Assessment of Randomised Controlled Trials (RCTs)
The Transplant Library contains records of all randomised controlled trials (RCTs) published in the field of transplantation from 1970 to present. The records of RCTs are updated every two weeks and retrieved from Medline (OvidSP and PubMed), the Cochrane Library (with permission) and by hand-searching conference proceedings.
Quality assessment
RCTs published from 2004 are rated for their methodological quality. The quality is assessed using the Jadad scale plus two additional items, namely the use of allocation concealment and an analysis based on intention to treat. Jadad scores range from 0 to 5 with trials scoring 3 or greater considered good quality trials. Each RCT is rated by two reviewers and after consensus on the methodological quality score the corresponding author of the RCT is contacted by email for verification. Any additional information regarding the quality items that is not included in the RCT report is published in the Transplant library.
The Jadad Scale
The Jadad scale is calculated using the seven items in the table below. The first five items are indications of good quality, and each counts as one point towards an overall quality score. The final two items indicate poor quality, and a point is subtracted for each if its criteria are met. The range of possible scores is 0 to 5.
- Was the study described as randomized (this includes words such as randomly, random, and randomization)?
Yes=1, No=0 - Was the method used to generate the sequence of randomization described and appropriate (table of random numbers, computer-generated, etc)?
Yes=1, No=0 - Was the study described as double blind?
Yes=1, No=0 - Was the method of double blinding described and appropriate (identical placebo, active placebo, dummy, etc)?
Yes=1, No=0 - Was there a description of withdrawals and dropouts?
Yes=1, No=0 - Deduct one point if the method used to generate the sequence of randomization was described and it was inappropriate (e.g. patients were allocated alternately, or according to date of birth, hospital number, etc).
Described but inappropriate = -1, Described and appropriate = 0 - Deduct one point if the study was described as double blind but the method of blinding was inappropriate (e.g. comparison of tablet vs. injection with no double dummy).
Described but inappropriate = -1, Described and appropriate = 0
Randomisation
A method to generate the sequence of randomization will be regarded as appropriate if it allowed each study participant to have the same chance of receiving each intervention and the investigators could not predict which treatment was next. Methods of allocation using date of birth, date of admission, hospital number or alternation should be not regarded as appropriate.
Double blinding
A study must be regarded as double blind if the word “double blind” is used. The method will be regarded as appropriate if it is stated that neither the person doing the assessments nor the study participant could identify the intervention being assessed, or if in the absence of such a statement the use of active placebos, identical placebos or dummies is mentioned.
Withdrawals and dropouts
Participants who were included in the study but did not complete the observation period or who were not included in the analysis must be described. The number and the reasons for withdrawal in each group must be stated. If there were no withdrawals, it should be stated in the article. If there is no statement on withdrawals, this item must be given no points. A flow diagram as recommended by the CONSORT statement is helpful in this regard.
Additional Items
Adequate allocation concealment
Concealment of allocation was considered adequate if patients and investigators who enrolled patients could not foresee the assignment. Adequate concealment included: central randomisation, pharmacy control, numbered or coded drug packs, or opaque, sealed and/or sequentially numbered envelopes.
Data analysis
The data analysis of trials is scored as one of four different analysis strategies:
- Strict intention to treat:
All patients are included in the analysis. Missing data are imputed in case of dropouts. - Available case analysis:
Data are analysed according to the assigned intervention for every participant for whom the outcome was obtained. Missing data are not imputed. - Modified ITT:
Data are analysed according to the assigned intervention. The analysis excludes participants who did not adhere to the protocol. For example, patients not transplanted or patients not receiving the study drug. - Per protocol analysis:
Only patients who sufficiently complied with the protocol are included in the analysis.
Useful references
Jadad AR, Moore RA, Carroll D, et al. Assessing the quality of reports of randomized clinical trials: is blinding necessary? Controlled Clinical Trials 1996; 17(1): 1-12 [PMID: 8721797]
The Consort Statement 2010. http://www.consort-statement.org
Intention to treat analysis. Transplant Evidence Blog, June 27, 2011. http://www.transplantevidence.com/blog/2011/06/intention-to-treat-analysis