Table of Contents  
Year : 2019  |  Volume : 6  |  Issue : 4  |  Page : 228-230

Decision-making in Surgery: How to assess the evidence

Associate Editor – IJVES, Narayana Institute of Vascular Sciences, Bengaluru, Karnataka, India

Date of Submission22-Nov-2019
Date of Decision11-Dec-2019
Date of Acceptance22-Nov-2019
Date of Web Publication20-Dec-2019

Correspondence Address:
Robbie K George
Associate Editor – IJVES, Narayana Institute of Vascular Sciences,Bengaluru, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijves.ijves_97_19

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How to cite this article:
George RK. Decision-making in Surgery: How to assess the evidence. Indian J Vasc Endovasc Surg 2019;6:228-30

How to cite this URL:
George RK. Decision-making in Surgery: How to assess the evidence. Indian J Vasc Endovasc Surg [serial online] 2019 [cited 2023 Jan 30];6:228-30. Available from:

Surgery is an art and a science. As the years have rolled by surgery moved from being the trade of the barbers to becoming a more refined and respectable science. Our knowledge of surgery rests on the work of various anatomists who dug up or bought corpses to study and dissect and also on the work of the many physiologists and scientists who unraveled the mysterious workings of the human body. Today, we live in a world dominated by fake news and alternative truths where knowing the truth from the untruths is increasingly difficult. This is compounded by an unbridled social media and a suspicious and sometimes hostile media and population. At such times, being aware of and knowing how to read and interpret evidence is of immense importance.

Over the past few decades, there has been an explosion of disseminated knowledge. The first steps in the widespread sharing of knowledge owe themselves to Gutenberg's invention of the printing press. This small step changed the way humankind accessed and shared knowledge. This eventually progressed to wide-scale scientific publishing in numerous journals. This was the first era of the information explosion, the solution to this was the Index Medicus, an encyclopedic tome that was accessed and cross-referenced to find references to articles of interest. Obtaining these articles was altogether another challenge and many of the older surgeons would remember making trips to central libraries like the National Library of Medicine in Delhi and digging in the dark and dusty shelves to locate that elusive article.

All of that changed with the arrival of the digital age and the Internet that brought on the second era of the information explosion. The challenge today, unlike in the past, is not of accessing or dissemination information but of identifying what is of good quality and relevance and then applying it to practice.

Suddenly the print media did not have an exclusive license on the dissemination of knowledge and anybody with access to a computer and the Internet could broadcast his/her thoughts, opinions, techniques, and biases to anyone willing to listen.

  What Is Evidence? Top

Today, each of us is expected to follow evidence-based practice. Evidence-based medicine had been defined as “the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients.” It is important to note the various caveats in that statement, especially when they apply to the inexact art of surgery.

The word “current” certainly suggests a possibility of change in the future – a change that represents new knowledge or discovery of new facts and not a reflection of failure of past science. The latter fact is especially difficult for the common man to understand.

The term “judicious” implies that as surgeons we must use our judgment in the appropriate application of the evidence. Blindly following guidelines and recommendations without applying clinical judgment to individual patients is a poor excuse for appropriate clinical care and an abdication of responsibility as a physician.

  Identifying the “good” Evidence Top

Evidence-based publications range from the letter to the editor and case reports to large multicenter randomized controlled trials (RCTs) and meta-analysis. Each of these various publications does not carry the same degree of reliability, reproducibility, or applicability to the clinical situation. This is especially so in surgical situations where there are numerous variations among patients and diseases that may have a disproportionate impact on outcomes. For instance, the level of the carotid bifurcation and its proximity to the hypoglossal nerve and the marginal mandibular nerve would have an impact on the cranial nerve palsy postendarterectomy for an individual patient, but this information was never captured in any of the numerous carotid trials.

What is common to all good studies, evidence, and guidelines is rigorous methodology. Studies that do not define their goals and methods clearly can often be fishing expeditions with numerous retrospective analyses of statistical data in an effort to get a magic P < 0.05 to deliver a positive result. Such data are often nonreproducible and unreliable. All good studies are identified by the clarity and rigor of the methods section of the paper. If the aim of the study and the methods by which the question is approached and the results analyzed are clearly specified and are reasonable the evidence produced, whether in a case series, a cohort study, an RCT or a guideline will likely be valid and reliable and of relevance to a practicing surgeon.

