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On the rheumatoid arthritis checklist, characters such as RF, ESR, CRP and other characters are often seen, and patients may not know what they mean, but in fact, this is the abbreviation of some indicators. Like RF, which refers to rheumatoid factor; ESR, which refers to erythrocyte sedimentation rate; CRP, refers to C-reactive protein. In addition to these three, what other blood tests are commonly done in rheumatoid patients, and what are the diagnostic implications of each?
Do you know what blood tests are done for rheumatoid?
(1) What is the significance of rheumatoid factor (RF)?
RF is an autoantibody closely associated with rheumatoid arthritis and is called rheumatoid factor because it was first detected in the blood of rheumatoid patients. When rheumatoid arthritis is suspected, RF is one of the first tests to be done. However, it should be noted that RF is not a specific indicator of rheumatoid arthritis, and RF may also be detected when there are other autoimmune diseases (such as Sjögren's syndrome, systemic lupus erythematosus, polymyositis, etc.), infectious diseases (such as tuberculosis, active hepatitis, etc.), and even about 5% of normal people.
Rheumatoid factor (RF) was first identified in rheumatoid patients
However, the higher the RF titer and the higher the positive RF value, the more likely it is to be diagnosed with rheumatoid arthritis compared to RF positivity from other causes.
It is also important to note that not all patients with rheumatoid disease will be positive for RF. RF is usually checked, mainly IgM, and about 70% of patients can be found to be RF positive in serum, but there are also a considerable number of patients who are diagnosed with normal RF and even anti-CCP, which is called seronegative rheumatoid arthritis.
In conclusion, RF is important in the diagnosis of rheumatoid arthritis, but it cannot be judged by a positive or negative RF alone, but also in combination with other indicators.
How to read RF indicators? 】
The results of rheumatoid factor also vary between laboratories and different assays, and usually include < 15 IU/ml, < 20 IU/ml, and < 25 IU/ml. The higher the rheumatoid factor titer, the more likely it is to be diagnosed and the more severe the disease is likely to be!
(2) What is the significance of anti-cyclic citrullinated peptide antibody (CCP) antibody?
Anti-CCP antibody is also an autoantibody, which belongs to the spectrum of anti-keratin antibodies. In the diagnosis of rheumatoid arthritis, it is actually more accurate than rheumatoid factor, and the specificity of anti-CCP antibodies for the diagnosis of rheumatoid arthritis is as high as 96%, and the sensitivity can be up to 76%. To put it simply, when a patient with arthralgia is found to be positive for anti-CCP antibody, the probability of suffering from rheumatoid arthritis is as high as 90%~95%. Especially for patients with joint pain, RF positive and anti-CCP antibody positive at the same time, there is a saying in our industry that "arthralgia + RF positive + anti-CCP antibody positive ≈rheumatoid arthritis".
The specificity of anti-CCP antibodies in the diagnosis of rheumatoid arthritis is very high
[How to see the anti-CCP index? 】
抗CCP抗体的正常参考值,当检测方法不同、仪器不同,参考值也不同,包括<5U/ml、<12U/ml、<15U/ml、<20U/ml等。 以<20U/ml为例:
- Negative – < 20 U/ml
- 弱阳性——20.0~39.9U/ml
- 阳性——40~59.9U/ml
- Strong positive – ≥60 U/ml
In general, patients with positive anti-CCP antibodies have faster disease progression, higher disease activity, more severe bone erosion, and a higher risk of visceral complications than negative patients!
(3) What is the significance of erythrocyte sedimentation rate (ESR)?
Erythrocyte sedimentation rate is a measure of the number of red blood cells that settle in the first hour, the higher the value, the faster the erythrocyte sedimentation rate, the faster the erythrocyte sedimentation rate, the more inflammation there is in the body. Therefore, ESR is an inflammatory marker, and its role is not to diagnose rheumatoid arthritis, but to determine the degree of inflammation of rheumatoid arthritis. Erythrocyte sedimentation rate (ESR) is not a specific indicator of rheumatoid arthritis, and many inflammatory conditions may lead to increased erythrocyte sedimentation rate, such as bacterial infection, rheumatic fever, tissue damage, etc., so it is not possible to conclude that rheumatoid arthritis is still active based on high ESR alone, but also to combine indicators with higher specificity and rule out interference.
Erythrocyte sedimentation rate (ESR) is an inflammatory marker used to determine the activity of rheumatoid arthritis
[How to see the ESR index? 】
Normal ESR values for adult males and females are:
- Male - 0~15 mm/h
- Female - 0~20 mm/h
When the ESR is greater than 15mm/h in men and 20mm/h in women, it is considered to be high ESR, and the higher the ESR value, the greater the possibility of inflammation!
(4) What is the significance of C-reactive protein (CRP)?
C-reactive protein, along with EFR, is an inflammatory marker and is used to determine inflammation and disease activity. C-reactive protein is a protein synthesized by the liver, which can precipitate and react with the C polysaccharide in pneumococcus, hence the name. When there is inflammation in the body, C-reactive protein will be elevated, so the increase in C-reactive protein is not specific to rheumatoid, and factors such as anemia and pregnancy can cause it to rise.
In rheumatoid patients, the positive rate of C-reactive protein is relatively high, as high as 80%~90%, and its level is related to the degree of inflammation, in the acute stage of inflammation, C-reactive protein will increase rapidly, reach a peak within 2~3 days, and with the alleviation of inflammation, it will quickly decrease, and it will come and go in a hurry. If C-reactive protein is high alone, it cannot be judged that rheumatoid is active, and it should also be combined with other indicators and symptoms.
Higher C-reactive protein may indicate greater inflammation
[How to see the CRP indicator?] 】
The normal reference value of CRP is generally <5 mg/L, and 10 mg/L is often used as the dividing line for judging aseptic infection and bacterial infection, less than 10 mg/L is aseptic infection, higher than 10 mg/L is bacterial infection, 80% of patients with bacterial infection have CRP > 100 mg/L, and antibiotic treatment is recommended when it is higher than 50 mg/L. For patients with rheumatoid arthritis, CRP is usually < 50mg/L, and a CRP higher than 100mg/L indicates a more severe disease!
The above four indicators are important indicators for the diagnosis and follow-up of rheumatoid
The above are the four most commonly used blood tests for rheumatoid arthritis, among them, RF and CCP are antibody indicators, which are mainly used to diagnose rheumatoid arthritis and warn of poor prognosis, and ESR and CRP are inflammatory indicators, which are mainly used to judge rheumatoid activity and mobility, and to warn of joint destruction. In addition, blood indicators, rheumatoid examination includes physical examination, imaging examination, rheumatoid patients should have regular follow-up, do these examinations to determine whether the treatment is effective, whether the disease is aggravated, according to the results of the examination to adjust the treatment plan immediately, we can refuse to over-check, but do not think that all examinations are superfluous, doctors do not have a keen eye, patients can not rely on their own feelings, want to control rheumatoid well, necessary examinations must be done regularly.