Validation testing of OUTPATSAT-35RT questionnaire to assess satisfaction in patients on outpatient radiotherapy in a large Indian cohort

Abstract

ABSTRACT Background: This study reports the psychometric properties of OUTPASAT-35RT questionnaire from a large Indian cancer cohort treated with ambulatory radiotherapy (RT) at a tertiary-care comprehensive cancer center. Materials and Methods: Adults with a pathologically proven diagnosis of cancer undergoing fractionated RT (≥10 fractions) with the ability to read and understand English, Hindi, or Marathi were accrued after written informed consent. Patients were administered a language-appropriate version of OUTPATSAT-35RT along with European Organization for Research and Treatment of Cancer (EORTC) generic quality-of-life questionnaire (QLQ-C30) at conclusion of RT (±3 days). Psychometric properties of OUTPATSAT-35RT were analyzed. Results: A total of 314 patients were accrued between 2018 and 2020. A negligible floor effect (<2%) but a high ceiling effect (>15%) was observed for OUTPATSAT-35RT. Multi-trait analysis revealed satisfactory validity and reliability of the questionnaire. Pearson’s correlation coefficient (PCC) of individual item score with own scale was >0.4 suggesting good convergent validity. Discriminant validity was satisfactory as the PCC with its own scale/own domain was greater than with other scales of the same domain and other domains of OUTPATSAT-35RT, respectively. Correlation of scales of OUTPATSAT-35RT with scales of QLQ-C30 demonstrated acceptable divergent validity (all values of PCC <0.3). Cronbach’s alpha was >0.7 suggesting good internal consistency. Test–retest reliability was good with intra-class coefficient being >0.7. Economic status was the only socio-demographic factor correlating significantly with OUTPATSAT-35RT scores; satisfaction of patients with the delivery of care increased with increasing family income. Conclusion: The psychometric properties of OUTPATSAT-35RT were found to be acceptable and satisfactory during validation testing in a large Indian cohort.