C4A and alkaline phosphatase measurement: One report indicates that the measurement of complement components (eg, C3 and C4) or complement fragments (C3c) does not have any implications for the management of AP.22 In contrast, another study has shown a significant correlation between attenuated complement components (eg, C1q, C3, and C4) or elevated complement fragments (C3a, C5a) and AP severity.23 Regarding serum complement factors, serum C3 and C4 levels fall significantly in AP.