C4a Level By RIA
Test Code
C4AR
Description
The complement system is part of our innate immune response. It is vital to our defense against invasive microorganisms. Complement activation can occur through the classical, lectin and alternative pathway, which then converge to a common terminal pathway. Activation of the complement pathway(s) results in the generation of biologicallly active peptides, also known as complement split products, and referred to as anaphylatoxins (C4a, C3a, C5a) which protect us from invasive microorganisms by enhancing inflammation, facilitating the clearance of immune complexes and apoptotic cells, enhancing cellular and antibody immune responses and altering vascular permeability, as well as smooth muscle contractility.
The anaphylatoxin C4a can be elevated above normal levels in many conditions associated with inflammation, including chronic fatigue syndrome, multiple sclerosis, immune complex diseases such as antiphospholipid syndrome and autoimmune conditions such as lupus. C4a is also an early marker of acute Lyme disease.
Collect
Plasma from a lavender top (K2 - EDTA) tube is the only acceptable sample type. Mix sample thoroughly. Keep tubes cold on wet ice or with a cold pack after collection.
Patient Prep
Within 30 minutes of venipuncture, centrifuge the collection tube at 1600 (±200) x g (rcf) at 4°C (± 2°C) for 15 (±1) minutes. Transfer the cell-free plasma to a clean tube and immediately store samples at -20°C, or freeze at -60°C or below in an ultra-low freezer.
Preferred volume: 1 mL
Plasma EDTA Stability:
-20°C - up to 4 weeks
-60°C or below in an ultra low freezer - up to 2 years
Ambient temperature for centrifugation is acceptable provided that the time between collection and storage is minimized (approximately 30 minutes).
Pediatric Collection
Minimum volume: 0.5 mL plasma, frozen.
Unacceptable Conditions
Thawed specimen or specimens stored at room temperature prior to shipment.
Storage Transport Temp
Send frozen plasma Priority Overnight via FedEx and in a well-insulated container on dry ice.
Stability
Plasma EDTA Stability:
-20°C - up to 4 weeks
-60°C or below in an ultra low freezer - up to 2 years
Notes
Additional testing time may be needed for less than perfect samples or confirmatory testing/reflex testing.
Performed
Monday - Friday
Methodology
Radioimmunoassay (RIA).
The I125 C4a Des Arg RIA system provides direct quantitative measurement of C4a in human plasma. This radioimmunoassay (RIA) method includes a pre-processing step to remove full length C4 from the sample to eliminate the potential cross-reactivity with measurement of C4a that is often associated with traditional sandwich ELISA methods.
Turnaround Time
7 - 10 business days.
Department
Complement Lab
Synonyms
RadioImmunoassay (C4a Level), C4ades Arg Level, C4ades Arg Level (C4a Level), C4 (C4a Level), C4 anaphylatoxin (C4a Level), C4a anaphylatoxin, Complement (C4a Level), C4AL
Study Offerings
CAP/CLIA
Related Tests
C3AR, C4, C5AR
Reference Interval
0 - 2830 ng/mL
Interpretation
Elevated C4a levels are indicative of classical and/or lectin pathway activation.
CPT Code
86160
New York Approved
Legacy
FDA
LDT