Objective: to develop a self-administered questionnaire (OPQ) to assess the patient's knowledge about osteoporosis.
Methods: An initial item pool of 71 questions was developed with input from clinicians involved in the management of patients with osteoporosis. It was piloted in ten patients for face validity and comprehension. The questionnaire was then administered to 50 first-time attendees at a specialist osteoporosis unit. After item analysis using index of difficulty and index of discrimination, 20 items were selected for the final questionnaire (OPQ). These were in the areas of general information (5), risk factors (7), consequences and treatment (four each).
Results: the average index of difficulty and index of discrimination (D) of the 20 items was 0.56 (>0.75 is suggestive of a poor discriminator) and 54.8% (D value of 50% is associated with highest level of item discrimination) respectively. This means that all the items actively discriminated between high and low scorers. The Flesch readability index was 74.3 (a score between 70 and 100 means a document is easily understood) and the reliability coefficient was 0.84 (acceptable range 0.8-0.9). Criterion validity (verification that the scale measures what it claims to measure) was confirmed by the method of contrasted groups where members of an osteoporosis awareness charity had a significantly higher score than the first time attendees (13.6 +/- 4.3 vs. 8.5 +/- 5.4; P=0.003).
Conclusions: we have developed a self-report, 20-item questionnaire (OPQ) to assess the patient's knowledge about osteoporosis. Psychometric analysis has shown that the items have a satisfactory index of difficulty and discrimination. The OPQ is internally reliable, valid and easily understandable. It can be used to identify individuals in need of educational interventions as well as assess the effectiveness of education efforts as a part of management of osteoporosis.