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Immunonephelometric determination of the C4b-binding protein
G Hafner1, W Ehrenthal, E Zimmer
1Institute of Clinical Chemistry and Laboratory Medicine, Johannes Gutenberg-University Mainz, Germany.
Insights
A new immunonephelometric assay provides rapid and specific measurement of C4b-binding protein (C4b-BP) in plasma. This method shows elevated C4b-BP in inflammation and decreased levels in patients on oral anticoagulants.
Area of Science:
- Clinical Chemistry
- Immunology
- Laboratory Medicine
Background:
- C4b-binding protein (C4b-BP) is a key regulator of the complement system.
- Accurate and efficient measurement of C4b-BP is crucial for understanding its role in various physiological and pathological conditions.
Purpose of the Study:
- To describe a fully mechanized immunonephelometric method for rapid and specific determination of C4b-BP in citrated plasma.
- To evaluate the method's performance characteristics and its clinical utility in different patient groups.
Main Methods:
- Development of a fully mechanized immunonephelometric assay using rabbit antiserum against human C4b-BP.
- Assay validation including measuring range, precision (intra- and interassay CVs), and correlation with electroimmunodiffusion.
- Analysis of C4b-BP concentrations in healthy subjects, patients with inflammation markers, and patients on heparin or oral anticoagulant therapy.
Main Results:
- The assay is rapid (6 min/determination), requires a small sample volume (80 µL), and has a measuring range of 10-200% of normal C4b-BP.
- High precision was observed with intra-assay CVs of 1.5-2.8% and interassay CVs of 4.0-4.6%.
- Significantly higher C4b-BP levels were found in subjects with inflammation markers (143%) compared to healthy individuals (97%). Decreased concentrations were observed in patients on oral anticoagulant therapy (78%) but not in those on heparin (90%).
Conclusions:
- The described immunonephelometric method is a reliable, rapid, and specific tool for C4b-BP quantification in clinical settings.
- C4b-BP levels are elevated during inflammation and reduced in patients undergoing stable oral anticoagulant therapy.
- This assay facilitates further research into the clinical significance of C4b-BP in various disease states.
Abstract:
A fully mechanised immunonephelometric method for the rapid and specific determination of C4b-binding protein (C4b-BP) in citrated plasma is described. The method utilizes commercially available rabbit antiserum against human C4b-BP and a nephelometer analyser. A single determination can be performed within 6 min, requiring 80 microliters sample volume. The measuring range is about 10 to 200% of normal C4b-BP. Precision is characterized by intraassay coefficients of variation between 1.5% and 2.8%, and interassay coefficients of variation between 4.0% and 4.6% for the same C4b-BP concentrations. The nephelometry of C4b-BP was correlated with electroimmunodiffusion (Laurell technique; r = 0.863, y = 0.909x+7.091, n = 79). C4b-BP concentrations (143%, 96-223%; median and 2.5th-97.5th percentile) from 83 subjects with increased inflammation markers C-reactive protein (> 10 mg/l), and fibrinogen (> 4.5 g/l) showing significantly higher C4b-BP concentrations compared to 151 obviously healthy subjects (97%, 68-141%; p < 0.001). In contrast to 81 patients with therapeutic heparinisation (90%, 60-131%) significant decreased concentrations were found in 90 subjects under oral anticoagulant therapy (OAT) in the stable state (78%, 44-125%; p < 0.001). Depending on different INR levels (< 2.5, n = 40: 71%, 63-85%; > 2.5, n = 50: 81%, 68-92%; median and 25th-75th percentile) no significant differences of C4b-BP concentrations could be measured.
