2 Evidence-Based Medicine: Levels of Evidence and Grades of Recommendation

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2

Evidence-Based Medicine: Levels of Evidence and Grades of Recommendation

Andrew J. Graham and Sean C. Grondin

recently, the term evidence-based clinical prac- tice (EBCP) has been used instead of EBM to indi- cate that this approach is useful in a variety of disciplines. In this chapter the terms are used interchangeably.

Two fundamental principles of EBM have been proposed.

The fi rst is that evidence alone is never enough to guide clinical decision making. Clini- cal expertise is required to place the evidence in context and advise individual patients while con- sidering their unique values and preferences. The second principle is that a hierarchy of evidence exists that is determined by the soundness of the evidence and the strength of the inferences that can be drawn from it.

It has been recognized that clinicians can embrace the philosophy of EBM either as practi- tioners of EBM or as evidence users.

A practitioner would adhere to the following fi ve steps:

1. Form clinical questions so that they can be answered.

2. Search for the best external evidence for its validity and importance.

3. Clinically appraise that evidence for its valid- ity and importance.

4. Apply it to clinical practice.

5. Self-evaluate performance as a practitioner of evidence-based medicine.

The evidence user searches for pre-appraised or preprocessed evidence in order to use bottom- line summaries to assist patients in making deci- sions about clinical care.

Evidenced-based medicine (EMB) is a philosoph- ical approach to clinical problems introduced in the 1980s by a group of clinicians with an interest in clinical epidemiology at McMaster University in Canada. The concepts associated with this approach have been widely disseminated and described by many as a paradigm shift. Others, however, have debated the usefulness of this approach.

In this chapter, we will provide a defi nition and rationale for an evidence-based approach to clin- ical practice. The central role of systems that grade clinical recommendations and levels of evidence will be outlined. Readers interested in a more in-depth review are advised to consult the Users’ Guide to the Medical Literature: A Manual for Evidence-Based Clinical Practice.

2.1. What Is Evidence-Based Medicine

Evidence-based medicine is a philosophical

approach to clinical problems that has arisen

from the physician’s need to offer proven thera-

pies to patients. In 1996, Sackett and colleagues

more formally defi ned EBM as “the conscien-

tious, explicit, and judicious use of current best

evidence in making decisions about the care of

individual patients.”

The goal of this approach

is to be aware of the evidence supporting a par-

ticular approach to a clinical problem, its sound-

ness, and the strength of its inferences. More

2.2. Why Use an

Evidence-Based Approach?

Proponents of EBCP report that the advantages to the physician who use an EBCP approach are that the practitioner acquires the ability to obtain current information, is able to perform a direct review of the evidence, and utilizes a interactive form of continuing medical education.

2.2.1. Obtain Current Evidence

The traditional method of acquiring information has been the review of textbooks and ongoing review of medical journals. Traditional texts have been shown to go out of date quickly. In one study, for example, the delay in the recommenda- tion of thrombolytic therapy for myocardial infarction was up to 10 years from when the pub- lished literature suggested it was advisable.

Due to the huge number and variety of journals, however, it is challenging even for the most dili- gent practitioner to stay current. With the devel- opment of modern technology that allows easy and rapid access to Medline and other full-text rapid internet access sites, an increasing number of busy practitioners have been able to obtain current evidence.

2.2.2. Direct Review of Evidence

Developing and maintaining critical assessment skills is essential in order to have an EBCP. The ability to perform a direct review of the evidence by the individual practitioner is felt to be a supe- rior method for appraising the literature com- pared to traditional review articles by experts.

In many instances, reviews by experts have been revealed to be of low scientifi c quality and felt to be infl uenced unfavorably by potentially unsys- tematic hierarchal authority. Given the time required to critically appraise the literature, however, preprocessed sources of EBM have been necessary for most surgeons to incorporate EBM into their practice.

2.2.3. Interactive Learning

Many consider an evidence-based approach to clinical practice an interactive form of learning

designed to improve physician performance.

