. Author manuscript; available in PMC: 2022 May 1.

Published in final edited form as: Transplant Cell Ther. 2021 Jan 28;27(5):380–388. doi: 10.1016/j.jtct.2020.12.002

Table 2.

Frameworks for assessing quality of evidence.

Framework	Quality rating	Definition
AHRQ⁷⁴	Good	Design and conduct of study addresses risk of bias with appropriate measurement of outcomes and analytic methods
	Fair	Do not meet criteria for good quality, no flaw likely to cause major bias, missing information often drives rating
	Poor	Inappropriate design, conduct, analysis, or reporting
GRADE^54–56	High	Randomized trials; or double-upgraded observational studies.
	Moderate	Downgraded randomized trials; or upgraded observational studies.
	Low	Double-downgraded randomized trials; or observational studies.
	Very low	Triple-downgraded randomized trials; or downgraded observational studies; or case series/case reports.
NCCN⁷⁵	High	Based upon factors of quality (e.g., trial design and how the results/observations were derives), quantity of data (e.g., number of trials, size of trials, clinical observations only), and consistency of data (e.g., similar or conflicting results across available studies of observations),
	Lower
	Any
SIGN¹⁴	1++	High-quality meta-analyses, systematic reviews of 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
	2++	High-quality systematic reviews of case-control or cohort studies; high-quality case-control or cohort studies with a very low risk of confound, 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	Nonanalytic studies, e.g., case reports of case series
	4	Expert opinion
USPHS/IDSA⁷⁶	I	Evidence from ≥1 properly randomized, controlled trial.
	II	Evidence for ≥1 well-designed clinical trial without randomization, from cohort or case-controlled analytic studies (preferable from >1 center), or from multiple time series or dramatic results from uncontrolled experiments.
	III	Evidence from opinions of respected authorities based on clinical experience, descriptive.

Abbreviations: AHRQ, Agency for Healthcare Research and Quality; GRADE, Grading of Recommendations Assessment, Development and Evaluation; NCCN, National Comprehensive Cancer Network; RCTs, randomized controlled trials; SIGN, Scottish Intercollegiate Guidelines Network; USPHS/IDSA, United States Public Health Service and Infectious Disease Society of America