The development and validation of the Cluster Headache Quality of life scale (CHQ)

Norazah Abu Bakar, Mariam Torkamani, Surat Tanprawate, Giorgio Lambru, Manjit Matharu, Marjan Jahanshahi

Cluster headache (CH) is a rare, excruciating and highly disabling primary headache disorder. Using non cluster headache specific measures, previous studies have shown that CH has a significant negative impact on patients' quality of life (QoL), but a CH-specific QoL scale is currently unavailable. Thus, the objective of this study was to develop and validate a CH-specific QoL scale. Based on a literature review, semi-structured patient interviews and expert panel consultation, we produced a 54-item questionnaire, which was pre-tested in a sample of CH patients and subsequently reduced to 47 items. The revised scale was then administered to CH sufferers attending a tertiary headache clinic and those registered with a patient group. A total of 406 completed questionnaires were received. To assess test-retest reliability, a subsample (N = 56) completed the scale on a second occasion, two weeks after the first. Standard statistical methods were used to analyse the data for validity and reliability. Item reduction and exploratory factor analysis led to 28-items, grouped into four subscales labelled "restriction of activities of daily living", "impact on mood and interpersonal relationships", "pain and anxiety", and "lack of vitality". The final CH-specific QoL scale, the CHQ, demonstrated satisfactory internal consistency (Cronbach's alpha > 0.9) and test-retest reliability (intraclass correlation coefficient > 0.8), with good internal construct validity between subscales (range 0.52-0.75) and convergent validity with other QoL measures. We have developed and validated the first patient-reported outcome measure of QoL specifically for CH sufferers, which may be used to monitor QoL in clinical care and research.