Electrochemiluminescence Immunoassay (ECLIA). Two-step immunoassay sandwich method with chemiluminescent detection.
Differentiation of bacterial versus viral respiratory tract infection; determination of treatment duration in respiratory tract infection s; diagnosis and monitoring of sepsis and septic shock; monitoring response to antibacterial therapy; diagnosis of systemic secondary infection post-surgery; diagnosis of other acute bacterial infections with systemic manifestations. Decisions regarding antimicrobial therapy should NOT be based solely on procalcitonin levels.
PCT < 0.10 ng/mL = Negative. PCT between 0.10 and 0.25 ng/mL = Low; bacterial infection is possible but unlikely. PCT between 0.25 and 0.50 ng/mL = Intermediate; bacterial infection is likely. PCT > 0.50 ng/mL = High; bacterial infection is very likely. Test result will be flagged abnormal > 0.25 ng/mL. If Negative, repeat 6-12 hours. Repeat once per day thereafter.
PCT has not been extensively studied in pediatrics to the same degree as in adult medicine – use PCT with caution in children and consider an infectious diseases consultation if there are doubts or questions about interpretation of the results.
PCT levels in patients with chronic kidney disease have been shown to be elevated in the absence of infection. The cut-offs may not be appropriate for patients with chronic kidney disease. Higher cut-offs have been proposed (Grace E Clin Infect Dis 2014) but not validated.
Serum concentrations of PCT are usually undetectable. PCT levels rise quickly in response to bacterial infection, within 2-4 hours, but may take as long as 6-12 hours to peak. It also has a half-life of about 24 hours. PCT can be contrasted with C-reactive protein (CRP) which takes longer to rise (12-24 hours), takes longer to peak (48 hours), is not as specific to bacterial infection, and is influenced by anti-inflammatory medications.
False Positives: neonates (<72 hours); postpartum women; massive necrosis (trauma/burn, prolonged non-septic shock); therapeutic cooling in post cardiac arrest; cytokine stimulants (OKT3, anti-lymphocyte globulins, alemtuzumab, IL-2, granulocyte transfusion); end-stage renal disease/hemodialysis; acute graft vs. host disease.
False Negatives: Early infection (repeat in 6-12 hours); Chronic infections (endocarditis, osteomyelitis, prosthetic device/graft infections); some localized infections (cellulitis, wound infections, intra-abdominal abscess); Mycoplasma infection.
For more information, see the UMHS Procalcitonin Usage Guidelines at: https://pharmwebsp.med.umich.edu/AC/Antimicrobial%20Use%20Guidelines/Gu… .