9.8.3 CONSORT and Critical Appraisal

Describes the CONSORT Statement: Recommendations for Improving the Quality of Reports of Parallel-Group Randomized Trials

The Consolidated Standards of Reporting Trials (CONSORT) statement was published in 1996 as a set of recommendations to improve the quality of reporting randomized controlled trials (RCTs). Since then, CONSORT has been revised and updated several times to reflect new developments and to provide more detailed guidance. The most recent version, CONSORT 2010, consists of a 25-item checklist and a flow diagram that outline the essential information that should be included in reports of parallel-group RCTs.

The checklist covers three main areas: (1) the introduction and methods, (2) the results, and (3) the discussion. Some of the items on the checklist include information about the trial design, participant recruitment and eligibility criteria, randomization and blinding procedures, interventions, outcomes, statistical methods, and adverse events. The flow diagram shows the flow of participants through each stage of the trial, from initial screening to analysis.

The CONSORT statement is an important tool for improving the quality of reporting RCTs and for helping readers to critically appraise the validity and applicability of the findings. By following the CONSORT guidelines, authors can ensure that their reports are complete, transparent, and accurate, which can enhance the credibility and usefulness of the research.

Critically Appraises Randomised Controlled Trials, Cohort and Case-Control Studies as Used to Address Therapy, Harm and Aetiology Questions

Critical appraisal of studies is an essential skill for healthcare professionals to ensure the validity and reliability of the evidence used to inform clinical decision-making. Different study designs are used to address various types of research questions, such as therapy, harm, and aetiology. In this teaching piece, we will discuss how to critically appraise randomized controlled trials (RCTs), cohort studies, and case-control studies.

Randomized controlled trials (RCTs):

RCTs are considered the gold standard for evaluating the efficacy of therapy or intervention. The critical appraisal of an RCT should focus on the following key aspects:

• Study design: The study should be a parallel-group RCT, with adequate randomization and blinding procedures.
• Sample size: The sample size should be large enough to detect a clinically significant difference between the intervention and control groups.
• Intervention: The intervention should be clearly described, and the duration, dose, and mode of administration should be specified.
• Outcomes: The primary and secondary outcomes should be relevant to the research question, and the methods used to measure them should be appropriate and reliable.
• Analysis: The statistical methods used should be appropriate, and the results should be reported with measures of precision and variability.

Cohort studies:

Cohort studies are used to investigate the association between exposure to a risk factor and the development of a disease or outcome. The critical appraisal of a cohort study should focus on the following key aspects:

• Study design: The study should be a prospective cohort study, with clear inclusion and exclusion criteria, and a follow-up period long enough to detect the outcome of interest.
• Exposure assessment: The exposure to the risk factor should be accurately measured, and the method used should be reliable and valid.
• Outcomes: The outcome of interest should be clearly defined, and the methods used to measure it should be appropriate and reliable.
• Confounding: The study should control for potential confounding factors that may affect the association between exposure and outcome.
• Analysis: The statistical methods used should be appropriate, and the results should be reported with measures of precision and variability.

Case-control studies:

Case-control studies are used to investigate the association between a risk factor and a disease or outcome by comparing a group of cases with a group of controls. The critical appraisal of a case-control study should focus on the following key aspects:

• Study design: The study should be a case-control study, with clear inclusion and exclusion criteria for cases and controls.
• Selection of cases and controls: The cases and controls should be selected from the same population, and the method used to select them should be appropriate and unbiased.
• Exposure assessment: The exposure to the risk factor should be accurately measured, and the method used should be reliable and valid.
• Confounding: The study should control for potential confounding factors that may affect the association between exposure and outcome.
• Analysis: The statistical methods used should be appropriate, and the results should be reported with measures of precision and variability.

Comparing the critical appraisal of randomized controlled trials, cohort, and case-control studies:

Study Type	Strengths	Weaknesses
Randomized Controlled Trials	Randomization minimizes selection bias Intervention and comparison groups are similar at baseline Randomization minimizes the likelihood of confounding Causal inferences can be made	May not be feasible or ethical to conduct May not be generalizable to all populations Blinding may not be possible Limited external validity
Cohort Studies	Can establish temporality Can study multiple outcomes Can assess the effect of multiple exposures Can calculate incidence rates	Selection bias can occur Confounding can occur May require long follow-up periods Limited generalizability
Case-Control Studies	Useful for rare diseases/outcomes Can assess multiple exposures Efficient for studying rare outcomes Can provide estimates of odds ratios	Selection bias can occur Recall bias can occur Cannot calculate incidence rates Cannot establish temporality

In conclusion, critical appraisal of studies is essential to ensure that the evidence used to inform clinical decision-making is valid and reliable. The key aspects to consider when critically appraising RCTs, cohort studies, and case-control studies are study design, sample size, intervention/exposure assessment, outcomes, confounding, and analysis.

References:

1. Critical Appraisal Skills Programme (CASP). CASP Checklists. Available from: https://casp-uk.net/casp-tools-checklists/.
2. Higgins JP, Thomas J, Chandler J, et al. Cochrane Handbook for Systematic Reviews of Interventions. Version 6.2. Cochrane, 2021. Available from: https://training.cochrane.org/hand
3. JAMAevidence. (2014). Users’ Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice, 3rd ed. The McGraw-Hill Companies, Inc.
4. Moher D, Schulz KF, Altman DG, et al. The CONSORT statement: revised recommendations for improving the quality of reports of parallel-group randomized trials. Ann Intern Med. 2001;134(8):657-662. doi: 10.7326/0003-4819-134-8-200104170-00011