Background Erythrocyte sedimentation rate (ESR), C reactive protein (CRP), C3 complement (C3), and lymphocyte count are markers of disease activity in patients with systemic lupus erythematosus (SLE).
Objectives Our aim was to identify a prediction tool for SLE disease activity with increased accuracy by combining the afore mentioned parameters, two by two, as ratios.
Methods We prospectively enrolled 130 SLE patients admitted consecutively to our department. Clinical and biological parameters were assessed in each patient. Disease activity was quantified using Systemic Lupus Activity Measure (SLAM) and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). For each patient we analyzed ESR/C3, CRP/C3, lymphocyte/ESR and lymphocyte/CRP ratios.
Results The mean age of our study group was 46.58±12.69 years old and 90% were female. SLAM was correlated with ESR/C3 (r=0.549, p<0.01), CRP/C3 (r=0.343, p<0.01) and lymphocyte/ESR ratios (r=-0.240, p=0.01) better than with ESR (r=0.486, p<0.01), CRP (r=0.229, p=0.02), C3 (r=0.175, p=ns) and lymphocyte number (r=-0.235, p=0.01) alone. SLEDAI was correlated with ESR/C3 (r=0.745, p<0.01), CRP/C3 (r=0.342, p<0.01) and lymphocyte/ESR ratios (r=-0.312, p<0.01) better than with ESR (r=0.663, p<0.01), CRP (r=0.235, p=0.01) and lymphocyte number (r=-0.324, p<0.01) alone.
In ROC curve analysis, ESR/C3 ratio predicted SLEDAI>10 with an AUC of 0.779, p<0.01 similar to ESR (AUC 0.782, p<0.01) and SLAM>10 with an AUC of 0.821, p<0.01 less than ESR (AUC 0.909, p<0.01). Lymphocyte/ESR ratio predicted SLEDAI>10 with an AUC of 0.754, p<0.01 and SLAM>10 with an AUC of 0.929, p<0.01.
ESR/C3 ratio was the best predictor for severe disease quantified as SLAM>20 with an AUC 0.998 (p<0.01) compared to the lymphocyte/ESR ratio (AUC 0.983, p<0.01) and ESR (AUC 0.974, p<0.01). Lymphocyte/ESR ratio (AUC 0.890, p<0.01) and ESR (AUC 0.886, p<0.01) were better to predict severe disease using SLEDAI>20 compared to ESR/C3 ratio (AUC 0.850, p<0.01).
Conclusions Lymphocyte/ESR and ESR/C3 ratios correlate with disease activity in SLE patients, possibly with higher accuracy compared to ESR, C3 and lymphocyte number alone.
Acknowledgements This paper is supported by POSDRU/159/1.5/S/137390.
Disclosure of Interest None declared