Use of serum procalcitonin to detect bacterial infection in patients with autoimmune diseases: a systematic review and meta-analysis.

OBJECTIVE To systematically review evidence of the accuracy of the procalcitonin test for diagnosis of bacterial infection in patients with autoimmune disease. METHODS The major databases Medline, EMBase, and the Cochrane Library were searched for studies published between January 1966 and October 2011 that evaluated procalcitonin, alone or in comparison with other laboratory markers such as C-reactive protein (CRP), as a diagnostic marker for bacterial infection in patients with autoimmune disease and provided sufficient data to permit construction of 2 × 2 tables. RESULTS Nine studies were included in the final meta-analysis. The area under the summary receiver operating characteristic curve values were 0.91 (95% confidence interval [95% CI] 0.88-0.93) for procalcitonin and 0.81 (95% CI 0.78-0.84) for CRP. In general, testing for procalcitonin was highly specific for identifying infectious complications, although it was not as sensitive as testing for CRP. Pooled sensitivity was 0.75 (95% CI 0.63-0.84) for procalcitonin tests and 0.77 (95% CI 0.67-0.85) for CRP tests. Pooled specificity was 0.90 (95% CI 0.85-0.93) for procalcitonin tests and 0.56 (95% CI 0.25-0.83) for CRP tests. The positive likelihood ratio for procalcitonin (7.28 [95% CI 5.10-10.38]) was sufficiently high to qualify procalcitonin testing as a rule-in diagnostic tool, while the negative likelihood ratio (0.28 [95% CI 0.18-0.40]) was not sufficiently low to qualify procalcitonin testing as a reliable rule-out diagnostic tool. CONCLUSION Procalcitonin has higher diagnostic value than CRP for the detection of bacterial sepsis in patients with autoimmune disease, and the test for procalcitonin is more specific than sensitive. A procalcitonin test is not recommended to be used in isolation as a rule-out tool.