Open access follow up for inflammatory bowel disease

doi:10.1136/bmj.320.7251.1730

BMJ 2000;320:1730 ( 24 June )

Letters

Open access follow up for inflammatory bowel disease

Would have been better to use t test than Mann-Whitney U test

Ability of any method of follow up to detect cancer must be stated

Authors' reply

Would have been better to use t test than Mann-Whitney U test

The first 150 words of the full text of this article appear below.

EDITOR $---$ Williams et al undertook a randomised trial to evaluate whether follow up of patients with inflammatory bowel diseaseis better with open access than with routine appointments.¹They compared primary and secondary care resource use and costsand concluded that open access follow up saves secondary careresources. This conclusion, however, is mistaken because theyused inappropriate statisticalmethods.

Resource use and cost data tend to have highly skewed distributions. As a result, the authors decided that standard parametricstatistical methods were not appropriate and assessed significanceby using a Mann-Whitney U test. Although this is consistent withconventional statistical guidelines,² it does not address thequestion of interest in economic evaluations. As the authors themselvesstate, "economic analysis is mainly concerned with a comparisonof means." Use of a Mann-Whitney U test, however, makes an overallcomparison of distributions in the two groups, in terms of both. . . [Full text of this article]

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Williams, J G, Cohen, D R, Russell, I T (2002). Clarifications: open access follow up for inflammatory bowel disease. BMJ 324: 1586-1586 [Full text]
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Rapid Responses:

Read all Rapid Responses

Confidence intervals should be used in reporting trials: Martin Bland
bmj.com, 23 Jun 2000 [Full text]
Re: Confidence intervals should be used in reporting trials: J G Williams
bmj.com, 6 Jul 2000 [Full text]
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