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How is ICP diagnosed?

How is ICP diagnosed?

There is no routine screening for ICP. It is not hard to understand why. One of the challenges is that the condition can present as early as 8 weeks and as late as 40 weeks. This means that women would need repeated screening throughout pregnancy. Also, as it is a relatively uncommon condition of pregnancy (affecting around 5,500 women a year in the UK), the cost implications of testing the whole pregnant population are obvious.

Instead, it is more likely that you will need to mention the itch, either at your antenatal appointment or by phoning the maternity day assessment unit/maternity helpline, and then tests will be performed.

  • To make the diagnosis of ICP, other liver conditions and causes of itching need to be ruled out first. These other conditions may include viral hepatitis, autoimmune hepatitis, and primary biliary cholangitis. It is a good idea to have a liver ultrasound scan in the pregnancy to to confirm that nothing else might be causing your symptoms and abnormal blood test results, but the presence of gallstones does not exclude a diagnosis of ICP – it is possible to have both ICP and gallstones. Research shows that women with ICP have a higher chance of either already having had gallstones or of developing them in later life.
  • Your doctor will need to ask you about your symptoms and may ask whether anyone else in your family has had liver problems during pregnancy.
  • Research and anecdotal (personal reporting) evidence has shown that some women may itch for several weeks before their blood tests show any abnormalities. It is therefore important that you continue to have these tests if you continue to itch.
Blood tests required:
  • Bile acid test – bile acids are chemicals produced in the liver to help with digestion. In ICP the flow of bile acids in the liver is reduced and they build up in the blood. A bile acid test is believed to be the most specific test for ICP and most experts in ICP will not confirm a diagnosis of ICP unless this is raised.

    Bile acids have their own circadian rhythm, which means that they naturally rise and fall (within normal reference ranges) over a 24-hour period. The time of day at which you have your blood taken to measure your bile acids can make a small difference to your result, and any increase (within normal reference ranges) doesn’t mean that your bile acids are going to become abnormal or are rising – it could simply be that you have had them tested at a time of day when they are generally a little higher. They also rise after eating, but there is no evidence to suggest that you need to fast for the test – in fact it’s possible that it’s better to know what they are after eating so that you can know how high they can become.

    Researchers don’t know for sure when the best time is to have bile acids measured if you are being tested for ICP or you have already been diagnosed with the condition, but we suggest that you leave around 90 minutes after eating before being tested as levels will have peaked by then. Given what we have written it may also make sense to be consistent about the time of day you have your test and what you have eaten beforehand. There has been no research about this either, but by doing this you will know that your results have not been affected by testing at different times or by eating different food.

    Not all hospitals perform the test and some hospitals have to send the blood sample elsewhere for testing. Ideally, you should be able to have the results within 48 hours, but we know that this is not possible for all women at the moment. It’s worth asking your health professional to chase your results if you know that they sometimes take longer to come back.

    Bile acids are thought to be harmful because they may be responsible for some of the complications that are known to be associated with ICP.

  • Liver function test (LFT) – this blood test looks at how well the liver is working by measuring the levels of different enzymes. One or more of the following enzymes may be measured in a liver function test – AST (aspartate transaminase), ALT (alanine transaminase), alkaline phosphatase or GGT (gamma-glutamyl transpeptidase). The AST and ALT levels are the ones that are used to support the diagnosis of ICP. Research has shown that transaminases sometimes rise before the bile acids. As noted above, experts will not diagnose ICP until the bile acids rise.

  • Reference ranges for blood tests. The table below gives the normal values to be expected in both non-pregnant women and pregnant women without ICP.

    The values may vary between laboratories – for example, some laboratories cite bile acids as low as <8.3 µmol/L as being abnormal, while others define abnormal as >14 µmol/L. This may be because of the different methods used to test the bile acids (liquid chromatography–mass spectrometry compared to enzymatic testing) or it may be that reference ranges could differ depending on the population involved – the lower range we have quoted seems to be pertinent to the Latina population.

    As always with ICP, more research is needed; as a charity, we believe that it’s important to have standardised reference ranges for bile acids, as the current situation is causing a lot of confusion and anxiety amongst women who are being tested for the condition.

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    (Click image to enlarge)

    Blood test reference ranges
    Source: Walker I, Chappell LC, Williamson C. Abnormal liver function tests in pregnancy. BMJ 2013;347:f6055.
References

EASL Clinical practice Guidelines: Management of cholestatic liver diseases. Journal of Hepatology 2009; 51: 237–267

Lee RH, Goodwin TM, Greenspoon J, Incerpi M. The prevalence of intrahepatic cholestasis of pregnancy in a primarily Latina Los Angeles population. J Perinatol 2006; 26: 527–532

Marschall HU. Management of intrahepatic cholestasis of pregnancy. Expert Rev Gastroenterol Hepatol 2015; 9(10): 1273–1279

Royal College of Gynaecologists. Obstetric Cholestasis (Green-top Guideline No. 43). https://www.rcog.org.uk/en/guidelines-research-services/guidelines/gtg43/ (currently awaiting revision).

Walker I, Chappell LC, Williamson C. Abnormal liver function tests in pregnancy. BMJ 2013;347:f6055.