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In the United States, approximately one out of every 400 adults has cirrhosis, or scarring of the liver. The prevalence of hepatitis depends on the strain; while there were only 30,000 cases of hepatitis A reported in the United States in 2016, more than 500 million people around the world are affected by hepatitis B and hepatitis C. According to Coucke and Lopez, 10% to 15% of American adults will develop gallstones, the most common cause of bile duct obstructions.
This guide provides an overview of the alkaline phosphatase (ALP) test, including what it involves and how it’s used to diagnose cirrhosis, hepatitis, and bile duct obstructions. It also includes a comprehensive overview of these three medical conditions.
The purpose of the ALP test is to determine if an individual has an abnormal amount of alkaline phosphatase in the blood. ALP is an enzyme found in the liver, kidneys, bones, and intestines. If the liver is damaged, it can leak ALP into the bloodstream, making the ALP test useful for diagnosing conditions that affect the liver. It can also be used to aid in the diagnosis of gallstones, bile duct obstructions, and certain problems with the bones.
The ALP test should be ordered if an individual has any symptoms of liver disease or liver damage. These symptoms include abdominal pain, nausea, vomiting, itchy skin, changes in the color of the stool or urine, weakness, fatigue, and unintended weight loss. Another sign of liver problems is jaundice, which is a yellowing of the skin. In some people, jaundice also causes the whites of the eyes to look yellow.
The ALP test is performed on a sample of blood drawn from one of the veins in the arm or hand.
No special preparation is required for the ALP test; however, ALP is usually tested as part of a liver function panel. Some components of the liver function panel can be affected by foods and beverages. Therefore, it may be necessary to fast overnight before having blood drawn for the test. Some medications can also affect the results of this test. It may be necessary to stop taking these medications several days before having blood drawn.
Cirrhosis is one of the most common diseases affecting the liver, and it develops when something damages the liver over a period of time. The damaged tissue is replaced by scar tissue, which can interfere with normal liver function by blocking the flow of blood. In some people, the presence of scar tissue in the liver can also prevent the organ from producing proteins that are needed for normal blood clotting, which could be life-threatening if an individual has surgery or sustains a serious injury.
Certain factors increase the risk of developing cirrhosis. One of the greatest risk factors is excessive alcohol consumption, as alcohol damages the cells in the liver, causing scar tissue to develop. Excessive alcohol consumption is defined by the American College of Gastroenterologists as more than two to three drinks per day for men and more than one to two drinks per day for women. Other risk factors for cirrhosis include hepatitis infections, diabetes, and obesity.
Cirrhosis causes many of the same signs and symptoms as other liver disorders. Jaundice is one of the most noticeable signs of this condition. Other symptoms of cirrhosis include lack of appetite, hair loss, weight loss, nausea, vomiting, and itchy skin. Some people also experience abdominal swelling due to an accumulation of fluid in the abdomen.
Hepatitis is an inflammation of the liver that usually develops due to the presence of a virus. This virus comes in several strains, but hepatitis B and C are the most common. Transmission of hepatitis B and hepatitis C occurs via contact with the body fluids of an infected person. This includes blood, vaginal secretions, and semen; therefore, these strains of hepatitis can be spread via sexual contact, a needle-stick injury, or the use of a needle or other sharp instrument that has been used to pierce or tattoo someone who has hepatitis B or C. A needle-stick injury is when someone, usually a health care provider, is accidentally pierced by a scalpel or needle that was used in the treatment of a patient with the hepatitis B or C infection.
The use of injectable drugs is the most significant risk factor for hepatitis B. People who’ve had surgery or blood transfusions also have a heightened risk of developing hepatitis B. Risk factors for hepatitis C include the use of non-sterile instruments for piercing or tattooing, the use of injectable drugs, and being born between 1945 and 1965. Researchers don’t know why being born during this time period increases the risk of developing hepatitis C, but it may have to do with the fact that hepatitis C infection rates in the United States were at their highest at this time.
Common signs and symptoms of hepatitis B and C infections include nausea, vomiting, abdominal pain, fever, unexplained weight loss, loss of appetite, and changes in the color of an individual’s urine or bowel movements.
A bile duct blockage develops when something interferes with the normal flow of bile from the liver to the small intestine and gallbladder. The most common cause of this condition is gallstones, hard chunks composed of bilirubin and cholesterol. Bilirubin is the chemical that gives stool its brown color. Other causes of bile duct blockages include bile duct cysts, bile duct inflammation, scarring inside the bile ducts, tumors, or an injury to the bile ducts that occurs during gallbladder surgery.
Several risk factors make it more likely that an individual will develop a bile duct obstruction. The risk of this condition is increased in people with a history of gallstones, pancreatic cancer, or pancreatitis; people who’ve recently had surgery on the bile ducts, a history of cancer in the bile ducts, and people who’ve sustained abdominal injuries.
