Trial	Examples of outcome assessments used	Comments
Beliveau28	Four categories of outcome: completely relieved, improved, unchanged, and worse. Three criteria had to be met for complete recovery: complete disappearance of pain plus full and free lumbar movements plus “greatly improved” straight leg raising	The vagueness of the criteria leaves them open to the subjectivity of the observer. What are full and free lumbar movements? How many degrees constitute “greatly improved” straight leg raising?
Snoek et al29	Divided pain into four categories: back pain, radiating pain, impulse pain, and pain that disturbed sleep. For radiating pain, diminished area of radiation was taken as improvement, whereas for all other categories complete disappearance was necessary	It is the degree not the distribution of pain that matters to a patient. Response in most other trials was graded, rather than complete relief or not. Comparison with other trials was thus impossible