6. Quality of evidence ratings for primary and secondary outcomes (based on Ryan 2016).

Outcome	Study quality RCT = high Non‐RCT = low	Risk of biasa No = 0 Serious = –1 Very serious = –2	Inconsistencyb No = 0 Serious = –1 Very serious = –2	Indirectness No = 0 Serious = –1 Very serious = –2	Imprecisione No = 0 Serious = –1 Very serious = –2	Publication biasf Undetected = 0 Strongly suspected = –1	Other Large effect = + 1 Dose effect = + 1 No plausible confound = + 1	GRADE
Mixed/regular word reading accuracy	High	No = 0	No = 0c	No = 0	Very serious = –2	Undetected = 0	—	Low
Non‐word reading accuracy	High	No = 0	No = 0c	No = 0	Very serious = –2	Undetected = 0	—	Low
Irregular word reading accuracy	High	No = 0	No = 0c	No = 0	Very serious = –2	Undetected = 0	Large effect = + 1	Moderate
Mixed/regular word reading fluency	High	No = 0	No = 0d	No = 0	Serious = –1	Undetected = 0	—	Moderate
Non‐word reading fluency	High	No = 0	No = 0d	No = 0	Serious = –1	Undetected = 0	—	Moderate
Reading comprehension	High	No = 0	No = 0d	No = 0	Very serious = –2	Undetected = 0	—	Low
Spelling	High	No = 0	No = 0d	No = 0	Very serious = –2	Undetected = 0	—	Low
Letter‐sound knowledge	High	No = 0	No = 0d	No = 0	Very serious = –2	Undetected = 0	—	Low
Phonological output	High	No = 0	No = 0d	No = 0	Very serious = –2	Undetected = 0	—	Low

^aJudged 'no' if 75% + studies contributing to an outcome are low in majority of biases. Judged 'serious' if 50% to 74% of studies contributing to an outcome are low in majority of biases. Judged 'very serious' if fewer than 50% studies contributing to an outcome are low in majority of biases. See 'Risk of bias' Figure 1 and 'Risk of bias' tables for bias ratings for each study.
 ^bJudged 'no' if I² less than 70%^d OR I² greater than 70% but assessment of heterogeneity analysis suggests it did not affect the reliability of results^c (see Subgroup analysis and investigation of heterogeneity). Judged 'serious' if I² = 70% to 85%; judged 'very serious' if I² greater than 85%.
 ^eJudged 'no' if confidence interval 0 to 0.3. Judged 'serious' if confidence interval 0.3 to 0.6. Judged 'very serious' if confidence interval 0.6 + (Schünemann 2011b).
 ^fJudged 'undetected' if funnel plot done on more than 10 studies (Sterne 2011), and no bias detected. Judged 'unsuspected' if funnel plot not constructed (too few studies) but bias not strongly suspected. Judged 'strong suspected' if funnel plot not possible (too few studies) and bias strongly suspected.