High AFP: what it means

Alpha-fetoprotein is a protein made in large amounts by a developing baby. Lab Tests Online UK explains that in pregnancy it moves across the placenta into the mother's blood, and levels in the mother tend to rise through the first half of pregnancy. In adults it is normally low, which is why a raised level can be a signal.

The meaning of a high result therefore depends on whether the person is pregnant, whether there is known liver disease, and what other results show. The sections below cover both settings.

In adults, Lab Tests Online UK says AFP is used to help detect and monitor cancers of the liver and testis. Increased AFP can be caused by liver cancer (hepatocellular carcinoma), a germ cell tumour of the testis, or, less commonly, other cancers, including ovary, stomach, bowel, lung, breast and lymphoma.

Cancer Research UK explains that some people with liver cancer have high AFP, and that AFP can be a tumour marker for liver cancer, but the level can also be raised in people with cirrhosis who do not have cancer. The doctor may check AFP before and after treatment to get an idea of how well it is working.

The same source states the general pattern in cancer: the higher the AFP, the bigger the tumour or spread, and AFP falls when the body responds to treatment. If it does not return to normal within about a month after therapy, some tumour may remain, and an increase after remission suggests recurrence. Tumours that originally produced AFP may however recur without a rise.

Lab Tests Online UK says that slightly increased AFP is common in people with chronic hepatitis or cirrhosis and does not indicate cancer. In those people AFP tests may be requested to detect hepatocellular carcinoma that may develop in the future.

The main risk factors for this cancer, according to the same source, are cirrhosis, most commonly caused by chronic infection with hepatitis B or C, alcohol misuse, and inherited conditions such as haemochromatosis. If you have chronic liver infection or damage, a high AFP could simply be due to the disease itself, but a sudden rise or a very high value would usually prompt a liver scan.

For one type of testicular tumour, a germ cell tumour, Lab Tests Online UK says AFP and hCG measurements help with diagnosis and are also mandatory in post-treatment monitoring, following guidelines that depend on the stage and treatment. The NHS lists blood tests and an ultrasound scan of the testicles as the main tests for suspected testicular cancer, with surgery to remove the testicle as the main treatment.

A raised AFP in a man with a testicular lump or swelling is therefore taken seriously and is looked at together with hCG, imaging and examination by a specialist team.

In pregnancy, AFP is measured as part of second-trimester maternal screening, typically between about 14 and 20 weeks, alongside hCG, unconjugated oestriol and sometimes inhibin-A. Lab Tests Online UK says that a raised AFP by itself might indicate the possibility of a neural tube defect such as spina bifida, although screening for these is now predominantly carried out by ultrasound scanning. AFP levels also tend to be lower than usual in pregnancies affected by Down's syndrome and higher in those affected by neural tube defects.

Screening is not perfect. The same source says that the quadruple test correctly identifies approximately 80% of Down's syndrome cases and incorrectly flags approximately 4% of healthy pregnancies, and that accurate dating of the pregnancy matters because wrong gestational age can make results falsely high or low. Results should be explained by a midwife, genetic counsellor or doctor, and further tests such as ultrasound are offered where needed. A high result in this setting is not a diagnosis.

These are the explanations described in the sources used for this page.

For adults, Lab Tests Online UK says that if AFP suddenly rises or is very elevated, the doctor will usually request a study of the liver such as ultrasound, CT or MRI, and that these scans can often spot liver cancers if present. A normal AFP cannot be used to exclude the diagnosis, which is why imaging is used when suspicion is high regardless of the number.

Because AFP is influenced by chronic liver disease, many clinicians repeat it before acting on a single mildly raised value. If you are in a pregnancy care pathway, your midwife or obstetrician will explain what the result means for you and what scan, if any, is recommended. In either case, a high result is a reason for further assessment rather than a diagnosis.