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Table 1 Overview of characteristics of 110 included randomized clinical trials

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

Characteristics  
Median sample size (range) 195 (13-817)
Median year of publication (range) 2006 (1998-2012)
Parallel group design 98 (89)
Crossover group design 10 (9)
Study run-in phase with placebo reported 2 (2)
Commercial funding 89 (81)
Single center study 9 (8)
Continent:
    Across continents 24 (22)
    Africa 1 (1)
    Asia 20 (18)
    Europe 16 (15)
    North America 23 (21)
    Oceania 2 (2)
    South America 5 (5)
Type of PDE-5 inhibitor:
    Sildenafil 55 (50)
    Vardenafil 28 (26)
    Tadalafil 27 (25)
Condition studied:
    Broad spectrum 68 (62)
    Cardiovascular disease 5 (5)
    Depression 5 (5)
    Diabetes 9 (8)
    Prostatic cancer 6 (6)
    Metabolic syndrome 3 (3)
    Multiple sclerosis 2 (2)
    Post-traumatic stress syndrome 2 (2)
    Spinal cord injury 2 (2)
    Renal failure 4 (4)
    Other 4 (4)
Risk of bias:
Random sequence generated adequately
    Low 22 (20)
    Unclear 88 (80)
    High 0 (0)
Allocation concealed adequately
    Low 16 (15)
    Unclear 93 (85)
    High 1 (1)
Participants blinded adequately
    Low 58 (53)
    Unclear 51 (46)
    High 1 (1)
Caregivers blinded adequately
    Low 17 (16)
    Unclear 93 (85)
    High 0 (0)
Outcome assessors blinded adequately
    Low 17 (16)
    Unclear 93 (85)
    High 0 (0)
Overall blinded adequately
    Yes 5 (5)
    No 48 (44)
    Unclear 57 (52)
Other study methods:
ITT analysis 5 (5)
Balanced baseline prognostic factors 82 (75)
Naïve to intervention 10 (9)
Outcomes  
Dichotomeous outcome, GEQ reported 69 (63)
Most common AEs reported* 70 (64)
Methods used to monitor AEs
Prospective or routine monitoring 22 (20)
Spontaneous reporting 13 (12)
Patient checklist, questionnaire or diary 4 (4)
Systematic survey of patients 1 (1)
Not clear 65 (59)
  1. Values are shown as numbers (%) unless stated otherwise. *In the case of phosphodiesterase-5 (PDE-5) inhibitors, the most common adverse events (AEs) are headache and flushing. GEQ, Global Efficacy Question; ITT, intention to treat.