Rasch analysis of the Herth Hope Index in cancer patients

BACKGROUND: The concept of hope has been measured using the Herth Hope Index (HHI) in different samples, but varying factor structures comprising different items from the HHI have been reported. Therefore, further testing with regard to the dimensionality of the instrument is recommended. Rasch modeling can be used to evaluate validity evidence of an instrument’s underlying structure, to identify items with poor fit to the rest of the scale, and to identify items that perform inconsistently across groups. The aim of this study was to assess the HHI’s psychometric properties in a sample of cancer patients using a Rasch model. Adult oncology outpatients (n = 167) with pain from bone metastasis were included, and medical records were reviewed for disease and treatment information. Patients completed the 12-item HHI, which measures various dimensions of hope using a 4-point Likert scale that ranges from 1 (strongly disagree) to 4 (strongly agree). The internal scale validity, person response validity, unidimensionality, and uniform differential item functioning were evaluated by applying a Rasch rating scale model. RESULTS: Five (42%) of the twelve items (#3, #4, #5, #6 and #7) did not meet the criterion set for item goodness-of-fit. After removing these 5 items, the resulting 7-item scale demonstrated acceptable item fit to the model, acceptable unidimensionality (52.6% of the variance explained), acceptable person goodness-of-fit, adequate separation, and no differential item function. CONCLUSION: A 7-item version of the HHI had better psychometric properties than the original 12-item version among patients with cancer-related pain. TRIAL REGISTRATION: The protocol ID is 158,707/V10 and it was registered on ClinicalTrials.gov as NCT00760305. Registered September 25, 2008.