Development and validation of the self-completed ascites impact measure to understand patient motivation for requesting a paracentesis

BACKGROUND The Ascites Impact Measure (AIM) was developed to record patients' daily experiences of symptoms that trigger a request for a paracentesis. METHODS Development of the AIM followed a rigorous step-wise approach, including a review of the literature, expert opinions, and qualitative research involving patients who experience symptomatic malignant ascites. The AIM's measurement properties were assessed using data from two international trials, including 59 ovarian cancer patients with symptomatic malignant ascites. RESULTS Following the literature review and expert discussions to develop the conceptual model, ten patients with symptomatic malignant ascites were interviewed in the item elicitation phase, resulting in a draft questionnaire with four questions. Validation analyses consisted of 59 patients pooled from two international trials. Inter-items correlations for the AIM were good (r > 0.60), except for the Pain item. Internal consistency reliability (α = 0.89) improved after removing the Pain item from the Total Symptom score (TSS). Test-retest reliability was sufficient. Scores significantly improved after paracentesis except for the Pain item. Preliminary estimates indicate that a two-point improvement on the three-item TSS (without the Abdominal Pain item) could be interpreted as clinically meaningful. CONCLUSION The Abdominal Pain item appears to behave differently than the other three items, and could be more related to cancer. While the validity of the AIM TSS (four-item) is acceptable, removing the Pain item from the TSS scoring algorithm demonstrated better construct validity. In addition, test-retest reliability and responsiveness were found to be similar to the results for the four-item AIM TSS. The Pain item should be used as a supplemental item to the three-item AIM TSS, as it provides additional information about the underlying cancer state.