Liver function test (LFT) abnormalities are common incidental findings in patients who show no other signs of hepatobiliary disease. They may also be found in patients who present with vague complaints, such as fatigue. The differential diagnosis of LFT elevations is extensive and ranges from fairly benign conditions to life-threatening disease in which early diagnosis is critical.
A focused and detailed medical history can usually help narrow the differential considerably. In this article, we discuss what to cover when taking the history of a patient with a persistent aminotransferase elevation. We also indicate when additional testing is needed—and which tests to order—to nail down a diagnosis. In a second article in a coming issue, we will describe appropriate workups for patients with a persistent, asymptomatic alkaline phosphatase elevation and for pregnant patients with abnormal LFT results.
WHEN TO EVALUATE ALT/AST ELEVATIONS
When you first notice an alanine aminotransferase (ALT) or aspartate aminotransferase (AST) level greater than the upper limit of normal in an asymptomatic patient or one with only vague symptoms, always repeat the test before proceeding with evaluation of any kind. The most common nonspecific symptom in a patient with chronic liver disease is fatigue.
If a second test establishes that the elevation is persistent, and if the value is greater than 3 times normal, evaluation is warranted. If the value is less than this, monitor the patient; if it remains elevated, no matter how slightly, initiate evaluation.
COMMON CAUSES OF AMINOTRANSFERASE ELEVATIONS
Because aminotransferase elevations have many and diverse possible causes, a useful history taking (Table 1) must cover considerable ground. A good history will narrow the differential diagnosis significantly and point you toward the most appropriate follow-up tests (Table 2).
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