Reliability, Validity and Important Difference Estimates for the NCCN-FACT Ovarian Symptom Index-18 (NFOSI-18)

Abstract

Objective: To evaluate psychometric performance of the NCCN-FACT Ovarian Cancer Symptom Index-18 (NFOSI-18) in advanced ovarian cancer. Methods: Cross-sectional, observational data from patients receiving treatment for ovarian cancer. Other measures included European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire core (EORTC QLQ-C30) and associated ovarian cancer module (EORTC QLQ-OV28) and Work Productivity and Activity Impairment. Internal consistency reliability, construct validity and anchor-based clinically important differences were assessed. Results: 897 patients were analyzed. Reliability was acceptable for all NFOSI-18 scores; construct validity was supported. Twelve anchors sufficiently correlated with NFOSI-18 scores and suggested clinically important differences: NFOSI-18 total score (5–7), disease-related symptoms – physical (3–4), disease-related symptoms – emotional (1), treatment side effects (2) and functional well-being (1–2). Conclusions: Results provide evidence of reliability and validity of NFOSI-18 scores. Generated CIDs will help improve interpretation of between-group treatment differences in clinical trials.

Lay abstract

The National Comprehensive Cancer Network Functional Assessment of Cancer Therapy – Ovarian Cancer Symptom Index-18 (NFOSI-18) is a questionnaire assessing the health of patients with ovarian cancer. When using such questionnaires, it is important to evidence that they produce consistent scores (referred to as reliability) and are aligned with other assessments of health (referred to as construct validity). It is also important to set guidelines on what constitutes a clinically important difference in scores, so clinicians and researchers can judge how effective new treatments are. This study analyzed data from 897 patients with advanced ovarian cancer, providing evidence of reliability and construct validity. Guidelines for clinically important differences were also provided. The findings support continued use of the NFOSI-18.

Keywords::

• clinically important difference
• interpretation
• NFOSI-18
• ovarian cancer
• patient-reported outcomes
• psychometric properties

Supplementary data

To view the supplementary data that accompany this paper please visit the journal website at: www.tandfonline.com/doi/suppl/10.2217/fon-2021-0358

Author contributions

A Trigg: formal analysis, methodology, visualization, writing – original draft; M Kelly: formal analysis, visualization, writing – original draft; L Iadeluca: methodology, project administration, supervision, writing – review & editing; J Chang: conceptualization, resources, writing – review & editing; A Moreno-Koehler: data curation, formal analysis, software, validation, writing – review & editing; A Yaworsky: methodology, project administration, supervision, writing – review & editing; M Krohe: conceptualization, methodology, writing – review & editing; A Rider: data curation, resources, writing – review & editing; JC Cappelleri: methodology, supervision, writing – review & editing; D Cella: methodology, supervision, writing – review & editing; K Cocks: conceptualization, methodology, supervision, visualization, writing – original draft.

Financial & competing interests disclosure

This trial was sponsored by Pfizer and is part of an alliance between Pfizer and Merck KGaA, Darmstadt, Germany. A Trigg, M Kelly, A Moreno-Koehler, A Yaworsky and K Cocks are employees of Adelphi Values. M Krohe was employed by Adelphi Values at the time the work was undertaken. Adelphi Values conducted the analyses conducted as part of this study. A Rider is an employee of Adelphi Real World. Adelphi Real World conducted the ovarian cancer DSP capturing the real-world evidence for the analyses conducted as part of this study. Adelphi were paid consultants to Pfizer in connection with the development of this manuscript. L Iadeluca, J Chang and JC Cappelleri are employees of Pfizer. D Cella is the President of FACIT.org and was a paid consultant to Pfizer for this research. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval through the FEKI (Freiburger Ethik-Kommission International; protocol #017/1742) and in the US by the Western Institutional Review Board (WIRB; protocol #20172679). Informed consent was obtained from all individual participants included in the study.

Data sharing statement

The data and source material used to conduct the analyses included in this manuscript are not publicly available. This manuscript does not report data from a clinical trial; the data presented in this manuscript is from a cross-sectional, real-world observational study.

Additional information

Funding

This trial was sponsored by Pfizer and is part of an alliance between Pfizer and Merck KGaA, Darmstadt, Germany. A Trigg, M Kelly, A Moreno-Koehler, A Yaworsky and K Cocks are employees of Adelphi Values. M Krohe was employed by Adelphi Values at the time the work was undertaken. Adelphi Values conducted the analyses conducted as part of this study. A Rider is an employee of Adelphi Real World. Adelphi Real World conducted the ovarian cancer DSP capturing the real-world evidence for the analyses conducted as part of this study. Adelphi were paid consultants to Pfizer in connection with the development of this manuscript. L Iadeluca, J Chang and JC Cappelleri are employees of Pfizer. D Cella is the President of FACIT.org and was a paid consultant to Pfizer for this research. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed