Serum procalcitonin for differentiating bacterial infection from disease flares in patients with autoimmune diseases

초록

Early differentiation between bacterial infections and disease flares in autoimmune disease patients is important due to differing treatments. Seventy -nine autoimmune disease patients with symptoms suggestive of infections or disease flares were collected by retrospective chart review. The patients were later classified into two groups, disease flare and infection. C-reactive protein (CRP) and serum procalcitonin (PCT) levels were measured. The C RP and PCT levels were higher in the infection group than the disease flare group (CRP,11.96 mg/dL & plusmn; 9.60 vs. 6.42 mg/dL &plusmn; 7.01, p = 0.003; PCT, 2.44 ng/mL &plusmn; 6.55 vs. 0.09 ng/mL & plusmn; 0.09, p < 0.001). The area under the ROC curve (AUC;95% confidence interval) for CRP and PCT was 0.70 (0.58-0.82) and 0.84 (0.75-0.93), which showed a significant difference (p < 0.05). The predicted AUC for the CRP and PCT levels combined was 0.83, which was not significantly different compared to the PCT level alone (p = 0.80). The best cut-off value for CRP was 7.18 mg/dL, with a sensitivity of 71.9% and a specificity of 68.1%. The best cut-off value for PCT was 0.09 ng/mL, with a sensitivity of 81.3% and a sensitivity of 78.7%. The PCT level had better sensitivity and specificity compared to the CRP level in distinguishing between bacterial infections and disease flares in autoim mune disease patients. The CRP level has no additive value when combined with the PCT level when differentiating bacterial infections from disease fla res. Key words: procalcitonin; autoimmune disease; C-reactive protein; bacterial infection