Question

I’ve been feeling generally more unwell for several months, so my GP has done some blood tests. They were all reported to be normal – apart from a slightly raised level of one test called a CRP. This is now going to be repeated. What is this test? Is it something that can be raised in ME? And what happens if it remains raised?

Answer

The CRP (C-Reactive Protein) blood test is a very useful but non-specific marker for infection or inflammation in the body. If the CRP level is raised, this suggests that there is some form of infection or inflammation occurring somewhere in the body – even though there may not be any obvious symptoms or signs that would help to demonstrate where in the body this is located.

The CRP test is not therefore diagnostic of any particular infection or inflammation – as there are many possible explanations for a raised level. These can range from specific infections through to inflammatory medical conditions such as Crohn’s disease, rheumatoid arthritis, and autoimmune diseases such as lupus/SLE. The level can also be raised in the later stages of pregnancy, when taking the contraceptive pill or HRT, and with obesity.

The CRP test, or a similar one called the ESR (erythrocyte sedimentation rate), should always form part of the raft of blood tests that are checked, and should be reported to be within normal limits, when a diagnosis of ME/CFS is being made or considered. When something is wrong, the CRP test usually rises and falls faster than the ESR test. In the case of ME/CFS, both the CRP and ESR test results should be within normal limits – but there are some circumstances (e.g. a recent infection) where they might be raised and people with ME/CFS do occasionally have a slightly raised CRP.

If the level is slightly raised, the test will probably be repeated. If the level remains raised, or is significantly raised, this should lead to a thorough re-evaluation of your clinical symptoms and possibly some further investigations to try and find the cause. I assume from what you are saying that consideration has been given to conditions that are sometimes misdiagnosed as ME/CFS and which cause an elevation of the CRP level – lupus/SLE for example.

Where the CRP level remains persistently raised, and the GP cannot find an explanation, referral to a hospital specialist will probably be necessary.

MORE INFORMATION:

• The use of ESR and CRP tests in ME/CFS are described in more detail in the Investigation section of the MEA purple book.
• The MEA has an information leaflet covering all the blood tests that should be checked before a diagnosis of ME/CFS is confirmed: Blood Tests Explained
• More detailed information on the CRP test