The development and validation of the daily electronic Endometriosis Pain and Bleeding Diary

BACKGROUND: The objective of this study was to develop and validate a daily electronic Endometriosis Pain and Bleeding Diary (EPBD) for assessing treatment-related changes in endometriosis symptoms from the patient's perspective in a clinical trial setting. METHODS: The EPBD items were developed based on clinician input and the results of 5 focus groups (N = 38) and 3 iterative sets of cognitive interviews (N = 22). The psychometric properties were evaluated using data collected in a usual-practice, non-intervention study conducted at 4 sites in the United States. Existing questionnaires were also administered to explore the construct validity of the EPBD. The development and validation processes were consistent with the recommendations in the 2009 FDA Patient Reported Outcomes Guidance to Industry. RESULTS: Focus group participants described 2 distinct types of pain (intermittent and continuous), which they felt were relevant and important to monitor. Participants also indicated that pain and bleeding/spotting associated with intercourse were important symptoms related to endometriosis. Cognitive interviews with additional endometriosis patients served to optimize item content, wording, and response options. Psychometric analyses found the EPBD items to behave as expected, for example, item-level means for subjects with severe endometriosis symptoms were higher (i.e., worse) compared with subjects with mild symptoms. Item-total correlations for the EPBD pain items (range 0.40-0.89) indicated that the items were related but not redundant. EPBD pain ratings correlated highly with the modified Brief Pain Inventory-Short Form Pain Intensity score (range 0.46-0.61). Women with severe endometriosis symptoms reported significantly higher intermittent and continuous dysmenorrhea and intermittent and continuous pelvic pain ratings and greater interference with daily activities compared with women with mild symptoms (all p < 0.01). CONCLUSIONS: The results of this study show that the 17-item EPBD reliably and validly characterizes the types of pain that endometriosis patients identified as being important. As a daily patient-reported assessment, it overcomes the significant potential for intra- and inter-rater variability and rater and recall bias that is inherent in the Biberoglu and Behrman Scale. Additional studies are required to confirm the dimensionality and optimal scoring of the EPBD, to corroborate the present results, and to assess other important measurement properties, such as responsiveness.