Table 1.

Scale for quality assessment of molecular association studies of fibromyalgia

Criteria	Score
Representativeness of cases
Consecutive/randomly selected from case population with clearly defined sampling frame	2
Consecutive/randomly selected from case population without clearly defined sampling frame or with extensive inclusion/exclusion criteria	1
No method of selection described	0
Representativeness of controls
Controls were consecutive/randomly drawn from the same sampling frame as cases	2
Controls were consecutive/randomly drawn from a different sampling frame as cases	1
Not described	0
Ascertainment of fibromyalgia
Clearly described objective criteria for diagnosis of fibromyalgia	2
Diagnosis of asthma by patient self-report or by patient history	1
Not described	0
Quality control of genotyping methods
Clearly described a different genotyping assay to confirm the data	1
Not described	0
Hardy-Weinberg equilibrium
Hardy-Weinberg equilibrium in controls	2
Hardy-Weinberg disequilibrium in controls	1
No checking for Hardy-Weinberg disequilibrium	0
Association assessment
Assess association between genotypes and fibromyalgia with appropriate statistics and adjustment for confounders	2
Assess association between genotypes and fibromyalgia with appropriate statistics without adjustment for confounders	1
Inappropriate statistics used	0