In the diagnosis of systemic rheumatic diseases, the term antiphospholipid antibody includes a variety of autoantibodies that differ in specificity. The target antigen is a negatively charged anionic phospholipid such as cardiolipin. Their reactivity in the serum of autoimmune patients requires a cofactor (β2-glycoprotein I, apolipoprotein H). Antiphospholipid antibodies can lead to false positive reactions in the syphilis test, ie, negative for VDRL-positive or spiro-specific antibody tests and positive for cardiolipin-complement fixation, which is one of the SLE classification criteria. In addition, it can cause lupus anticoagulation, leading to prolongation of APTT.

Basic Information

Specialist classification: growth and development check classification: immunological examination

Applicable gender: whether men and women apply fasting: not fasting

Analysis results:

Below normal:

Normal value:
no

Above normal:

negative:
normal.

Positive:
Prompt the presence of immune system diseases.

Tips: Different detection methods have different sensitivities and are used to detect different antibodies. Normal value

Normal human antiphospholipid antibodies are negative.

Clinical significance

(1) SLE According to the detection method and its sensitivity, the positive rate of antiphospholipid antibodies in SLE can reach 15% to 70%. The antibody-positive SLE patients are associated with arterial and venous thrombosis, habitual abortion, thrombocytopenia, Coombs-positive hemolytic anemia, and some rare symptoms, but the degree of correlation and clinical sensitivity of various test methods to these symptoms and Specificity, each report is not consistent. High titers of anti-cardiolipin IgG antibodies, abnormalities in positive lupus anti-agglutination tests, and positive antibodies to quiescent cells are high-risk indicators of these conditions. Retrospective studies have found that antiphospholipid antibodies appear before these symptoms.

(2) Primary antiphospholipid syndrome (APS) such as thrombosis, habitual abortion, thrombocytopenia, hemolytic anemia, reticular leukoplakia, various neurological symptoms, and antiphospholipid antibody positive, inconsistent with SLE or other diseases Diagnostic criteria can be diagnosed as primary APS. A small part turned into SLE.

(3) Other diseases:

Antiphospholipid antibodies are not SLE or APS specific antibodies, they exist at different frequencies in the following conditions

A variety of rheumatic and non-rheumatic diseases, such as rheumatoid arthritis, adolescent chronic arthritis, ankylosing spondylitis, psoriatic arthritis, various connective tissue diseases and vasculitis, polymyalgia rheumatism and rheumatic fever.

Hematological, myeloproliferative and lymphoma diseases.

Myocardial infarction.

Eddie is sick.

Drug-induced lupus syndrome.

A variety of viral infections, such as HIV, EBV, parvovirus B19; bacterial infections such as spirochetes, syphilis, tuberculosis, Rocky Mountain spotted fever, and protozoal infections.

5% healthy people, the positive rate increased with age.

There is usually no correlation between these antibodies and the aforementioned conditions except for primary APS or SLE. In addition, the HLA alleles DRw53 and DR4 or DR7 are only associated with primary APS, and in some cases, with antiphospholipid antibody-positive SLE.

Precautions

(1) Assay method: APTT and similar tests are commonly used to detect antiphospholipid antibodies (lupus anticoagulant, LAC) in citrate anticoagulated plasma. Different reagents have different sensitivities to LAC, and the dilution ratios used are also different. Different assays have different sensitivities and are used to detect different classes of antibodies. None of the experimental systems detect all antiphospholipid antibodies. The consistency of cardiolipin antibodies detected by ELISA and agglutination test is about 60% to 70%, and sometimes the different reactivity of antiphospholipid antibodies can be related to different diseases. For example, the VDRL test is associated with syphilis, but it is very poor with SLE-like antiphospholipid antibodies. Cofactor β2 glycoprotein is required for the detection of antibodies in patients with SLE or primary APS.

(2) Lupus anticoagulant: The term lupus anticoagulant refers to the phenomenon of anticoagulant effect in vitro, and this correlation in vivo may not involve anticoagulant but a prethrombotic effect.

(3) Sample heating: As described in anti-histone antibodies, the patient's serum heating can lead to an increase in ELISA results or false positives of anti-phosphorus antibodies, which is associated with heat inactivation of complement in serum (56 ° C, 30 min). At least in part due to the release of antiphospholipid antibodies due to excretion of endogenous phospholipids.

Β2-glycoprotein I:

2-2-glycoprotein I is not only a necessary cofactor for detecting typical phospholipid antibodies of SLE and APS, but is itself a self-target antigen in these diseases. Reaction with β2-glycoprotein I:

It can distinguish serum from serotonin and HIV-infected anti-cardiolipin-positive serum from patients with autoimmune diseases.

SLE patients and APS typical syndrome seem to have a better correlation with traditional phospholipid antibodies.

Inspection process

(1) ELISA: A fixed phospholipid is used, mainly using cardiolipin as an antigen, and human or bovine β2-glycoprotein I as a cofactor. Class-specific labeling antibodies can distinguish between different anti-phospholipid anti-antibodies. It can be calibrated with international reference materials.

(2) agglutination method: acquired suppressor, lupus anticoagulant.

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Adverse reactions and risks

There are no related complications and hazards.