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Systematic Reviews for Health Sciences and Medicine

An introduction to systematic reviews, with examples from health sciences and medicine

Critical Appraisal

Critical appraisal is the process of judging the validity and quality of a research paper.

Major points to consider when appraising systematic reviews include:

  • Is the study valid?

  • What are the results, and are they significant?

  • Are the results applicable?


Critical Appraisal Tools

Critical Appraisal Skills Programme (CASP)
Ten questions to help you make sense of a systematic review

AMSTAR 2
A critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both

STROBE - designed for epidemiological studies

EQUATOR network listing over 300 sets of reporting guidlelines

Crowe and Sheppard (2011) summarising 44 critical appraisal tools


PRISMA checklist - not a quality instrument but helpful for identifying elements to look for in a systematic review. 

SPIRIT checklist - not a quality instrument but helpful for identifying elements to look for in a systematic review. 


Further Reading

Greenhalgh, T. (1997). How to read a paper. The Medline database. BMJ, 315(7101), 180-3

Greenhalgh, T. (1997). How to read a paper. Getting your bearings (deciding what the paper is about). BMJ, 315(7102), 243-6

Greenhalgh, T. (1997). How to read a paper: Assessing the methodological quality of published papers. BMJ, 315(7103), 305-8

Greenhalgh, T. (1997). How to read a paper. statistics for the non-statistician. i: Different types of data need different statistical tests. BMJ, 315(7104), 364-6

Greenhalgh, T. (1997). How to read a paper. statistics for the non-statistician. ii: "significant" relations and their pitfalls. BMJ, 315(7105), 422-5

Greenhalgh, T. (1997). How to read a paper. papers that report drug trials. BMJ, 315(7106), 480-3

Greenhalgh, T. (1997). How to read a paper. papers that report diagnostic or screening tests. BMJ, 315(7107), 540-3

Greenhalgh, T. (1997). How to read a paper. papers that tell you what things cost (economic analyses). BMJ, 315(7108), 596-9

Greenhalgh, T. (1997). Papers that summarise other papers (systematic reviews and meta-analyses). BMJ, 315(7109), 672-5

Greenhalgh, T, & Taylor, R. (1997). Papers that go beyond numbers (qualitative research). BMJ, 315(7110), 740-3


Data Extraction

Data extraction is the process of transcribing information from the primary studies under review to a standard form or template that has been designed to capture all of the detail relevant to the meta-analysis.

Double data extraction is preferred for accuracy - this is when two researchers extract the data independently and discuss any discrepancies or consult a moderator to arrive at consensus.

Further Reading

Buscemi, N., Hartling, L., Vandermeer, B., Tjosvold, L., & Klassen, T. P. (2006). Single data extraction generated more errors than double data extraction in systematic reviews. Journal of clinical epidemiology, 59(7), 697-703. Full Text