Mild hemolysis, such as that caused by hereditary spherocytosis and other disorders, can also result in elevated unconjugated bilirubin values, but hemolysis is not usually present if the hematocrit and blood smear are normal.
The presence of hemolysis can be confirmed by testing other markers, such as haptoglobin, or by measuring the reticulocyte count. Severe defects in bilirubin transport and conjugation can lead to markedly elevated unconjugated bilirubin levels, which can cause serious neurologic damage kernicterus in infants.
However, no serious form of liver disease in adults causes elevation of unconjugated bilirubin levels in the blood without also causing elevation of conjugated bilirubin values. When a patient has prolonged, severe biliary obstruction followed by the restoration of bile flow, the serum bilirubin level often declines rapidly for several days and then slowly returns to normal over a period of weeks. The slow phase of bilirubin clearance results from the presence of delta-bilirubin, a form of bilirubin chemically attached to serum albumin.
Clinical laboratories can measure delta-bilirubin concentrations, but such measurements are usually unnecessary if the physician is aware of the delta-bilirubin phenomenon. Although the serum albumin level can serve as an index of liver synthetic capacity, several factors make albumin concentrations difficult to interpret. Albumin has a plasma half-life of three weeks; therefore, serum albumin concentrations change slowly in response to alterations in synthesis.
Furthermore, because two thirds of the amount of body albumin is located in the extravascular, extracellular space, changes in distribution can alter the serum concentration. In practice, patients with low serum albumin concentrations and no other LFT abnormalities are likely to have a nonhepatic cause for low albumin, such as proteinuria or an acute or chronic inflammatory state.
Albumin synthesis is immediately and severely depressed in inflammatory states such as burns, trauma and sepsis, and it is commonly depressed in patients with active rheumatic disorders or severe end-stage malnutrition.
In addition, normal albumin values are lower in pregnancy. The prothrombin time PT does not become abnormal until more than 80 percent of liver synthetic capacity is lost. This makes PT a relatively insensitive marker of liver dysfunction. However, abnormal PT prolongation may be a sign of serious liver dysfunction. Because factor VII has a short half-life of only about six hours, it is sensitive to rapid changes in liver synthetic function. Thus, PT is very useful for following liver function in patients with acute liver failure.
An elevated PT can result from a vitamin K deficiency. This deficiency usually occurs in patients with chronic cholestasis or fat malabsorption from disease of the pancreas or small bowel. A trial of vitamin K injections e. The PT should improve within a few days. Measurement of the blood ammonia concentration is not always useful in patients with known or suspected hepatic encephalopathy.
Ammonia contributes to hepatic encephalopathy; however, ammonia concentrations are much higher in the brain than in the blood and therefore do not correlate well. Thus, blood ammonia concentrations show only a mediocre correlation with the level of mental status in patients with liver disease.
It is not unusual for the blood ammonia concentration to be normal in a patient who is in a coma from hepatic encephalopathy. Blood ammonia levels are best measured in arterial blood because venous concentrations can be elevated as a result of muscle metabolism of amino acids. Blood ammonia concentrations are most useful in evaluating patients with stupor or coma of unknown origin.
It is not necessary to evaluate blood ammonia levels routinely in patients with known chronic liver disease who are responding to therapy as expected. The classes indicate severity of liver dysfunction: class A is associated with a good prognosis, and class C is associated with limited life expectancy. Transection of the oesophagus for bleeding oesophageal varices.
Br J Surg ;—9. For elective general abdominal surgery, perioperative mortality is in the neighborhood of several percent for patients who fall into the Child class A, 10 to 20 percent for those in class B and approximately 50 percent for those in class C. The presence of cirrhosis by itself is not an indication for liver transplantation, and transplantation is rarely performed in patients who fall into Child class A. For example, the year survival rate is as high as 80 percent in patients with hepatitis C and cirrhosis who have Child class A liver function and no variceal bleeding.
Already a member or subscriber? Log in. Interested in AAFP membership? Learn more. Address correspondence to David E. Johnston, M. NE, Albuquerque, NM — Reprints are not available from the author. Kaplan MM. Laboratory tests. Diseases of the liver 7th ed. Philadelphia: Lippincott, — Kamath PS. Clinical approach to the patient with abnormal liver function test results. Mayo Clin Proc. Theal RM, Scott K.
Evaluating asymptomatic patients with abnormal liver function test results. Am Fam Physician. If your doctor sends your blood to an off-site laboratory, you may receive the results within several days. These results are typical for adult men.
Normal results vary from laboratory to laboratory and might be slightly different for women and children. Your doctor will use these results to help diagnose your condition or determine treatment you might need. If you already have liver disease, liver function tests can help determine how your disease is progressing and if you're responding to treatment. Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission.
This content does not have an English version. This content does not have an Arabic version. Overview Liver function tests are blood tests used to help diagnose and monitor liver disease or damage. Request an Appointment at Mayo Clinic. Share on: Facebook Twitter. Sign In or Create an Account.
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Google Scholar. Select Format Select format. In addition, prevent low B6 levels by refraining from smoking, overindulging in alcohol, and maintaining a healthy body weight. ALT is an enzyme used to assess liver health. Low levels are generally considered good and are usually not a cause for concern. However, in some cases a low ALT can be a result of an underlying medical condition, such as vitamin B6 deficiency or chronic kidney disease. Factors that deplete B6, including smoking and alcoholism, can also decrease ALT levels.
This post is part of a three-part series about ALT. Learn more about the functions of ALT and why doctors order the test here. If your ALT levels are high, read this post. Joe Cohen won the genetic lottery of bad genes.
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Vitamin B6 deficiency may decrease ALT levels. Smoking likely lowers ALT in healthy people but increases it in people with liver disease. ALT can decrease in response to regular exercise, hormone replacement and birth control pills, or in chronic kidney disease.
A couple of studies have found a link between low ALT levels and a higher risk of heart disease. However, this relationship is unlikely to be causal. Low ALT levels in older people have been associated with higher mortality. Takeaway ALT is an enzyme used to assess liver health.
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