There are more than 100 types of rheumatic diseases, most of which are complex. Many patients who have visited the rheumatology department may have a community that there is a wide range of laboratory tests. In fact, laboratory tests are very important in the diagnosis and treatment of rheumatic diseases to help diagnose, determine the activity of the disease and evaluate the prognosis. The following are the rheumatology tests routinely performed in our hospital and the significance of the results.
1.Blood sedimentation (ESR).
Generally speaking, ESR tends to be elevated during the active phase of rheumatic diseases and decreases after treatment remission. However, many other diseases such as infections, tumors, anemia can also appear ESR elevated, so you can not assume that high ESR is rheumatic disease.
2, C-reactive protein (CRP).
As with ESR in the clinical are indicators of rheumatic disease activity. But also not rheumatic disease-specific indicators, in the case of infection and trauma will also be significantly elevated.
3, rheumatoid factor (RF).
RF in rheumatoid arthritis in the positive rate of 60% -80%, the diagnosis of rheumatoid arthritis has some significance. Two misconceptions that need to be corrected are.
(1) RF is not a specific indicator of rheumatoid arthritis, RF positive does not equal is rheumatoid arthritis. Many other rheumatic diseases such as systemic lupus erythematosus, dry syndrome, etc. will also appear RF positive, in addition to RF can also be seen in chronic infections, chronic hepatitis, normal elderly people can also appear low titer RF;
(2) RF negative can not exclude rheumatoid arthritis.
4, anti-streptococcal hemolysin O (ASO).
Many people think that high anti-O is rheumatism, but it is not true. Elevated anti-O only suggests a recent hemolytic streptococcal infection, as for the presence of rheumatism also need to be judged according to the patient’s age and other clinical manifestations.
5. HLA-B27.
HLA-B27 is the name of a gene in the body, and more than 90% of patients with ankylosing spondylitis are HLA-B27 positive. However, it is important to note that HLA-B27 positivity is not the same as ankylosing spondylitis. The prevalence of HLA-B27 in the general population is about 5%, while the prevalence of ankylosing spondylitis is only 0.3%, meaning that only about 3 out of 100 HLA-B27 positive individuals may have ankylosing spondylitis. Moreover, about 10% of patients with ankylosing spondylitis are also HLA-B27 negative.
Therefore, a positive HLA-B27 alone cannot diagnose ankylosing spondylitis, and a negative HLA-B27 likewise cannot rule out ankylosing spondylitis.
6. 13 anti-nuclear antibodies.
ANA is a preliminary screening test for rheumatic diseases, especially connective tissue diseases, and is extremely important for the diagnosis of rheumatic diseases. Most rheumatic patients can have a positive ANA, for example, 90-98% of patients with SLE are positive. However, ANA positivity can also be seen in a small number of normal individuals (especially the elderly), chronic infections, liver disease, and the use of certain medications.
There are many patients who remain positive for ANA or whose titers do not decrease during treatment, leading some of them to worry that the disease is not under control, when in fact ANA titers are not related to disease activity. Anti-dsDNA antibodies are specific for SLE, and generally speaking, the increase of its titer is related to the activity of lupus disease, and the titer will decrease after the disease is controlled.
ENA antibodies include anti-Sm, RNP, SSA50/62, SSB, CENP-B, Scl-70, Jo-1, anti-nucleosome antibodies and anti-ribosomal P protein antibodies, which are mainly used in SLE, subacute cutaneous lupus (SCLE), mixed connective tissue disease (MCTD), scleroderma (SSc), dry syndrome (SS) and polymyositis/dermatomyositis (PM/DM) and other autoimmune rheumatic diseases for diagnosis and differential diagnosis.
Anti-Sm is a marker antibody for SLE, and a positive test confirms the diagnosis of SLE; anti-RNP antibody can be found in the sera of patients with MCTD, SLE, SSc, etc.; anti-SSA50/62 and anti-SSB antibodies are usually seen in patients with SLE and SS; anti-CENP-B is seen in a subtype of SSc; anti-Jo-1 antibody is specific for dermatomyositis/polymyositis; anti Scl-70 antibody is a marker antibody for SSc and a sign of poor prognosis; anti-nucleosome antibody and anti-ribosomal P protein antibody are more specific antibodies for SLE.
7. Anti-cardiolipin antibody (ACL) and anti-B2-GP1 antibody.
These two antibodies tend to indicate a predisposition to arteriovenous thrombosis and are closely related to SLE. patients with ACL-positive SLE are prone to thrombosis, thrombocytopenic purpura and other symptoms, and female patients are prone to habitual abortion.
8.Anti-neutrophil cytoplasmic antibody (ANCA).
ANCA is a serum marker of systemic vasculitis, which is valuable for differential diagnosis and prognosis estimation of vasculitis disease, and is an important indicator of disease activity. ANCA titers are elevated at the onset (relapse) of the patient.
① cytoplasmic type (c-ANCA) or PR3-ANCA: mainly associated with Wegener’s granulomatous vasculitis;
② perinuclear type (P-ANCA) or MPO-ANCA: can be produced in patients with microscopic polyangiitis.
9. Immunoglobulins.
Elevated immunoglobulins are commonly seen in patients with SLE and SS and are associated with disease activity. Patients with ankylosing spondylitis may also have elevated IgA.
10. Complement C3,C4.
Decreased complement levels in patients with SLE generally imply SLE activity, while elevated complement often suggests infection.
In summary, the interpretation of rheumatic disease laboratory results is a very complex issue, requiring doctors to combine the patient’s condition with a comprehensive analysis of judgment, in order to make a more objective and correct diagnosis.