Screening Patients PreOperatively and Avoiding "Test Addiction"

Screening patients prior to surgery is an important part of the perioperative process, but many institutions suffer from "test addiction" (1).  Completing lab tests and other diagnostic tests solely on a 'routine' has been shown to be both unnecessary and potentially harmful to patients (2).  Patient health assessment and screening can be facilitated by such tests, but only if the tests are clinically indicated and their results are assessed in a timely manner.

It is a misconception that completing a battery of preoperative testing will prevent medico-legal issues, particularly if documentation and follow-up on abnormal results are not completed (3).  Large trials have demonstrated as low as 1% of tests provide abnormal findings, when done on patients where there was no clinical indication for the testing, but the testing was performed because it was the institution's policy or routine. (3)

The value of the preoperative screening lies in the clinician's assessment; lab tests then serve as an additional resource to confirm suspicions.  For example, where there are concerns of cardiac disease, an ECG would be ordered to assess for the presence of Q waves, arrhythmias, or signs of cardiac ischemia.  A second example of appropriate testing is completing a CBC for patients currently on anticoagulant treatment, or having surgery where moderate to large blood loss is expected.  Having baseline values in such situations is supported by guidelines of the Canadian Anesthesiologists' Association (CSA), the Guidelines Advisory Committee (GAC) of the Ontario Medical Association, and the National Institute for Clinical Excellence (NICE).  See Table One.

Table One:  Summary of Recommended PreOperative Tests

It has been consistently demonstrated in trials that even when abnormal values are found from preoperative testing, the plan of care or patient outcome is often not influenced.  Only 4% of patients with an abnormal preoperative ECG had a postoperative complication (3).  Further, 92% of abnormal CXRs could be predicted on the basis of cardiopulmonary disease or presenting symptoms.  This certainly reinforces the value of the clinician's assessment in preoperative screening.

Following the guidelines of the CSA, GAC and NICE should be part of the clinician's decision making when ordering preoperative diagnostic tests.

Many hospitals and ambulatory care centres continue to suffer from "test addiction" despite the availability of published guidelines.  The incidence of unindicated preoperative screening tests is 50-60% (7).

PeriAnesthesia nurses play a valuable role in both patient advocacy and compliance to best practices.  Increased awareness of established guidelines can help discourage unnecessary testing, which can also lead to delays in surgery, further testing (where abnormals are found which may be false-positives) and patient dissatisfaction.  It is disheartening to instruct a patient that they must jump through several logistical hoops to have more invasive tests completed, when a clinically unindicated test has provided a border line abnormal result.

Evidence-based guidelines should be in place at all facilities, and easily accessible to health care providers.  Implementation of such guidelines has been shown to decrease the number of preoperative tests, with no implication to patient safety (8).  An additional benefit of following current recommendations is a reduction in costs to an already stretched health care system.  This is welcome news to administrative staff, but should not be the guiding purpose of reviewing and updating institutional policies around preoperative assessment and screening of surgical patients.

Overall, considering that numerous trials have shown a low predictive value of commonly obtained preoperative lab tests, the value of the testing must outweigh its disadvantages (1).  See Figure One. 

Clinicians should only order tests if clinically indicated, or the outcome of an abnormal result will influence perioperative management of the patient.

Figure One:  Weighing the benefits and costs of perioperative testing:

Written by Heather Ead

References:

1.  Attali, M. et all. (2006).  The Mount Sinai Journal of Medicine.  A cost-effective method for reducing the volume of laboratory tests in a university-associated teaching hospital. (5)787-94.

2.  Van Klei, W.A. et al. (2003).  Euro J of Anasth.  Role of history and physical examination in preoperative evaluation.  (20) 612-18.

3.  Smetana & Macpherson (2003).  The Medical Clinics of North America.  The case against routine preoperative laboratory testing.  (87) 1-6.

4.  Canadian Anesthesiologists' Society Guidelines on the Preanesthetic Period (2001).

5.  Ontario Pre-Operative Testing Grid.  www.gacguidelines.ca

6.  Preoperative tests Clinical Guideline (2003).  National Institute for Clinical Excellence.

7.  Mantha, S. et al.  (2005).  J of Clinical Anesthesia.  Usefulness of routine preoperative testing:  a prospective single-observer study.  (17) 51-57.

8.  Ferrando, A.  (2005).  International Journal for Quality in Health Care.  Guidelines for preoperative assessment:  impact on clinical practice and costs. (17) 323-329