Some Observations on Liver Function Tests *

Recent advances in the treatment of liver disease and the increased prevalence of infectious hepatitis have stimulated interest in tests of liver function. These have proved useful both in diagnosis and in following the course of liver disease. Their value, however, has been questioned by some and overrated by others. In approaching this problem it is well to recognize at the outset that liver function tests are not a substitute for a careful history and physical examination, that, at best, they are confirmatory diagnostic aids, and that their interpretation demands an understanding of their physiologic basis and recognition of their limitations. The term "liver function test" is somewhat misleading and, unless its implications are fully understood, may be the basis for misunderstanding and misinterpretation. In the first place, few of the tests employed actually measure normal physiologic functions of the liver. Thus, while changes in the level of serum albumin and bilirubin or in the excretion of galactose may indicate disturbances in normal functions, the excretion of a foreign dye, such as bromsulphalein, cannot be regarded as a measure of any of the normal functions of the liver, even though it may reflect abnormalities in them indirectly. Secondly, some of the tests measure changes, which, while they may disclose the presence of pathological processes in the liver, do not necessarily imply any abnormality in its functions. The changes in the serum globulin pattern, which occur so frequently in a variety of liver diseases, and which may be crudely measured by such tests as the cephalin-cholesterol flocculation and the thymol turbidity, are examples. Lastly, many of the abnormalities resulting from impairment of function or from pathological changes in the liver may also occur in other diseases not affecting that organ, as, for example, the increase in serum alkaline phosphatase which accompanies certain bone diseases. It is not surprising, then, to learn that abnormal function tests do not necessarily imply any impairment of function or the presence of any structural derangement of the