Introduction
A number of laboratory tests are available to test the health and function of the liver (Table 37.1). In this chapter, a review of the evaluation of elevated transaminase will be presented.
Table 37.1 Common liver chemistry tests
Adapted from Green & Flamm [7].
| Liver test | Clinical implication of abnormality |
| Alanine aminotransferase (ALT) | Hepatocellular damage |
| Aspartate aminotransferase (AST) | Hepatocellular damage |
| Bilirubin | Cholestasis, impaired conjugation or biliary obstruction |
| Alkaline phosphatase | Cholestasis, infiltrative diseases or biliary obstruction |
| Prothrombin | Synthetic function |
| Albumin | Synthetic function |
| Gamma-glutamyltransferase (GGT) | Cholestasis or biliary obstruction |
| Bile acids | Cholestasis or biliary obstruction |
| Lactate dehydrogenase (LDH) | Hepatocellular damage, not specific for hepatic damage |
Transaminases include alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and are markers of hepatocellular injury. The prevalence of elevated transaminases in the US has been found to be as high as 9.8% [1]. Comparing data from the National Health and Nutrition Examination Survey (NHANES) from 1988–1994 and 1999–2002, it appears that there has been a significant rise in the prevalence of elevated transaminases in the US [1]. It is likely that more sensitive assays account for at least some of this apparent rise, but the current prevalence of elevated transaminases is closely associated with risk factors for nonalcoholic fatty liver disease (NAFLD), suggesting that obesity and insulin resistance may be important predictors of chronic liver dysfunction.
While this is not the focus of this brief chapter, the differential diagnosis of elevated transaminases in pregnancy must always include pre-eclampsia/HELLP. In patients beyond 20 weeks gestation, it is important to look for other features of these conditions including hypertension, proteinuria, thrombocytopenia, hemolysis and elevated creatinine and maintain a high index of suspicion for these diagnoses which can be an important cause of both maternal and fetal morbidity and mortality (see Chapters 6 and 9).
Elevated transaminases are often encountered as an incidental finding in the pregnant woman. Common clinical scenarios include the pregnant patient who is less than 20 weeks gestation, is asymptomatic, and has mildly abnormal transaminases or the pregnant woman in the latter half of pregnancy who is screened for pre-eclampsia and has isolated elevation of transaminases with no other features of pre-eclampsia or HELLP. Although the clinician must maintain continued vigilance for the development of pre-eclampsia, it is important to investigate for other causes of elevated transaminases. This chapter will focus on the evaluation and etiology of nonobstetric causes of mild to moderate elevation of transaminases (less than five times normal) in the asymptomatic patient.
The differential diagnosis of elevated transaminases is quite broad and includes many rare and unusual conditions.
Therefore, a stepwise approach to the evaluation of these laboratory abnormalities is often the most efficient and cost-effective. Once pre-eclampsia and HELLP syndrome have been ruled out, the evaluation should begin with a search for the most common causes of mild, asymptomatic elevated transaminases (Table 37.2). If the initial evaluation does not produce a diagnosis, then the next step is to test for the less common causes including rare liver disorders and nonhepatic causes of elevated transaminases.
Table 37.2 Top five causes of mild, asymptomatic nonobstetric causes of elevation of liver enzymes once pre-eclampsia and HELLP syndrome have been ruled out
| Risk factors | Diagnosis | |
| Nonalcoholic fatty liver disease (NAFLD) | Hyperlipidemia, obesity, and diabetes | No serologic tests. Ultrasound with diffuse fatty infiltration is suggestive. Biopsy needed to confirm diagnosis |
| Viral hepatitis | IV or intranasal drug use, blood transfusion, contaminated needles, sexual exposure | HbsAg, Hbs Ag, Hbc Ab ELISA for HCV Ab to screen HCV RNA to confirm |
| Medications | Female Common drugs include NSAID, antibiotics, statins, antiepileptic drugs and antituberculosis drugs | Medication history to screen Diagnosis confirmed if LFTs abnormalities resolve with discontinuation of drug |
| Hemochromatosis | Family history of hemochromatosis Symptoms include fatigue, abdominal pain, arthralgias Can cause congestive heart failure and diabetes | Iron saturation test (serum iron/TIBC) to screen Genetic testing or liver bipsy to confirm |
| Alcohol | Family history of alcoholism, depression | CAGE questionnaire to screen for problem drinking (2 questions answered positively suggests problem drinking) Have you ever felt you should cut down on your drinking? Have people annoyed you by criticizing your drinking? Have you ever felt bad or guilty about your drinking? Have you ever had a drink first thing in the morning to steady your nerves or get rid of a hangover (an “eye-opener”)? AST:ALT ratio >2.0 is suggestive Liver biopsy needed to confirm |
In order to recognize the most common causes of mild asymptomatic elevated transaminases, the practitioner should be familiar with the clinical presentation and unique features of each condition.
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