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Understanding Lab Tests: Entire Lesson

for Veterans and the Public

Understanding Lab Tests: Entire Lesson

Laboratory tests: Overview

Once you've been diagnosed with hepatitis C, your VA doctor probably will order a number of tests to learn about your overall health, to decide whether drug therapy is appropriate, and to learn about your body's internal functioning (including how well your liver is working).

Some tests will be done very soon after you've been diagnosed with hepatitis C, while other tests will continue to be done on a regular basis. These tests will monitor your health and help you and your doctor decide when treatment is appropriate (or, if you've already begun treatment, whether it's working).

In the following sections, you can learn about the tests, why your doctor may have ordered them, and what the results mean.

Note:

Normal values for laboratory tests can vary from one lab to another. Check with your doctor on the normal range for your lab tests.

Tests of the liver

If you have hepatitis C, most likely, your doctor will check blood tests of your liver. There's a handful of liver tests and it is helpful to know what each of them means. Here, we explain common liver blood tests and how to understand your results:

Liver panel

A "liver panel" usually refers to several lab tests performed as a group. Depending on the physician or the laboratory, a liver panel usually includes tests for AST, ALT, bilirubin, and alkaline phosphatase.

Liver enzymes

Usually, the term "liver enzymes" refers to the AST and the ALT.

Liver function tests (LFTs)

The phrase "liver function tests" or "LFTs" is commonly used by patients and physicians. Many patients and physicians use the term to describe the AST and ALT. However, this is not correct--the AST and ALT do not measure the function of the liver.

The true function of the liver is actually best measured by the PT, INR and albumin. Therefore, if you are getting a PT, INR or albumin, these tests can determine how the liver is "functioning."

ALT (SGPT)

ALT, or alanine aminotransferase, is 1 of the 2 "liver enzymes." It is sometimes known as serum glutamic-pyruvic transaminase, or SGPT. It is a protein made only by liver cells. When liver cells are damaged, ALT leaks out into the bloodstream and the level of ALT in the blood is higher than normal.

signs of an unhealthy liver

Scroll over image to see an animation of liver enzymes leaking into the blood.

Explanation of test results:

A high ALT level often means there is some liver damage, but it may not be related to hepatitis C. It is important to realize the ALT level goes up and down in most patients with hepatitis C. The ALT level does not tell you exactly how much liver damage there is, and small changes should be expected. Changes in the ALT level do not mean the liver is doing any better or any worse. The ALT level does not tell you how much scarring (fibrosis) is in the liver and it does not predict how much liver damage will develop.

Other things to know:

  • Many patients with hepatitis C will have a normal ALT level.
  • Patients can have very severe liver disease and cirrhosis and still have a normal ALT level.
  • When a patient takes treatment for hepatitis C, it is helpful to see if the ALT level goes down.

AST (SGOT)

AST, or aspartate aminotransferase, is 1 of the 2 "liver enzymes." It is also known as serum glutamic-oxaloacetic transaminase, or SGOT. AST is a protein made by liver cells. When liver cells are damaged, AST leaks out into the bloodstream and the level of AST in the blood becomes higher than normal. AST is different from ALT because AST is found in parts of the body other than the liver--including the heart, kidneys, muscles, and brain. When cells in any of those parts of the body are damaged, AST can be elevated.

Explanation of test results:

A high AST level often means there is some liver damage, but it is not necessarily caused by hepatitis C. A high AST with a normal ALT may mean that the AST is coming from a different part of the body. It is important to realize that the AST level in most patients with hepatitis C goes up and down. The exact AST level does not tell you how much liver damage there is, or whether the liver is getting better or worse, and small changes should be expected. However, for patients receiving treatment for hepatitis C, it is helpful to see if the AST level goes down.

Other things to know:

  • The AST level is not as helpful as the ALT level for checking the liver.
  • Many patients with hepatitis C will have a normal AST level.
  • Patients can have very severe liver disease or cirrhosis and still have a normal AST level.

Bilirubin

Bilirubin is a yellowish substance that is created by the breakdown (destruction) of hemoglobin, a major component of red blood cells.