  Levels of Evidence Top

One of the early attempts to classify evidence into levels was by the Canadian Task Force on the Periodic Health Examination in 1979.[1] This was further clarified and modified by Sackett[2] in 1989. Both systems placed RCTs as the most reliable form of evidence. While RCTs no doubt occupy the top spot in published literature, it must however be understood that the best quality of evidence depends on the question being asked. Different types of studies are appropriate for answering different types of questions – is it about treatment, prognosis, diagnosis, or health economics/decision analysis. Therefore, knowing which kind of study best answers the question is very important. [Table 1] illustrates the value of the kinds of study that are appropriate for prognostic studies,[3] for example, the outcomes of untreated critical limb-threatening ischemia. [Table 2] stratifies the value of different study types that would best answer a question regarding therapeutic interventions and its outcomes,[3] for example, an evaluation of the results of angioplasty versus stenting for critical limb-threatening ischemia.
Table 1: Levels of evidence for prognostic studies[3]

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Table 2: Levels of evidence for therapeutic studies

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  Guidelines and Their Place in Evidence-Based Practice Top

Currently, there are a plethora of surgical learned societies and consequently a plethora of guidelines. Guidelines suffer from the same challenges of being of variable quality.

Various vascular societies provide guidelines that are a synthesis of evidence and a ready reckoner for practice.

In 2006, the Society for Vascular Surgery (SVS) began developing clinical guidelines for what were considered to be clinical questions of high value. Multidisciplinary committees were formed and followed the Grading of Recommendations, Assessment, Development and Evaluation framework. Details of how the committees arrived their conclusions were reported in 2011 by Murad et al.[4]

Once a clinical question is defined, data are collated from various sources. Very often, direct comparative evidence as from a well-conducted RCT is not available for framing a guideline. Unlike other specialties where often only RCTs are included for meta-analysis, the SVS has chosen to systematically synthesize evidence from observational and case series as well. While this may run contrary to a more purist approach, it reflects the complexity of surgical case presentation and interventions.

The SVS also takes a pragmatic approach to the grading of quality evidence and classifies it into three categories: low (C), moderate (B), and high (A) based on the details outlined in [Table 3].[4]
Table 3: Rating the quality of evidence

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The same methodology was used in the creation of the current Global Vascular Guidelines.[5]

This practice of using what may be classed as low-quality evidence has been followed not only in vascular surgery by SVS but also by the American College of Cardiology and American Heart Association. In fact, only 11% of the guidelines of these two societies were based on the level of evidence.

However, it is reasonable to accept guidelines that are created by a structured methodological process by experts, provided they clearly highlight these recommendations as consensus statements or conditional recommendations. This warns the surgeon that significant clinical judgment is needed in applying the guideline to their individual patient. These areas also highlight gaps in knowledge and targets for future research. A review of the recent Global Vascular Guidelines lists a number of recommendations as “good practice statement” that reflect exactly this approach.

  Conclusion Top

The digital age we live in is also the age of information overload. In this era, it is important for every surgeon to assess with a keen eye the “evidence” presented and to choose how it shall affect the practice of vascular surgery for the individual.

  References Top

The periodic health examination. Canadian Task Force on the Periodic Health Examination. Can Med Assoc J 1979;121:1193-254.  Back to cited text no. 1
Sackett DL. Rules of evidence and clinical recommendations on the use of antithrombotic agents. Chest 1989;95:2S-4S.  Back to cited text no. 2
Burns PB, Rohrich RJ, Chung KC. The levels of evidence and their role in evidence-based medicine. Plast Reconstr Surg 2011;128:305-10.  Back to cited text no. 3
Murad MH, Montori VM, Sidawy AN, Ascher E, Meissner MH, Chaikof EL, et al. Guideline methodology of the Society for Vascular Surgery including the experience with the GRADE framework. J Vasc Surg 2011;53:1375-80.  Back to cited text no. 4
Conte MS, Bradbury AW, Kolh P, White JV, Dick F, Fitridge R, et al. Global vascular guidelines on the management of chronic limb-threatening ischemia. J Vasc Surg 2019;69:3S-125S.e40.  Back to cited text no. 5


  [Table 1], [Table 2], [Table 3]


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  What Is Evidence?
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