Supplementary molecular saliva testing improves detection of respiratory viruses
Testing both expectorated saliva and nasopharyngeal aspirates (NPAs) can substantially improve the detection of respiratory viruses as compared with testing of NPA alone, although the viral load is lower in the saliva than in the NPA for most patients, according to a study.
The study included 258 hospitalized adult patients with suspected respiratory infections. Expectorated saliva was collected without using any special devices. On the other hand, antigen detection by direct immunofluorescence assay (DFA) was used in the routine testing for respiratory including influenza A, influenza B, parainfluenza viruses 1 to 3, respiratory syncytial virus, human metapneumovirus (hMPV) and adenovirus.
In the first group of 159 patients, NPAs tested positive for respiratory viruses. When the viral load was measured using quantitative reverse transcription PCR, 27 patients (17 percent) were found to have higher viral loads in the saliva than in the NPA.
In the second group of 99 patients, the NPAs tested negative for respiratory viruses. Additional testing of NPA and saliva specimens were performed using multiplex PCR. The concordance rate between NPA and saliva was found to be 83.8 percent. Multiplex PCR detected viruses in saliva samples from 16 patients, accounting for nine patients (56.3 percent) who had at least one virus unable to be detected in the NPA.
Of note, potential changes in the antiviral treatment or infection control practice could have occurred in six of the nine patients with additional viruses detected in their saliva. “The three patients with influenza A virus infection could have been given neuraminidase inhibitor, whereas the three patients with hMPV should have been placed under contact precaution,” researchers said.
In addition to NPA, nasopharyngeal swabs and nasal or throat swabs/washes are considered to have the highest detection rate for respiratory viruses and are thus the recommended upper respiratory tract specimen types for diagnostic testing of respiratory viruses, they noted.
On the other hand, saliva can be easily provided by patients without the use of complex, invasive procedures. However, saliva is rarely used for the detection of respiratory viruses as the specimen is generally considered to have inferior sensitivity vs other respiratory tract specimens, they continued.
Given the finding that supplementary molecular testing of saliva can improve the detection of respiratory viruses, researchers recommended collection of saliva specimens from patients with a suspected respiratory virus infection but a negative test for respiratory viruses.
“Furthermore, saliva should be evaluated as the specimen type in a diagnostic testing for novel respiratory viruses. This approach will ultimately lead to improvement in the management of patients and the prevention of community or nosocomial spread of infections,” researchers said.