Studies designed to examine the effectiveness of continuing medical education have found that traditional didactic approaches are inferior to interactive forms of learning at changing physi- cian performance.

Once the learner has acquired the necessary skills for EBCP, interactions with students and fellow learners reinforces the active process of learning and becomes the starting point for self-appraisal.

Ironically, the evidence that EBM works is from observational studies that have suggested that recommendations arising from an evidence- based approach are more consistent with the actual evidence than traditional approaches.

The second piece of evidence suggested to dem- onstrate the effectiveness of EBM is gathered from studies that show that those patients who get the treatment supported by high-quality evidence have better outcomes than those who do not.

2.3. What Is the Role of Grades of Recommendation and Levels of Evidence?

An evidence-based approach to clinical practice is said to have two fundamental principles. First, evidence alone is never enough to make a clinical decision, and, second, a hierarchy of evidence exists to guide decision making.

The proponents of an evidence-based approach

defi ne evidence very broadly as any empirical

observation about the apparent relation between

events. Thus, evidence can come from unsystem-

atic clinical observations of individual clinicians

to systematic reviews of multiple randomized

clinical trials. The different forms of evidence

may each provide recommendations that result

in good outcomes for patients but it is clear that

some forms of evidence are more reliable than

others in giving guidance to surgeons and their

patients. It is for this reason that a hierarchy of

the strength of evidence has been proposed to

further guide decision making. The assumption

is that the stronger the evidence the more likely

the proposed treatment or diagnostic test will

lead to the predicted result.

The hierarchy of strength of evidence for treat- ment decisions (as opposed to diagnostic tests) is shown in Table 2.1.

The hierarchy represents a combination of rea- soning and the study of different methodologies used to study treatments. The highest level of evidence will not be familiar to most thoracic surgeons. N of 1 trials were developed to address the fi nding that no single treatment is always effective for every patient. N of 1 trials involve a patient and his/her physician, usually treating a stable chronic illness, being blinded to random- ized periods of taking a placebo or an active medication in random sequence and then decid- ing if the drug was or was not effective. Clearly, N of 1 trials have no relevance for patients having surgical procedures!

Given that N of 1 randomized, controlled trials are not feasible for thoracic surgical procedures, the fundamental underpinning of the hierarchy is the superiority of well-done, randomized, con- trolled trials (RCT) as compared to observational studies, physiological studies, and unsystematic observations. The majority of surgical and tho- racic surgical research consists of observational or physiological studies or unsystematic observa- tions. The superiority of randomized trials as compared to observational studies is still debated by some methodologists and some thoracic sur- geons, as seen in debates regarding the National Emphysema Treatment Trial (NETT) for Lung Volume Reduction Surgery.

The supporters of evidence-based clinical practice would defi ne the observations of an experienced clinician as unsystematic observa- tions. They acknowledge that profound clinical insights can come from experienced colleagues but that these are limited by small sample size

and “defi ciencies in human process of making inferences.”

Physiological studies are defi ned as studies in which the measured outcome is a physiological parameter such as blood pressure, forced expiratory volume in 1 s (FEV

), and exer- cise capacity, rather than patient important end points such as quality of life, frequency of hospi- talizations, morbidity, and mortality.

Why do evidence-based advocates place such emphasis on RCT for selecting treatment for patients? First, observational studies are not an experimental design, so each patient is deliber- ately chosen, not randomly selected, thus leading to an unavoidable risk of selection bias. The selected patients may, therefore, have systematic differences in outcome that are due not to the given treatment but rather the selection process.

Second, is the observation that the results of RCT have not been predicted by prior observa- tional or physiological studies. We would like to outline examples in which RCT provided surpris- ing results in relation to both the general medical literature and to studies of adjuvant treatments of lung cancer.

