Routine screening laboratory testing for surgery persists even though it is generally unnecessary1–4 and adds considerably to the cost of health care. Up to 80% of surgeons, consulting internists, and anesthesiologists order testing that they themselves think unnecessary in the belief that “medical-legal considerations,” institutional rules, or a physician other than themselves will require it.5 Institutional guidelines on preoperative testing can reduce the number of unnecessary tests.6–8 However, the incidence and effectiveness of use of such guidelines nationwide are unknown. When one service (in this case, the Department of Anesthesiology) was given responsibility for preparing the patient for surgery, with sole authority to order laboratory testing and medical consultation, the number of both decreased by >50%.9 Whether the more important factor was “one service” or anesthesia is unknown.
Our institution has had guidelines in place for preoperative laboratory testing for >5 years. These guidelines were developed by a committee composed of surgeons and anesthesiologists. They had been distributed to all surgeons and were posted in our presurgical evaluation unit. We performed an internal analysis that revealed considerable unnecessary testing. We subsequently performed a nationwide survey to determine factors influencing surgeons' and anesthesiologists' ordering of unnecessary preoperative laboratory tests and consultations. Differences among specialties were predicted.
With permission from the IRB, 2 undergraduate volunteers surveyed the charts of 1000 consecutive patients scheduled for surgery at our institution between July and August 2006. After laboratory testing had been completed, tests outside of our institutional guidelines were counted as “unnecessary” (Fig. 1). The end point analyzed was the number of patients with zero versus at least one unnecessary test (see Results) among each successive batch of 100 patients. The Freeman-Tukey transformation10 was applied to each of the n = 10 batches, the Student 1-sample t test was applied among batches to calculate the lower confidence level, and then the inverse transformation was taken.11 For reliability, each student received instruction and surveyed 10 randomly selected charts before data collection. Concordance between the students was >98%. After 500 charts were surveyed, the students were again tested on 10 randomly selected charts, and concordance was again >98%.
The subsequent United States national survey was designed by 4 of the authors. The survey authors prepared 4 standardized clinical scenarios with increasingly complex medical histories: a 23-year-old woman for inguinal herniorrhaphy (general surgery), a 45-year-old woman for laparoscopic ovarian cystectomy (gynecology), a 50-year-old man for total hip replacement (orthopedics), and a 50-year-old man for hemithyroidectomy (otolaryngology), as shown in Table 1. The 20 surveyed anesthesiologist directors of preoperative evaluation units at academic medical centers (85% response rate) and the 400 anesthesiologists (44% response rate) were each sent the same 4 clinical scenarios. The surveys sent to 400 general surgeons (43% response rate), 400 gynecologists (37% response rate), 400 orthopedists (28% response rate), and 400 otolaryngologists (27% response rate) each shared the specialty's scenario with that of the anesthesiologists. The survey also asked the respondent's age, specialty, and gender, and contained questions regarding factors that influenced the respondent to order a particular test. Before being mailed, the survey was tested by 3 members of the Department of Anesthesiology not otherwise associated with the study and at least 1 member of each of the 4 surgical specialties, and suggestions for improvement were incorporated. A wide range of tests, from routine tests to obviously unnecessary tests, was included (Table 2).12
Members of the American College of Surgeons were selected randomly. The physicians chosen were the first physician in each state whose surname began with B, D, F, H, J, L, and so on. Anesthesiologists to whom the survey was sent were selected randomly from members of the American Society of Anesthesiologists. Again, the chosen physicians were the first listed in each state whose last name began with, B, D, etc. Ten physicians of each specialty were identified per state to obtain a national distribution. The survey was initially mailed to the first 8 physicians identified in each state. If a survey was returned as undeliverable, then it was sent to an additional physician in the same specialty, from the same state. The surveys were sent by mail with a self-addressed stamped envelope. They were mailed 3 times over a 1-year period.
An e-mail query was sent to national organizations in each surgical specialty, inquiring whether their organization had published guidelines with recommended preoperative laboratory testing.
Statistical analysis of the survey was performed using StatXact-9 (Cytel Inc., Cambridge, MA). Because response rates were <50% for all specialties, analyses focused on relationships among responses. Monte Carlo simulation to accuracy within 0.1% was used to calculate 95% lower confidence limits (CLs) and P values for the relative risks of different groups of physicians to order at least 1 unnecessary test. Association of this end point with the above-described factors potentially influencing preoperative test ordering (Table 3) was assessed using Wilcoxon-Mann-Whitney test for ranked variables and Fisher exact test for binary variables. Effect sizes (and corresponding adequacy of sample sizes to test associations) were assessed by Hodges-Lehmann confidence intervals for differences between groups. A Kendall τ was used to test for association between numbers of unnecessary tests ordered by each physician and predictive factors. Additionally, qualitative methods were used to understand predictive factors, including sending e-mails to professional organizations for the surgical specialties included in our survey looking for recommendations regarding preoperative testing.
More than half of the 1000 surveyed records had at least 1 unnecessary test based on our institutional guidelines (Fig. 1, 95% lower CL = 52%). The finding motivated our national survey.
The 17 preoperative directors unanimously considered 36 of the 72 combinations of test or consult (“test”) and scenario to be unnecessary (Table 2). These 36 tests were designated the “unnecessary tests” for analysis of the following survey results.
