Changes in levels of serum complement C3,C4,and C1q in active systemic lupus erythematosus patients and their diagnostic and differential diagnostic value
Objective To observe the changes in levels serum complement C3,C4,and C1q of patients with active systemic lupus erythematosus(SLE),and to analyze their diagnostic efficacy for SLE as well as their differential diagnostic efficacy for SLE and SLE complicated with lupus nephritis(LN).Methods Forty-five patients with active SLE were en-rolled as the observation group,including 24 SLE patients with LN and 21 patients with SLE alone(non-LN group).Addi-tionally,38 healthy individuals undergoing routine health examinations were included as the control group.Serum levels of complement C3,C4,and C1q were measured using immunoturbidimetry.Receiver operating characteristic(ROC)curves were drawn to assess the diagnostic performance of C3,C4,and C1q for SLE and to evaluate their differential diagnostic ef-ficacy in distinguishing SLE and SLE with LN.Results Serum levels of complement C3,C4,and C1q were significantly lower in the observation group than in the control group(all P<0.05).The C3 level was lower in the LN group than in the non-LN group(P<0.05).When the cut-off value of C3 was 0.915,the Youden index was 0.646,with the sensitivity of 77.78%,specificity of 86.84%,and the area under the ROC(AUC)of 0.863 7 in diagnosing SLE(95%CI:0.783 4-0.944 0,P<0.05).When the C4 cut-off value was 0.155,the Youden index was 0.592,with the sensitivity of 64.44%,the specificity of 94.74%,and the AUC of 0.826 6 in diagnosing SLE(95%CI:0.737 3-0.916 0,P<0.05).When the cut-off value of C1q was 13.85,the Youden index was 0.440,with the sensitivity of 46.67%,the specificity of 97.37%,and the AUC of 0.690 4 in diagnosing SLE(95%CI:0.574 2-0.806 5,P<0.05).When the three factors were combined,the sensitivity in diagnosing SLE was 75.56%,the specificity was 92.11%,and the area under the ROC was 0.867 8(95%CI:0.790 0-0.945 7,P<0.05).When the cut-off value of C3 was 0.83,the Youden index was 0.357,and its sensitivity in differentiating whether SLE was accompanied by LN was 83.33%,its specificity was 52.38%,and the AUC was 0.6915(95%CI:0.532 3-0.850 7,P<0.05).When the cut-off value of C4 was 0.165,the Youden index was 0.268,and its sensitivity in differentiating whether SLE was accompanied by LN was 79.17%,its specificity was 47.62%,and the AUC was 0.591 3(95%CI:0.420 9-0.761 6,P>0.05).When the cut-off value of C1q was 17.1,the Youden index was 0.345,and its sensitivity in differentiating whether SLE was accompanied by LN was 91.67%,its specificity was 42.86%,and the AUC was 0.637 9(95%CI:0.469 3-0.806 5,P>0.05).When the three factors were combined,their sensitivity in differentiating whether SLE was accompanied by LN was 100.00%,their specificity was 38.10%,and the AUC was 0.694 4(95%CI:0.535 3-0.853 6,P<0.05).Conclusions The levels of serum complements C3,C4 and C1q in patients with SLE decrease.Detecting these three indicators is helpful for the di-agnosis of SLE and for differentiating whether SLE is accompanied by LN.
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