Explanation of test results:

As red blood cells age, they are broken down naturally in the body. Bilirubin is released from the destroyed red blood cells and passed on to the liver. The liver excretes the bilirubin in fluid called bile. If the liver is not functioning correctly, the bilirubin will not be properly excreted. Therefore, if the bilirubin level is higher than normal, it may mean that the liver is not functioning correctly.

Other things to know:

  • Levels of bilirubin in the blood go up and down in patients with hepatitis C.
  • When bilirubin levels remain high for prolonged periods, it usually means there is severe liver disease and possibly cirrhosis.
  • High levels of bilirubin can cause jaundice (yellowing of the skin and eyes, darker urine, and lighter-colored bowel movements).
  • Elevated bilirubin levels can be caused by reasons other than liver disease.
  • Total bilirubin is made up of 2 components: direct bilirubin and indirect bilirubin.
  • Direct bilirubin + indirect bilirubin = total bilirubin.

Albumin

Albumin is a protein made by the liver. Albumin prevents fluid from leaking out of blood vessels into tissues.

Explanation of test results:

A low albumin level in patients with hepatitis C can be a sign of cirrhosis (advanced liver disease). Albumin levels can go up and down slightly. Very low albumin levels can cause symptoms of edema, or fluid accumulation, in the abdomen (called ascites) or in the leg.

Other things to know:

  • A low albumin level can also come from kidney disease or malnutrition or acute illness.
  • A low albumin level causing fluid overload is often treated with diuretic medications, or "water pills."

Prothrombin time

Prothrombin is a protein made by the liver. Prothrombin helps blood to make normal clots. The "prothrombin time" (PT) is one way of measuring how long it takes blood to form a clot, and it is measured in seconds (such as 13.2 seconds). A normal PT indicates that a normal amount of blood-clotting protein is available.

Explanation of test results:

When the PT is high, it takes longer for the blood to clot (17 seconds, for example). This usually happens because the liver is not making the right amount of blood clotting proteins, so the clotting process takes longer. A high PT usually means that there is serious liver damage or cirrhosis.

Other things to know:

  • Some patients take a drug called Coumadin (warfarin), which elevates the PT for the purpose of "thinning" the blood. This is not related to having liver disease because it is the Coumadin causing the PT to be high.
  • The test called INR measures the same factors as PT and is used instead of PT by many doctors. See "INR."

Alkaline phosphatase

Alkaline phosphatase (often shortened to alk phos) is an enzyme made in liver cells and bile ducts. The alk phos level is a common test that is usually included when liver tests are performed as a group.

Explanation of test results:

A high alk phos level does not reflect liver damage or inflammation. A high alk phos level occurs when there is a blockage of flow in the biliary tract or a buildup of pressure in the liver--often caused by a gallstone or scarring in the bile ducts.

Other things to know:

  • Many patients with hepatitis C have normal alk phos levels.
  • Hepatitis C treatment usually does not affect alk phos levels.
  • Alk phos is produced in other organs besides the liver--it is also found in the bones and the kidneys.
  • If your alk phos level is high, your doctor will probably order additional tests to determine why.

INR (international normalized ratio)

International normalized ratio (INR) is blood-clotting test. It is a test used to measure how quickly your blood forms a clot, compared with normal clotting time.

Explanation of test results:

A normal INR is 1.0. Each increase of 0.1 means the blood is slightly thinner (it takes longer to clot). INR is related to the prothrombin time (PT). If there is serious liver disease and cirrhosis, the liver may not produce the normal amount of proteins and then the blood is not able to clot normally. When your doctor is evaluating the function of your liver, a high INR usually means that the liver is not working as well as it could because it is not making the blood clot normally.

Other things to know:

  • Some patients take a drug called Coumadin (warfarin), which elevates the INR, for the purpose of "thinning" the blood.
  • The INR is another way of measuring the blood-clotting time and it is easier to determine than the PT.

Platelets

Platelets are cells that help the blood to form clots. The platelet number or "platelet count" in the blood is measured as part of the complete blood count (CBC).

Explanation of test results:

Platelet counts in a patient who has cirrhosis are often low. But low platelet counts can also come from other causes, including certain medications. Interferon treatment can reduce platelet counts. When the platelet count is extremely reduced, this condition is known as "thrombocytopenia." If a platelet count is too low, the patient cannot make normal clots and may bruise more easily.

