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Balk EM, Earley A, Hadar N, et al. Benefits and Harms of Routine Preoperative Testing: Comparative Effectiveness [Internet]. Rockville (MD): Agency for Healthcare Research and Quality (US); 2014 Jan. (Comparative Effectiveness Reviews, No. 130.)

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

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Benefits and Harms of Routine Preoperative Testing: Comparative Effectiveness [Internet].

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Key Findings and Strength of Evidence

We identified 57 studies that reported clinically pertinent outcomes in patients who had routine or per protocol preoperative testing performed. However, only 14 of the studies provided direct comparisons between routine or per protocol testing and ad hoc or no testing, and only two studies compared routine with per protocol testing. Furthermore, only seven of the comparative studies were RCTs, three of which were conducted in patients undergoing cataract surgery. The large majority of data come from cohort studies that provided evidence only about how frequently procedures or anesthesia were canceled, delayed, or altered in response to preoperative testing.

In summary, there is a high strength of evidence from three well-conducted RCTs, that consistently found that for patients scheduled for cataract surgery, preoperative ECG, metabolic panel (or glucose), and CBC have no effect on total perioperative complications or procedure cancellation (Table 17). In contrast, there is insufficient evidence for the effect of routine preoperative testing in all other surgeries and populations. There is also insufficient evidence to estimate a difference in outcomes based on whether preoperative testing was conducted routinely or per protocol. There are one RCT and five nonrandomized studies of routine or per protocol testing in adults undergoing various elective surgeries; however, these studies were highly heterogeneous in populations, elective surgeries, and tests used. Four of these studies compared routine or per protocol testing with ad hoc testing, but in the only one of these studies to report rates of testing, tests were generally ordered more frequently in the ad hoc group. Since the true effect of routine (or per protocol) testing can be assessed only when compared with no (or limited) testing, these studies add little to any answer about the effectiveness of routine testing. Furthermore, the nonrandomized studies were all fundamentally flawed in that they failed to adjust for differences among study groups in the patients, surgeries, surgeons, anesthetics used, anesthesiologists, or other possible confounders. These studies generally found lower rates of postoperative complications and deaths among patients undergoing routine or per protocol testing, but the heterogeneity and flaws in the studies preclude any confidence in the accuracy or validity of the findings. However, while there is no evidence regarding minimally invasive surgeries similar to cataract surgery, it may be valid to conclude that routine preoperative testing in these other low-risk surgeries would also have no effect.

Table 17. Routine or per protocol preoperative testing: Findings and strength of evidence.

Table 17

Routine or per protocol preoperative testing: Findings and strength of evidence.

There is insufficient evidence for all other categories of procedures and patients, for all other outcomes of interest, and regarding more detailed analyses of differences in how testing is performed. In particular, there is no comparative evidence regarding quality of life or satisfaction, resource utilization, or harms. Among comparative studies, there is insufficient reported evidence regarding how outcomes may differ in different subgroups of patients, or how the effect of preoperative testing may vary based on the risk of the surgical procedure, or other factors.

The apparent difference in the effect of routine or per protocol testing in patients undergoing cataract and general elective surgery is arguably not surprising. Cataract surgery is a very low risk procedure, safe enough to be done in an ophthalmologist's office, that is minimally invasive and usually requires only local anesthesia with sedation. Other than increases in vagal tone, there is little reason to expect cardiac strain in the typical patient undergoing cataract surgery. While the patients are typically elderly, and thus have a relatively high rate of comorbidities, they are generally not suffering from any acute illnesses. In contrast, general elective surgeries in adults encompass a wide range of patients and surgeries, including many with acute or serious medical conditions and highly invasive cardiothoracic, abdominal, and vascular surgeries. These patients are intrinsically at higher risk of perioperative complications and thus, conceptually, may benefit more from preoperative tests that pick up correctable abnormalities that may be associated with complications.

