BMJ  2005;330:94 (8 January), doi:10.1136/bmj.330.7482.94-a

Letter

Inappropriateness of randomised trials for complex phenomena

Single trial is never enough evidence to base decisions on

EDITOR—Kotaska outlines the importance of care providers' skill and the experience of a unit when assessing non-pharmacological treatments such as vaginal breech delivery in randomised trials.¹ We agree that evaluation of non-pharmacological treatment raises specific methodological issues, including the skill of care providers.²

Care providers are part of the intervention to be tested, and having highly skilled or experienced care providers in one arm and low skilled or less experienced care providers in the other could lead to bias. Equally, bias can occur when care providers have more experience in performing one of the interventions tested than the other. However, appropriate methodological planning of randomised trials could circumvent this bias. To allow the surgical procedure to be assessed in the context of the skills required to achieve it, care providers participating in a surgery trial could be trained and selected only if they achieve set standards,³ selected according to their experience of the procedure,⁴ or patients could be randomised not to operations but to care providers, who would deliver their treatment of preference.⁵

Vaginal breech delivery is a complex procedure Credit: MOTHER AND BABY PICTURE LIBRARY

 

Kotaska's article was an interesting example of potential bias linked to care providers' experience; the author generalises when concluding that complex procedures are poorly amenable to the methods of large multicentre randomised trials. Condemning all multicentre randomised trials that assess complex interventions when considering one imperfect randomised controlled trial seems as inappropriate as defining a new standard of care for vaginal breech delivery based on a single trial that is potentially biased.

Isabelle.boultron{at}bch.ap-hop-paris.fr, Département d'Epidémiologie, Biostatistique et Recherche Clinique, INSERM EMI 0357, Groupe Hospitalier Bichat-Claude Bernard (AP-HP), Faculté de Médecine Xavier Bichat, Université Paris VII, 46 rue Henri Huchard, 75877 Paris, France

Département d'Epidémiologie, Biostatistique et Recherche Clinique, INSERM EMI 0357, Groupe Hospitalier Bichat-Claude Bernard (AP-HP), Faculté de Médecine Xavier Bichat, Université Paris VII, 46 rue Henri Huchard, 75877 Paris, France

INSERM CIC 202, Tours, France

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Competing interests: None declared.

References

1. Kotaska A. Inappropriate use of randomised trials to evaluate complex phenomena: case study of vaginal breech delivery. BMJ 2004;329: 1039-42. (30 October.)[Free Full Text]
2. Boutron I, Tubach F, Giraudeau B, Ravaud P. Methodological differences in clinical trials evaluating nonpharmacological and pharmacological treatments of hip and knee osteoarthritis. JAMA 2003;290: 1062-70.[Abstract/Free Full Text]
3. Feldon SE, Scherer RW, Hooper FJ, Kelman S, Baker RS, Granadier RJ. Surgical quality assurance in the ischemic optic neuropathy decompression trial (IONDT). Contr Clin Trials 2003;24: 245-354.
4. Barnett HJ, Taylor DW, Eliasziw M, Fox AJ, Ferguson GG, Haynes RB. Benefit of carotid endarterectomy in patients with symptomatic moderate or severe stenosis. North American Symptomatic Carotid Endarterectomy Trial Collaborators. N Engl J Med 1998;339: 1415-25.[Abstract/Free Full Text]
5. McCulloch P, Taylor I, Sasako M, Lovett B, Griffin D. Randomised trials in surgery: problems and possible solutions. BMJ 2002;324: 1448-51.[Free Full Text]

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