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Table 3 Assessment of the quality of studies included in current meta-analysis against the Newcastle-Ottawa criteria [16]

From: Cannabis exposure and risk of testicular cancer: a systematic review and meta-analysis

Author Year Adequacy of case definition Representativeness of cases Selection of controls Definition of controls Comparability of cases and controls Ascertainment of exposure Same ascertainment for cases and controls Non-response rate Author comment
Daling, et al. [9] 2009 Yes, with independent validation (1) Consecutive or obviously representative series of cases (2) Community controls (3) No history of disease (4) Cases and controls comparable (study controls for age and other factors) (5) Interview not blinded to case/control status (6) Yes (7) Rate different (Response rate: cases 67.5 %/controls 43.3 %) (8) Low response rate among controls (risk of selection bias). Largest study; strongest contributor to summary estimates
Trabert et al. [7] 2011 Yes, with independent validation (9) Consecutive or obviously representative series of cases (10) Community controlsa (11) No history of disease (12) Cases and controls comparable (study controls for age and other factors) (13) Self- completed questionnaire (14) Yes (15) Rate different (Response rate: cases 38.2 %/controls 73.3 %) (16) Low response rate among cases. Controls recruited as friends of cases (risk of selection bias)
Lacson et al. [8] 2012 Yes, with independent validation (17) Consecutive or obviously representative series of cases (18) Community controls (19) No history of disease (20) Cases and controls comparable (study controls for age and other factors) (21) Interview not blinded to case/control status (22) Yes (23) Same rate for both groups (Response rate: cases 81.0 %/controls 78.7 %) (24) Minimised to those aged 18–35 (limits representativeness)
  1. Explanation of categorisations is presented in Additional file 2 alongside its corresponding number
  2. aControls derived from friends of cases