29, 42
The anchor evidence for Chapter 29. Specific assays (anti-Xa, PT) retain their meaning on a circuit; global assays (ACT, aPTT) do not. Never act on an isolated ACT.
Isolated single-parameter change versus simultaneous multi-parameter change
Saifee NH, Brogan TV, McMullan DM, Yalon L, Matthews DC, Burke CR, Chandler WL. ASAIO J 2020;66(2):230-237. DOI 10.1097/MAT.0000000000000993
Head-to-head evaluation of ACT, aPTT, anti-Xa and PT against directly measured heparin, antithrombin and coagulation factor levels
Single centre; mixed population; the multi-parameter condition is modelled rather than a clinical outcome study
Anti-Xa correlated with heparin r=0.97 and with antithrombin r=0.98, unaffected by other parameters. PT correlated with coagulation factors r=0.88. ACT correlated with coagulation factors r=0.99, was insensitive to heparin below 0.5 U/mL, and correlated with NEITHER heparin nor factors when multiple parameters changed together. Authors describe ACT as too insensitive to heparin, sensitive to too many other factors, and too imprecise to be useful.
Adult and paediatric ECLS patients, with in vitro parameter-variation experiments alongside patient samples