The classic example often given to demonstrate the potentially misleading conclusions drawn from studies with physiological end points is the study of the anti-arrhythmic drugs fl ecainide and encainide, in which nonrandomized studies were shown to decrease the physiological end point of frequency of ventricular arrhythmias in patients after myocardial infarction. The RCT subsequently carried out using a patient-impor- tant end point of cardiac deaths and arrests found a relative risk (RR) of 2.64 [95% confi dence inter- val (CI), 1.60–4.36]; a substantially increased risk among patients on the active drug versus those on placebo.

An example drawn from thoracic surgery dem- onstrates the limitations of lower forms of evi- dence and highlights the important contributions thoracic surgeons have made toward proving the importance and power of RCT and validating the evidence hierarchy. The studies of adjuvant intra- pleural bacillus Calmette–Guerin (BCG) for stage I non-small cell lung cancer (NSCLC) demon- strate the limitations nicely. The initial studies suggesting that an infectious immune stimulant would improve survival in the treatment of lung T ABLE 2.1. Hierarchy of strength of evidence for treatment

decisions.

N of 1 randomized, controlled trial Systematic reviews of randomized trials Single randomized trial

Systematic review of observational studies addressing patient-important outcomes

Physiological studies (studies of blood pressure, cardiac output, exercise capacity, bone density, and so forth)

Unsystematic observations

cancer came from observational studies that suggested that postoperative empyema improves survival in lung cancer.

An elegant pathophysi- ological mechanism of immune stimulant was proposed. This was followed by supportive animal physiological studies and a small randomized trial in which a subgroup analysis suggested that immune stimulation via BCG would confer a survival advantage as adjuvant therapy for lung cancer.

Unfortunately, this was not shown to be the case when the theory was tested in a well- conducted RCT by the Lung Cancer Study Group.

The evidence-based approach to surgery implies that physiological rationale or observa- tional studies usually predict the results of RCT.

However, this may not always be the case. Thus, the hierarchy of evidence has ranked RCT above other forms of study. The evidence-based approach hierarchy is, however, not proposed as an absolute. For example, in the case where observational studies show an overwhelming advantage for treatment, such as insulin for the treatment of ketoacidosis, RCT are not required.

The majority of treatments, however, do not dem- onstrate an overwhelming advantage for a par- ticular form of treatment and major treatment decisions of common problems therefore require evidence from RCT in order to provide the best advice to patients.

2.4. Grading Systems of Recommendations and Levels of Evidence

The hierarchy of evidence has been formulized by a wide variety of groups into different class- ifi cations of levels of evidence and grades of recommendation. The proliferation of such clas- sifi cations, each being slightly different from each other, has led to the formation of an international working group whose mandate is to reach agree- ment on a standardized classifi cation.

Given that a single classifi cation has not been universally accepted, we have suggested the use of the Oxford Centre for Evidence-based Medi- cine Grades of Recommendations and Levels of Evidence (Table 2.2). The strengths of this clas- sifi cation are that it was developed by leaders in

the fi eld of EBM, it allows assignment of studies for not only therapy but for diagnostic tests as well, and it has been used in studies exploring methodology in thoracic surgery.

The limita- tions are that it is detailed and may appear complex to those not familiar with the fi eld.

A number of aspects of the Oxford Centre for Evidence-based Medicine Grades of Recommen- dations and Levels of Evidence are worthy of highlighting. The bottom line for an evidence- based user is the grades of recommendation A through D. In the clinical setting, the levels of evidence of applicable studies are determined and then examined to assign the grade of recom- mendation. An A level recommendation is the strongest possible.

For those surgeons who have an interest in a deeper understanding, the initial step is to deter- mine the methodological nature of the clinical question. Thoracic surgeons will likely be inter- ested in questions regarding the choice of therapy or diagnostic test. For example, a surgeon may wish to advise a patient regarding the role of adjuvant chemotherapy following lung cancer resection. The surgeon would then examine existing studies and use the fi rst column of the table to assign the appropriate level of evidence.

The surgeon will note that level 1a is assigned to systematic reviews with homogeneity of RCT.

