What complement pattern is seen in active SLE?

Active SLE typically shows low C3 and low C4 due to immune complex-mediated classical pathway activation. Hypocomplementemia correlates with nephritis activity. C3 recovers more slowly than C4.

What does isolated low C4 suggest?

Isolated low C4 suggests: C4A or C4B null allele (common in SLE), C4 deficiency, hereditary angioedema (C1 inhibitor deficiency consuming C4), or normal variant. C3 is preserved in these conditions.

Can complement help differentiate lupus nephritis flare from infection?

Low complement + rising anti-dsDNA + active urinary sediment strongly favors lupus nephritis flare. Infection raises CRP and WBC but typically does not reduce complement levels.

Complement C3/C4 Consumption Pattern Interpreter

Interpret complement C3 and C4 levels to differentiate lupus activity, cryoglobulinemia, APLS, and hereditary angioedema. Low C3+C4 suggests immune complex consumption (SLE, hepatitis C cryoglobulinemia), isolated low C4 suggests C4 deficiency or angioedema.

⚕ Clinical Disclaimer: These calculators are for educational and reference purposes only. Always verify results with qualified clinical judgment and current clinical guidelines. Do not use as a sole basis for medical decisions.

How to Use

Enter the values for the scenario you are assessing. Interpret complement C3 and C4 levels to differentiate lupus activity, cryoglobulinemia, APLS, and hereditary angioedema. Low C3+C4 suggests immune complex consumption (SLE, hepatitis C cryoglobulinemia), isolated low C4 suggests C4 deficiency or angioedema. Use the c3/c4 consumption result to inform your calculation.

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