The reliability of saliva as a sample for the detection of hepatitis A immunoglobulins under various sampling conditions

Background: Saliva is increasingly being investigated as an alternative to serum for diagnostic and epidemiological testing even though antibody levels are substantially lower in buccal cavity fluids. However, there has been little study on whether buccal cavity activity and/or the timing of saliva sampling affects the diagnostic outcome, particularly in seropositive subjects. The absence of influence by these factors may be critical to the use of saliva for pre-vaccination screening for example.

Objectives: The effects of eating, brushing of teeth and circadian rhythm on the measureable salivary immune status of 42 healthy individuals known to be serum and saliva anti-HAV positive were examined.

Study design: A total of 141 saliva samples obtained from the 42 healthy subjects, before and after meals, before and after brushing of teeth and at various timepoints throughout the day, were assayed for total anti-HAV using an in-house saliva based enzyme-immunoassay, previously shown to have a 100% correlation in terms of sensitivity and specificity with a serum based assay.

Results: The results indicated that total anti-HAV titres varied according to the time of day and that eating had no significant effect on the total anti-HAV titre, but brushing of teeth did. Titres never varied to the extent that a result was falsely negative at any timepoint.

Conclusion: These results confirm the usefulness of saliva as a diagnostic sample for the detection of hepatitis A antibody, regardless of sampling times, eating or tooth-brushing.