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Test Code C341Q Complement C3 and C4 with Anti-C1q Antibodies, Serum


Specimen Required


Supplies: Sarstedt Aliquot Tube, 5 mL (T914)

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1.5 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial


Secondary ID

621739

Useful For

Evaluating patients with suspected anti-C1q vasculitis

 

Predicting renal involvement in patients with systemic lupus erythematosus

Profile Information

Test ID Reporting Name Available Separately Always Performed
C3 Complement C3, S Yes Yes
C4 Complement C4, S Yes Yes
AC1Q Anti-C1q Antibodies, IgG, S Yes Yes

Method Name

AC1Q: Enzyme-Linked Immunosorbent Assay (ELISA)

C3, C4: Nephelometry

Specimen Type

Serum

Specimen Minimum Volume

0.9 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 7 days
  Frozen  21 days

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Reference Values

C3:

75-175 mg/dL

 

C4:

14-40 mg/dL

 

AC1Q:

<20 U/mL (Negative)

20-39 U/mL (Weak Positive)

40-80 U/mL (Moderate Positive)

>80 U/mL (Strong Positive)

Interpretation

A positive result for anti-C1q antibodies may support a diagnosis of anti-C1q vasculitis or renal involvement in patients with systemic lupus erythematosus in the appropriate clinical context.

 

A negative result indicates no detectable IgG antibodies to C1q and does not rule out a diagnosis.

 

A decrease in C3 levels to the abnormal range is consistent with disease activation in systemic lupus erythematosus.

Method Description

C3:

C3 is measured by immunonephelometry. Antiserum to C3 is mixed with patient serum, the light scatter resulting from the antibody interaction with C3 is measured, and the signal is compared to standard concentrations of C3.(Instruction manual: Siemens Nephelometer II Operations. Siemens, Inc; Version 2.4, 07/2019; Addendum to the Instruction Manual 2.3, 08/2017)

 

C4:

C4 is measured by immunonephelometry. Antiserum to C4 is mixed with patient serum, the light scatter resulting from the antibody interaction with C4 is measured, and the signal is compared to standard concentrations of C4.(Instruction manual: Siemens Nephelometer II Operations. Siemens, Inc; Version 2.4, 07/2019; Addendum to the Instruction Manual 2.3, 08/2017)

 

Anti-C1q antibodies, IgG:

Testing for antibodies to C1q is accomplished using a laboratory-developed immunoassay.(Unpublished Mayo method)

Day(s) Performed

C3, C4: Monday through Friday

AC1Q: Wednesday

Report Available

2 to 8 days

Specimen Retention Time

2 weeks

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

86160 x2

83520

LOINC Code Information

Test ID Test Order Name Order LOINC Value
C341Q C3 and C4 with Anti-C1q, IgG, S In Process

 

Result ID Test Result Name Result LOINC Value
C3 Complement C3, S 4485-9
C4 Complement C4, S 4498-2
AC1Q Anti-C1q Antibodies, IgG, S 44702-9