Most of the evidence was from cohort studies. However, the nature of the intervention under consideration (preoperative testing) makes the lack of a direct comparator (no testing) among these studies particularly problematic in terms of interpreting the findings. Regardless of the specific preoperative tests used or how they are implemented, the rate of perioperative complications, due to either the procedure or the anesthesia, will always depend primarily on the underlying risks of the surgical procedure, the type of anesthesia used, the skill and experience of the surgeons and anesthesiologists, the medical condition of the patients, and the quality of perioperative care. The risk of perioperative complications when preoperative testing was conducted, without information about the risk of complications without testing (or only ad hoc testing), does not provide information on the effect of testing on those risks. An adequate comparator is needed that controls for the myriad other factors that impact perioperative complications.

Study Limitations

Across nonrandomized studies, there was a lack of adjustment for possible confounders. They all failed to control for cluster effects, particularly those related to individual surgeons or surgical experience. Six of the nonrandomized studies compared different time periods within an institution before or after implementation or removal of a preoperative testing policy. Furthermore, institutional differences between the time periods (such as incremental improvements in surgical techniques, anesthesia, or nursing care) were not accounted for. The bias that can result from the lack of adjustment (e.g., by propensity score) was best exemplified in the nonrandomized study that compared concurrent surgeries. In one of the two comparative studies comparing routine versus per protocol testing with hemostasis tests on children undergoing tonsillectomy and/or adenoidectomy, the comparison was really between the bleeding complication rates of the 2 most experienced surgeons (who used a testing protocol in 2624 children) and those of the 11 less experienced surgeons (who did routine testing in 1750 children total). Arguably, the finding that perioperative bleeding was more common in the latter group provides evidence that surgical experience and skill are predictors of complications and says little or nothing about whether preoperative testing may (or may not) have prevented any bleeding episodes.

Intrinsic Limitations of Research on Preoperative Testing

Another limitation of the evidence that would be difficult to overcome also relates to the nature of the intervention. Preoperative testing does not in and of itself affect the outcomes of interest (except resource utilization and possibly quality of life/satisfaction, although there are no data on these outcomes). Instead, the preoperative tests potentially cause the health care providers to alter a patient's management—by implementing an intervention to correct or account for the abnormal test; by delaying, canceling, or changing the procedure or anesthesia; or by making changes to postoperative care. Additionally, the preoperative test may be useful for perioperative management to use as a reference (e.g., to know whether a measure has changed in a postoperative test compared with the preoperative test—for example, whether an ECG abnormality is new or not). Thus, the value of any preoperative test is fully dependent on the health care providers and their response to abnormal tests. One could expect responses to vary among surgeons, anesthesiologists, primary care physicians, nurse practitioners, and other providers. One could also expect them to vary among individual providers across hospitals, settings (e.g., urban vs. rural), geographic regions, and a myriad of other health care provider variables. However, none of these factors were accounted for in the studies. This limitation further hampers the interpretation of the evidence, particularly from the cohort studies, but also arguably from the unadjusted nonrandomized studies.

Interpretation of the evidence is further complicated by the wide variability in clinical practice in the thoroughness of preoperative H&P (and whether it is done) and the general lack of reporting regarding H&P in the studies. This could have an important impact on what tests are conducted ad hoc (i.e., in the comparator arms of the studies). Rather than leading to more or less testing, it can lead to more appropriate testing since the tendency to order tests based on a “shotgun” approach will be reduced. But H&P could be considered equivalent to a “test” performed by the clinician (instead of the laboratory or radiology technician), which may—or may not—have value independent of true preoperative tests. Furthermore, H&P is intrinsically nonstandardized and heterogeneous depending on the specific questions asked and the details of the examination. Traditionally, H&Ps have been completed in the surgical clinics and on the day of surgery by the anesthesiology teams. More recently, preoperative assessment clinics staffed by perioperative medicine specialists are becoming more common. These clinics focus on optimizing patients for their perioperative course, and a thorough H&P is the cornerstone of that process. However, none of the studies specifically investigated testing in this setting and none of the studies compared different locations or protocols of care.

