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Effects of the UK Biobank collection protocol on potential biomarkers in saliva.

BACKGROUND
The UK Biobank (UKB) is a national epidemiological study of the health of 500 000 people, aged 40-69 years, who completed health-related tests and a questionnaire and gave samples of blood and urine. Salivas collected from 120 000 of these subjects were transported at 4°C and were placed in ultra-low temperature archives at up to 24 h after collection. The present study assessed how changes in saliva composition under UKB conditions influence a range of potential biomarkers resulting from holding saliva at 4°C for 24 h.


METHODS
Unstimulated whole-mouth saliva samples were collected from 23 volunteers aged 45-69 years. Salivas were split into aliquots some of which were immediately frozen at -80°C, whereas others were stored at 4°C for 24 h and then frozen at -80°C, mimicking the UKB protocol.


RESULTS
Assessment of mRNA by real-time polymerase chain reaction revealed no difference between samples that were analysed after the UKB protocol and those that were immediately preserved. Immunochemical analysis showed some loss of β-Actin under UKB conditions, whereas other salivary proteins including cytokines and C-reactive protein appeared to be unaffected. Cortisol and showed no reduction by UKB conditions, but salivary nitrite was reduced by 30%. The oral microbiome, as revealed by sequencing 16S rRNA genes, showed variations between subjects, but paired samples within subjects were very similar.


CONCLUSIONS
Our results suggest that many salivary components remain little affected under UKB collection and handling protocols, suggesting that the resource of 120 000 samples held in storage will be useful for phenotyping subjects and revealing potential prognostic disease biomarkers.