C1q Complement Component Level
Label Mnemonic: C1QFX
Epic Lab Code: LAB2763
Downtime Form: A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery
Commercial Mail-out Laboratory
5231 RCP
Specimen Instructions:
1. Immediately after drawing the specimen, place the tube on wet ice.
2. Spin down and separate serum from clot.
3. Aliquot serum and immediately freeze serum.

Fasting preferred.
Collection Medium:
Red top tube 5 mL (Clot Activator)
Preferred Minimum: 1.0 mL serum
Absolute Minimum: 0.5 mL serum
Delivery Instructions:
Mix well and place on wet ice. Keep on ice and deliver to laboratory immediately.
Turn Around Time:
1-3 days upon receipt at reference laboratory
Reference Range:
34-63 U/mL
Interpretive Data:
Low levels of complement may be due to inherited deficiencies, acquired deficiencies, or due to complement consumption (eg, as a consequence of infectious or autoimmune processes).

The measurement of C1q activity is an indicator of the amount of first component of complement (C1) present. Absent C1q levels in the presence of normal C3 and C4 values are consistent with a C1 deficiency. Low C1q levels in the presence of low C4 but normal C3 may indicate the presence of an acquired inhibitor (autoantibody) to C1 esterase inhibitor.
Use For:
*Diagnosis of first component of complement (C1) deficiency
*Investigation of a patient with an absent total complement (CH50) level

The total complement (CH50) assay (COM / Complement, Total, Serum) should be used as a screen for suspected complement deficiencies before ordering individual complement component assays. A deficiency of an individual component of the complement cascade will result in an undetectable CH50.

Absent (or low) C1q functional levels in the presence of normal C1q antigen levels should be replicated with a new serum specimen to confirm that C1q inactivation did not occur during shipping.
CPT Code:
See also:
C1 Inhibitor, Protein, Serum
See Additional Information:
Specimens Requiring Immediate Delivery