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Platelet C4d is highly specific for systemic lupus erythematosus.
Jeannine S Navratil1, Susan Manzi, Amy H Kao
1University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Arthritis and Rheumatism
|February 1, 2006
Summary
Platelet-bound C4d is a highly specific biomarker for systemic lupus erythematosus (SLE). This finding may help diagnose SLE and understand its vascular complications.
Area of Science:
- Immunology
- Hematology
- Rheumatology
Background:
- Complement-activation product C4d deposits on erythrocytes in systemic lupus erythematosus (SLE).
- Abnormal C4d levels are observed on erythrocytes in SLE patients.
- The presence of C4d on human platelet surfaces in SLE is not well-established.
Purpose of the Study:
- To investigate C4d deposition on human platelet surfaces.
- To determine if platelet-bound C4d can serve as a biomarker for SLE.
Main Methods:
- Cross-sectional study involving 105 SLE patients, 115 patients with other diseases, and 100 healthy controls.
- Flow cytometry and scanning confocal microscopy were used to examine platelet C4d levels.
- Statistical analyses identified clinical variables associated with platelet C4d.
Main Results:
- Platelet C4d was detected in 18% of SLE patients, showing high specificity for SLE diagnosis.
- Platelet C4d was 100% specific for SLE versus healthy controls and 98% specific versus other diseases (P < 0.0001).
- Platelet C4d correlated significantly with lupus anticoagulant, anticardiolipin antibodies, SLE disease activity, low C4, elevated ESR, and erythrocyte C4d levels.
Conclusions:
- Platelet-bound C4d is a highly specific biomarker for SLE.
- This finding may aid in SLE diagnosis and understanding antiphospholipid antibody-associated thrombotic complications.