Psychometric properties of the HIT-6 among patients in a headache-specialty practice

Objective.-To evaluate the performance and score interpretability of the Headache Impact Test (HIT-6) questionnaire in a headache patient population. Background.-The HIT-6 is a standardized questionnaire designed to assess headache-related disability. Norms have been established using randomly sampled respondents from the general population. This study evaluated the psychometric properties of the HIT-6 scale among new adult patients who presented for treatment at a university headache-specialty practice. Methods.-Participants were 309 new patients who presented for treatment at a headache-specialty clinic in an academic medical center. Results.-Respondents ranged in age from 18 to 91 years, with an average age of 41 years (SD = 13 years) and were predominantly female (77%). Over half (57%) experienced chronic daily headache. Scores ranged from 38 to 78, with an average of 65.6 (SD = 7.0) and the majority (87%) had "severe impact" (60 or higher). The scale showed high reliability (alpha= 0.87) and an exploratory factor analysis showed large loadings from |0.57| to |0.86| and suggested a single disability factor. Scores were moderately negatively correlated with Short Form Health Survey (SF-36) subscales, ranging from -0.22 for mental health to -0.57 for social functioning. Item response theory analyses showed that half of the items functioned well across the disability continuum, while the remaining items discriminated between low and high levels of headache impact. Conclusions.-These findings suggest that the HIT-6 is useful for assessing headache-related disability among patients who seek headache-specialty care.