Patients are instructed to avoid certain medications and foods before a hepatic function panel to ensure the integrity of blood specimens. A trained healthcare provider will disinfect skin and wrap an elastic strap around the arm to visualize a vein. Blood will be drawn and put into a sample container. The sample must be placed in the correctly colored cap, as the various color caps have a particular additive associated with them.

According to the International Standard ISO 6710, the light green cap contains lithium-heparin and used for the hepatic function panel.[20] After the specimen is collected and fulfill the requirements, they go for testing.

ALT levels can increase due to certain drugs, which should be avoided before testing. Drug hepatotoxicity can be nonidiosyncratic (predictable) or idiosyncratic (unpredictable). Also, drug-associated hepatotoxicity can classify as immune-mediated and non-immune mediated. The incidence of drug-induced liver injury is 19 cases per 100,000 persons. The most common drug causing drug-induced liver injury is amoxicillin/clavulanate.[21][22][23] Hepatitis E infection can masquerade drug-induced liver injury in 3% to 13% of the cases.[24] Tacrine, a medication indicated for Alzheimer disease, was withdrawn from the market because of significant liver injury. This medication caused elevations of ALT levels that trended as high as 20 times the normal reference level.[25] 

Up to 5% of patients on statin medications were found to develop elevations in ALT.[26] Ceftriaxone, phenytoin, carbamazepine, cotrimoxazole, and allopurinol have been reported to cause liver injury. Also, tricyclic antidepressants, imipramine, and amitriptyline have links to transient elevations in ALT.[27] Elevation of serum ALT and AST has been reported in patients taking these medications isoniazid, pyrazinamide, rifampicin, ibuprofen, or dapsone.[28] The website maintained by the National Institute of Diabetes and Digestive Diseases (NIDDK) is a valuable resource to clinicians and researchers interested in liver hepatotoxicity and other drugs that can causes increases in serum ALT. As stated earlier, periods of intense exercise should be avoided before testing, as it can also increase alanine transaminase levels.[29]

Results of a hepatitis panel should correlate with the initial findings in a complete history and physical examination. A thorough review should include important questions regarding the patient’s age, past medical history (diabetes, obesity, hyperlipidemia, inflammatory bowel disease, celiac sprue, thyroid disorders, autoimmune hepatitis, and acquired muscle disorders, alcohol consumption, medication use, toxin exposure, and family history of genetic liver conditions (Wilson’s disease, alpha-1-antitrypsin deficiency, hereditary hemochromatosis).

A review of systems should also include signs and symptoms of chronic liver disease such as jaundice, ascites, peripheral edema, hepatosplenomegaly, gynecomastia, testicular hypotrophy, muscle wasting, encephalopathy, pruritus, and gastrointestinal bleeding.[30] Other tests that help determine the cause of elevated transaminase levels found on a hepatitis panel include fasting lipid levels, hemoglobin A1C level, fasting glucose, complete blood count with platelets, a complete metabolic panel, iron studies, hepatitis C antibody, and hepatitis B surface antigen testing.[30]

A hepatitis panel’s reference ranges can fluctuate amongst different laboratories. Reported values also can vary depending on gender, body mass index, and past medical history. In the workup for elevated transaminase levels, repeat liver enzymes are typically not necessary.[31]

• Normal serum alanine aminotransferase (ALT) is 7-56 U/L.
• Normal serum aspartate aminotransferase (AST) is 0 to 35 U/L.
• Normal serum alkaline phosphatase (ALP) is 41 to 133 U/L.
• Normal serum gamma-glutamyl transferase (GGT) is 9 to 85 U/L.
• Normal serum total bilirubin is 0 to 1.2 mg/dL.
• Normal albumin is 40 to 60 g/L.

It is essential to consider that any liver cell injury can cause an increase in ALT serum levels. Although there are specific hepatic diseases that are associated with an elevation in ALT levels, there is no correlation between the absolute peak of the ALT elevation and the magnitude of hepatic injury. It is common to see increases in both AST and ALT serum levels concomitantly. ALT levels greater than 1000 U/L should consider acute ischemic liver injury, severe drug-induced liver injury, or acute viral hepatitis. Other causes include common bile duct stones, and hepatitis E infection.[32]

Viral hepatitis is liver inflammation from hepatitis A, B, C, D, and E. Acute hepatitis A, in comparison with both Hepatitis C and B, is associated with higher increases in serum ALT and AST levels, reaching the levels of 3000 to 4000 IU/L for each. The diagnosis of chronic hepatitis will have elevations in ALT levels for greater than six months.[31] Common clinical signs of viral hepatitis include jaundice, anorexia, fatigue, vomiting, fever, nausea, and hepatomegaly. The risk factors for viral hepatitis include travel to areas where hepatitis is endemic, multiple sexual partners, occupational exposure to chemicals and hepatotoxicants, and intravenous drug use. Hepatitis serology labs should also be ordered to confirm the diagnosis and the type of viral hepatitis.

