ECONOMICS AND HEALTH SYSTEMS RESEARCH - The Prevalence and Predictive Value of Abnormal Preoperative Laboratory Tests in Elderly Surgical Patients - IMPLICATIONS: The prevalence of abnormal preoperative electrolyte values and thrombocytopenia was small and had low predictive values. Although more prevalent, abnormal hemoglobin, creatinine, and glucose values were also not predictive of postoperative adverse outcomes. Routine preoperative testing for hemoglobin, creatinine, glucose, and electrolytes on the basis of age alone may not be indicated in geriatric patients. Rather, selective laboratory testing, as indicated by history and physical examination, which will determine patient's comorbidities and surgical risk, seems to be indicated./