Part Four of a Data Collection Form:
Study Quality

Before we discuss the design and use of a data extraction form for recording information about the quality of the included studies, we first need to understand some principles and issues surrounding the assessment of study quality and how it relates to Systematic Reviews. Before progressing further, complete Module 9: Assessing the Quality of Studies, then return to here.

Now that you have a grasp of the process of assessing the quality or validity of your included trials, we need to think about how you are going to do this in your review.

Think about the method you wish to use, describing set criteria such as allocation concealment, blinding and withdrawals; or using a particular quality assessment scale. Look at your review group's module on The Cochrane Library and see if they have a preferred method.

Once you know how you are going to do your validity assessment, you can design this component of your data collection form. If you are assessing whether a study met certain key criteria you need to list them, using either a checklist or the categorising of risk of bias table as outlined in Section 6.7.2 of the Reviewers' Handbook. Some examples of criteria you may wish to include are:

• Selection Bias (Was the study randomised? Was allocation concealment adequate?)
• Performance Bias (Were participants and care providers blind to the intervention? Were there any co-interventions?)
• Attrition Bias (Were all participants randomised accounted for in the anaysis? Were any withdrawers described?)
• Detection Bias (Was there a blinded assessment of outcome)
• Analysis (Was the analysis appropriate?)

If you are using a specific published validity assessment scale (and there are many) you will need to reproduce it as part of your form.

Design your form now, bearing in mind all the aspects of validity assessment you wish to use. You will need to test out how your form works, but we will discuss that later.