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Unpublished rating scales: A major source of bias in randomised controlled trials of treatments for schizophrenia

  • Max Marshall (a1), Austin Lockwood (a1), Caroline Bradley (a2), Clive Adams (a3), Claire Joy (a3) and Mark Fenton (a3)...
Abstract
Background

A recent review suggested an association between using unpublished scales in clinical trials and finding significant results.

Aims

To determine whether such an association existed in schizophrenia trials.

Method

Three hundred trials were randomly selected from the Cochrane Schizophrenia Group's Register. All comparisons between treatment groups and control groups using rating scales were identified. The publication status of each scale was determined and claims of a significant treatment effect were recorded.

Results

Trials were more likely to report that a treatment was superior to control when an unpublished scale was used to make the comparison (relative risk 1.37 (95% C11.12–1.68)). This effect increased when a ‘gold-standard’ definition of treatment superiority was applied (RR 1.94 (95% C11.35–2.79)). In non-pharmacological trials, one-third of ‘gold-standard’ claims of treatment superiority would not have been made if published scales had been used.

Conclusions

Unpublished scales are a source of bias in schizophrenia trials.

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Copyright
Corresponding author
Dr Max Marshall, University of Manchester, Department of Community Psychiatry, Guild Academic Centre, Royal Preston Hospital, Sharoe Green Lane, Preston PR2 9HT
Footnotes
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Declaration of interest

None. No funding.

Footnotes
References
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Adams, C. (1998) Cochrane Schizophrenia Group's Register of Randomised Controlled Trials. The Cochrane Library. Oxford: Update Software.
Begg, C., Cho, M. & Eastwood, S. (1996) Improving the quality of reporting of randomized controlled trials: the CONSORT statement. Journal of the American Medical Association, 276, 637639.
Bowling, A. (1991) Measuring Health. Milton Keynes: Open University Press.
Gotzsche, P. C. (1989) Methodology and overt and hidden bias in reports of 196 double-blind trials of nonsteroidal, antiinflammatory drugs in rheumatoid arthritis. Controlled Clinical Trials, 10, 3156.
Landis, J. R. & Koch, G. G. (1977) The measurement of observer agreement for categorical data. Biometrics, 33, 159174.
Marshall, M. & Lockwood, A. (1999) Assertive community treatment for people with severe mental disorders (Cochrane Review). In The Cochrane Library. Oxford: Update Software.
Royal College of Psychiatrists (1994) Psychiatric Instruments and Rating Scales. A Select Bibliography (2nd edn). Occasional Paper OP23. London: Royal College of Psychiatrists.
Sanders, C., Egger, M., Donovan, J., et al (1998) Reporting on quality of life in randomised controlled trials: bibliographic study. British Medical Journal, 317, 11911194.
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The British Journal of Psychiatry
  • ISSN: 0007-1250
  • EISSN: 1472-1465
  • URL: /core/journals/the-british-journal-of-psychiatry
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Unpublished rating scales: A major source of bias in randomised controlled trials of treatments for schizophrenia

  • Max Marshall (a1), Austin Lockwood (a1), Caroline Bradley (a2), Clive Adams (a3), Claire Joy (a3) and Mark Fenton (a3)...
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