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Can we trust patient reported outcomes in the absence of blinding?

Can we trust patient reported outcomes in the absence of blinding? . Fiona Campbell, Mike J. Bradburn , Amitabh Deka. Canadian Cardiovascular Society Angina Score. Angina Score – sensitivity analysis. PROs. Landmark development – routine use introduced into the NHS in 2009

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Can we trust patient reported outcomes in the absence of blinding?

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  1. Can we trust patient reported outcomes in the absence of blinding? Fiona Campbell, Mike J. Bradburn, AmitabhDeka

  2. Canadian Cardiovascular Society Angina Score

  3. Angina Score – sensitivity analysis

  4. PROs Landmark development – routine use introduced into the NHS in 2009 USA Food and Drug Administration recommend their inclusion in clinical trials

  5. Blinding/Masking Patients/participants Caregivers Outcome assessors

  6. Evidence of bias in absence of blinding – links to previous work Lack of double blinding exaggerated treatment effects (ratio of odds ratios 0.83 (95% CI 0.71 to 0.96)) Schulz et al 1995 Lack of double blinding in subjective outcomes exaggerated treatment effects (ratio of odds ratios 0.75 (95% CI 0.61 to 0.93)) Woods et al 2008

  7. What did we add? • Focus on PROs, rather than subjective/objective • Develop a method to look at continuous outcomes • A focus on patient blinding

  8. Is the effect the same across disease types? • If bias exists are some PROs more robust than others? • What methods are at present being used to control for bias in the absence of blinding in subjective outcomes in Cochrane reviews?

  9. Methods: Cochrane Systematic Reviews Focused on asthma, arthritis, coronary heart disease, COPD 1 reviewer extracted data from meta-analysis our inclusion criteria

  10. Inclusion criteria for the SR had to have performed a MA PRO and an objective measure (eg. blood test) trials of interventions where blinding was possible trials that included both an unblinded and a blinded study in the same outcome

  11. Data extracted details of outcome measure details of blinding effects of the interventions methods of assessment of bias in the review

  12. Statistical methods • Outcomes tended to be continuous – presentation concentrates on these • For each outcome in each review calculate: • Pooled standardised mean difference (SMD), i.e. (T - C) /  • Unblinded studies SMDU • Blinded studies SMDB • Impact of blinding is SMDU - SMDB

  13. Results • Preliminary! • Not what we expected! • Limited data – 11 reviews.

  14. Conclusion At present we have found no evidence that in this limited number of chronic conditions (in interventions where blinding was possible) that PROs are biased in the absence of blinding.

  15. Discussion Blinding can be broken – rarely assessed and reported – maybe blinded studies were not blind so that may account for lack of effect Is bias previously seen in subjective outcomes observer bias? What are the implications for interventions where blinding is not possible?

  16. Ways forward… Broaden the scope to include more reviews Develop statistical methods to pool the data

  17. Thank you. f.campbell@sheffield.ac.uk

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