Low complement items play different roles on the classification performance of SLICC-2012, EULAR/ACR-2019, and SLERPI

Area of Science:

• Rheumatology
• Immunology
• Clinical Diagnostics

Background:

• Systemic lupus erythematosus (SLE) classification criteria are crucial for diagnosis and management.
• Low complement levels (hypocomplementemia) are common in SLE but their impact on classification performance is debated.
• Existing criteria include complement levels, but their diagnostic utility requires further investigation.

Purpose of the Study:

• To evaluate the association between low complement levels and the performance of SLE classification criteria.
• To compare the sensitivity and specificity of SLICC-2012, EULAR/ACR-2019, and SLERPI before and after excluding low complement items.
• To assess the clinical significance of low C3 and C4 levels in SLE patients.

Main Methods:

• Retrospective analysis of 352 SLE patients and 385 individuals with positive antinuclear antibodies.
• Comparison of SLICC-2012, EULAR/ACR-2019, and SLERPI performance with and without the low complement item.
• Analysis of clinical characteristics associated with low C3 and C4 levels.

Main Results:

• Excluding low complement decreased sensitivity but increased specificity for SLICC-2012 and EULAR/ACR-2019.
• SLERPI showed stable classification performance after excluding low complement.
• Patients with both low C3 and C4 levels had distinct clinical features and higher classification scores.

Conclusions:

• Low complement levels significantly improve the sensitivity and early classification of SLE, particularly for SLICC-2012.
• The combined assessment of low C3 and C4 levels holds clinical relevance in SLE classification.
• SLERPI demonstrates robust performance irrespective of complement levels.