The present invention concerns diagnostic methods for coagulation testing involving determining anticoagulant activity elicited by a first anticoagulant in a sample comprising measuring a first Factor Xa activity in a body fluid test sample of said subject, measuring a second Factor Xa activity in at least one calibrator sample comprising a predefined anticoagulation activity for a second anticoagulant, calculating an universal parameter for the anticoagulation activity comprised in the test sample based on the first and the second measured Factor Xa activities and comparing the said parameter for the anticoagulation activity with predefined ranges of expected anticoagulation activity for at least three anticoagulants. Further provided is a computer program code assisting the method as well as a system for carrying out the said method as well as a kit.