Matthew R. Pincus, Philip M. TiernoJr., Maly Fenelus, Wilbur B. Bowne, Martin H. Bluth McPherson: Henry’s Clinical Diagnosis and Management by Laboratory Methods, 22nd ed. Copyright © 2011 Saunders, An Imprint of Elsevier Chapter 21 – Evaluation of Liver Function
Perhaps the most frequently ordered laboratory test for detecting liver-associated coagulation abnormalities is PT and its associated measurement, the international sensitivity ratio, as described in Part 5. The PT measures the efficacy of the extrinsic clotting system in which factor VII is activated by tissue factor, as discussed in Part 5; because factor VII is uniquely synthesized in the liver, its measurement can be used to evaluate liver function status. Often, PT is computed as the international normalized ratio (INR), which attempts to standardize all PT measurements relative to a “gold standard” PT-measuring method, using the international sensitivity index (ISI), as described in Part 5.