Among the 175 anesthesiologists responding, 54% did not order an unnecessary test, and 24% ordered just one. The maximum was 10 unnecessary tests. The probability distribution of the number of unnecessary tests was geometric (χ2 test of fit P = 0.323), with the proportion unnecessary tests p = 50%. This finding is important because p is the geometric distribution's sole parameter. Thus, knowing the percentage of the physicians ordering at least 1 unnecessary test provides just as much information as the number of such tests. This is the basis for our subsequent analysis.
Comparison was made between anesthesiologists and gynecologists for the gynecology case, anesthesiologists and otolaryngologists for the otolaryngology case, etc (Tables 1 and 4). Anesthesiologists were 53% less likely to order at least 1 unnecessary test relative to gynecologists for the cystectomy scenario, 64% less likely than general surgeons for the herniorrhaphy scenario, 66% less likely than otolaryngologists for the thyroidectomy scenario, and 67% less likely than orthopedists for the hip replacement scenario. The 95% lower CLs were all >40%.
Of the specialty organizations queried, only the American College of Surgeons and the American Association of Orthopedic Surgeons responded. Both reported no guidelines regarding preoperative laboratory testing.
Because these results suggest value to anesthesiologists being engaged institutionally in preoperative testing, we explored how anesthesia departments can achieve consistent performance. Among 17 potential predictors studied, only year of training was statistically significant (Table 3). Anesthesiologists trained after 1979 were 48% less likely to order at least 1 unnecessary test than those completing training in or before 1979 (95% CL >29%).
More than half of our patients had at least 1 unnecessary test despite repeated dissemination of testing guidelines within the institution. This adds to the cost of health care, without appreciable benefit. Similarly, the national survey showed not even a suggestion of a benefit in reducing unnecessary tests from institutional or anesthesia department guidelines. Tests can become simply part of an expected routine.13 We recommend other facilities screen for unnecessary tests.
Our data suggest that institutions can reduce costs by having anesthesiologists order the preoperative tests, which is itself a function of anesthesiologists' institutional engagement.14 However, anesthesia groups should be cognizant of potential heterogeneity within groups based on time since training, because their younger physicians may be more cognizant of what are unnecessary tests.
The number of unnecessary tests per simulated patient followed a geometric distribution. This result reveals that the percentage of an anesthesiologist's patients with at least 1 unnecessary test may provide just as much information over a long period as the number of unnecessary tests per patient. Feedback on adherence to guidelines could be done simply by reporting to each anesthesiologist the percentage of his or her patients with any unnecessary tests. We recommend that future multicenter observational studies aim to confirm this result using real data from many hospitals, because guidelines alone have far less influence on anesthesiologists' behavior influencing costs15 than guidelines combined with individualized feedback.16–19
Many studies have demonstrated that routine preoperative testing rarely changes management or improves surgical outcome.1–4 History and physical examination, not laboratory testing, may be the most important components of a preoperative evaluation.20,21 The American Society of Anesthesiologists has stated that routine laboratory and diagnostic screening testing is unnecessary for asymptomatic patients.22 Chung et al.3 recently concluded that no laboratory tests are needed for healthy, ambulatory patients. We are unaware of any nationally accepted guidelines on preoperative testing. Strikingly, there was not a single test in Table 2 that the anesthesiologist directors of preoperative clinics unanimously agreed was necessary. In contrast, Table 2 shows consensus for many tests and labs for what is unnecessary. We considered the extremes of complete agreement as to what was unnecessary to enhance validity of our results, and followed up with sensitivity analysis as well (Table 4). Future studies should focus on mechanisms to establish more uniformly accepted guidelines for preoperative laboratory testing.
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21. Roizen MF. Preoperative laboratory testing: necessary or overkill? Can J Anaesth 2004;51:R1–6
22. American Society of Anesthesiologists Task Force on Preanesthesia Evaluation. Practice advisory for preanesthesia evaluation: a report by the American Society of Anesthesiologists Task Force on Preanesthesia Evaluation. Anesthesiology 2002;96:485–96
Robert I. Katz, MD, helped design the study, conduct the study, analyze the data, and write the manuscript. This author has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files. Franklin Dexter, MD, PhD, helped analyze the data and write the manuscript. This author has seen the original study data, reviewed the analysis of the data, and approved the final manuscript. Kenneth Rosenfeld, MD, helped design the study. This author has seen the original study data, reviewed the analysis of the data, and approved the final manuscript. Laura Wolfe, BA, helped conduct the study. This author has seen the original study data, reviewed the analysis of the data, and approved the final manuscript. Valerie Redmond, BA, helped conduct the study. This author has seen the original study data, reviewed the analysis of the data, and approved the final manuscript. Deepti Agarwal, MD, helped conduct the study. This author has seen the original study data, reviewed the analysis of the data, and approved the final manuscript. Irim Salik, MD, helped conduct the study. This author has seen the original study data, reviewed the analysis of the data, and approved the final manuscript. Karen Goldsteen, PhD, helped design the study and analyze the data. This author has seen the original study data, reviewed the analysis of the data, and approved the final manuscript. Melody Goodman, PhD, helped analyze the data. This author has seen the original study data, reviewed the analysis of the data, and approved the final manuscript. Peter S.A. Glass, MB, helped design the study and write the manuscript. This author has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
Franklin Dexter is the Statistical Editor and Section Editor for Economics, Education, and Policy for the Journal. This manuscript was handled by Steve Shafer, Editor-in-Chief, and Dr. Dexter was not involved in any way with the editorial process or decision.
Peter S.A. Glass is Section Editor of Ambulatory Anesthesiology for the Journal. This manuscript was handled by Steve Shafer, Editor-in-Chief, and Dr. Glass was not involved in any way with the editorial process or decision.