-inferences from systematic review

Molecular diagnosis of malaria through nucleic acid-based amplification test is important to detect low-density, sub-microscopic and residual infections, as well as to prevent importations and re-establishment. Reliance on single/limited molecular targets could be detrimental as evidenced by false-negative PfHRP2-based RDTs, and the same may apply to PCR targets. No systematic exploration of the commonly used PCR targets has yet been documented.

A systematic search was made using a previously generated database through PubMed® and Google Scholar® and supplemented by additional searches. All studies that used PCR for detecting Plasmodium infections were included in this study. Further information was retrieved on molecular targets used and the type of PCR assay used. An independent search was also made to explore the identification/development of newer molecular targets.

Almost all studies (93%) used 18S rRNA gene as a molecular target. Nested PCR alone (68%) was the most frequently used assay. Eighty-five percent of the studies that exploited the 18S rRNA gene target and nested PCR used the approach developed in 1993.

Overreliance on a solitary molecular target (18S rRNA gene) for many years might be a cause for concern. Research is needed to validate newer multi-copy targets in terms of limit of detection, robust reproducibility, reduced costs, and a possibility of multiplexing.