Salivary Immunoassay Diagnoses Dengue Fever

An antigen capture technique has been used to test the saliva of febrile patients for the presence of dengue virus (DENV) antibodies.

This assay, which detects the specific immunoglobulin A (IgA) of DENV in salivary samples, has been evaluated in the early phases of a dengue infection.

Scientists at the Environmental Health Institute, Singapore National Environment Agency (Singapore, Singapore) have developed an antigen capture anti-DENV IgA (ACA) enzyme-linked immunosorbent assay (ELISA) technique for the diagnosis of dengue fever. They collected 69 saliva samples from dengue-confirmed patients at three time points, using Oracol saliva collection swabs (Malvern Medical Development Ltd., Barbourne UK). Blood samples were collected at the same time.

The ACA-ELISA on saliva had an overall sensitivity of 70% in the first three days after fever onset and subsequently rose to over 90% between the third day and eighth day following fever onset. The same technique on sera gave similar results. The sensitivity of ACA-ELISA in saliva was higher than that of the PanBio immunoglobulin M (IgM) Capture ELISA (Alere Inc., Waltham, MA, USA), on sera. The IgM assay detected only 10% of the dengue-confirmed patients after one to three days of fever, and only rose to around 90% after six days of fever. The specificity of the ACA-ELISA test was also found to be high at 97%. Among the 75 DENV-negative control patients, only one patient tested positive, at day seven and day 27, respectively.

The investigators noted that the saliva assay eliminates the need to collect blood from dengue-suspected patients and is painless, nonintrusive, and reduces the risk of needle stick injury. Moreover, the ELISA-based technique is simple and cost effective. Patients, especially the very young and the old, will be more willing to undergo a dengue test. Together, these benefits can potentially improve surveillance and early detection of cases, which in turn can translate to prompt dengue control effort. Due to its high sensitivity among secondary dengue infections, this technique could be very useful in highly endemic areas where the majority of the dengue cases are secondary. Dengue fever is the most common identifiable cause of acute febrile illness among travelers returning from South America, South Central Asia, Southeast Asia, and the Caribbean. The study was published online on May 10, 2011, in the Public Library of Science (PLoS) journal Neglected Tropical Diseases.

Related Links:
Singapore National Environment Agency
Malvern Medical Development Ltd.
Alere Inc.