What does ALT (SGPT) test reveal about your liver function?
Your liver is a highly vital organ and performs many essential functions for you. It aids in digestion of food by producing a fluid called bile. It helps in removal of waste products and other toxins from your blood and produces proteins and cholesterol. It is beneficial to know about liver function tests which consist of tests checking the function of liver including your bilirubin, albumin, prothrombin time and those for liver damage for checking liver enzymes.
What is ALT?
Let us learn about ALT. ALT or Alanine transferase, formally known as Alanine aminotransferase is also called SGPT or Serum Glutamic-Pyruvic Transaminase. This enzyme is found mainly in your liver. Smaller amounts of ALT are in your kidneys and other organs too.
Your body uses ALT to break down food into energy. ALT levels in the blood are low under normal conditions. In case your liver is damaged, it will release more ALT into your blood and levels will rise. In addition to liver disease, serum ALT activity may be affected by a number of factors including age, gender, body mass index (BMI), serum lipid levels, serum glucose levels, smoking, alcohol consumption and physical activity.
Indications of ALT testing
ALT test is recommended by your doctor if you have risk factors or symptoms of liver disease.
Risk factors which increase your probability for liver disease include:
- exposure to Hepatitis virus
- excess intake of alcohol
- consumption of medications causing liver damage
- family history of liver disease
Symptoms of liver disease include:
- Pain in abdomen
- Yellow skin or eyes (jaundice)
- Extreme fatigue
- Dark-colored urine
- Light-colored stool
- Itchy skin
ALT as indicator of liver disease
You must be aware of the important role which serum ALT plays in providing information about your liver health. Serum ALT levels can effectively identify an ongoing liver disease process indicating injury to liver cells as well as detect in apparent liver disease with no symptoms. We will review what ALT reveals about your liver function in:
a) Asymptomatic conditions b) Symptomatic conditions namely Non-alcoholic Fatty Liver Disease (NAFLD), Viral Hepatitis, Alcoholic Liver disease, Autoimmune Liver disease, Medication induced Hepatoxicity, Genetic and Metabolic Liver diseases
In case you do not have any symptoms of liver disease, elevation of ALT depends upon the history and physical examination, the length of time that ALT has been elevated and the level of ALT elevation. The recent American Gastroenterological Association guideline regarding the management of abnormal liver chemistry tests proposes that in addition to liver chemistries, history and physical examination, an initial serologic evaluation includes a prothrombin time; albumin; complete blood count with platelets; hepatitis A, B, and C serologies and iron studies. Further testing may include ultrasonography, biopsy and other serum studies if elevation persists after observation period.
The level of ALT also guides the urgency and extent of further investigation. A serum ALT level less than 5 times the upper limit of the normal range should be rechecked before an extensive work-up is undertaken. If elevated ALT levels are confirmed and if they remain persistently elevated, additional work-up is indicated. ALT levels greater than 5 times the upper limit of the normal range suggest a potentially serious, active liver disease process and work-up should be initiated at the earliest.
In case you have elevated ALT levels with symptoms such as fatigue, anorexia or pruritus, the probability of clinically significant liver disease increases. You definitely will want to review the following conditions:
Non-alcoholic Fatty Liver Disease (NAFLD)
You are at risk for NAFLD if you have obesity, Diabetes and hyperlipidemia. Raised levels of ALT can be associated with metabolic syndrome, characterized by insulin resistance which presents with hyperglycemia, hyperlipidemia, abdominal obesity and hypertension. Testing for your ALT levels will facilitate timely diagnosis of NAFLD before irreversible fibrosis of the liver is established.
Elevated ALT levels may correlate with the progression of NAFLD. More than 60% of men and 45% of women in the United States are overweight, at least one third of whom are obese. Studies have estimated that approximately 75% of those with obesity or Diabetes have NAFLD and elevated levels of ALT with greater propensity for further liver damage.
It is good to know that the most common chronic blood-borne infection in the United States is chronic Hepatitis C Virus (HCV) infection. Anyhow, there is variation in your ALT levels in HCV and values may occasionally fall into the normal range. As HCV infection is commonly asymptomatic, rise in ALT levels noted upon routine blood testing often stimulate the work-up to establish diagnosis of HCV. In a long-term study to identify candidates for antiviral therapy for Hepatitis C infection, it was found that 29% of HCV-infected patients with initially normal ALT values, when followed, will develop persistently elevated ALT levels and 57% will develop transient elevation in ALT levels within 5 years.
Similarly, Hepatitis B Virus (HBV) Infection is a blood borne infection and common in certain risk groups such as individuals with a history of injection drug use or on hemodialysis, having multiple sex partners or health care providers exposed to infected blood. Chronic HBV infection is also frequently asymptomatic, sometimes discovered due to your elevated ALT level identified upon routine blood testing. Thus, ALT is useful not only in determining the presence of significant liver disease and need for treatment but also in gauging the future progression in the natural history of the infection.
Other liver conditions
The excess consumption of alcohol and use of many medications including prescription, over-the-counter medications and herbal preparations have been associated with elevated ALT levels. Autoimmune Hepatitis, metabolic disorders such as Hereditary Hemochromatosis and genetic disorders such as Wilson disease and Alpha-1-Antitrypsin deficiency may also be identified by recognition of mild to moderate elevations of ALT activity
In this way, considering the role of ALT in asymptomatic and symptomatic liver conditions, it becomes an important marker of liver function and an essential indicator of health and disease.