A judicious approach to ordering lab tests

Narrowly out-of-range tests. Test results that fall just outside the “normal” range may be of questionable significance. When an asymptomatic patient has mildly elevated liver enzymes, should additional tests be ordered to avoid missing a treatable disorder? In these scenarios, a history, including possible contributing factors such as alcohol or substance misuse, must be paired with the clinical presentation to assess pre-test probability of a particular condition.¹⁴ Repeating a narrowly out-of-range test is an option in patients when follow-up is possible. Alternatively, you could pursue watchful waiting and monitor a minor abnormality over time while being vigilant for clinical changes. This whole-patient approach will guide the decision of whether to order additional testing.

Habitually paired tests. Reflexively ordering tests together often contributes to unnecessary testing. Examples of commonly paired tests are serum lipase with amylase, C-reactive protein (CRP) with erythrocyte sedimentation rate (ESR), and TSH with free T4 to monitor patients with treated hypothyroidism. These tests add minimal value together and can be decoupled.^15-17 Evidence supports ordering serum lipase alone, CRP instead of ESR, and TSH alone for monitoring thyroid status.

Unnecessary routine preoperative testing and testing sequelae for cataract surgery was calculated to cost Medicare up to $45.4 million annually

Some commonly paired tests may not even be necessary for diagnosis. The well-established Rotterdam Criteria for diagnosing polycystic ovary syndrome specify clinical features and ovarian ultrasound for diagnosis.¹⁸ They do not require measurement of commonly ordered follicle-­stimulating hormone and luteinizing hormone for diagnosis.

Serial rather than parallel testing, a “2-step approach,” is a strategy made easier with the advent of the electronic medical record (EMR) and computerized lab systems.⁸ These records and lab systems allow providers to order reflex tests, and to add on additional tests, if necessary, to an existing blood specimen.

Repetitive laboratory testing. Repetitive inpatient laboratory testing in patients who are clinically stable is wasteful and potentially harmful. Interventions involving physician education alone show mixed results, but combining education with clinician audit and feedback, along with EMR-enabled restrictive ordering, have resulted in significant and sustained reductions in repetitive laboratory testing.¹⁹

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