Table 2.
Summary of findings.
| Outcomes | Anticipated Absolute Effects * (95% CI) | Relative Effect (95% CI) | No. of Participants | Certainty of the Evidence (GRADE) | |
|---|---|---|---|---|---|
| Risk with Placebo | Risk with Selenium | ||||
| TPO-Ab (LT4-treated population, 3 months) | - | SMD 0.53 lower (0.89 lower to 0.17 lower) |
- | 840 (12 trials) |
⨁◯◯◯ Very low a,b,c |
| TPO-Ab (LT4-treated population, 6 months) | - | SMD 1.95 lower (3.17 lower to 0.74 lower) |
- | 476 (6 trials) |
⨁◯◯◯ Very low a,b,c |
| TPO-Ab (Non-LT4-treated population, 3 months) | - | SMD 1.40 lower (2.27 lower to 0.54 lower) |
- | 750 (5 trials) |
⨁⨁◯◯ Low b,c |
| TPO-Ab (Non-LT4-treated population, 6 months) | - | SMD 1.93 lower (3.09 lower to 0.77 lower) |
- | 808 (7 trials) |
⨁⨁◯◯ Low b,c |
| TPO-Ab (Non-LT4-treated population, 12 months) | - | SMD 3.14 lower (6.49 lower to 0.21 higher) |
- | 274 (3 trials) |
⨁◯◯◯ Very low b,c,d |
| TG-Ab (LT4-treated population, 3 months) | - | SMD 0.23 lower (0.49 lower to 0.02 higher) |
- | 481 (7 trials |
⨁⨁◯◯ Low c,d |
| TG-Ab (LT4-treated population, 6 months) | - | SMD 0.50 lower (1.15 lower to 0.15 higher) |
- | 320 (4 trials) |
⨁◯◯◯ Very low a,b,c,d |
| TG-Ab (Non-LT4-treated population, 3 months) | - | SMD 0.67 lower (0.99 lower to 0.34 lower) |
- | 155 (2 trials) |
⨁⨁⨁◯ Moderate c |
| TG-Ab (Non-LT4-treated population, 6 months) | - | SMD 2.13 lower (3.59 lower to 0.67 lower) |
- | 405 (5 trials) |
⨁⨁◯◯ Low b,c |
| TG-Ab (Non-LT4-treated population, 12 months) | - | SMD 2.32 lower (7.04 lower to 2.41 higher) |
- | 274 (3 trials) |
⨁◯◯◯ Very low b,c,d |
| Adverse effects | 12 per 1000 | 38 per 1000 (12 to 79) |
RR 2.93 higher (0.93 higher to 6.11 higher) | 669 (8 trials) |
⨁⨁◯◯ Low a,d |
* The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). Abbreviations: SMD, standardized mean difference; RR, risk ratio. GRADE Working Group grades of evidence: High certainty (⨁⨁⨁⨁): We are very confident that the true effect lies close to that of the estimate of the effect. Moderate certainty (⨁⨁⨁◯): We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. Low certainty (⨁⨁◯◯): Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect. Very low certainty (⨁◯◯◯): We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect. a Downgraded one level because of risk of bias. b Downgraded one level because of inconsistency. c Downgraded one level because of indirectness. d Downgraded one level because of imprecision, including wide confidence intervals, lack of participants, and lack of events.