The Catch-22 of appraisals on the quality of observational studies.
Groenwold
R H H
RH
Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Stratenum 6.131, PO Box 85500, 3508 GA Utrecht, The Netherlands. r.h.h.groenwold@umcutrecht.nl
Rovers
M M
MM
D035843:Biomedical Research / Q000592:standards*; D057189:Checklist; D032921:Consensus; D006801:Humans; D011785:Quality Assurance, Health Care / Q000592:standards