Box 4.

—Case study: prognosis in elbow disorders

• Hudak et al carried out a systematic review of the evidence regarding prognostic factors that affect the duration of elbow pain and outcomes.¹² Selected papers were subjected to a detailed quality assessment by using a scheme adapted from other publications. Each paper was assessed on six dimensions: case definition, patient selection, follow up (completeness and duration), outcome, information about prognostic factors, and analysis. Each dimension was scored from 0 to 2 or 3. The authors' prespecified minimum requirements for studies providing strong evidence (number of studies out of 40 meeting the criteria in brackets) were:

• Provided an operational definition of cases (15)
• Included an inception cohort (defined in relation to onset of symptoms) or a survival cohort that included a subset of patients in whom duration of symptoms was less than 4 months (5)
• Showed follow up of more than 80% of cases for at least 1 year (8)
• Used a blinded and potentially replicable outcome measure appropriate to the research question (20)
• Used adequate measurement and reporting of potential prognostic factors (36)
• Provided crude proportions for at least one of response, recovery, and recurrence (34)

• Papers were identified from a comprehensive literature search of multiple databases. The authors included the search strategy they used.
• Of the 40 eligible studies assessed using the above criteria, none provided “strong evidence” and just four provided “moderate evidence,” none of which followed patients for more than one year. The authors note that several studies with excellent follow up were not based on inception cohorts. Only three of the 40 studies had used a statistical method to derive results adjusted for other factors.
• Among the four providing evidence of a “moderate level” there was variation in study design (one case series, three randomised trials), patient selection, interventions, and length of follow up. As a consequence meta-analysis was not attempted. The authors made several suggestions for the methodological requirements for future studies.