A comparison of two primary care trials on tennis elbow:
issues of external validity
Nynke Smidt 1*, Martyn A Lewis 2, Elaine M Hay 2, Daniëlle AWM van der Windt 1, Lex M Bouter 1 and Peter Croft 2
1 Institute for Research in Extramural Medicine, Netherlands
2 Keele University, United Kingdom
* To whom correspondence should be addressed. E-mail: n.smidt{at}vumc.nl.
Accepted 21 March 2005
 | Abstract |
|---|
Objective: To assess the clinical heterogeneity
across
two studies with respect to study population,
interventions and outcome measures, and to evaluate the
influence of these sources of heterogeneity on the
results of the studies.
Methods: The individual patient data of two
randomised
controlled trials was used, both investigating the
effectiveness of conservative treatments in 164 and 185
patients with a tennis elbow in primary care,
respectively. Patients were allocated at random to a
treatment with steroid injection, wait-and-see policy,
NSAIDs, placebo tablets, or physiotherapy. Outcome
measures included severity of the main complaint,
inconvenience of the elbow complaints, pain during the
day, elbow disability, pain-free grip strength and
global improvement. All outcomes were assessed at one,
six and twelve months after randomisation.
Results: The two study populations were similar
with
respect to age, gender, co-morbid neck/shoulder
complaints, and baseline scores for the severity of
pain. However, significant differences were observed for
employment status, duration of elbow complaints,
dominant side affected, previous history of elbow
complaints, and use of painkillers. Local injections
differed between the two studies with respect to volume,
number and steroid preparation. However, after 1, 6 and
12 months, the treatment effects of steroid injections
were very similar between the study populations.
Conclusion: Despite large differences in study
population at baseline, the responses to steroid
injections were remarkably similar. Also the responses
to other conservative interventions and the placebo
treatment were very consistent, suggesting a uniform
course of a tennis elbow and a lack of influence of
clinical heterogeneity.
Keywords:
NSAIDs, physiotherapy, randomized controlled trial, steroid injections, tennis elbow
