This document discusses negative trials in neurosurgery. It lists several negative trials led by Drs. Patel, Bervini, Lai, Gragnaniello, Paramasvaran, and Liu. Negative trials can be inconclusive with inadequate power/methodology or show clear evidence of no effect or harm. Reasons for negative results include issues with trial design, size, bias, analysis, and inclusion/exclusion criteria affecting generalizability. Negative studies should still be published to acknowledge participant contributions, contribute to scientific knowledge, avoid publication bias, and fulfill funding conditions. Lessons from negative trials include whether the intervention warrants further research, continued use in select populations, or should be abandoned.

1. Negative trials in neurosurgery –
What positives can we take from them?
Neurosurgery debate
31 May 2012
Negative trials 1

2. Negative trials in neurosurgery
• Dr Patel - SAMMPRIS (2011)
• Dr Bervini - COSS (2011)
• Dr Lai - IHAST (2005)
• Dr Gragnaniello - Vertebroplasty (2009)
• Dr Paramasvaran - INTERPHONE (2010)
• Dr Liu - DECRA (2011)
Negative trials 2

3. What is a negative study?
• Inconclusive ‘no evidence of effect’
– Inadequately powered, poor methodology
• Clear evidence of ‘no effect’
– Well designed, adequately powered
• Clear evidence of harm
– Sandercock, 2011 (Int J Stroke)
Negative trials 3

4. Why a negative result?
• Internal validity
– Trial design
– Study size (power effects)
– Bias
– Statistical analysis
• External validity
– Inclusion/exclusion criteria
– Generalisability
Negative trials 4

5. Why should a negative study be published?
• Ethical
– Participants’ contribution should be acknowledged
• Scientific
– Contribute to knowledge
• Systematic reviews
– Publication bias
• Funding conditions
Negative trials 5

6. What can we learn from a negative study?
• Should the intervention be subjected to
further studies?
• Should the intervention continue in selected
populations?
• Should the intervention be abandoned?
Negative trials 6

7. Presentations
• 10 minutes presentation
• 5 minutes questions
• Assessment
– Oral presentation
– Use of visual material
– Critical appraisal – internal validity
– Critical appraisal – external validity
– Response to questions
Negative trials 7