Objectives: This study aimed to compare the YHLO chemiluminescence immunoassay (CLIA) with the Crithidia luciliae immunofluorescence test (CLIFT) to detect anti-dsDNA antibodies and its correlation with disease activity in systemic lupus erythematosus (SLE).
Method: In total, 208 patients diagnosed with SLE, 110 other autoimmune patients, 70 infectious disorders patients, and 105 healthy people were enrolled in this study. Serum samples were tested using CLIA in a YHLO chemiluminescence system and CLIFT.
Results: The overall agreement between YHLO CLIA and CLIFT was 76.9% (160/208), with a moderate correlation (kappa = 0.530, p < 0.001). The sensitivity of YHLO CLIA and CLIFT were 58.2% and 55.3%, respectively. The specificity of YHLO CLIA and CLIFT were 95.1% and 99.3%, respectively. The sensitivity of YHLO CLIA was increased to 66.8% with a specificity of 93.6% when the cut-off value was set at 24 IU/mL. Spearman's correlation coefficient between the quantitative results of YHLO CLIA and the titers of CLIFT was 0.59 (p < .01). A significant correlation was found between the anti-dsDNA results detected by YHLO CLIA and the SLE Disease Activity Index 2000 (SLEDAI-2K). Spearman's correlation coefficient between YHLO CLIA and SLEDAI-2K (r = 0.66, p < .01) was higher than that of CLIFT (r = 0.60, p < .01).
Conclusions: Good correlation and agreement were found between YHLO CLIA and CLIFT. In addition, there was a significant correlation between YHLO CLIA and the SLE Disease Activity Index, which was superior to that of CLIFT. The YHLO chemiluminescence system is recommended for the assessment of disease activity.
Keywords: Crithidia luciliae immunofluorescence test; anti-dsDNA antibodies; chemiluminescence immunoassay; systemic lupus erythematosus.