It is critical to understanding the table that sur- geons appreciate that systematic reviews are not the same as traditional narrative reviews. Sys- tematic reviews of published and unpublished data are carried out in an explicit fashion. The criteria for locating articles, assigning method- ological criteria, and combing data are explicitly stated and are repeatable by another investigator.

Following the location of evidence regarding adjuvant chemotherapy for lung cancer, a level of evidence could be assigned to each paper and then a grade of recommendation determined.

Given a secure understanding of the soundness of the proposed treatment, the thoracic surgeon can use his/her clinical expertise to determine if the proposed treatment is appropriate for an individual patient after due consideration of factors such as local expertise, patient values, and patient preferences.

Depending on the nature of the clinical ques-

tion, the surgeon may fi nd high levels of evidence

T ABLE 2. 2. O xford C entre for E videnc e- b ase d Me dicine Lev els of E videnc e ( M ay 2 00 1) . Di ff erential diagnosis /s ymptom Le ve l T h er ap y/ p re ve nt io n, e ti ol og y/ ha rm P ro gn os is D ia gn os is p re va le n ce s tu d y E co n om ic a n d d ec is io n anal ys es 1a SR (w it h homogeneit y* ) o f R C Ts SR ( w it h homogeneit y* ) of inc eption SR ( with homogeneit y* ) of lev el 1 SR ( with homogeneit y* ) of SR ( with homogeneit y* ) of lev el 1 c ohor t studies ; CD R† validat ed in diagnos tic s tudies ; C DR† with 1 b prospe ct iv e co hor t studies e conomic s tudies dif feren t popula tions s tud ies f rom di ff erent clinic al centres 1b Indiv idual RC T ( w ith nar ro w Indiv idual inception cohor t s tud y Va lid at in g* * co h or t s tu d y w it h g oo d† †† Pr os p ec ti ve co h or t s tu dy with Analysis b as ed on clinic ally s ensible Co nf id en ce In te rv al ‡) w it h ≥ 80 % follo w- up ; CD R† re fe re n ce sta n da rd s; o r C D R † t est ed g ood f ol lo w -u p**** co sts o r a lt ern at iv es ; sy st em at ic validat ed in a single population within on e clinic al c ent er review (s ) of the evidenc e; and including multiwa y sensitivit y a na ly se s 1c All or none § A ll o r n on e c as e- se ri es A b so lu te Sp Pi ns a n d Sn N ou ts †† A ll o r n on e c as e- se ri es A b so lu te b et te r- va lu e o r wo rs e- va lu e a nalyses†††† 2a SR (w it h homogeneit y* ) o f co h or t SR ( w it h homogeneit y* ) o f e it h er SR ( w it h h om og en ei ty *) o f l eve l SR ( w it h h om og en ei ty *) o f 2b SR ( w it h h om og en ei ty *) o f l eve l s tudies retrospe ct iv e co hor t studies or > 2 d ia gn ost ic st ud ie s an d be tt er st ud ie s > 2 e conomic s tudies untreat ed c ontrol groups in RC Ts 2b In d iv id ua l co h or t s tu d y ( in cl ud in g l ow Re tr os p ec ti ve co h or t s tu d y o r f ol lo w - Ex p lo rato ry ** co h or t s tu d y w it h Re tr os p ec ti ve c ohor t s tudy , or Analysis b as ed on clinic ally s ensible q ua lit y RC T; e.g ., < 80 % f ol lo w -u p ) up o f u nt re ate d co nt ro l p at ie nt s i n g oo d† †† referenc e st andards ; C DR† poor follo w- up c osts o r a lt ern at iv es ; limite d review (s ) a n RC T; d er iv at io n of CD R† o r af ter der iv at io n, o r v alidate d o n ly o n of t h e ev iden ce, o r singl e s tu die s; validate d on split -s ample § § § only split -s ample § § § or dat ab as es and including multiwa y s ensitivit y a na ly se s 2c “O ut comes” res earch ; e colo gic al s tudies “O ut comes” res earch Ec olo gic al s tudies A udit or out comes res earch 3a SR (w it h homogeneit y* ) o f c as e- co nt ro l SR ( w it h h om og en ei ty *) o f 3b a n d SR ( w it h h om og en ei ty *) o f 3b SR ( w it h h om og en ei ty *) o f 3b a n d s tudies bet ter s tudies and bet ter s tudies bet ter s tudies 3b In d iv id ua l c as e- co nt ro l s tu d y N on co ns ec ut ive s tu d y; o r w it h ou t N on co ns ec ut ive co h or t s tu d y, Analysis base d on limit ed alt ern at iv es or co ns is te ntly applie d referenc e or v er y lim it ed p op ul at io n co st s, p oo r quali ty e st imate s of dat a, s tandards but including s ensitivit y analys es incor p or ating clinic ally s ensible variations. 4 C as e- se ri es (a n d poor qualit y c ohor t Case -series ( and poor qualit y Case -c on trol s tudy , poor or Case -series or s uper seded A nalys is with no sen sitivit y a nalys is and c as e- con tr ol studies §§ ) pr ogno st ic c ohor t studies ** *) nonindependent referenc e st andard referenc e st andards 5 Ex per t opinion without e xplicit critic al Ex per t opinion withou t explicit Ex per t opin ion without explicit critical Ex per t opi ni on without explicit Ex per t opin ion without explicit critic al appr ais al, or b as ed on ph ysiolo g y, cr itic al appr ais al , or b as ed on appr ais al, or b as ed on ph ysiolo g y, cr itic al appr ais al , or base d on apprais al , or base d on e conomic b ench re search, or “ fir st pr inciple s” ph ysiolo g y, b ench re search, or b ench re search, or “ fir st pr inciple s” ph ysiolo g y, b ench re search, the or y or “ fir st pr inciple s” “ fir st pr inciples” or “ fir st pr inciples”

