Overview: C1-Inhibitor Quantitative TestIntroduction: The C1-Inhibitor Quantitative Test measures C1 esterase inhibitor levels to diagnose hereditary angioedema, causing swelling or abdominal pain. Aligned with 2023 AAAAI guidelines, it uses an immunoassay for high sensitivity, aiding in autoimmune screening. This test is critical for guiding diagnosis, treatment, and improving outcomes in immunology for patients with suspected hereditary angioedema.
Other Names: C1 Esterase Quant Assay, HAE Quantitative Test.
FDA Status: Laboratory-developed test (LDT), meeting immunology standards for diagnostic accuracy.
Historical Milestone: C1-inhibitor testing began in the 1960s with angioedema research. Quantitative assays emerged in the 1980s, and by the 2000s, immunoassays improved diagnostic accuracy.
Purpose: Diagnoses hereditary angioedema, guides treatment, and monitors C1-inhibitor levels in patients with swelling or abdominal pain.
Test Parameters: 1. C1 Esterase Inhibitor
Pretest Condition: No fasting required. Collect serum or plasma at any time. Report symptoms like swelling or abdominal pain, and list medications like C1-inhibitor replacement.
Specimen: 2-5 mL serum (SST) or 2-4 mL plasma (NaCit). Centrifuge within 1 hour. Transport in a biohazard bag within 8 hours.
Sample Stability at Room Temperature: 8 hours
Sample Stability at Refrigeration: 7 days
Sample Stability at Frozen: 6 months
Medical History: Document swelling episodes, abdominal pain, or family history of hereditary angioedema. Include current medications, especially C1-inhibitor therapy.
Consent: Written consent required, detailing the tests purpose, diagnostic implications, and potential need for C1-inhibitor replacement therapy.
Procedural Considerations: Uses an immunoassay to measure C1-inhibitor levels. Results are available in 3-5 days, supporting clinical decisions.
Factors Affecting Result Accuracy: Recent C1-inhibitor therapy or improper storage can affect results. Hemolysis may degrade samples.
Clinical Significance: Low C1-inhibitor levels confirm hereditary angioedema, prompting replacement therapy. Normal levels suggest alternative diagnoses.
Specialist Consultation: Consult an allergist for result interpretation. An immunologist referral is advised for complex cases.
Additional Supporting Tests: C1-inhibitor functional test, C4 complement test, or genetic testing to confirm hereditary angioedema.
Test Limitations: False negatives may occur with recent therapy. Results require clinical correlation.
References: AAAAI HAE Guidelines, 2023; Journal of Allergy and Clinical Immunology, Zuraw BL, 2022.
