Qualitative exploration of the renal stone patients' experience and development of the renal stone-specific patient-reported outcome measure

Objectives To investigate the experience of patients living with renal calculi via a qualitative methodology, aiming to develop and validate a disease-specific patient-reported outcome measure (PROM) for renal stones, the Cambridge Renal Stone PROM (CReSP). Patients, Subjects and Methods Patients with radiologically confirmed renal calculi who had undergone a range of management options were invited to focus groups or semi-structured interviews to elicit patient input and generate the PROM content. The developed renal stone PROM underwent validity studies included Cronbach's alpha for internal consistency, Spearman's and Pearson's correlation coefficients for test-retest reliability. Discriminant validity was assessed by Pearson's correlation coefficients vs the EuroQol five-dimensional five-level questionnaire (EQ-5D-5L). Our project has Health and Social Care Research Ethics Committee approval. Results A total of 106 subjects participated in creating the newly developed PROM. In all, 36 patients were invited to 22 semi-structured interviews and four focus groups, until reaching saturation. Major issues reported, and themes selected for the renal stone PROM included pain, anxiety, limitations to social life and tiredness, urinary symptoms, dietary changes' impacts, and gastrointestinal tract symptoms. Reliability analysis for 30 patients to determine internal consistency using Cronbach's alpha with a mean (range) of 0.91 (0.90-0.93) within domains and Cronbach's alpha between domains was 0.92. Average inter-item Pearson's and Spearman's correlation within domains was performed, with a Pearson's correlation mean (range) of 0.77 (0.73-0.85) and Spearman's correlation mean (range) of 0.72 (0.63-0.77). The test-retest Pearson's correlation mean (range) was 0.85 (0.57-0.95). Validity assessment was performed for 20 patients vs 20 controls. Pearson's correlation with EQ-5D-5L was -0.74, showing the newly developed PROM successfully discriminated patients with kidney stones. Our final renal stone PROM consists of 14 questions that are rated on a Likert scale; the higher the score, the worse the effect on a patient's quality of life. Conclusions Although pain was the most frequent symptom, other health-related and social well-being issues significantly impacted patients' lives. Our validated patient-derived CReSP is a new instrument, specifically tailored to measure renal stone disease health outcomes from the patient's point of view.