Any management changes due to abnormal test results (and presumably any subsequent changes in perioperative outcomes) would be the same regardless of whether testing was done routinely, per protocol, or at the clinician's discretion. Therefore, the variability in ad hoc testing could have an important impact on the comparison of outcomes between ad hoc and routine or per protocol testing. Without good descriptions in studies of typical H&P or the triggers to order ad hoc tests, it is difficult to interpret the applicability of the studies to the general (or any specific) population and the comparison among different testing regimens. Likewise, variations in how abnormal test results are handled at different surgical centers or based on different types of surgery will have a direct impact on the potential effect of preoperative testing. If an abnormal test result is less likely to be acted on in some settings, the value of testing will be reduced in those settings. However, unless centers where studies are conducted use a rigorously followed protocol for posttesting care and other centers follow similar protocols, it may not be possible to overcome this limitation to the applicability of any research into routine preoperative testing.

Limitations of Cohort Studies

Because of the underlying lack of interpretability of the complication rates in these studies, we restricted analyses to “process” outcomes related to decisions about whether the procedure or anesthesia was altered based on testing. These included cancellation or delay of surgery, changes in either the planned surgery or anesthesia, and overall changes in patient management. To the extent possible, based on the reported data, we focused on decisions that were made specifically because of test results (presumably abnormal results), but most studies did not clearly define their outcomes, requiring us to assume this was the case. However, the information to be gleaned from most of these studies was limited. When no procedures were canceled or delayed and no changes were made to either the planned procedure or anesthesia, it may be reasonable to conclude that the testing was of no value at least up to the time that the procedure was performed. However, the assumption that the testing was of no value overall requires that the postoperative course also be unaffected by the availability of the preoperative tests. In reality, it is likely that some abnormal preoperative tests, such as an elevated glucose, would alter perioperative management, such as more intensive glucose monitoring.

Interpreting the finding that a certain (nonzero) percentage of procedures were canceled, delayed, or changed is not straightforward. First, one must make a conclusion as to whether the cancellations, delays, or changes were warranted. Second, one must make assumptions about whether the patients' outcomes were changed. If a procedure was canceled or delayed, at a certain level the patient's immediate health care was worsened, assuming the planned surgery was necessary. However, it is unknowable whether the delay or cancellation may have prevented a complication that would have been worse than the prolongation of the disease state necessitating surgery. Third, one must make a determination as to whether the testing led to changes in care sufficiently rarely (below some percentage threshold) that the testing is of sufficiently limited value to safely forego it, or whether the changes in care occur frequently enough that they can be assumed to be an important tool or predictor regarding surgical management.

With these caveats, the following conclusions can be made from the cohort studies. In all preoperative testing scenarios for which more than a single study was available (i.e., approaching a sufficient evidence base to form a conclusion), testing resulted in some changes in management. In other words, the evidence suggests that in most situations, routine preoperative testing will result in some delay or cancellation of the procedure or some change to anesthetic management or surgical procedure. However, it is not possible to say whether the changes led to benefit or harm for patients. That said, the only studies that directly compared outcomes in subsets of patients were cohort studies that evaluated change in patient management, including specialty consultations or nonsurgery-related changes in patient care. Two studies suggest that change in management from CXR is more common for older patients (primarily >60 years), and one study each suggests that the effect of ECG is similar in men and women, but that CXR results in change in management in more men, those with higher ASA category, those with respiratory disease, and those with “major” surgeries planned (as opposed to “minor” or other surgeries), particularly in patients undergoing thoracic, cardiac, and vascular surgeries. Two studies suggest that change in management from CXR is more common for older patients (primarily >60 years). Two studies also looked at CXR and ECG by sex and other factors. One of these studies suggests that the effect of ECG is similar in men and women, but the second study suggests that CXR results in change in management in more men, those in a higher ASA risk category, those with respiratory disease, and those with “major” surgeries planned (as opposed to “minor” or “standard” surgeries), particularly in patients undergoing thoracic, cardiac, and vascular surgeries. However, given the small number of studies that compared outcomes in different subgroups of patients, together with the unknown connection between changing patient management and true patient outcomes, it is premature to conclude that the differences found are clinically important.

