Predictive Performance of Serum Procalcitonin for the Diagnosis of Bacterial Meningitis after Neurosurgery

BACKGROUND Postoperative bacterial meningitis (PBM) is a serious potential complication after neurosurgery. Early diagnosis and introduction of antimicrobial therapy are necessary to reduce the rate of fatal outcomes from PBM. However, PBM is not easily differentiated from postoperative aseptic meningitis (PAM), which usually has favorable clinical outcomes. Serum procalcitonin (S-PCT) has been found to be a useful marker for distinguishing community-acquired bacterial from viral meningitis. We investigated the predictive performance of S-PCT for PBM in patients who underwent neurosurgery. MATERIALS AND METHODS Between September 2009 and August 2010, we prospectively collected data from patients who underwent neurosurgery and had cerebrospinal fluid (CSF) pleocytosis within 14 days of surgery. Based on the CSF culture results, patients were categorized as either PBM or PAM cases. We compared the laboratory test results including S-PCT levels between PBM and PAM cases, and investigated the predictive performance of S-PCT for PBM. RESULTS During the study period, PBM and PAM occurred in 14 and 64 patients, respectively. There was no significant difference in CSF profiles between PBM and PAM cases. S-PCT level ≥ 0.15 ng/mL (50.0% vs. 20.0%, P = 0.07) and C-reactive protein (CRP) level ≥ 2.5 mg/dL (75.0% vs. 46.5%, P = 0.16) tended to be more frequent in PBM than in PAM cases. A blood white blood cell (B-WBC) count ≥ 9,500/mm(3) was more frequently found in PBM cases (85.7% vs. 50.8%, P = 0.02) than in PAM cases. For the diagnosis of PBM, an S-PCT level ≥ 0.15 ng/mL had a specificity of 80.0%. The combined criteria of a CRP level ≥ 2.5 mg/dL, B-WBC count ≥ 9,500/mm(3), and an S-PCT level ≥ 0.15 ng/mL had the highest specificity (92.6%) of all the criteria. An S-PCT level ≥0.15 ng/mL had low sensitivity (50.0%), and the combined criteria of CRP level ≥ 2.5 mg/dL, B-WBC count ≥ 9,500/mm(3), and S-PCT level ≥ 0.15 ng/mL had an improved sensitivity of 85.7%. However, the sensitivity did not significantly differ from that of a B-WBC count ≥ 9,500/mm(3) (85.7%). CONCLUSIONS S-PCT showed limited performance for the diagnosis of postoperative meningitis. However, it could be a useful adjunct for the improvement of diagnostic sensitivity when used in combination with other inflammatory markers.