Pr od uc ed by B ob Ph ill ip s, C hr is B al l, D ave S ac ke tt , D ou g B ad en oc h, S ha ro n S tr au s, B ri an H ay n es , M ar ti n D awe s si n ce N ove m b er 1 99 8. Us er s c an a d d a m in us si gn “ – ” to d en ote t h e l eve l o f t ha t f ai ls to p rov id e a co n cl usi ve a ns w er b ec au se o f: • EI TH ER a s in gl e r es ul t w it h a w id e co nf id en ce i nte rv al ( su ch t ha t, f or e xa m p le, a n AR R i n a n R C T i s n ot s ta ti st ic al ly s ig ni fi ca nt b ut w h os e co nf id en ce i nte rv al s f ai l to e xc lu d e c lin ic al ly i m p or ta nt b en ef it o r h ar m ) • O R a s ys te m at ic r ev ie w w it h t ro ub le so m e ( an d s ta ti st ic al ly s ig ni fi ca nt ) h ete ro g en ei ty . • Su ch e vi d en ce i s i n co n cl us iv e, a n d t h er ef or e c an o n ly g en er ate g ra d e D r eco m m en da ti on s. *B y h om og en ei ty we m ea n a s ys te m at ic r ev ie w t ha t i s f re e o f wo rr is om e v ar ia ti on s ( h et er og en ei ty ) i n t h e d ir ec ti on s a n d d eg re es of r es ul ts b et w ee n i n d iv id ua l s tu di es . N ot a ll s ys te m at ic r ev ie w s w it h s ta ti st ic al ly si gn if ic an t het erogeneit y need be w orri some , a n d no t all w orri some het erogeneit y need be s ta ti stically s ign if ic an t. A s no te d ab ove, s tu d ie s d is p la yi n g wo rr is om e h ete ro g en ei ty s h ou ld b e t ag g ed w it h a “ – ” a t t h e en d o f t h ei r d es ig na te d l eve l. †C lin ic al D ec is io n R ul e. ( Th es e a re a lg or it hm s o r s co ri n g s ys te m s w hi ch l ea d to a p ro gn os ti c e st im at io n o r a d ia gn os ti c c ate g or y. ) ‡S ee n ote # 2 f or a d vi ce o n h ow to u n d er st an d, r ate a n d u se t ri al s o r o th er s tu di es w it h w id e co nf id en ce i nte rv al s. M et w h en all p at ie nt s d ie d b ef or e t h e Rx b ec am e a va ila b le , b ut s om e n ow s urv iv e o n i t; o r w h en s om e p at ie nt s d ie d b ef or e t h e Rx b ec am e a va ila b le , b ut none n ow d ie o n i t. § § By poor q ua lit y co h or t s tu d y w e m ea n o n e t ha t f ai le d t o c le ar ly d ef in e c om p ar is on g ro up s a n d /o r f ai le d t o m ea su re e xp os ur es a n d o ut co m es in t h e s am e (p re fe ra b ly b lin d ed ), o b je ct iv e w ay i n b ot h e xp os ed an d n on -e xp os ed i n d iv id ua ls a n d /o r f ai le d to i d en ti fy o r a p p ro p ri at el y co nt ro l k n ow n co nf ou n d er s a n d /o r f ai le d to c ar ry o ut a s u ff ic ie nt ly l on g a n d co m p le te f ol low -u p o f p at ie nt s. B y p oo r q ua lit y ca se -c on tr ol st ud y we m ea n o n e t ha t f ai le d to c le ar ly d ef in e co m p ar is on g ro up s a n d /o r f ai le d to m ea su re e xp os ur es a n d o utco m es i n t h e s am e ( p re fe ra b ly b lin d ed ), o b je ct iv e w ay i n b ot h c as es a n d co nt ro ls a n d /o r f ai le d to id en ti fy o r a p p ro p riate ly co nt ro l k n ow n co nf ou n d er s. § § § Sp lit -s am p le v al id at io n i s a ch ie ve d b y c ol le ct in g a ll t h e i nf or m ation in a single tr anche , then ar ti fi