Table 1 Evidence levels were classified in accordance with the SIGN methodology
From: Proposed guidelines for the diagnosis and management of methylmalonic and propionic acidemia
Evidence level | Criteria |
|---|---|
1++ | High quality meta-analyses, systematic reviews of randomized control trials (RCTs), or RCTs with a very low risk of bias. |
1+ | Well conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias. |
1− | Meta-analyses, systematic reviews or RCTs, or RCTs with a high risk of bias. |
2++ | High quality systematic reviews of case-control or cohort studies or high quality case-control or cohort studies with a very low risk of confounding bias, or chance and a high probability that the relationship is causal. |
2+ | Well conducted case-control or cohort studies with a low risk of confounding, bias, or chance and a moderate probability that the relationship is causal. |
2+ | Case-control or cohort studies with a high risk of confounding, bias, or chance and a significant risk that the relationship is not causal. |
3 | Non-analytic studies, e.g. case reports, case series. |
4 | Expert opinion. |