CALCA and viral meningitis: In this study, CSF PCT levels were 4.714 ± 1.59 ng/mL in bacterial meningitis versus 0.1327 ± 0.03 ng/mL in patients with viral meningitis versus <0.1 ng/mL in patients with non-infectious diseases, with the authors concluding that S–PCT can be helpful in distinguishing bacterial meningitis from viral meningitis and other noninfectious CNS diseases [25].