Is serial testing required to diagnose imported malaria in the era of rapid diagnostic tests? Pasricha JM et al. Am J Trop Med Hyg 2013; 88: 20-23.
This timely clinical audit addresses a very practical issue: do we really need to go on repeating serial laboratory tests for malaria when the first test is negative?
- In a series of 388 case of malaria diagnosed between 1999 and 2010 in three Melbourne labs, only nine were detected after an initial negative blood film and rapid diagnostic test.
- Seven of these were due to Plasmodium vivax
- The majority had recently received antimalarial treatment.
The current recommendation is to obtain serial blood films over 48hr to reduce the risk of missing cyclical, low level or sequestered parasites. The increasing use of rapid diagnostic tests to exclude malaria has raised doubts about the need for serial testing. In the low-prevalence context of most Australian city hospitals, a shorter malaria screening protocol could have a big impact on patients waiting for usually negative results.
However, there is a potentially high cost of getting the screening procedure wrong and missing a P. falciparum infection before it progresses to complicated or severe malaria. Pasricha et al. interpret their data conservatively, noting that this is the first study of its kind, even if it was retrospective in design. Their recommendation is for larger, prospective studies to assess the safely to a shorter malaria screening serial. Surely this is a worthy goal for a national project?