Other things to know:

  • If the platelet count drops too low (below 50,000, for example) when a patient is receiving interferon, doctors may recommend that the interferon dosage be reduced.

Total protein

Total protein level is a measure of a number of different proteins in the blood. Total protein can be divided into the albumin and globulin fractions.

Explanation of test results:

Low levels of total protein in the blood can occur because of impaired function of the liver.

Tests of hepatitis C

If you have hepatitis C virus, you are likely to have a doctor recommend a few different hepatitis C blood tests, not just one. It is helpful to understand what each of these blood tests mean. Here we explain the common blood tests of hepatitis C and the meaning of test results.

Hepatitis C antibody (HCV Ab, anti-HCV)

This is the first test for determining whether you have been infected with hepatitis C. The results will come back as either positive or negative.

Explanation of test results:

If this test result is positive, it means your body was exposed to the hepatitis C virus and made antibodies (for more information, see "Antibody" section under Associated Lab Tests). However, it does not tell you whether you are still infected with hepatitis C. If the antibody test result is positive, you should be tested for hepatitis C RNA (see "Hepatitis C RNA"), which determines whether you are chronically infected. The lab might perform this RNA test automatically if your hepatitis C antibody test is positive or your doctor might need to order the Hepatitis C RNA test separately.

If the antibody test result is negative, it means you have not been infected with the hepatitis C virus, and further testing for hepatitis C usually is not needed.

Other things to know:

  • After a successful course of treatment for hepatitis C, the hepatitis C antibody remains detectable, but the hepatitis C RNA will be undetectable.
  • Any patient with a positive test result for the hepatitis C antibody should have additional tests to determine whether or not the virus is still active.

Hepatitis C RNA qualitative testing

The qualitative HCV RNA tests use either a process called polymerase chain reaction (PCR) or a process called transcription-mediated amplification (TMA). Either type of qualitative test will report whether the hepatitis C virus is present in the bloodstream or not. The result is reported as either "detected" or "not detected."

Explanation of test results:

If a qualitative RNA test is positive (detected), then it is confirmed that the patient has chronic hepatitis C. The "qualitative" test is more accurate than the "quantitative" test because qualitative tests are able to detect very low levels of the virus.

Other things to know:

  • If a patient has a quantitative test that shows no detectable virus, but has a positive result with the qualitative test, it means there is a very low level of virus that can be detected only with the qualitative test.
  • The qualitative test will show a negative result when patients have a successful response to interferon treatment.
  • The qualitative test result also will be negative when patients clear the hepatitis C virus on their own, soon after infection, or "spontaneously."

Hepatitis C RNA quantitative testing

The quantitative HCV RNA tests measure the amount of hepatitis C virus in the blood. The result will be an exact number, such as "1,215,422 IU/L." Many people refer to the quantitative measurement as the hepatitis C "viral load."

Explanation of test results:

There are 2 situations in which a quantitative test is useful:

The quantitative HCV RNA test is checked before a patient starts treatment.

For each patient, the result can be described as either a "high" viral load, which is usually >800,000 IU/L, or a "low" viral load, which is usually <800,000 IU/L. Knowing the viral load before starting treatment is useful because patients with "high" viral loads can have a difficult time getting the virus to become completely undetectable on treatment. Patients with "low" viral loads have a better chance of getting their virus to become completely undetectable on treatment.

The quantitative HCV RNA test is used to monitor a patient who is currently on treatment.

The response to treatment is considered good when the quantitative HCV RNA measurement drops and the virus eventually becomes completely undetectable.

Other things to know:

  • The viral load measurement does not tell us anything about the severity of a patient's liver disease or the degree of fibrosis (scarring). For that information, the patient would need a liver biopsy.
  • It is not necessary to check the viral load repeatedly unless a patient is on treatment or is considering treatment.
  • If a quantitative HCV RNA result is reported as "<615 IU/L," this means that the quantitative test cannot measure the hepatitis C virus. It may mean that there is no detectable HCV RNA at all, but it may mean that the level of virus is just too low for the test to pick it up. A qualitative test should then be performed to see if there is any detectable hepatitis C virus at all (see previous screen: "Hepatitis C RNA Qualitative Testing").
  • If a quantitative HCV RNA results is "<615 IU/L" but the qualitative test is "detected" then the hepatitis C virus is present in the bloodstream, but at a very very low level, too low to be measured by a quantitative test.

