Patient accrual and quality of participation in a multicentre study on myeloma: a comparison between major and minor participating centres.

The participation of minor centres in randomized trials has been questioned because of inferior quality of participation. We have studied this issue in a multicentre trial on myeloma, in which 574 patients were included from 99 participating centres in Sweden, Norway and Denmark from 1 June 1990 until 4 November 1992. Two hundred and eight patients were entered from university hospitals (n = 13), 172 from major county hospitals (n = 25), defined by a population base of > or = 100,000 inhabitants, and 194 from minor county hospitals (n = 61) with a population base of < 100,000 inhabitants. The accrual rate was similar for the three hospital categories, averaging 54% of all reported cases, corresponding to 38% of the expected number of newly diagnosed cases. The adherence to the study protocol from an administrative point of view was judged by the completeness of follow-up forms and the delay in the notification of deaths, and from a clinical point of view by the dose intensity for the principal drugs of the study, melphalan and interferon. For all studied measures of quality, the values were similar for the three hospital categories. We conclude that with due informative and educational support, minor centres can make a considerable contribution to the patient material of a large randomized trial without impairing the quality of the study.