Supplementary Table 2. Results of quality assessment of the NIH tool for case-control studies.
Author Year 1 2 3 4 5 6 7 8 9 10 11 12 Score
Lee et al 2017 Y Y N Y Y Y Y N Y Y CD N fair
Quality of included studies was assessed using the National Institutes of Health (NIH) Quality Assessment tool for Case-Control Studies 1=Was the research question or objective in this paper clearly stated and appropriate?; 2=Was the study population clearly specified and defined?; 3=Did the authors include a sample size justification?; 4=Were controls selected or recruited from the same or similar population that gave rise to the cases (including the same timeframe)?; 5=Were the definitions, inclusion and exclusion criteria, algorithms or processes used to identify or select cases and controls valid, reliable, and implemented consistently across all study participants?; 6=Were the cases clearly defined and differentiated from controls?; 7=If less than 100 percent of eligible cases and/or controls were selected for the study, were the cases and/or controls randomly selected from those eligible?; 8=Was there use of concurrent controls?; 9=Were the investigators able to confirm that the exposure/risk occurred prior to the development of the condition or event that defined a participant as a case?; 10=Were the measures of exposure/risk clearly defined, valid, reliable, and implemented consistently (including the same time period) across all study participants?; 11=Were the assessors of exposure/risk blinded to the case or control status of participants?; 12=Were key potential confounding variables measured and adjusted statistically in the analyses? If matching was used, did the investigators account for matching during study analysis? CD=cannot be determined; NA=not applicable; NR=not reported; N=no; Y=yes.