Liver function tests (LFTs) are routinely used to screen for liver disease. A correct interpretation of LFT abnormalities may suggest the cause, severity, and prognosis of an underlying disease. Once the diagnosis has been established, sequential LFT assessment can be used to assess treatment efficacy.
Abnormal LFTs are frequently encountered in clinical practice, since elevation of at least one LFT occurs in more than 20% of the population.1 Many patients with abnormal LFTs, however, do not suffer from structural liver disease, since these tests can be influenced by factors unrelated to significant liver damage or liver function loss. During normal pregnancy, for example, serum albumin levels fall due to plasma volume expansion, and alkaline phosphatase (ALP) levels rise due to placental influx. Patients who have elevated transaminase levels may not suffer from liver disease, but rather from cardiac or skeletal muscle damage. Conversely, patients who suffer from advanced liver disease, such as chronic hepatitis or compensated liver cirrhosis, may have normal LFTs.
In short, the assessment of LFTs can represent a challenge for physicians. The observations above demonstrate the need for a firm understanding of the individual LFT, and the ability to interpret the results in the light of a specific clinical setting. Such an understanding is not merely a goal on its own, but may serve as a template to avoid mistakes in interpreting LFT abnormalities.
In the following sections, we discuss several mistakes frequently made in the interpretation of LFTs and how to avoid them. Most of the discussion is evidence based, but where evidence is lacking the discussion is based on extensive clinical experience.