Preoperative testing aims to provide results that will guide preoperative, intraoperative and postoperative care, particularly results that may change the intended plans. Preoperative laboratory blood investigations in asymptomatic patients undergoing low risk surgery are of little value in detecting abnormalities that will alter patient management and/or improve outcomes. Even when minor abnormalities in laboratory values are detected in asymptomatic patients, adverse outcomes are rare. Clinical history and physical examination should be used to determine the need for laboratory blood testing before low risk surgery; that is, test on the basis of patient and surgical factors.
Similarly, in the absence of positive clinical findings, or significant history, abnormal chest X-ray or spirometry results are uncommon. Positive results, in the absence of symptoms or signs, are unlikely to significantly influence perioperative management. Although the diagnostic yield of preoperative chest X-rays increases with age, most abnormalities reflect chronic disorders and when performed in asymptomatic patients do not impact on anaesthetic management or perioperative outcome. In other words, chest X-ray results are not predictive of postoperative pulmonary complications in most patients. Preoperative chest X-rays may, however, be appropriate prior to cardiac and thoracic surgery and as part of oncological evaluation. There is insufficient evidence to support spirometry as an appropriate tool to stratify risk of postoperative adverse respiratory events. Spirometry may be of value in lung resection surgery, unexplained dyspnoea, and uncertainty about whether known airflow obstruction is optimally reduced. Rather than performing these investigations routinely for surgery, decisions should be individualised, depending on patient history and examination.
Further, for all of these tests, lack of symptoms, signs or known disease increases the likelihood that positive findings are false positives exposing patients to the risks of unnecessary further testing.