Basic information from the ME Association on CRP and ESR (inflammatory marker) blood tests in ME/CFS:
The CRP (C-Reactive Protein) blood test is a very useful non specific marker for infection or inflammation in the body
If the level is raised, it 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 the location in the body where this is occurring
The test is not therefore diagnostic of any particular infection or inflammation - as there are many possible explanations for a raised CRP level ranging from specific infections through to inflammatory bowel disease, 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
This test, or a similar one called the ESR (erythrocyte sedimentation rate), should ALWAYS form part of the raft of blood tests that are checked when a diagnosis of ME/CFS is being made or considered
The CRP test rises and falls faster than the ESR
In the case of ME/CFS, both the CRP and ESR test results should be within normal limits - but there are some circumstances (eg a recent infection) where it might be raised
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 the clinical symptoms and 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 do 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.
The use of ESR and CRP tests in ME/CFS are described in the Investigation section of the 2017 MEA purple book:
http://www.meassociation.org.uk/201...earch-masterwork-now-available-19-april-2017/
More detailed information on the CRP test here:
http://labtestsonline.org.uk/understanding/analytes/crp/tab/test/
More info on ESR test here:
http://labtestsonline.org.uk/understanding/analytes/esr/tab/test/
Dr Charles Shepherd
Hon Medical Adviser MEA