Long-term validity and reliability of a patient survey instrument designed for general dental practice

To consider the extent to which the validity and reliability of the Denplan Excel Patient Survey (DEPS) has been confirmed during its development and by its use in general dental practice and to explore methods by which any survey instrument used in general dental practice might be validated and tested for reliability.

DEPS seeks to measure perceived practice performance on those issues considered to be of greatest importance to patients. Content validity was developed by a literature review and tested in a pilot study. Criterion validity was tested by comparing patient retention in a payment plan for practices achieving the highest DEPS scores with those attaining the lowest scores over a two year period (surveys completed between 2010 and 2012). Reliability was assessed using the test/re-test method for 23 practices with approximately a three year time interval between tests. Internal consistency was tested by comparing Net Promoter Scores (NPS - which is measured in DEPS) attained by practices with their Patient Perception Index (PPI) as measured by the ten core questions in DEPS.

Practices in the pilot study strongly endorsed the content validity of DEPS. The 12 practices with the highest scores in the DEPS slightly increased their number of patients registered in Denplan payment plans during a two year period. The 12 lowest scoring practices saw 7% of their patients de-register during the same period. The 23 practices selected for the test/re-test study averaged more than 250 responses for both the test and re-test phases. The magnitude and pattern of their results were similar in both phases, while, on average, a modest improvement in results was observed. Internal consistency was confirmed as NPS results in DEPS closely mapped PPI results. The higher the measurement of perceived quality (PPI) the more likely patients were to recommend the practice (NPS).

Both through its development and use over the last four years The DEPS has demonstrated good validity and reliability. The authors conclude that this level of validity and reliability is adequate for the clinical/general care audit purpose of DEPS and that it is therefore likely to reliably inform practices where further development are indicated. It is important and quite straightforward to both validate and check the reliability of patient surveys used in general dental practice so that dental teams can be confident in the instrument they are using.