Reliability and validity of the 6-item Headache Impact Test in chronic migraine from the PROMISE-2 Study

DOI: https://doi.org/10.1007/s11136- 020- 02668- 2

Abstract-Summary We examined the reliability and validity of the 6-item Headache Impact Test (HIT-6) specifically on patients with chronic migraine (CM) from the PROMISE-2 clini- cal trial.

The conceptual framework of HIT-6 was evaluated using baseline data from the

PROMISE-2 study (NCT02974153; N = 1072).

Using baseline and week 12 data, convergent and discriminant validity of the

HIT-6 was evaluated by correlation coefficients.

Sensitivity to change was assessed by evaluating correlations between HIT-6

scores and change scores for other established reference measures.

Known-groups analyses demonstrated that the HIT-6 total score can distinguish

between clinically meaningful CM subgroups.

The HIT-6 was successfully calibrated using IRT with data from PROMISE-2. Results from these analyses were generally consistent with previous literature and provided supportive evidence that the HIT-6 is well suited for measuring the impact of headache and migraine in the CM population.

Extended: The impact of this homogeneity was evident in the screening and baseline HIT-6 scores that resulted in what were likely attenuated estimates of test– retest reliability; we recommend that this be re-examined in a prospective observa- tional study to examine the accuracy of this supposition and provide a more complete understanding of the psychometric soundness of the HIT-6 in the CM population.

Introduction Previous research has shown associations between CM and increased headache impact and disability as well as decreased health-related quality of life (HRQoL) [320–323].

One of these, the 6-item Headache Impact Test (HIT-6) [142], recommended by the American Headache Society [324], is intended to measure the impact of head- ache on daily life, with higher scores reflecting greater migraine impact [325].

The HIT-6 measures headache-related impact on six items, including severe headache pain, limitations to usual daily activities, the wish to lie down, fatigue, negative affect, and limitations to concentration.

A substantial body of literature supports the HIT-6 as a precise and reliable PROM for assessing the impact of headache in the general headache population, as well as in patients with migraine [142, 325–329].

Much of the previous research has evaluated the broad headache population, and there is limited work specifically focused on use of the HIT-6 in CM, which is a particularly debilitating condition with features unique from other headache and migraine disorders.

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Personal and Societal Burden

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Methods For the reported item-level analyses (item-level descriptive statistics, latent variable modeling, classical test theory analyses), the ordinal HIT-6 responses were coded as: never = 1, rarely = 2, sometimes = 3, very often = 4, and always = 5.

To be conservative, no imputation for missing data was used in these analyses, meaning that HIT-6 total scores were not to be calculated for any observations with missing item responses.

To assess internal consistency/reliability, classical test theory analyses (i.e., item-total correlations, coefficient alpha, and alpha with item removed) were com- puted for the HIT-6 using baseline data, along with the IRT-based reliability plot and the IRT-based marginal reliability estimate.

Consistent with the HIT-6 manual [330] and the assumptions underlying coeffi- cient alpha, only HIT-6 observations with complete item responses were used for the internal consistency reliability analyses.

Results Complete observations for the HIT-6 items were present as both baseline and Week 12 (i.e., if a patient was presented the HIT-6, all items were answered).

Patients in PROMISE-2 had HIT-6 total scores in the severe range at base-

line [331].

The observed correlation between frequency of MMDs and the HIT-6 total score at baseline, which was lower than anticipated, may be attributable to the fact CM patients needed to have a relatively high migraine frequency at baseline to meet study inclusion criteria.

The primary exception was that the PGIC correlation (r = 0.57) was noticeably greater than expected (0.10–0.30), indicating that change in the HIT-6 total score may be a more robust assessment of general headache impact on patients than ini- tially expected.

Discussion Subsequent studies using a variety of headache patient samples found HIT-6 total scores to be associated, as expected, with numerous other migraine-specific PROM scores as well as with general health and HRQoL measures and with objective head- ache and migraine outcomes [142, 326, 327, 329, 332–336].

In the same study’s open-label phase (in which previously placebo-treated patients received active treatment), the HIT-6 total scores retained the demonstrated decrease from baseline but the differences between treatment groups were no longer statistically significant, as would be expected.

The impact of this homogeneity was evident in the screening and baseline HIT-6 scores that resulted in what were likely attenuated estimates of test–retest reliabil- ity; we recommend that this be re-examined in a prospective observational study to examine the accuracy of this supposition and provide a more complete understand- ing of the psychometric soundness of the HIT-6 in the CM population.

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Conclusion This body of work examined the reliability and validity of the HIT-6 in patients with CM using data from the large PROMISE-2 clinical trial.

The short administration time, easy scoring, and interpretability of the HIT-6 make it an excellent tool for use in applied research, clinical trials, and clinical practice settings so that broader patient experience can be assessed.

Acknowledgement A machine generated summary based on the work of Houts, Carrie R.; McGinley, James S.; Wirth, R.  J.; Cady, Roger; Lipton, Richard B. 2020  in Quality of Life Research.

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Economics

Machine generated keywords: cost, erenumab, mmd, productivity, preventive, migraine day, costeffectiveness, qaly, day, headache day, use acute, societal, loss, billion, annual.

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