DIAGNOSTIC TEST 890

C1q Antibodies

Diagnostic test for antibodies against C1q. For suspected Hypocomplementemic urticarial vasculitis syndrome or SLE with renal involvement.

Indication

Suspicion of Hypocomplementemic urticarial vasculitis syndrome or SLE with renal involvement

Sample material

Serum

  • Minim. volume: 0,5 mL

EDTA-plasma

  • Minim. volume: 0,5 mL

Transport

  • Within Sweden: frozen
  • International: frozen

Method

ELISA

Reference interval

<10 negative, 10-15 borderline

Result

Results are reported as negative, borderline, or positive with a ratio.

Interpretation

Autoantibodies against C1q are often seen in severe SLE in combination with low levels of C1q and are associated with lupus nephritis. In hypocomplementemic urticarial vasculitis syndrome (HUVS), antibodies against C1q are found in almost all cases (>95%). The antibodies recognize different epitopes of C1q in SLE and HUVS, respectively, but, at higher levels, can usually be distinguished by Western blot.

In SLE, the antibody level usually decreases following immunomodulatory treatment.

References

  • Chao C et al. BMJ Case Rep. 2025. Rare presentation of hypocomplementaemic urticarial vasculitis syndrome (HUVS) overlapping with systemic erythematosus lupus (SLE) and small lymphocytic lymphoma (SLL). PMID: 39933844
  • Marzano AV et al. J Allergy Clin Immunol. 2022. Urticarial vasculitis: Clinical and laboratory findings with a particular emphasis on differential diagnosis. PMID: 35396080

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How to order

This test is available worldwide for hospitals, clinics, and physicians.

  1. Print and complete the request form

    Download the request form. Clearly state the name and phone number of the referring hospital, clinic, or physician.

  2. Prepare your samples

    Serum: At least 0.5 mL serum (plain serum tubes without additives).
    EDTA Plasma: At least 0.5 mL blood plasma (EDTA tubes).

  3. Send samples and request form

    Within Sweden
    Send samples frozen to:
    Envelopes and smaller boxes:
    Wieslab AB, Box 50117, 20211 Malmö, Sweden

    Larger boxes and frozen samples:
    Wieslab AB, Lundavägen 151, 21224 Malmö, Sweden

    International
    Send samples frozen to:
    Wieslab AB, Lundavägen 151, 21224 Malmö, Sweden

Read our sampling instructions for more information

Last updated: 2025-12-05