By Dr Gajan Srikanthan, Director of Clinical Pathways, Lumeon

Doctors around the world undertake an estimated 234 million major surgical procedures every year. And they do preoperative testing before elective surgeries in an effort to predict complications that may prompt preventive measures or even cancellation.

Preoperative laboratory testing includes assessing complete blood count, hemostasis, blood gases, renal function, liver function, electrolytes, C-reactive protein (CRP), pregnancy screening, urine analysis, or a set of any of these. Physicians also consider preoperative tests such as electrocardiogram and red blood count to be valuable baseline assessments to help the detection of subsequent changes. But little is known about the effectiveness of these baseline assessments.

Essentially, surgical patients often undergo extensive preoperative diagnostics where the investment is not justified by the benefits.

Some studies report that 60–70% of laboratory tests ordered before general surgery are not required, considering patient history and physical examination results. This discrepancy is particularly severe for low-risk ambulatory surgery patients, 93% of whom don’t require such tests and who rarely see a change in management as a result of having them. Patients with no comorbidities have an overall incidence of complications of less than 1% yet receive at least one preoperative test in 54% of cases.

But if so much preoperative laboratory testing is done, perhaps it must be valuable? Does it lead to changes in clinical management? Does it reduce peri- and post-operative complications such as mortality or morbidity (including complications and adverse events) in patients undergoing elective, non-cardiac surgery? Similarly, do preoperative tests of the respiratory system, such as spirometry and chest x-rays, prevent complications in those patients?

The answers may surprise you.

What does the evidence say?

There is every reason to cultivate a healthy skepticism about abundant preoperative testing. Here’s what we know:

  • There is no evidence to support routine preoperative testing of younger patients undergoing low-risk surgeries, who make up the majority of the patients presenting for non-cardiac surgery in clinical practice.
  • Preoperative testing in adults undergoing elective, non-cardiac surgery should be performed only for patients with pre-existing diseases or risk factors, or for those whose history and physical examination reveal indications for such conditions.
  • There is no evidence of any benefit from hemoglobin testing of healthy, asymptomatic patients who show no clinical signs of anemia or hematological disease.
  • Similarly, evidence suggests that white blood count (WBC) and CRP should only be performed in selected patients, such as those with risk factors, clinical signs of systemic inflammation, or a concerning history or physical examination, as well as in joint replacement surgeries, to exclude a systemic inflammation predisposing for infection of the implanted prosthesis.
  • Evidence suggests that hemostasis testing and liver function testing should only be performed in patients with risk factors, history, or physical examination raising suspicion for such conditions.
  • Evidence suggests that spirometry and chest X-ray should only be performed in patients with pre-existing pulmonary disease, or with risk factors and symptoms such as dyspnoea (on exertion), coughing, or signs of airway obstruction.
  • Significant evidence exists that routine preoperative testing in patients undergoing cataract surgery is unnecessary.

In conclusion

Over-testing in otherwise fit and healthy patients is common, but there is no sensible explanation of why this is the case. If basic principles of medicine are followed, preoperative tests should only be performed where a patient’s medical history and physical examination justify it.

The bottom line is that the best practice for preoperative testing is to avoid doing baseline laboratory studies in patients without significant systemic disease (ASA I or II) who are undergoing low-risk surgery. Elimination of unindicated tests in low-risk patients promotes patient safety, improves quality of care, and results in substantial cost savings.