Hepatitis C RIBA

The hepatitis C recombinant immunoblot assay (RIBA) is the confirmation test for the hepatitis C antibody.

Explanation of test results:

If the result of the HCV RIBA is positive, this confirms that the detection of a hepatitis C antibody (anti-HCV) was a true positive, meaning that there has been infection with hepatitis C in the past.

If the HCV RIBA result is negative, it means there has not been infection with hepatitis C. If an earlier hepatitis C antibody (anti-HCV) test had been positive, then this was a false positive.

Other things to know:

  • Even if the HCV RIBA result is positive, only the test of HCV RNA (viral load) can detect whether the hepatitis C virus is still present in the body.
  • HCV RIBA is not a test that is needed for most patients. Usually, it is performed by blood banks to check for hepatitis C in people who donate blood.

Hepatitis C genotype

The hepatitis C genotype is a type or "strain" of hepatitis C virus. There are 6 genotypes of hepatitis C around the world. In the United States, 3 genotypes are common:

  • Genotype 1
  • Genotype 2
  • Genotype 3

These can be further specified as:

  • Genotype 1a or 1b
  • Genotype 2a or 2b
  • Genotype 3a or 3b

The genotype of hepatitis C does not change over time. It needs to be tested only once. If you are treated for hepatitis C, your genotype will determine your treatment plan, such as which medications are prescribed and how long the treatment will be.

Viral load

The viral load of hepatitis C refers to the amount of virus present in the bloodstream.

A viral load test is usually measured with the hepatitis C RNA quantitative test; a blood sample will be taken by needle from a vein in your arm.

Viral load tests are often used with hepatitis C treatment to help determine response to treatment by comparing the amount of virus in your blood before, during, and after treatment.

If you have lower levels of virus in your blood when you start treatment, you may have a better chance of getting rid of the virus.

Associated lab tests

Patients with hepatitis C often have a wide variety of blood tests requested by their doctor. In addition to tests of hepatits C and tests of the liver, you may have tests of your kidney, blood counts, thyroid and others.

It is especially important to understand these tests if you are taking hepatitis C treatments. Here we explain the meaning of some of the most common blood tests you may want to understand.

White blood cells (WBCs)

This test measures the total number of white blood cells (WBCs). There are 5 main types of WBCs: neutrophils, eosinophils, basophils, monocytes, and lymphocytes. Each type does a slightly different job. All of them help fight infection.

Explanation of test results:

WBCs are produced in the bone marrow, an area in the middle of many bones. Low WBC "counts"may develop as a side effect of interferon treatment. A low WBC count may be caused by cirrhosis of the liver, alcohol use, medications, or other medical conditions.

Neutrophils

Neutrophils are a type of white blood cell. Your neutrophil level is also known as the absolute neutrophil count (ANC).

Explanation of test results:

Neutrophils play a key role in inflammation, formation of pus, and destruction of bacteria. Your doctor will check your ANC regularly if you are taking interferon treatment. If the ANC falls too low, your doctor may reduce the dosage of interferon treatment. Additionally, if the ANC falls too low, your doctor may prescribe additional medication to try to boost the ANC back up.

Other things to know:

  • The ANC is more important than the total WBC count in terms of determining interferon dosages.
  • Even if the ANC falls during interferon treatment, it will return to its normal level once treatment is stopped.
  • Your total WBC count includes neutrophils plus the 4 other types of WBCs (eosinophils, basophils, monocytes, and lymphocytes).
  • Laboratories will report both the total WBC count and the ANC.

Hemoglobin

Hemoglobin is a protein within red blood cells. Hemoglobin allows red blood cells to carry oxygen to the rest of the body.

Explanation of test results:

Measuring hemoglobin levels helps to estimate the number of red blood cells in the body. A low hemoglobin level is referred to as "anemia." If hemoglobin levels are very low, patients may feel tired easily.

