By Ruth Whittington ([email protected])

Part 3 – Conducting an observational study

Last month, we looked at the differences between observational studies and randomised controlled trials (RCTs). Here, we look at designing and conducting an observational study.

Observational studies should be conducted to high standards. You can use the following checklist when designing observational studies; all studies should be reviewed by a medical research committee.

  • Non interventional: there must be no randomisation, and nothing in the study design that directs or interferes with the initial physician decision or subsequent care. No test results should be requested unless performed in the normal course of treatment. Data collection should be performed at normally scheduled visits. Additional patient questionnaires may be required.
  • Scientifically valuable: the study must address a valid scientific question and have clear objectives and endpoints.
  • Study design and size: The study design should clearly meet the research objectives. The study should be large enough to have adequate statistical power. As there is a high possibility of treatment switching, the study design needs experienced and thorough statistical input from the beginning
  • Safety reporting: the study design should consider the need to collect safety data. Alternative mechanisms to monitor safety may be adequate, and adverse event reporting may not be required in non-interventional studies.
  • Analysis plan: this should be finalised before the data become available, to minimise potential bias.
  • Publication plan: this should be discussed with external investigators, and key publications should be agreed in principle. In observational studies in poorly researched areas, the baseline data can be of great value and interest to clinicians, so you should allow for some publications here as well as at later stages in the study.
  • Patient consent: appropriate consent should be obtained. Typically, this is simpler than for an RCT, but is required where new patient data are collected (for example, quality of life questionnaires) and may be required before agreeing that existing data can be shared by the investigator.
  • Ethical consent: appropriate ethics committee approval should be obtained.
  • Appropriate reimbursement: investigators should be reimbursed for their time only, and not paid an amount that might be perceived as a subsidy for drug cost or act as an incentive. The last thing you want is for physicians’ decisions for treatment to be influenced.
  • Where observation is concerned, chance favours only the prepared mind.