Serum procalcitonin levels in bacterial and viral meningitis

Background and objectives

Serum procalcitonin (PCT) levels increase in invasive bacterial, but not in viral infections. In patients with meningitis, the initial differential diagnosis of bacterial or viral infection is frequently difficult. The aim of this study was to test the hypothesis that serum procalcitonin levels are elevated in patients with bacterial meningitis and remain within normal limits in viral meningitis.

Patients and methods

We prospectively evaluated 30 patients (13 men and 17 women, mean age 52 years), with acute bacterial (n = 16) or viral (n = 14) meningitis. Upon admission, cerebrospinal fluid (CSF), scrum PCT, C-reactive protein (CRP), white blood cell (WBC) count, and lactate were analysed. Blood and CSF cultures, CFS Gram stains and serological studies were performed. Sepsis was categorised according to the Society of Critical Care Medicine consensus criteria. Outcome was assessed upon discharge using the Glasgow Outcome Scale.

Results

Patients with viral meningitis were younger and had a shorter hospital stay. Fourteen of 16 patients with bacterial, but only five of 14 patients with viral meningitis were in a septic condition upon admission. Upon discharge, 12 patients were without any symptoms, nine patients were moderately, and nine severely disabled. No patient died. Upon admission, PCT, CRP, white blood cell and CSF leukocyte counts, CSF protein and lactate were higher, and the serum/CSF ratio was lower in patients with bacterial meningitis as compared with viral meningitis (P < 0.001). PCT was the parameter with the highest specificity (100%) for bacterial infections but was false-negative in five patients with bacterial meningitis (a sensitivity of 69%).

Conclusion

Our results indicate that PCT is a useful additional parameter to differentiate bacterial from viral meningitis. In patients with viral meningitis and even if viral sepsis is present. PCT levels do not increase. Elevated PCT levels indicate a bacterial origin with high specificity.