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Table 2 Enhanced placebo effects and nocebo effects

From: Do randomized clinical trials with inadequate blinding report enhanced placebo effects for intervention groups and nocebo effects for placebo groups?

  IIEF-EF scores for placebo groups IIEF-EF scores for intervention groups
ROB domain No. of studies (no. of participants)* Studies with low ROB (95% CI) (IV) Studies with unclear or high ROB (95% CI) (IV) Differencea(95% CI) Between MA-homogeneity Q (P value) Studies with low ROB (95% CI) (IV) Studies with unclear or high ROB (95% CI) (IV) Differenceb(95% CI)
Summary 4 ROB-domains 5 (1,202)/16 (3,006) 1.92 (0.64 to 3.20) 1.56 (0.93 to 2.20) 0.33 (-0.96 to 1.62) 20 (0.48) 9.40 (6.96 to 11.83) 8.33 (7.29 to 9.37) -1.0 (-1.35 to 3.47)
Allocation concealment 13 (2,487)/48 (11,169) 1.82 (1.14 to 2.50) 1.75 (1.37 to 2.12) 0.07 (-0.8 to 0.93) 58 (0.88) 9.10 (7.94 to 10.26) 8.34 (7.63 to 9.05) 0.78 (-0.65 to 2.20)
Blinding participant 42 (9,159)/19 (3,442) 1.88 (1.45 to 2.31) 1.43 (0.95 to 1.91) 0.42 (-0.33 to 1.16) 64 (0.35) 8.39 (7.69 to 9.10) 8.23 (7.28 to 9.19) 0.16 (-1.02 to1.33)
Blinding caregiver 17 (3,652)/42 (8,652) 1.94 (1.18 to 2.69) 1.77 (1.40 to 2.15) 0.17 (-0.61 to 0.96) 56 (0.54) 8.46 (6.92 to 10.01) 8.64 (8.15 to 9.13) -0.25 (-1.50 to 1.00)
Blinding outcome assessor 17 (3,278)/42 (9,659) 1.82 (0.99 to 2.65) 1.84 (1.48 to 2.21) -0.02 (-0.83 to 0.79) 57 (0.52) 8.59 (7.15 to 10.03) 8.43 (7.80 to 9.06) 0.15 (-1.12 to 1.41)
  1. Impact of unblinding on summary changes from baseline International Index of Erectile Functioning-Erectile Functioning domain (IIEF-EF) scores with 95% CI with estimates of noceboa, enhanced placebob, placebo, and intervention effects. *Studies with low risk of bias (ROB) versus studies with unclear or high ROB. MA: Meta-Analysis, Q: Cochran’s Q, IV; Inverse Variance.