There is no comparative evidence regarding quality of life or satisfaction, changes in anesthesia or procedure, resource utilization, or harms. Among comparative studies, there is no (or insufficient) reported evidence regarding how outcomes may differ in different subgroups of patients (e.g., based on age, sex, medical status, or anesthesia risk category) or how the effect of preoperative testing may vary based on the risk of the surgical procedure, the type of anesthesia planned, the indication for surgery, who orders or responds to the results of the preoperative tests, whether testing is done routinely (in everyone) or per protocol, or the length of time prior to the planned procedures that the tests are conducted.

Limitations of Systematic Review

We relied mainly on electronic database searches and perusal of reference lists to identify relevant studies. Unpublished relevant studies may have been missed. We also kept the review focused on the evidence that most directly addresses the comparative effect of routine (or per protocol) preoperative testing versus ad hoc or no testing. Thus, we did not review the wide range of indirect evidence from which conclusions about whether testing might be of value might be inferred. The Statement of Work in the Introduction spells out the broader research questions that were not addressed here. The decision to narrow the scope of the review was made in part due to time and resource constraints. Future updates of this review may be able to broaden the scope of the research questions, particularly if it remains the case that there are few eligible comparative studies.

The conclusions, to a large extent, reflect the limitations of the underlying evidence base. Our ability to address most of the issues raised by the Key Questions was hampered by a paucity, or complete lack, of data, particularly from comparative studies.


The applicability of the evidence is limited, with the exception of the studies of cataract surgery. The cataract RCTs had similar findings, despite being conducted in different settings, in different countries, and with somewhat different eligibility criteria and study designs. Furthermore, the first trial was conducted in nearly 20,000 patients. This all implies that the conclusion that there is no effect of routine testing with ECG, a basic metabolic panel, and blood counts for cataract surgery is likely to be broadly applicable. The applicability of the findings for adults undergoing a range of elective surgeries is less clear. The studies evaluated different tests in different populations receiving different surgical procedures and did not adequately report the conditions under which ad hoc testing was done (i.e., the extent of H&P or the triggers to order testing).

Comparison With Prior Systematic Reviews and Guidelines

In 2003, the United Kingdom-based NICE published the only prior broad evidence review (with a guideline) we identified that addresses these Key Questions.9 We included all studies identified in the NICE review that met our eligibility criteria. In contrast with our review, which was structured to identify which patients undergoing which procedures could benefit (or be harmed) by routine testing, the NICE review was structured by test, regardless of procedure or patient characteristics. The principal difference in conclusions between NICE and the current review relates to tests for cataract surgery, since two of the three trials we used were not published until after the NICE review was conducted. Otherwise, the NICE review was similar in that it found insufficient evidence. Specifically, it found that the evidence could not directly inform their guideline for CXR, ECG, CBC, hemostasis tests, biochemistry tests, urinalysis, pregnancy tests, sickle cell testing, or pulmonary function testing. A Health Technology Assessment subsequent to the NICE review conducted a limited systematic review in 2008 (published in 2012) of blood and pulmonary function tests in low- or medium-risk patients,10 but included no studies comparing testing versus no testing. A recent Cochrane review focused on RCTs of routine preoperative testing for cataract surgery and came to the same conclusion found here, based on the same studies we included.11

The American College of Physicians wrote an evidence-based guideline in 2006 on preoperative testing to reduce perioperative pulmonary complications for patients undergoing noncardiothoracic surgery.83 The associated systematic review evaluated patient- and procedure-related risk factors and laboratory predictors of postoperative pulmonary complication rates.84 Their conclusions are based primarily on 27 studies with multivariable analyses, but they also included 83 studies with univariable data. However, they did not consider whether testing was done routinely, per protocol, or ad hoc. Given the state of the evidence, the guideline recommendations for which tests to use or not use in which patients are based on whether various predictors have been associated with pulmonary complications, as opposed to whether routine or per protocol testing has been found to reduce or mitigate pulmonary complications.

