Digital Library - Preoperative Laboratory Testing

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Introduction

The appropriateness of preoperative laboratory tests has been extensively examined. ^{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18, 19,20,21,22,23,24,25,26,27,28,29} Numerous studies have documented that the routine use of preoperative laboratory tests in selected patient populations has contributed little to the medical management of the patient or to ensuring superior medical outcomes.^9-12 The issue of rising medical costs has brought into question the appropriateness of many diagnostic strategies, including preoperative evaluation. Despite data suggesting that some routine laboratory evaluations may be unnecessary, there is little evidence that practice patterns have changed.

According to Roizen ³⁰ the combination of history and physical examination is the best tool for optimal evaluation of patients and optimal selection of laboratory tests. The primary problem with ordering batteries of laboratory tests for all patients is that laboratory tests are not very good screening devices for disease. In addition, the subsequent extra tests that physicians order as a follow-up to supposedly abnormal results are costly. More important is the fact that non indicated tests often represent additional risk to the patient, increase medicolegal risk to the physician, and render ORs in outpatient centers and hospitals inefficient.

Laboratory Tests as Effective Screening Devices

In the perioperative setting, the anesthesiologist may alter the care of the patient based on preoperative laboratory test results. If a preoperative test suggests a change in the care of an individual such that the health of the patient is improved or a problem is averted, that test has been beneficial to the patient. However, if a laboratory test result is borderline "normal" or slightly outside the reference range values, it may inconvenience, or worse, harm the patient.

On the whole, not much benefit arises from unindicated routine laboratory testing. In a controlled multiphasic screening of 1500 patients, Olsen and coworkers ³¹ found no difference in morbidity between control groups and groups who had screening tests performed. Durbridge and colleagues ³² compared 1500 patients randomly assigned to undergo or not undergo screening tests on admission. With respect to length of hospital stay or patient outcome, no benefit resulted from the 8363 extra tests performed for the group undergoing screening tests. Narr et al. ⁹ found that more than 3000 ASA I or II patients failed to benefit from laboratory testing.

Many studies have compared the yield from indicated (warranted based on history or risk group) versus unindicated preoperative testing. ^{17,18,23,33,34,35,36,37,38,39,40,41,42} Few unindicated tests have yielded beneficial changes in perioperative care. At most, only 16 patients of more than 16,000 who had unindicated preoperative tests ordered benefited from such testing.³⁰ Most abnormalities in asymptomatic patients do not reflect the presence of disease. Patients who benefit from preoperative testing, have risk factors, symptoms, or other history that suggest further testing.

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