The overall aim of the study is to determine whether point-of-care (bedside) Activated Partial Thromboplastin Time (APTT) testing would be better than laboratory APTT testing in the PICU population (restricted to children under 16 years of age). To do this the investigators need to compare both forms of testing in the following areas:~Accuracy - using laboratory results as our control the investigators want to ascertain how reliable Point-of-care (bedside) testing with the Hemochron Signature Elite is by comparing paired samples. The Hemochron Signature Elite Whole Blood Microcoagulation System is a battery-operated, hand-held instrument that performs individual point-of-care coagulation tests, including APTT, on fresh or citrated whole blood. The Hemochron Signature Elite instrument is CE marked and complies with multiple safety standard requirements and directives. The investigators know that the Hemochron Signature Elite is not 100% accurate compared to the laboratory but the degree of inaccuracy, particularly in the paediatric population is not clear, if within acceptable & predictable limits the investigators would still be able to use this in clinical practice.~Time efficiency - in view of the fact the Hemochron Signature Elite is on PICU, results from this will be almost immediately available. The investigators then want to measure exactly how long it takes from the moment the laboratory sample is taken for the results to be available.~Cost-effectiveness - the investigators want to compare the costs of these two types of testing in detail, including costs for the Hemochron Signature Elite machine, Hemochron Signature Elite cuvettes, laboratory Clotting Screen bottles, laboratory Clotting Screen analysis, and maintaining the two different types of equipment. The investigators will also take into account any other regular costs (e.g. porters to take samples to the laboratory when the pod system is down). The investigators plan on seeking assistance from senior paediatric colleagues with more experience of health economics in doing a costs minimisation analysis
The overall aim of the study is to determine whether point-of-care (bedside) Activated Partial Thromboplastin Time (APTT) testing would be better than laboratory APTT testing in the PICU population (restricted to children under 16 years of age).