To meet the evidence users' requirement for qualitative systematic review, it is necessary to establish an evidence classification system for it. The Confidence of the Evidence from Reviews of Qualitative research (CERQual) approach was developed for evidence classification of qualitative systematic review. Four components contribute to the assessment in CERQual: (1) Methodological limitations: Refer to problems in the design or conduct of the primary studies which need to be evaluated by specific tools used for methodological assessment of qualitative research. (2) Relevance: Relevance is the extent to which the objective, population etc. of included studies are applicable to the review question. (3) Coherence: It is the extent to which the review finding is consistent with the results in primary studies or the patterns, differences across primary studies, were explained reasonably. (4) Adequacy of data: Refer to the degree of richness and quantity of data supporting a review finding. Finally, integrate each of the components and rate the confidence of individual review finding as high, moderate, low or very low confidence. CERQual provides a transparent method for assessing the confidence of evidence from reviews of qualitative research. It may facilitate the use of qualitative research in evidence-informed decision making and guideline development processes. This article will introduce CERQual approach in detail and give an example to explain how to use it.
In response to the specific requirements of nutrition research, Schwingshackl’s research group developed the NutriGrade grading system, which independently assessed the quality of evidence in randomized controlled trials and cohort studies in nutrition, aiming to summarize the associations or effects between different nutritional factors and outcomes and meet the specific needs of evidence users. It has the advantages of novel classification, quantifiability, independence and pertinence, and it has better consistency, fairness, reliability and feasibility. Well-designed prospective cohort studies are more feasible in the field of nutrition than randomized controlled trials. The grading of the evidence quality for cohort studies included the following eight items: a) risk of bias, study quality, and study limitations; b) precision; c) heterogeneity; d) directness; e) publication bias; f) funding bias; g) effect size; and h) dose-response. Based on the evaluation results of the above items, the evidence quality could be divided into four grades: high (8-10), moderate (<8), low (<6), and very low (<4). The purpose of this paper was to introduce the basic principles, specific contents, and application methods of the NutriGrade grading system for cohort studies and cite examples to provide references for relevant researchers.