Evidence-Βased Μedicine & Cochrane

Dr. James Manos (MD)

September 26, 2015

Evidence-based medicine (EBM) & Cochrane meta-analyses

Evidence-based medicine (EBM)

Today, 'evidence-based medicine' (EBM) is the aim of practicing medicine. EBM is based on scientific evidence rather than empirical knowledge. 

EBM recognizes that many aspects of health care depend on individual factors such as quality and value of life judgments, which are only partially subject to scientific methods. EBP seeks to clarify those parts of medical practice that are, in principle, subject to scientific methods and to apply these methods to ensure the best prediction of outcomes in medical treatment, even as debate continues about which outcomes are desirable.

Also, a meta-analysis may involve just a few RCTs (randomized controlled trials). For example, they investigate only 3 - 4 studies or even 1 - 2 studies, so it is impossible to reach a safe conclusion. Moreover, a study may have a short duration, influencing the results. So, the length of a study is essential. Follow–up is also crucial. 

All the available randomized controlled trials (RCTs) that are double (or triple) – blind and placebo-controlled are included. Two reviewers assess the available experiments and decide which will be incorporated based on particular ‘inclusion criteria.’ The statistics of the studies are evaluated for statistical flaws. The overall quality of the included studies (including sample, duration, follow–up, etc.) is assessed.

Today it is essential to check if a treatment helps patients. There is a specific way of testing it: Evidence-Based Medicine. Also, several trials and research are published in databases. These databases are also available online, such as ‘Medline’/PubMed at http://www.ncbi.nlm.nih.gov/pubmed

MedlinePlus is another site on https://www.nlm.nih.gov/medlineplus/ with a database on various medical issues that are often explained in simple language so that laypeople can read them.

Evidence-Based Medicine analyzes several randomized controlled trials (RTCs included in a meta-analysis such as the ones that the Cochrane database publishes) and ends up to a safe conclusion about whether a dietary supplement or a medication helps a disease. A guideline is published to guide doctors and scientists worldwide about its safe use.

Evidence-based medicine (EBM) aims to apply the best available evidence gained from the scientific method to clinical decision-making. It seeks to assess the strength of evidence of the risks and benefits of treatments (including lack of treatment) and diagnostic tests. This helps clinicians understand whether a treatment will benefit or harm. Evidence quality can be assessed based on the source type (from meta-analyses and systematic reviews of triple-blind, randomized, placebo-controlled clinical trials) and other factors, including statistical validity, clinical relevance, currency, and peer-review acceptance. 

Evidence-based medicine recommendations, according to the US Preventive Service Task Force, can be categorized into the following categories:

·        Level A: Good scientific evidence suggests that the clinical service's benefits substantially outweigh the potential risks. Clinicians should discuss the service with eligible patients.

·        Level B: there is at least good scientific evidence suggesting that the benefits of the clinical service outweigh the potential risks. Clinicians should discuss the service with eligible patients.

·        Level C: there is at least good scientific evidence suggesting that there are benefits provided by the clinical facility. However, the balance between benefits and risks is too close for making general recommendations. Clinicians need not offer it unless there are individual considerations.

·        Level D: there is at least good scientific evidence suggesting that the risks of the clinical service outweigh the potential benefits. Clinicians should not routinely offer the service to asymptomatic patients.

·        Level I: scientific evidence is lacking, has poor quality, or is conflicting, so the risk against benefits balance cannot be assessed. Clinicians should help patients understand the uncertainty surrounding the clinical service.

The databases, such as ‘Cochrane,’ that publish meta-analyses on several medical topics (e.g., medical disease and also treatment with drugs) 

Many published studies are biased. An example is when a drug company sponsors a study. A significant issue is that many studies are poorly designed. They may have a small sample (e.g., it is different to involve five subjects and different to involve 5,000 subjects), and they may have statistical flaws and/or inadequate information on the statistical methods and the results. Also, they may not be placebo-controlled or double-blind and may not be randomized controlled. 

In conclusion, many studies are poorly designed, so we need to check first if the quality of an investigation is good or poor. Cochrane meta-analysis is based on well-designed studies that fulfill the inclusion criteria. The Cochrane database (containing meta-analyses) is vital in following 'evidence-based medicine.' A meta-analysis is published on a specific topic, e.g., if glucosamine sulfate, a dietary supplement, helps patients with knee osteoarthritis. Traditional herb use for a specific medical condition does not necessarily mean it is effective, as this must be proven scientifically. It should be effective compared to a placebo. 

Then, with an overview of the results, the authors assess the studies considering matters such as statistics or other quality flaws. In this way, Cochrane’s reviewers come to a safe conclusion. This may be direct (e.g., that a specific drug helps or not in a particular disease) or may just be that well-organized and/or large studies are needed, or that the available data is insufficient regarding the number of included RCTs or their quality, to end to a safe conclusion, so more research is needed. 

The Cochrane database on the published meta-analyses of various medical issues includes simple language abstracts that laypeople can read.

The point is that the most essential thing in a study is if it is of good – quality and if the results are repeated in the following studies. Thus, the role of Cochrane in publishing meta-analyses for several medical issues is vital.

For databases with meta-analyses, you may visit

http://www.cochrane.org/

http://onlinelibrary.wiley.com/

Thanks for reading!

Reference:

·        http://en.wikipedia.org/wiki/Evidence_based_medicine (Retrieved 1 August 2012)

·        Simon C., Everitt H., Kendrick T., Oxford Handbook of General Practice, Oxford Medical Publications, 2^nd edition, 2005.

·        Evidence-Based Medicine, p. 668 – 669, Longmore M., Wilkinson I.B, Davidson E.D., Foulkes A., Mafi A.R., Oxford Handbook of Clinical Medicine, Oxford Medical Publications, 8^th edition, 2010.

·        Evidence-Based Medicine, p. 489, Collier J., Longmore M., Brinsden M., Oxford Handbook of Clinical Specialties, Oxford Medical Publications, 7^th edition, 2006.