ciall y div iding this into “ d er ivation” and “validation” s amples. †† A n “ A bsol ut e S p Pi n” is a d ia gnos ti c f ind in g whose S pecif icit y i s so h igh th at a P os itiv e res ult rules -in t h e d ia gn os is . A n “ A b so lu te Sn N ou t” i s a d ia gn os ti c f in di n g w h os e Se ns itivit y i s so h igh th at a N eg at iv e r es ul t ru les -out the di agnos is. ‡‡ G oo d, b et te r, b ad, a n d wo rs e r ef er to t h e co m p ar is on s b et w ee n t re at m en ts in te rm s o f t h ei r c lin ic al r is ks a n d b en ef it s. ††† Good r ef er en ce s ta n da rd s a re i n d ep en d en t o f t h e te st , a n d a p p lie d b lin d ly o r o b je ct iv el y to a p p lie d to a ll p at ie nt s. Po or r ef er en ce s ta n da rd s a re h ap ha za rd ly a p p lie d, b ut s ti ll i n d ep en d en t o f t h e te st . Us e o f a n on in d ep en d en t r ef er en ce s ta n da rd ( w h er e t h e “ te st ” i s i n cl ud ed i n t h e “ re fe re n ce, ” o r w h er e t h e “ te st in g ” a ff ec ts t h e “ re fe re n ce ’) im p lie s a l eve l 4 s tu d y. †††† Bet te r- value trea tmen ts are clearly as good but cheaper , or be tt er a t the s ame or reduc ed c os t. W or se -value trea tmen ts are a s g oo d a n d m or e e xp en si ve, o r wo rs e a n d t h e e qu al ly o r m or e e xp en si ve. ** Va lid at in g s tu di es te st t h e q ua lit y o f a s p ec if ic d ia gn os ti c te st , b as ed o n p ri or e vi d en ce. A n e xp lo ra to ry s tu d y co lle ct s i nf or m at io n a n d t raw ls t h e d at a ( e.g ., u si n g a r eg re ss io n a na ly si s) to f in d w hi ch f ac to rs a re “s ig ni fi ca nt ”. ** *B y p oo r q ua lit y p ro gn os ti c co h or t s tu d y we m ea n o n e i n w hi ch s am p lin g w as b ia se d i n f avo r o f p at ie nt s w h o a lr ea d y h ad t h e t arget out come , or the measurement of out comes was ac co mplishe d in < 80 % o f st ud y p at ie nt s, o r o utco m es we re d ete rm in ed in a n u nb lin d ed, n on ob je ct ive w ay , o r t h er e w as n o co rr ec ti on f or co nf ou n di n g f ac to rs . **** G oo d f ol lo w -u p i n a d if fe re nt ia l d ia gn os is st ud y i s > 80 % , w it h a d eq ua te t im e f or a lte rn at iv e d ia gn os es to e m er g e ( e.g ., 1 – 6 m on th s a cu te, 1 – 5 ye ar s c hr on ic) . Grades of recommenda tion A co ns is te nt le ve l 1 st ud ie s B co ns is te nt le ve l 2 o r 3 s tu di es or e xt ra p ol at io ns f ro m le ve l 1 s tu d ie s C l eve l 4 st ud ie s or e xt ra p ol at io ns f ro m le ve l 2 o r 3 s tu d ie s D l eve l 5 ev id en ce or t ro ub lin gl y i n co ns is te nt o r i n co n cl us ive s tu d ie s o f a ny l eve l “E xt ra po la ti ons” a re wh er e d ata is use d i n a si tu at io n wh ic h h as p ote nti al ly cl in ic al ly im po rt ant d if fe re nc es th an th e o ri gi n al study s ituation . So u rc e: T h e Ce nt re f or Ev id en ce -B as ed M ed ic in e. Le ve ls o f e vi d en ce a n d g ra d es o f r eco m m en da ti on . O xf or d : T h e Ce nt re . A va ila b le f ro m h tt p :/ /w w w .c ebm.net /lev els _ of_evidenc e. asp . A cc essse d 25 A ugus t 20 05 .