Other things to know:

  • The hemoglobin level is related to the hematocrit (see next screen: "Hematocrit").
  • Low hemoglobin levels can develop during treatment with interferon and ribavirin.
  • Often, lowering the dosage of ribavirin will help bring the hemoglobin level back up.
  • Often, a medication called Epogen can be used by patients receiving treatment to bring the hemoglobin level back up.

Hematocrit

The hematocrit is sometimes known as "red blood cell count." The hematocrit is the percentage of red blood cells in the total contents of your blood.

Explanation of test results:

A low hematocrit is referred to as "anemia." If the hematocrit is very low, patients may feel tired easily.

Other things to know:

  • The hematocrit is directly related to the hemoglobin level (see previous screen: "Hemoglobin").
  • Low hematocrits can develop during treatment with interferon and ribavirin.
  • Often, lowering the dosage of ribavirin will help bring the hematocrit back up.
  • Often, a medication called Epogen can be used by patients receiving treatment to bring the hematocrit back up.

Creatinine

The level of creatinine in your body is a marker of kidney function. Creatinine comes from the breakdown of creatine, a muscle protein. Properly functioning kidneys remove creatinine from the blood.

Explanation of test results:

High levels of creatinine mean that the kidneys are not functioning normally. When creatinine levels rise gradually, there are not usually any symptoms, and the higher levels can be detected only with blood tests.

Other things to know:

  • Certain medications can cause high levels of creatinine.
  • A high creatinine level is sometimes referred to as "renal insufficiency."
  • If your creatinine level is too high, you may not be able to receive hepatitis C treatments.

TSH (thyroid-stimulating hormone)

TSH is a hormone produced by the pituitary gland in the brain. TSH causes the thyroid gland (located in the neck) to produce thyroid (T4 and T3).

Explanation of test results:

Having a high TSH level means you are "hypothyroid." Symptoms can include fatigue, constipation, and weight gain. When there are low levels of thyroid hormone (hypothyroidism), the TSH becomes elevated as the body tries to increase thyroid production.

Having a low TSH level means you are "hyperthyroid." Symptoms can include weight loss and nervousness. When there are high levels of thyroid hormone (hyperthyroidism), the TSH falls as the body tries to slow thyroid production.

Other things to know:

  • Interferon treatment can cause thyroid changes, so you could see a TSH level rise or fall when you are receiving interferon.
  • Occasionally, patients on interferon need to take medication to correct their TSH levels.
  • Hepatitis C itself also can cause thyroid changes, even without the interferon treatment.
  • In general, thyroid problems are common and occur without hepatitis C.

Glucose

Glucose is also called "blood sugar." It comes from the breakdown of foods and from production of glucose by the liver.

Explanation of test results:

When the glucose (or blood sugar) level is higher than normal, this is known as "hyperglycemia." Patients whose fasting glucose levels are higher than 126 mg/dL are considered to have diabetes mellitus. Patients who have hepatitis C and have diabetes mellitus may have a more difficult time controlling their glucose while receiving interferon treatment.

Other things to know:

  • Most people who have a family history of diabetes, are overweight, or are older than 50 should have a fasting glucose level checked by their doctor.
  • If you develop diabetes, it is not necessarily related to your hepatitis C.
  • If you already have diabetes, it is very important to work to get your glucose levels well controlled. Poorly controlled diabetes can lead to "fatty liver" in addition to the hepatitis C infection of the liver.
  • Fatty liver and hepatitis C together can make liver disease much worse.

Hepatitis B virus testing

HBsAg (hepatitis B surface antigen)

A positive test result means you are infected with hepatitis B.

HBsAb (hepatitis B surface antibody)

A positive test result means you have antibodies to hepatitis B. If you also test positive for HBcAb, then you were infected or exposed to hepatitis B virus in the past, cleared the virus, and are now "immune" (protected) against another infection with hepatitis B. If you test positive for HBsAb but negative for HBcAb, then you were vaccinated against hepatitis B and are protected by the vaccination.

HBcAb (hepatitis B core antibody)

A positive test result means you once were infected with hepatitis B.

HBV DNA (hepatitis B DNA)

A positive test result means you have the hepatitis B virus in the bloodstream and this is called "chronic hepatitis B." You may be right for hepatitis B drug treatments. A negative result means you do not have hepatitis B replicating or circulating in the bloodstream and you do not need hepatitis B drug treatments.

