RESUMO
BACKGROUND: Routine preoperative laboratory testing is not recommended for American Society of Anesthesiologists classification 1 or 2 patients before low-risk ambulatory surgery. METHODS: The 2017 National Surgical Quality Improvement Program data set was retrospectively queried for American Society of Anesthesiologists class 1 and 2 patients who underwent low-risk, elective outpatient anorectal, breast, endocrine, gynecologic, hernia, otolaryngology, oral-maxillofacial, orthopedic, plastic/reconstructive, urologic, and vascular operations. Preoperative laboratory testing was defined as any chemistry, hematology, coagulation, or liver function studies obtained ≤30 days preoperatively. Demographics, comorbidities, and outcomes were compared between those with and without testing. The numbers needed to test to prevent serious morbidity or any complication were calculated. Laboratory testing costs were estimated using Centers for Medicare and Medicaid Services data. RESULTS: Of 111,589 patients studied, 57,590 (51.6%) received preoperative laboratory testing; 26,709 (46.4%) had at least 1 abnormal result. Factors associated with receiving preoperative laboratory testing included increasing age, female sex, non-White race/ethnicity, American Society of Anesthesiologists class 2, diabetes, dyspnea, hypertension, obesity, and steroid use. Mortality did not differ between patients with and without testing. The complication rate was 2.5% among tested patients and 1.7% among patients without tests (P < .01). The numbers needed to test was 599 for serious morbidity and 133 for any complication. An estimated $373 million annually is spent on preoperative laboratory testing in this population. CONCLUSION: Despite American Society of Anesthesiologists guidelines, a majority of American Society of Anesthesiologists class 1 and 2 patients undergo preoperative laboratory testing before elective low-risk outpatient surgery. The differences in the rates of complications between patients with and without testing is low. Preoperative testing should be used more judiciously in this population, which may lead to cost savings.