Page 332 - Drug Class Review

Final Report Update 1 Drug Effectiveness Review Project

APPENDIX C. Quality Criteria

Assessment of Internal Validity
To assess the internal validity of individual studies, the EPC adopted criteria for assessing the internal
validity of individual studies from the US Preventive Services Task Force and the NHS Centre for
Reviews and Dissemination.

For Controlled Trials:

Assessment of Internal Validity

1. Was the assignment to the treatment groups really random?
Adequate approaches to sequence generation:
Computer-generated random numbers
Random numbers tables
Inferior approaches to sequence generation:
Use of alteration, case record numbers, birth dates or week days
Not reported

2. Was the treatment allocation concealed?
Adequate approaches to concealment of randomization:
Centralized or pharmacy-controlled randomization
Serially-numbered identical containers
On-site computer based system with a randomization sequence that is not
readable until allocation
Other approaches sequence to clinicians and patients
Inferior approaches to concealment of randomization:
Use of alteration, case record numbers, birth dates or week days
Open random numbers lists
Serially numbered envelopes (even sealed opaque envelopes can be
subject to manipulation)
Not reported

3. Were the groups similar at baseline in terms of prognostic factors?

4. Were the eligibility criteria specified?

5. Were outcome assessors blinded to the treatment allocation?

6. Was the care provider blinded?

7. Was the patient kept unaware of the treatment received?

8. Did the article include an intention-to-treat analysis or provide the data needed to calculate it (i.e.,
number assigned to each group, number of subjects who finished in each group, and their results)?

9. Did the study maintain comparable groups?

10. Did the article report attrition, crossovers, adherence, and contamination?

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