Serum Procalcitonin for Differentiating Bacterial Infection from Disease Flares in Patients with Autoimmune Diseases

Abstract

Early differentiation between bacterial infections and disease flares in autoimmune disease patients is important due to different 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 CRP and PCT levels were higher in the infection group than the disease flare group (CRP,11.96 mg/dL ± 9.60 vs 6.42 mg/dL ± 7.01, P = 0.003; PCT, 2.44 ng/mL ± 6.55 vs 0.09 ng/mL ± 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 specificity 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 autoimmune disease patients. The CRP level has no additive value when combined with the PCT level when differentiating bacterial infections from disease flares.

Procalcitonine, Nitric oxide and C-Reactive Protein concentrations in rats with experimentally-induced infectious and noninfectious inflammation

“…After a bacterial stimulus in healthy volunteers, the PCT concentration rise within 4 hr, reaching peak levels after 6 hours, and maintaining a plateau between 8 and 24 hr (29). PCT levels do not increase or slight increase in localised inflammation or infection that no systemic finding (17).…”

“…Sometimes, discrimination of infectious and noninfectious inflammations is difficult because of similar clinical and laboratory findings (17). The differantiation of inflammation and diagnosis of the disease is important for selecting the appropriate treatment and thus preventing complications in the long term (29).…”

“…When bacterial infections or septicemia occurs, PCT level increases in circulating blood. The origin of the PCT during infectious conditions are considered to be extrathyroidal such as lung, liver, pancreas, colon and other organs (17). PCT behaves like an acute phase protein similar to other positive reactants, such as CRP, the production of which is also increased by inflammatory stimuli, including infections (23).…”

“…NO, is produced by macrophages and many other cell types in response to inflammation or infection (11). NO levels may be useful to determine inflammation and diseases (17). Some reporters demonstrated NO concentrations can help to use in discrimination of the inflammation (5,13).…”

C - reactive protein: An inflammatory marker with specific role in physiology, pathology, and diagnosis

“…66 Additional determination of procalcitonin can add specificity in the case of bacterial infections. 67 The above information is also helpful to distinguish infection from an autoimmune flare. Similarly, the rate of change in CRP levels can differentiate tuberculosis from bacterial pneumonia.…”