Assessing liver function

Unlike in renal medicine, there is no simple method of estimating liver function because  

This chapter will look at how a judgement can be made about the extent of a patient s liver dysfunction. These tools can be used along with other chapters in the book to assist in making the correct choice of drug and dosage for each patient. 

Any of the above used in isolation may lead to an inaccurate assessment and hence potentially inappropriate drug use. A patient with the same LFTs as another may have very different signs and symptoms. 

It is clear from these examples that it is essential to be able to assess accurately which patients need to have their liver function taken into consideration when prescribing. 

The following sections of this chapter look at the individual components of LFTs and how they need to be considered as a group, over time, to interpret them effectively. Also discussed is what other test results, signs and symptoms indicate, along with methodologies, such as Child-Pugh, which are used to compare individuals liver function. 

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Some of the information (discussed previously in Chapter 4) needed to assess liver function can be found in the patient s medical notes (e.g. laboratory results). However, it is generally useful to speak to an... 

Having assessed liver function, you need to go back to basic principles of pharmacokinetics what does the liver normally do and what types of dysfunction may affect drug handling In Chapter 5 we have incorporated the theory with practical advice that you can apply to a patient. Chapter 6 considers the impact of a drug s side-effect profile on a patient with liver dysfunction. 

Bergquist et al. (35) presented examples in which several laboratory tests that are commonly used to assess liver function provide a more reliable indication of impaired drug metabolic clearance than does the... 

Several multianalyte diagnostic methods have been marketed to assess the level of liver fibrosis, such as Fibroscan and Fibrotest.39 These tests may leave room for improved biomarkers however, the accuracy of the biopsy method has also been questioned as a source of error in evaluation of these studies. Additional liver biomarkers are needed that improve on the specificity of ALT to differentially diagnose injury severity, or improve on the sensitivity of serum bilirubin or serum albumin and clotting factors to help assess liver function. 

Most investigators who have used indocyanine green to assess liver function have measured its FDR or PDR (C16,1128, M17). Some values for FDR in normals are listed in Table 4. 

The standard battery of biochemical tests used to assess liver function usually includes the measurement of the activity in plasma of one of the aminotransferases [either aspartate aminotransferase (AST) or alanine aminotransferase (ALT)]. Such measurements are performed to assess the integrity of the hepatocyte membrane. The measurement of AST provides poor organ specificity due to the ubiquitous nature of the enzyme and both ALT and AST are relatively poor at detecting damage that is occurring to the centrilobular hepatocytes. The inadequacy of the aminotransferases at detecting centrilobular liver damage may be... 

A test that can be used to assess liver function when other liver function tests are normal. It is a test of the ability of the liver to conjugate and excrete the dye bromsulphthalein (BSP). It consists of an intravenous injection of the dye followed by the collection of blood specimens up to 45 minutes after the injection. Bromsulphthalein is then measured in the serum samples by adding alkali which renders the dye purple. In normal subjects less than 5% of the dose should remain in the circulation after 45 minutes. Increased retention of BSP is a sensitive index of hepatic dysfunction although false positives may occur if there is impaired circulation in the liver. 

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