HBeAg (hepatitis B e antigen)

A positive test result means you have the hepatitis B virus in the bloodstream. If you are HBV DNA positive but this HBeAg test result is negative, then you still have the hepatitis B virus in your bloodstream.

Hepatitis A antibody total

A positive test result means you have been infected with hepatitis A in the past or were vaccinated against hepatitis A in the past but are now immune (protected) against being infected with hepatitis A virus in the future.

AFP (Alfa-fetoprotein)

AFP is a protein that is present in patients with liver disease. AFP is also a "tumor marker" and may be used to see if a patient has liver cancer. (Liver cancer is also called hepatocellular carcinoma).

Explanation of test results:

A high level of AFP might mean that a patient has liver cancer. However, sometimes the AFP is high when there is active liver disease but no cancer. Usually, the AFP test needs to be interpreted by a doctor in combination with pictures of the liver taken with ultrasound or CT scan.

Other things to know:

  • An elevated AFP level needs to be interpreted by your doctor. A high AFP level may just mean you have an active liver.
  • AFP can be elevated in other types of cancers and in a normal pregnancy.

Antibody

Antibodies are part of the immune system's response to infection. Once an infection has taken place, the body makes antibodies, which become detectable in the bloodstream. Different antibodies fight different infections.

Explanation of test results:

If you have a positive test result for a specific antibody, it means that your body has had an immune response to that specific infection. It does not necessarily mean you are still infected--it does mean that you were infected at some point in the past.

The hepatitis C antibody test is explained under Hepatitis C tests.

Hepatitis A antibody total

Explanation of test results:

A positive test result means you have been infected with hepatitis A in the past or were vaccinated against hepatitis A in the past but are now immune (protected) against being infected with hepatitis A virus in the future.

Resources

General hepatitis resources

  • Glossary
    Definitions of terms commonly used with viral hepatitis and related conditions.
  • American Liver FoundationLink will take you outside the VA website. VA is not responsible for the content of the linked site.
    A national nonprofit organization dedicated to the prevention, treatment, and cure of hepatitis and other liver diseases through research, education, and advocacy. Web site features a database directory of hepatitis clinical trials, lay-oriented facts sheets, and links to additional resources.
  • Centers for Disease Control and Prevention: Viral HepatitisLink will take you outside the VA website. VA is not responsible for the content of the linked site.
    Information on all types of viral hepatitis from the CDC's National Center for Infectious Diseases. Site features related CDC guidelines and recommendations as well as training materials, slide sets, fact sheets, and key CDC hepatitis documents.
  • HCV AdvocateLink will take you outside the VA website. VA is not responsible for the content of the linked site.
    Web site of the Hepatitis Support Project, whose goal is to offer support to those who are affected by hepatitis C and related coinfections. Information and education is provided, as well as access to support groups.
  • Hepatitis B FoundationLink will take you outside the VA website. VA is not responsible for the content of the linked site.
    A nonprofit organization dedicated to finding a cure and improving the quality of life of those affected by hepatitis B worldwide through research, education, and patient advocacy. Features information in English, Chinese, Korean, and Vietnamese.

HIV/Hepatitis C coinfection resources

  • VA National HIV/AIDS Web SiteLink will take you to our HIV/AIDS internet site
    Information on HIV/AIDS for health care providers and patients from the Department of Veterans Affairs.
  • HIV/AIDS/Hepatitis C Nightline:
    Hotline providing support for people with HIV or hepatitis C and their caregivers during the evening and nightime hours. 1-800-273-AIDS or 415-434-AIDS; 5 pm - 5 am Pacific time. Also offers Spanish-language hotline at: 1-800-303-SIDA or 415-989-5212.
  • NATAP: HepatitisLink will take you outside the VA website. VA is not responsible for the content of the linked site.
    Recognizing that coinfection with viral hepatitis among people with HIV is a growing problem, the National AIDS Treatment Advocacy Project (NATAP) has developed an extensive amount of information on hepatitis, both in the context of HIV coinfection and as a separate illness. NATAP provides coverage of key conferences, maintains a selection of hepatitis articles, and features an ask-the-expert forum on hepatitis C.