and grades of recommendation. Many thoracic surgical procedures only have level 4 or 5 evi- dence.

This does not invalidate the process, but rather allows the surgeon to be aware of limita- tions of the data and potentially to identify criti- cal areas where further higher level studies could be performed.

2.5. Limitations of EBCP and Preprocessed Evidence

Most medical and surgical specialties have embraced the principles of EBM. However, discus- sions persist among doctors as to whether or not EBM represents a time-consuming “cookbook”

approach to patient care that ignores patient values. Although EBCP has a number of limita- tions, we feel these limitations are outweighed by the advantages of an evidence-based approach.

One of the biggest concerns among busy practicing surgeons is the large amount of time required to develop and maintain an EBCP.

Increasingly, surgeons must juggle a signifi cant operative workload, clinical visits, hospital patient care, on-call responsibilities, research, and administrative duties. Adding the time and cost to acquire a variety of new skills, such as critically appraising the literature and grading current evidence, is overwhelming if not impos- sible. A potential solution is to become a knowl- edgeable user of EBM using preprocessed evidence such as the evidence-based summaries in this book. This text combines the selected authors’

individual clinical expertise with an evidence- based summary of the literature to provide the reader with information on the management of complex thoracic surgery problems.

Another limitation to EBCP is that it places less weight on hierarchical authority and nonsystem- atic clinical observations; a concept which is counterintuitive to traditional surgical training and practice. This observation, combined with the fact that many surgeons do not embrace the best evidence because of their personalities (self- confi dence, the need for rapid clinical decisions, and decisive actions during surgery), may lead to a diminished willingness to incorporate EBM principles into their practice.

Although the limitations that have been dis- cussed are signifi cant, we believe they can be overcome. Improving the number and quality of available research trials and teaching the princi- ples of EBM in undergraduate and graduate medical training will be important for establish- ing the widespread use of EBM.

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