Knowledge Measure for Ovarian Cancer Research (KnoMOR): Development and psychometric testing results of a patient-centered knowledge measure (029)

Abstract

<b>Objectives:</b> Knowledge is a prerequisite to informed choice. There are no validated measures of ovarian cancer (OC) to assess patients' knowledge systematically. Through efforts to create shared medical decision tools for OC, we sought to develop and validate an OC knowledge measure with sub-scales focusing on general knowledge and maintenance therapy (MT) to assess patients' understanding of their disease and treatment. <b>Methods:</b> Gaps in OC and MT knowledge were identified from qualitative interviews with patients and non-medical caregivers. Content experts supplemented these gaps with key facts that OC patients should know. Sample questions were drafted, iteratively refined with feedback from content experts, and cognitively tested with nine patients. The knowledge measure (true/false/not sure and multiple choice) was administered to women with OC and then re-administered 30 days later to assess test-retest reliability. "Not sure" answers were coded as incorrect. Reading level was assessed by the Flesch-Kincaid Grade Level test. Item difficulty (% of correct responses) and item uncertainty (% of "not sure" responses) were calculated for each question. Internal consistency reliability was assessed using the Kuder-Richardson Formula 20 (KR-20). Test-retest reliability was estimated with the intraclass correlation coefficient (ICC). Physicians were recruited from a national convenience sample to test for known-group validity. The percentage of correct responses to the OC and MT scales were compared for physicians and patients with an independent samples t-test. <b>Results:</b> The 31-item (14 OC general knowledge, 17 MT knowledge) measure was completed by 146 OC patients, 65 newly diagnosed and 81 with recurrent disease recruited between October 2020 and June 2021. A total of 27 physicians participated. Two items were dropped due to ceiling effects or overlapping constructs, resulting in a 29-item knowledge measure (12-item general OC knowledge; 17-item MT knowledge scales) with a reading level of grade 11.3. Additional items with high item uncertainty were retained due to their importance in informed decision-making and potential to be impacted by decision support interventions. Internal consistency reliability of the final scale was acceptable (OC scale, KR-20: 0.80, MT scale, KR-20: 0.76). Test-retest reliability was good (OC scale, ICC: 0.70, MT scale, ICC: 0.79). There were significant differences in knowledge between patients and physicians on the OC scale (patients' mean correct responses, 58.7%; physicians' mean correct responses, 88.1%; p<0.001). Similarly, patients answered 43.9% of MT questions correctly compared to 84% of physicians (p<.001). <b>Conclusions:</b> We developed a brief, valid, and reliable indicator of ovarian cancer patients' knowledge of key concepts central to making an informed decision about MT. The patient-centered measure is a simple and convenient tool that can be incorporated into a broader assessment of the quality of patients' decision-making about ovarian cancer.