Inter-examiner reliability of salivary diagnostic tests in a practice-based research network

Patient salivary characteristics are being measured as part of the Northwest PRECEDENT (Practice-based REsearch Collaborative in Evidence-based DENTistry) study on caries risk assessment. Prior to the implementation of these salivary diagnostic tests in a practice-based cohort study, inter-examiner reliability was assessed for resting salivary pH, stimulated salivary flow rate, pH and buffering capacity.

An initial evaluation of inter-examiner reliability of the 4 salivary tests was conducted among 6 dental auxiliary examiners using a convenience sample of 40 dental students. An in complete block design was used to assign samples to examiners (3 examiners per sample and 20 samples per examiner). Inter-examiner reliability testing was conducted on a patient population representative of the practice-based network in 4 member practices. Two dental assistants per practice independently conducted the salivary tests on samples provided by a random selection of 20 to 25 patients. A separate analysis was performed for each study. For each test, an inter-examiner reliability index was computed.

Results from two studies are reported. In the first, stimulated salivary flow rate demonstrated excellent inter-examiner reliability, and resting salivary pH showed high inter-examiner reliability, while buffering capacity and stimulated salivary pH had moderate and very low inter-examiner reliability, respectively. In the second, inter-examiner reliability was excellent for the stimulated salivary flow rate and the resting salivary pH. The inter-examiner reliability for the stimulated salivary pH was also high and the stimulated salivary buffering capacity test had moderate reliability.

The small variance in stimulated salivary pH and buffering capacity in dental students may have artificially made the reliability appear low in the first attempt at inter-examiner reliability testing. In the second study, all 4 tests had an accept able performance.