Amit S Patel1, Richard J Siegert2, Sabrina Bajwah3, Kate Brignall1, Harry R Gosker4, John Moxham1, Toby M Maher5, Elisabetta A Renzoni5, Athol U Wells5, Irene J Higginson3, Surinder S Birring6. 1. Division of Asthma, Allergy and Lung Biology, King's College London, Denmark Hill, London SE5 9RS, UK. 2. Person Centred Research Centre, Health and Rehabilitation Research Institute, AUT University, North Shore campus, 90 Akoranga Drive, Northcote, Auckland 0627, New Zealand. 3. Department of Palliative Care, Policy and Rehabilitation, Cicely Saunders Institute, King's College London, Bessemer Road, London SE5 9PJ, UK. 4. Department of Respiratory Medicine, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Center, Minderbroedersberg 4-6, 6211 LK Maastricht, The Netherlands. 5. Interstitial Lung Disease Unit, Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK. 6. Division of Asthma, Allergy and Lung Biology, King's College London, Denmark Hill, London SE5 9RS, UK. Electronic address: Surinder.birring@nhs.net.
Abstract
OBJECTIVES: Rasch analysis has largely replaced impact factor methodology for developing health status measures. The aim of this study was to develop a health status questionnaire for patients with interstitial lung disease (ILD) using impact factor methodology and to compare its validity with that of another version developed using Rasch analysis. STUDY DESIGN AND SETTING: A preliminary 71-item questionnaire was developed and evaluated in 173 patients with ILD. Items were reduced by the impact factor method (King's Brief ILD questionnaire, KBILD-I) and Rasch analysis (KBILD-R). Both questionnaires were validated by assessing their relationship with forced vital capacity (FVC) and St Georges Respiratory Questionnaire (SGRQ) and by evaluating internal reliability, repeatability, and longitudinal responsiveness. RESULTS: The KBILD-R and KBILD-I comprised 15 items each. The content of eight items differed between the KBILD-R and KBILD-I. Internal and test-retest reliability was good for total scores of both questionnaires. There was a good relationship with SGRQ and moderate relationship with FVC for both questionnaires. Effect sizes were comparable. Both questionnaires discriminated patients with differing disease severity. CONCLUSION: Despite considerable differences in the content of retained items, both KBILD-R and KBILD-I questionnaires demonstrated acceptable measurement properties and performed comparably in a clinical setting.
OBJECTIVES: Rasch analysis has largely replaced impact factor methodology for developing health status measures. The aim of this study was to develop a health status questionnaire for patients with interstitial lung disease (ILD) using impact factor methodology and to compare its validity with that of another version developed using Rasch analysis. STUDY DESIGN AND SETTING: A preliminary 71-item questionnaire was developed and evaluated in 173 patients with ILD. Items were reduced by the impact factor method (King's Brief ILD questionnaire, KBILD-I) and Rasch analysis (KBILD-R). Both questionnaires were validated by assessing their relationship with forced vital capacity (FVC) and St Georges Respiratory Questionnaire (SGRQ) and by evaluating internal reliability, repeatability, and longitudinal responsiveness. RESULTS: The KBILD-R and KBILD-I comprised 15 items each. The content of eight items differed between the KBILD-R and KBILD-I. Internal and test-retest reliability was good for total scores of both questionnaires. There was a good relationship with SGRQ and moderate relationship with FVC for both questionnaires. Effect sizes were comparable. Both questionnaires discriminated patients with differing disease severity. CONCLUSION: Despite considerable differences in the content of retained items, both KBILD-R and KBILD-I questionnaires demonstrated acceptable measurement properties and performed comparably in a clinical setting.
Authors: Aish Sinha; Amit Suresh Patel; Richard J Siegert; Sabrina Bajwah; Toby M Maher; Elizabeth A Renzoni; Athol U Wells; Irene J Higginson; Surinder S Birring Journal: BMJ Open Respir Res Date: 2019-02-18