The ACC/AHA also wrote an evidence-based guideline (in 2007) on perioperative cardiovascular evaluation prior to noncardiac surgery.12 The committee reviewed more than 400 new articles (since 2002) on a broad range of topics, including preoperative evaluation, perioperative and cardiac risk and complications, and noncardiac surgery. Among several topics they covered on perioperative management, they provide recommendations on stepwise noninvasive and invasive cardiac testing based on patients' risk factors and symptoms, Although, the guideline does not specify the evidence used for each recommendation, all recommendations are level B or C meaning that the recommendations are based on either single comparative studies, a small number of conflicting comparative studies, or on expert opinion. Apparently, the guideline did not rely on comparative studies of the effect of routine or per protocol testing since only one of the comparative studies (on cataract surgery85) eligible for this review was cited in the guideline.

In 2012, the ASA reported an updated practice advisory for preanesthesia evaluation.1 They issued a practice advisory, as opposed to a guideline, “because of the lack of sufficient numbers of adequately controlled trials.”1 They systematically searched for studies with “evidence linkages, consisting of directional statements about relationships among specific preanesthesia evaluation activities and clinical outcomes” that could assess causality. They found no studies that met their criteria, so they also reviewed “descriptive literature” (reports of frequency or incidence) and case reports. All of their advisories about the use of specific tests were based on noncomparative observational studies with associative or descriptive statistics, i.e., not on evidence regarding the comparative effect of routine or per protocol testing.

Ongoing Research

A search on July 11, 2013 in the registry (of “preoperative,” “presurgical,” “preprocedural,” and related terms) identified only one potentially relevant record of a study that would meet eligibility criteria for this review. The study, whose status is “unknown,” plans to compare the use of cardiac stress tests or no testing in patients undergoing colorectal surgery. They plan to report on patient outcomes, patient satisfaction, and resource usage.a

Evidence Gaps

Table 18 summarizes the evidence gaps with regard to the two Key Questions and subquestions of this systematic review.

Table 18. Evidence gaps.

Table 18

Evidence gaps.

Future Research

As noted above, this review identified major gaps in the published evidence on the comparative effectiveness and safety of routine and per protocol preoperative testing. We believe that the following evidence gaps can be fruitful areas for future research:

