Table 2.

GRADE assessment of the outcomes

Certainty assessment							№ of patients	Effect		Certainty
No. of studies	Study design	Risk of bias	Inconsistency	Indirectness	Imprecision	Other considerations	Zn	Placebo	Absolute (95% CI)
Number connection test
3	randomized trials	seriousa	not serious	not serious	not serious	publication bias strongly suspected strong associationb	116	111	SMD 0.97 lower (1.75 lower to 0.19 lower)	MODERATE
Digital symbol test
2	randomized trials	seriousa	not serious	not serious	seriousc	publication bias strongly suspected strong associationb	70	67	SMD 0.44 higher (0.12 lower to 1 higher)	VERY LOW
Serum ammonia lev
2	randomized trials	seriousa	not serious	not serious	seriousc	publication bias strongly suspected strong associationb	70	67	MD 10.86 lower (25.73 lower to 4.01 higher)	VERY LOW

CI Confidence interval, SMD Standardized mean difference, MD Mean difference

Explanations

^aWe downgraded by one level for serious risk of bias: one study was unblinded

^bPublication bias was not assessed due to the limited numbers of included trials

^cWe downgraded by one level for serious imprecision: the wide confidence interval contains significant benefits and harm