Alejandro R. Jadad Bechara - The Jadad Scale

The Jadad Scale

The Jadad scale appears to produce robust and valid results in an increasing number of empirical studies. The scale includes three items that are directly related to bias reduction: randomization; blinding; description of withdrawals and drop outs. These are presented as questions to elicit ‘yes’ or ‘no’ answers and produces scores from 0 to 5. A trial could be judged as having poor quality if it is awarded 2 points or less. Studies that obtain 2 or less points have been shown to produce treatment effects which are 35% larger, on average, than those produced by trials with 3 or more points. Although some concerns have been expressed about the inter-observer reliability of the assessments, the scale has been cited over 7,000 times in the biomedical literature and has been used successfully to identify systematic differences in over 1,000 reviews of trials in many areas of health care.