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Table 1 Grading system for strength of evidence

From: Patient centred variables with univariate associations with unplanned ICU admission: a systematic review

Strength of Evidence Criteria
Strong ≥2 high-quality studies showing positive association between the presence of a variable and the outcome
AND
No studies showing a negative association
Moderate One high-quality AND one lesser-quality study showing association
AND
No studies showing negative association
Weak > 2 low-quality studies showing positive association
OR
Only one high-quality study showing positive association
Negative ≥ 1 high-quality study showing negative association (inverse relationship)
AND
No studies showing a positive association
Inconclusive Associations present in only one low-quality study
OR
No studies of any quality showing univariate association
OR
Presence of positive and negative associations from different articles, regardless of study quality