Ischemic liver injury, also known as ischemic hepatitis, occurs when there is an acute reduction in blood perfusion to the liver, leading to necrosis of hepatic centrilobular cells on histology.[33] The occurrence of hepatic damage is higher in septic shock, where a decrease in blood perfusion to the liver is due to infection. A recent study revealed the incidence of abnormally elevated ALT was more sensitive to the diagnosis of ischemic hepatitis due to septic or hypovolemic shock.[33] In the evaluation of septic shock as a potential cause for ischemic liver injury, serum lactate, serum CRP, blood counts, D-dimer levels, and blood cultures should be measured. 

Medications can account for an elevation in ALT. Paracetamol toxicity (also known as acetaminophen) has been shown in a recent study, to account for almost half of the drug-induced liver injuries.[32] In paracetamol toxicity, the levels of serum ALT are usually higher than 1,000 U/L.[32] Therefore, paracetamol toxicity should be among the differential diagnosis of patients presenting with acute liver failure.[32] A review of patient hepatotoxic medicines is vital in ensuring the proper diagnosis. Drugs associated with an elevation of transaminases include tacrine, imipramine, amitriptyline, isoniazid, pyrazinamide, rifampicin, ibuprofen, nimesulide, cotrimoxazole, phenytoin, and dapsone.[21][22][23]

Non-alcoholic fatty liver disease (NAFLD) should merit consideration among the most common cause of abnormally elevated ALT levels in asymptomatic patients. NAFLD is the accumulation of fat within the liver in patients who do not consume alcohol. NAFLD has the potential to progress into hepatic fibrosis and cirrhosis, thus increasing liver-related morbidity and mortality. NAFLD is usually associated with higher ALT and GGT levels in patients with impaired glucose tolerance or type 2 diabetes mellitus. Risk factors for NAFLD include morbid obesity, hyperglycemia, hypertriglyceridemia, hypertension, and decreased insulin sensitivity. a NAFLD fibrosis score and radiological imaging such as CT or MRI of the liver should be considered to assess the severity and progression of NAFLD. The diagnosis of NAFLD is made with the presence of steatosis in 5% or greater of hepatocytes.[32][34]

In 1957, DeRitis described in a publication the ratio between AST and ALT in the diagnosis of viral hepatitis, where ALT is usually higher than AST.[35] Later, the usefulness of this ratio has been highlighted in alcoholic hepatitis, where AST is mostly more elevated than ALT. Therefore, the ratio between AST and ALT is >2.0 for alcoholic hepatitis, and 1.5 to <2.0 in acute viral hepatitis, and >1.0 in fibrosis and cirrhosis. However, many laboratories do not include this ratio in their reports because it is not specific, and AST can be affected by hemolysis. The ratio is affected by the number of days post-exposure and the severity of the disease. Another important factor is the relatively short half-life of AST (18 hours) compared to ALT (47 hours) and the fact that gender requires consideration, and there is an intra-individual variation of both AST and ALT.[36]

The collection of blood samples carries significant safety risks for both personnel and patient if done improperly. Structured curricula designed to standardize the practice of collecting blood samples, educate participants on the risks, and addressing common errors that occur can increase lab safety.

Healthcare workers should demonstrate a degree of competency before working with patients. Personal protective equipment and antiseptics should be utilized by healthcare workers to prevent accidental contamination of blood samples or infection. Personal protective equipment includes single-use nonsterile gloves, eye protection, and masks if there is a potential for blood exposure. Equipment such as trays or tube holders should be cleaned and disinfected if used on multiple patients. Disposal of all needles and syringes must be considered immediately after use. The use of a sharps container can decrease the risk of a needle-stick injury from occurring.[20]

Multi-disciplinary rounds are a time in which medical and other health providers can collaborate and work together to enhance patients' healthcare outcomes. Clinicians may review the significance of the hepatic function test panel in correlation with the medical history and physical examination of each patient to early detect any drug-induced hepatic injury and build a differential diagnosis. Changes in the patient's patterns of ALT and AST over time, or other liver function tests may necessitate a referral to gastroenterologists for consultation. Clinical pharmacists can also advise about potential contraindications or hepatotoxic medication interactions. The charge nurse of each floor can communicate updates on a patient's response to treatment, other recent laboratory orders, and current disposition. A multi-disciplinary approach can ensure a higher quality of care for each patient and enhance outcomes.[37]