Scire et al used the serum procalcitonin concentration in the evaluation of a patient with an autoimmune disease who is febrile. This can reduce the unnecessary use of antibiotics. The authors are from the University of Pavia.
Patient selection: autoimmune disease with fever (> 38°C)
A serum procalcitonin > 0.5 ng/mL was associated with systemic infection.
A serum procalcitonin <= 0.5 ng/mL is not associated with systemic infection.
This is helpful in distinguishing a disease flare from systemic infection.
Exception: A patient with adult-onset Still's disease (AOSD) can have an elevated procalcitonin concentration without systemic infection. The elevation in serum procalcitonin may be marked and may be linked to levels of TNF-alpha.
A patient with an infection who is successfully treated will show a decline in the serum procalcitonin concentration.
Performance:
• The sensitivity was 75% and specificity 75% for all patients. The specificity increased to 89% if patients with AOSD are excluded.
• The area under the ROC curve is 0.80 for all patients and 0.90 if AOSD is excluded.
• CRP and ESR were more sensitive (95%, 100%) for infection but were nonspecific.
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