Blinding Measured: A Systematic Review of Randomized Controlled Trials of Acupuncture

Table 1

Blinding scenarios [13].

Experimental arm (verum)	Control arm (sham)	Possible blinding and clinical effectiveness interpretations	Trials number (%)
Random guess	Random guess	Ideal, possibly most ideal from the scientific or statistical perspective	8 (15)
Random guess	Opposite guess	Rare	2 (4)
Random guess	Unblinded	Possibly little treatment effect and completely no effect in control arm	3 (6)
Unblinded	Unblinded	Possibly problematic. Treatment effect in experimental arm and no treatment effect in control arm (e.g., patients tend to know what to expect)	4 (7)
Unblinded	Opposite guess	Ideal (e.g., patients tend to have wishful thinking, strong placebo effect, and any treatment administered is perceived as real treatment)	25 (46)
Unblinded	Random guess	Possibly problematic. Treatment effect in experimental arm and no treatment effect in control arm (e.g., patients do not know what to expect in the absence of treatment)	12 (22)
Opposite guess	Opposite guess	Rare	0 (0)
Opposite guess	Random guess	Rare	0 (0)
Opposite guess	Unblinded	No treatment effect at all; patients may have low expectations	0 (0)