  • RCTs to evaluate the comparative effectiveness of preoperative testing: RCTs remains the best study design to minimize bias. A common complaint about RCTs is that they have limited applicability, largely due to their narrow scope. However, the current nonrandomized studies have limited applicability because they are too inclusive and do not adequately account for vast heterogeneity of elective procedures, potential tests, information about typical H&P, triggers for ad hoc testing, processes for obtaining and handling the test results, and patients themselves. More focused studies evaluating specific tests or panels of tests in well-defined patients undergoing a narrow set of procedures will be of greater value to clinicians and decisionmakers deciding who should be routinely tested preoperatively. RCTs are of particular value in evaluating preoperative testing to maximize the likelihood of balancing patients between groups. In all studies, regardless of design, confounding will be a particularly important analytic concern, especially as it relates to the likelihood of both abnormal test results and perioperative complications based on a patient's age, comorbidities, and other characteristics. Again, RCTs can best minimize allocation bias and confounding. If the current RCT evidence from cataract surgery is considered to be sufficiently convincing by ophthalmologists, hospitals, payers, and other policymakers, then an argument can be made that no further RCTs are needed to investigate the value of routine preoperative ECGs, basic metabolic panel, or complete blood count. However, given that there is only a single 38 year old RCT for any other procedure (pediatric elective surgery), RCTs for all other procedures, in all populations, and for all specific tests are warranted. Conducting a series of such trials appears to be quite feasible, given the large number of elective procedures performed at many hospitals (or surgical clinics), the low cost of the intervention (since in many situations the trial will primarily involve randomizing patients to either receive tests that are already available to them or withholding those tests, as opposed to requiring resources to cover the costs of additional interventions), and that only a short-term postoperative followup is required (during hospitalization or up to 1 to 3 months). Somewhat more complex trials to organize upfront, cluster randomized trials, where centers or units are randomized as opposed to individual patients, can also provide informative data, provided that they are analyzed appropriately. Cluster randomized trials may be easier to run since the randomization procedure is much simpler. Trials should collect sufficient data to effectively stratify patients based on the major variables of interest (procedures, tests, comorbidities, etc.) or alternatively, multiple trials should be run, each focused on a specific aspect of the research question. In particular, since it is likely that the effect of preoperative testing will vary substantially based on the specific surgery (as suggested by the different effects found between cataract trials and general surgery studies), trials should either focus on a single type of surgery or, at a minimum, stratify their results by surgery or surgery risk class. Furthermore, studies should stratify their results based on patient risk category, such as ASA category, and comorbidities. They should capture the full range of perioperative outcomes, including patient quality of life/satisfaction and resource utilization. They should be sufficiently powered to evaluate, at a minimum, total major perioperative complications. Preferably they should be sufficiently powered to cover specific major complications, such as death. They should also be sufficiently powered to allow for a priori subgroup analyses and analyses specific to (at least some) individual procedures and tests.
    • Likely, the major hurdle in conducting new RCTs is that there is no private source of funding (e.g., pharmaceutical or device manufacturers) since, by definition, preoperative tests are common, universally available tests. However, we believe that finding the balance between maximizing periprocedural risk and harm reduction and minimizing wasteful resource utilization ought to make this question of interest to funders and policymakers.
  • Observational studies for the comparative effectiveness of preoperative testing: Observational studies can provide a lesser level of evidence to provide information on the comparative effectiveness of alternative preoperative testing strategies. However, the intrinsic heterogeneity and risk of confounding requires that great care and attention be given to how the data are analyzed (e.g., with a priori subgroup analyses) and whether it is possible to adequately adjust for fundamental differences among nonrandomized cohorts of patients having or not having testing done. At a minimum, observational studies need to be adjusted for differences in patient and surgical characteristics and to control for cluster effects of individual surgeons or based on surgical experience. The common approach used by nonrandomized comparative studies to date is to compare patients before and after a hospital policy change. However, these analyses are subject to temporal trend biases, where patient care changes over time in multiple ways independent of the change in testing policy, and these changes are unknown, cannot be quantified, or cannot be otherwise adequately adjusted for. A few examples include the use of new surgical equipment, changes in surgical techniques and training, and changes in the health status of the patients. To be of use, observational studies should include concurrent patients who do or do not receive testing and who are as similar as possible. Even then, it will be important to use strong statistical methods to adjust analyses for differences in the cohorts unrelated to testing and confounders (e.g., propensity score or instrumental variable methods). Quantitative bias analyses could be used to address concerns regarding unobserved confounding in nonrandomized studies. Although the use of observational data always requires additional assumptions for valid inference on treatment effects (compared to randomized designs), well designed observational studies may be able to offer valuable information regarding the effectiveness and adverse effects of routine or per protocol preoperative testing. All the suggestions made for RCTs regarding focusing or stratifying analyses based on surgical, patient, and other study characteristics also apply to observational studies.
  • Decision models: In the face of a paucity of reliable evidence regarding the benefits, harms, and resources used with routine or per protocol preoperative testing, decision analyses may be of value to delineate plausible estimates of the range of how beneficial (or harmful) and resource-intensive preoperative testing could be. Such analyses could be useful to rank tests and procedures by likely benefit and thus help to prioritize research for specific tests and procedures. Such models will require direct evidence of the comparative effect of testing, as reviewed here, along with other indirect evidence including the likelihood of (specific) perioperative complications (for specific procedures), the likelihood that specific tests will diagnose conditions that would impact the rate of complications, the effects of correcting or ameliorating any such conditions, whether a test result could be acted on to impact the rate of complications, the likelihood of true and false positive test results, and the effects of delaying or canceling the procedures.

