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Table 1 Factors that may lead to downgrading or upgrading of evidence in the GRADE approach

From: Oral nutritional supplements for preventing surgical site infections: protocol for a systematic review and meta-analysis

Criteria for downgradingBy how many levels
1. Serious risk of biasSerious (- 1) or very serious (- 2) limitation to study quality
2. Serious inconsistence between studiesImportant inconsistency, lack of agreement between studies or conflicting results (- 1)
3. Serious indirectnessUncertainty with generalisability of population or outcomes (- 1) or with both population and outcomes (- 2)
4. Serious imprecisionImprecise or sparse data (- 1)
5. Likely publication biasHigh probability of reporting bias (- 1)