Jaundice is also one of the most significant signs of bile duct obstructions. Other signs and symptoms of this condition include itchy skin, abdominal pain on the right side of the body, fever, dark urine, vomiting, nausea, and pale stools.
Before the ALP test can be performed, the individual must provide a blood sample. This sample is usually obtained by a phlebotomist, which is a person who’s been trained to draw blood and handle the specimens correctly. During a blood draw, the phlebotomist ties a tourniquet around the individual’s upper arm to make the veins easier to see and feel. After identifying the puncture site that will be used, the phlebotomist cleanses the individual’s skin to eliminate bacteria and reduce the risk of infection. Once the needle is inserted into the target vein, the phlebotomist uses a collection tube to collect enough blood for analysis. Laboratory personnel use a technique called enzyme immunoassay to determine the amount of ALP in the blood.
No single treatment plan works for every person with cirrhosis, so it’s important to work with a licensed medical professional to determine the best way to prevent additional liver damage and control the symptoms of this disease. People who developed cirrhosis as a complication of a hepatitis infection may take medications to suppress the hepatitis virus. In people who developed cirrhosis due to excessive alcohol consumption, stopping alcohol use is usually one of the key recommendations. An individual with alcohol use disorder may be referred to a rehabilitation program to address any issues that could be contributing to their alcohol addiction. In some people, a condition called nonalcoholic fatty liver disease causes scarring of the liver. These people may be advised to lose excess weight or follow a special diet to help them maintain a healthy weight.
Some people with hepatitis B respond well to a treatment called pegylated interferon alpha, which combines polyethylene glycol with interferon. The PEG helps the interferon remain in the individual’s system longer, making it more convenient to use. People who take pegylated interferon alpha to treat hepatitis B only have to take it once per week, compared with several times per week for other treatments. Not all people with hepatitis B respond well to pegylated interferon alpha; these people may need to take other medications to suppress the hepatitis B virus.
Pegylated interferon can also be used to treat hepatitis C, except it’s combined with ribavirin when used for this purpose. Pegylated interferon combined with ribavirin is more effective than other treatments for hepatitis C, but because it’s a form of chemotherapy, it can cause serious side effects.
Treatment for this condition aims to remove the source of the blockage, allowing bile to flow normally. For an individual with a bile duct blockage caused by gallstones, endoscopic retrograde cholangiopancreatography (ERCP) may be needed. During this procedure, a doctor inserts an endoscope into the mouth and advances it through the esophagus and stomach until it reaches the small intestine. After locating the opening where the bile ducts meet the duodenum, the doctor inserts a catheter into the ducts and injects a dye that makes the ducts easier to see on an X-ray machine. Once the source of the blockage is located, the doctor uses medical instruments to remove the stones or break them up. ERPC may also be used to treat blockages caused by tumors.
A normal ALP level usually ranges from 20 to 140 international units per liter; however, some labs have different reference ranges. The normal range for a particular lab will be printed on the report with the results.
Not necessarily. Because ALP is found in other parts of the body, such as the bones and kidneys, it’s possible to have an elevated ALP level and still have normal liver function.
Additional tests may be needed if the ALP test result is abnormal. For people with any of the risk factors for liver problems, the ordering physician will review the results of the ALP test as well as other indicators of liver function. These indicators include total protein, albumin, and bilirubin. If these tests are also abnormal, a health care provider is likely to order an ultrasound or CT scan to determine if the liver has any structural or functional abnormalities.
If the other liver function tests are normal, it’s possible the excess ALP is coming from a source other than the liver. A health care provider may order a basic metabolic panel to assess the individual’s kidney function or isoenzyme tests to determine if the high ALP level stems from a problem with the bones. Isoenzyme testing can distinguish ALP released by the bones from ALP released by the liver based on the structure of each substance.
The ALP test has relatively few risks. Any time an individual has blood drawn, there is a risk that bacteria from the skin will get into the bloodstream and cause an infection; however, the risk is low. Some people feel ill while they are having blood drawn, but this usually goes away once the needle is removed from the vein and a bandage has been placed over the insertion site.
High ALP levels are more concerning than low ALP levels, but a low ALP level can be a sign of certain medical problems. These problems include protein deficiency, malnutrition, and Wilson disease, a genetic disorder that causes copper to accumulate in the body’s tissues.
|American Liver Foundation||www.liverfoundation.org||The American Liver Foundation offers educational materials for people living with hepatitis, cirrhosis, and other liver disorders.|
|Hepatitis Foundation International||www.hepatitisfoundation.org||HFI provides information about hepatitis for patients and their caregivers.|
|MedlinePlus||www.medlineplus.gov||Access additional information on laboratory testing via the U.S. National Library of Medicine.|
|National Institute of Diabetes and Digestive and Kidney Diseases||www.niddk.nih.gov||The NIDDK provides in-depth information on hepatitis, cirrhosis, and other diseases affecting the liver and bile ducts.|
|American College of Gastroenterology||www.gi.org||Read articles written by experts in the field of gastroenterology.|