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Diagnostic value of serum complement C3 and C4 levels in Chinese patients with systemic lupus erythematosus

Hejun Li1, Shunping Lin, Shangchih Yang

  • 1Department of Rheumatology, Union Hospital, Fujian Medical University, 29 Xinquan Road, Fuzhou, 350001, China, tanklhj@163.com.

Clinical Rheumatology
|January 20, 2015
PubMed

Insights

Low serum C3 and C4 complement levels, particularly when low simultaneously, significantly improve the diagnosis of systemic lupus erythematosus (SLE). Testing both C3 and C4 together enhances diagnostic sensitivity for SLE.

Area of Science:

  • Immunology
  • Rheumatology
  • Clinical Diagnostics

Background:

  • Hypocomplementemia involving C3, C4, and CH50 was proposed in 2009 as an immunologic criterion to improve systemic lupus erythematosus (SLE) classification sensitivity.
  • The diagnostic utility of low serum complement C3 and C4 levels in Chinese SLE patients requires further evaluation.

Purpose of the Study:

  • To assess the diagnostic value of low serum complement C3 and C4 levels in Chinese patients diagnosed with SLE.
  • To determine optimal cut-off values for C3 and C4 for SLE diagnosis.
  • To evaluate the impact of including hypocomplementemia in SLE classification criteria.

Main Methods:

  • Retrospective analysis of 2452 patients (158 with SLE, 2294 with other diseases).
  • Receiver operating characteristic (ROC) analysis to determine optimal C3 and C4 cut-off levels.
  • Prevalence assessment of low C3/C4 levels alone and simultaneously in SLE and non-SLE groups.
  • Evaluation of antinuclear antibody (ANA) sensitivity and likelihood ratios.

Main Results:

  • Optimal C3 cut-off: 0.785 g/L (sensitivity 77.9%, specificity 81.5%).
  • Optimal C4 cut-off: 0.145 g/L (sensitivity 80.1%, specificity 83.2%).
  • Simultaneously low C3 and C4 levels were significantly more prevalent in SLE patients (73.42%) compared to other diseases.
  • Inclusion of hypocomplementemia increased SLE classification by 16.18%.
  • High prevalence of hypocomplementemia (41.94%) observed in patients with hematological disease.

Conclusions:

  • Simultaneously low C3 and C4 levels are valuable diagnostic indicators for SLE, significantly enhancing diagnostic sensitivity.
  • Low C3 or C4 levels alone are insufficient as immunological criteria for SLE diagnosis; simultaneous testing is crucial.
  • Hypocomplementemia improves SLE classification sensitivity and holds diagnostic importance.

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