Saliva Testing a Painless Alternative for Malaria Diagnosis

DEHLI (Reuters Health) – Diagnosis of malaria by polymerase chain reaction (PCR) testing of saliva is non-invasive and comparable to the current gold standard blood smear examination, a multicenter group of researchers reports.

A rapid test for malaria that has a high sensitivity and specificity “could potentially avert more than 100,000 malaria-related deaths each year and save nearly $200 million that is spent on unnecessary treatments annually,” Dr. Davis C. Nwakanma from the Medical Research Council, Fajara, Banjul, Gambia and his team and colleagues estimate.

Dr. Nwakanma and his team his team compared the diagnostic accuracy of nested and quantitative PCR testing of saliva, urine and blood with the gold standard blood smear microscopy in 386 Gambian out-patients with suspected malaria.

Saliva PCR for malaria returned a sensitivity and specificity of 73% and 97%, respectively, and a correlation of 0.58 with blood microscopy, the researchers report in the June1st issue of The Journal of Infectious Diseases. The correlation of blood and urine PCR for estimation of malarial parasite density was 0.94 and 0.20 as compared to the gold standard, they add.

“Presently, the saliva testing assay may be applied in malaria research but not for deciding the treatment options for patients because of sensitivity and time-to-assay-completion issues,” Dr. Nwakanma told Reuters Health.

“Saliva could be used for rapid testing, as a new generation of point of care DNA-based tests are currently being developed by several research groups, Dr. Colin Sutherland from the London School of Hygiene and Tropical Medicine, and author of a related editorial told Reuters Health. “However, some adaptation to the use of saliva as starting material in these tests would be needed, and it is uncertain how sensitive such tests would be.”

“Saliva sampling is a promising less-invasive approach,” the researchers conclude.

J Infect Dis 2009;199:1561-1563,1567-1574.