A total number of 236 migraine patients were screened. Out of 236 patients, 79 patients fulfilled the inclusion criteria and enrolled in the study. Sixty-nine patients completed the study . Ten (12.6%) patients did not turn up after the first compilation of MIDAS and HIT-6 questionnaires. In the study, 47 patients resided in the urban area and 22 patients were from the rural background.
Comprehensibility of the questionnaires
Overall, the comprehensibility of the MIDAS was good. Fifty-two patients (75.3%) had difficulty in understanding item B of the MIDAS and had to be helped while filling the questionnaire at the first compilation. Two patients (2.8%) needed to be explained the difference between missed days and more than 50% reduction in the productivity in various domains of daily activity.
For the MIDAS questionnaire all the subgroups filled every item except housewives, who missed out on item 1 and item 2, where the number of days missed or more than 50% reduction in productivity at work or school were asked, respectively. The reason for not excluding housewives from the data analysis was that they accounted for a considerable percentage of patients (31.2%, n = 22). Therefore, mean for item 1 and item 2 could be calculated only for 47 patients after excluding housewives. For the rest of the items and total scores, the mean was calculated for all the 69 patients. Similarly test–retest correlation coefficient for item 1 and item 2 was calculated for 47 patients only, as the housewives did not fill responses to these items. Test–retest correlation coefficient for the rest of the items and total scores was calculated for all the patients (n = 69), as responses to these were filled by every patient. The internal consistency was possible only after excluding the housewives as they missed out on item 1 and 2 of the MIDAS questionnaire. For illiterate patients (n = 10) the questionnaire was administered by the physician at all visits.
HIT-6 questionnaire had excellent comprehensibility and none of the patients had difficulty in filling the questionnaire. HIT-6 was uniformly applicable to all the participants and all the items were answered by every participant. Both the questionnaires were well comprehended by the patients irrespective of their rural or urban background. There was no difference between the urban and rural subgroups with regard to the reliability and validity of these questionnaires.
MIDAS and HIT-6 Scores
The mean of the total and individual item scores in different compilations of questionnaires in all patients as well as after dividing them into occupational and education-wise subgroups is shown in Tables , , and .
MIDAS and HIT-6 scores at different compilations
Occupation-wise Comparison of MIDAS and HIT-6 Scores
Education-wise comparison of MIDAS and HIT-6 Scores
Grade stratification and change
During the first compilation 79.7% patients were in MIDAS grades 3 and 4, and 84% patients had high HIT-6 scores (56 and above). At the second compilation 81.1% patients were in MIDAS grades 3 and 4, and 78.3% patients had high HIT-6 scores (56 and above). There was no significant change or shift in the grades between the first and second compilations for both the questionnaires.
Test–retest reliability and internal consistency
For test–retest reliability, the participants completed the MIDAS and HIT-6 questionnaires twice; first at the initial visit and then after three weeks (n = 69). Test–retest correlation coefficients for the total scores as well as for the individual items are shown in . Test–retest correlation coefficients were calculated for: (1) All the patients, (2) after excluding housewives, (3) after excluding illiterate patients, and (4) after excluding both housewives and illiterate patients. For the MIDAS, correlation coefficients between the first and second compilations for all items (except for Item B) as well as for total scores were strong (r > 0.80). For item B, it was weak. The trend was similar in all four groups. The correlation between the total HIT-6 score at the first and second compilations was also strong in the first three groups of patients. However, for the fourth group (after excluding both housewives and illiterate patients), it was moderate(r = 0.64).
The internal consistency of the MIDAS score was high (Cronbach α > 0.9) at all the three compilations. For the HIT-6 score, the internal consistency was high (Cronbach α > 0.7) at the first and third compilations. At the second compilation, it was moderately acceptable (Cronbach α = 0.67).
Validation of the MIDAS and HIT-6 questionnaires
Both MIDAS and HIT-6 total scores correlated well with the headache diary equivalent. The correlation was 0.91for MIDAS and 0.77 for HIT-6 .
Validation of MIDAS and HIT-6 with Headache Diary Equivalent
Correlation between MIDAS and HIT-6
Overall, a moderate-to-weak correlation (r = 0.64 to 0.48) was seen between MIDAS and HIT-6 scores, at all the three compilations .
Correlation between MIDAS and HIT-6 Questionnaire