Systematic Review Service

Data collection, also called data extraction, is performed for each included study independently by two reviewers.

But first, members of the team, including the statistician if there is one, must work together to determine which data to collect from the studies included in the review. This should be completed at the protocol stage and included in the protocol itself.

It is recommended that once you have determined the data to extract, the team pilot the extraction template on several included studies to make sure it functions as anticipated and is understood by everyone performing extraction.

Data collection should be guided by your research question. Frequently collected data includes but is not limited to:

• Basic study information: Authors, publication date, clinical trial number.
• Study type: Prospective, retrospective, mixed methods, case series, controlled trial.
• Study characteristics: Setting, location, recruitment methods, eligibility criteria.
• Participants: Number included, number lost to follow-up, sex, age, race, ethnicity, diagnosis/es, comorbidities.
• Interventions/Exposures: Dosage, time frame, method of administration, staff performing intervention, follow-ups, exposure times.
• Comparisons: Placebo, standard-of-care, no comparison given.
• Outcomes: Measurements used, effects measured, time frames, adverse events

Systematic reviews collect data from studies, not publications. If the same study is represented in multiple publications, determine which one is the most up-to-date or complete, and use that report to extract the data of interest.

If a publication does not include the necessary information, contact the authors to see if they can provide it. If they can not, or if they do not reply, list this as a reason for exclusion.

Learn more from the Cochrane Handbook and the Institute of Medicine of the National Academies.

Your MSK librarian can help create a separate Covidence project for pilot testing your template.

Data extraction is a step many researchers have difficulty with, so Covidence created a free eBook on this for researchers to download: A Practical Guide to Data Extraction for Intervention Systematic Reviews.

Covidence offers a fully customizable data extraction template. Once your team has finalized the template, Covidence has two reviewers perform the extraction, followed by conflict resolution either by consensus or by a third reviewer.

Learn more: