The eculizumab level (free anti-C5) is a measurement of the serum level of eculizumab (Soliris®, Alexion Pharmaceuticals), a humanized IgG4 monoclonal antibody directed against the complement protein C5. By binding to C5, eculizumab prevents cleavage of C5 to its active fragments C5a and C5b, thereby preventing formation of C5b-9 and halting the process of complement-mediated cell destruction.
Adequate dosage and dosing interval of eculizumab results in a complete blockade of activation of the terminal complement pathway. If a patient is not being adequately dosed with eculizumab, breakthrough activation of the complement system and subsequently disease reactivation may occur. Along with clinical markers of disease activity and other laboratory measures of terminal complement pathway activity (such as CH50, C5a, and sC5b-9), the eculizumab level may be used to guide therapeutic decision making as to adequate dosage and dosing interval.
Reference Interval
Eculizumab is considered to be present in a therapeutic level in aHUS if the trough serum concentration is >99 µg/mL (Legendre CM et al, NEJM 2013), and in PNH if the serum concentration is >35 µg/mL (Hillmen P et al, NEJM 2004).
CPT Codes
80299
Collection
Collect
Blood in 6mL Red Top
Minimum Collection Volume
1 mL blood or 0.5 mL serum
Shipping/Handling Instructions (Lab Use Only)
Critical: Spin, Pour, Freeze. 0.5mL Serum in Clear Aliq.
The eculizumab level (free anti-C5) is a measurement of the serum level of eculizumab (Soliris®, Alexion Pharmaceuticals), a humanized IgG4 monoclonal antibody directed against the complement protein C5. By binding to C5, eculizumab prevents cleavage of C5 to its active fragments C5a and C5b, thereby preventing formation of C5b-9 and halting the process of complement-mediated cell destruction.
Adequate dosage and dosing interval of eculizumab results in a complete blockade of activation of the terminal complement pathway. If a patient is not being adequately dosed with eculizumab, breakthrough activation of the complement system and subsequently disease reactivation may occur. Along with clinical markers of disease activity and other laboratory measures of terminal complement pathway activity (such as CH50, C5a, and sC5b-9), the eculizumab level may be used to guide therapeutic decision making as to adequate dosage and dosing interval.
Reference Interval
Eculizumab is considered to be present in a therapeutic level in aHUS if the trough serum concentration is >99 µg/mL (Legendre CM et al, NEJM 2013), and in PNH if the serum concentration is >35 µg/mL (Hillmen P et al, NEJM 2004).
