Original ArticleThe Short-Form Headache Impact Test (HIT-6) was psychometrically equivalent in nine languages
Introduction
Headache is a very common ailment [1] that can have a significant impact on a person's daily functioning and quality of life. Tension-type headaches, one of the most common primary headache disorders, affect about 40% [2] of adults. Migraines, a debilitating headache disorder, affect 3–8% of males and 11–18% of females in developed countries [3], with about a third of sufferers having two or more attacks each month lasting from 4 to 72 hours. Despite its very high prevalence, most migraine sufferers do not seek medical consultation for their headaches [4], and nearly half of migraine sufferers are underdiagnosed [5] or misdiagnosed [1], [6], [7], [8]. Clearly, the suffering experienced by migraineurs is often overlooked.
The experience of severe headaches can be very debilitating. Patients are likely to miss work during severe headache episodes. Their ability to carry out their daily activities is often impaired and quality of life is diminished [9]. In fact, both patients and physicians often underestimate the severity and debilitating effects of headaches. Because many patients find it difficult to describe the degree of their headache disability to their doctor, the ability of physicians to prescribe appropriate treatment is often compromised. In an attempt to enable patients and physicians to work in partnership, by providing physicians and patients a valid quantification of headache disability that can aid in clinical decisions, the Headache Impact Test (HIT and HIT-6) was developed [8], [9]. This survey, in its original (HIT) or short form (HIT-6), quantifies the impact of headache on sufferers' lives, thereby facilitating communication around the level of disability between physicians and patients, which is likely to be helpful in improving physician diagnosis and treatment of migraine [8], [9], [10].
Recently, disability has become an endpoint of interest in clinical trials of headache treatments. Given that the burden of headache, its resulting disability, and treatment benefits are patient-defined [1], the widespread availability of HIT-6 in multiple languages can facilitate evaluations performed on an international basis. To date, HIT-6 has been translated into more than 28 languages [11]. Although the reliability and validity of this test have been demonstrated for the general U.S. population [8], [9], the psychometric properties and equivalence of item functioning of the HIT-6 translations have not been examined. The assessment of equivalence across multiple languages is important to determine whether it is appropriate to combine results from different languages for analysis. The purpose of this study is to examine the psychometric properties and item functioning of the HIT-6 in 11 languages across 14 countries.
Section snippets
Study population
Individuals who consulted their primary care physician for headache in a primary care setting were invited to participate in a prospective, international, open-label study designed to examine the association of headache impact as assessed by HIT-6 and International Headache Society migraine diagnosis [12]. Headache sufferers who consented to participate self-completed the HIT-6 (Table 1) and provided responses orally to a survey on headache characteristics at study enrollment. Of a total of
Subject characteristics
Participants were between 18 and 65 years of age (average 40 years), 84% were female, and 87% were Caucasian. On average, subjects had a history of headache of 15 years and reported 3 to 12 headaches per month. About 81% had been previously diagnosed with migraine, and 55% reported their usual headaches as severe.
Data completeness
The percent of missing data for each item was very low, with all but four languages showing 0% missing data on all items: Hebrew (3.8% for Item 4), Dutch (2.2% for Item 6), German
Discussion
Three stages can be distinguished in the evaluation of the translation and cross-cultural equivalence of a questionnaire: (1) the translation process, (2) evaluating the psychometric properties of the scale and the assumptions underlying item and scale scoring, and (3) evaluating the equivalence of interpretations across countries [24]. A previous study evaluated the translation process for 27 translations of HIT-6, including all the languages used in the present study [11]. In the process of
Conclusions
Six translations of the HIT-6 demonstrated good psychometric properties and equivalence of item functioning (U.S. English, Canadian English, French, Greek, Hungarian, UK English), with five additional translations showing adequate properties (Portuguese, German, Hebrew, Spanish, Dutch) (Table 6). Finnish and Slovakian translations may need improvement of a single item. The applicability of the HIT-6 in South African English should be explored further.
Acknowledgments
We would like to thank Barbara Gandek for general comments on earlier versions of the manuscript and thank Michael DeRosa for his extensive help with table development. This study was supported by a grant from GlaxoSmithKline.
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