Table 3 Criteria for evaluating the quality of headache prevalence studies
Quality factor | Score | ||||
|---|---|---|---|---|---|
-4 | 1 | 2 | 3 | 4 | |
Sampled population | Not stated, or clinic population, or members of patient organization | Selected population (eg, health-plan members, work-place, college students) [increase score by 2 if this met the specific purpose of the study] | General population or community-based sample from defined region within a country, or school-based (for children) | General population or community-based sample from whole country | |
Sampling method | Not stated | No (or failed) attempt to secure representativeness | Random sample uncorrected for population demographics | Total defined population, or random sample corrected for population demographics | |
Number of respondents | Not stated | 250-1,000 | 1,000-1,500 | 1,500-2,500 | >2,500 |
Participation rate | Not stated, or <40% | 50-59% | 60-69% | 70-79% | >80% |
Access | Not stated | Self-administered (unsupervised) questionnaire | Telephone or face-to-face interview by untrained or unspecified interviewer(s) | Telephone or face-to-face interview by trained lay interviewer(s), medical students or nurses | Face-to-face interview with headache expert [reduce score by 1 if interviews restricted to screen-positive sub-sample] |
Validation of diagnostic instrument | Instrument not specified or not validated | Validated, but sensitivity and/or specificity <60% | Validated, but sensitivity and/or specificity <70% | Validated only in screen-positive sub-sample, or in clinic or unspecified sample, but sensitivity and specificity ≥70% | Validated in target population or similar, and sensitivity and specificity ≥70%, or all diagnoses made in face-to-face or telephone interviews by headache expert |
Diagnostic criteria, and application of “probable” diagnoses | Not stated | Stated, other than ICHD | ICHD (or reasonable modification), but uncertain or inappropriate analysis of “probable” diagnoses | ICHD (or reasonable modification) with clear exposition regarding “probable” diagnoses | |
Prevalence time frame | Not specified or not appropriate to the study purpose | Not specified, but terminology implies “present” or “current” or “recent” headache | Other specified period appropriate to the study purpose | Point, 1-day, 1-year or lifetime | |