Regardless of the design of future studies, to allow answers to the main question of the value of routine (or per protocol) preoperative testing, it is important that a large number of studies be conducted covering a wide range of scenarios, but that they are specific enough to allow applicability for decisions to be made for particular patients undergoing particular procedures in a given setting. These various scenarios include differences in patient populations (e.g., by age, comorbidities, and other risk factors), procedures (e.g., either specific surgeries or categories of procedures by risk), tests that may be of benefit (depending on patient and procedure), differences in how testing typically occurs and the triggers for ad hoc testing, who orders and follows up on test results, surgical center type and setting, timing of the testing, and so forth. Alternative prioritization approaches may be reasonable. Initially focusing on people who are most likely to have life-threatening perioperative complications, including older patients, those in higher ASA categories, those with important comorbidities, and those undergoing higher-risk surgeries would allow for relatively small, low-resource, studies that would be adequately powered. In these cases, complications would be more common and test abnormalities may also be more common. Not only would studies of these groups have the greatest potential to affect patients most likely to have complications, but the studies would also be better powered due to the higher complication rates than in lower-risk populations. Further studies of patients at high risk of surgical bleeding (for example children undergoing tonsillectomy and/or adenoidectomy) are also warranted. Alternatively, one could argue that future research should focus on lower-risk populations and surgeries (e.g., Grades 1, 2, and possibly 3 surgeries; see Table 1). While these studies would need to be relatively large, due to low complication rates, the findings of these studies may have the greatest impact since they would address more common surgeries and more typical patients. Furthermore, hospitals, clinicians, and patients may be more willing to forgo preoperative testing in low- rather than high-risk settings. We believe it is likely that higher-risk patients undergoing higher-risk procedures would continue to have preoperative testing done regardless of evidence showing the testing to be ineffective. Given the different arguments that could be made about who to include in future studies, and limited resources to conduct such research, this topic may be worthy of undergoing a formal value of information analysis.86

Given the large number of elective procedures performed annually in the U.S. and the large number of tests that can be ordered routinely, further data are needed regarding resource utilization. Both RCTs (either within centers or cluster randomized across centers) and observational studies can provide useful information on costs of tests, costs of changes in management (including delay or cancellation), costs of followup testing and treatment, and costs of complications.


With the exception of cataract surgery, there is a paucity of reliable evidence regarding the benefits, harms, and resource utilization associated with routine or per protocol preoperative testing for all tests used for all procedures. There is a high strength of evidence, which is broadly applicable, that ECG, basic metabolic panel (biochemistry), and CBC have no effect on important clinical outcomes in patients scheduled for cataract surgery, including total perioperative complications and procedure cancellations. But despite several nonrandomized studies, there is insufficient evidence regarding the value of routine or per protocol preoperative testing for other procedures and populations. Based on studies with a high risk of bias, there is a possibility that complications and deaths occurred more commonly among patients undergoing ad hoc as opposed to routine or per protocol testing. This raises a caution against extrapolating the cataract findings to other surgeries and populations who may be at higher risk of complications due to the nature of the procedures or underlying illnesses and comorbidities. The evidence is insufficient to clarify specifically which routinely conducted (or per protocol) tests may be of benefit (or no benefit) for which patients undergoing which procedures. There is insufficient evidence to make conclusions related to the effect of routine versus per protocol testing. There is no evidence regarding quality of life or satisfaction, resource utilization, or harms of testing. There is also no evidence regarding how the value of testing may differ based on the risks of a specific surgical procedure, the type of anesthesia planned, the indication for surgery, comorbidities or other patient characteristics, the structure of testing (e.g., whether ordered through a specialized preoperative clinic), by who orders the tests (e.g., surgeon vs. anesthesiologist vs. primary care physician), or the length of time prior to the procedure that the tests are conducted. Given the large number of patients undergoing elective surgery, there is a clear need to develop better evidence for when routine or per protocol testing improves patient outcomes and what the harms may be.



Cardiopulmonary Exercise Testing and Preoperative Risk Stratification (CPX or CPEX). ClinicalTrials‚Äč.gov Identifier: NCT00737828.


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