Another test based on the PT or aPTT assays can be employed to quantify the actual amount of factor present in a factor-deficient patient sample.
This assay involves mixing various dilutions of a patient sample with the specific factor-deficient reagent plasma. The various "mixture" results are then plotted against a standard curve correlating with factor activity levels. When developing the standard curve, at least 3 points must be plotted to ensure accuracy when utilizing the curve for patient factor activity assays.
Once the standard curve has been constructed and all points plotted, the approximate amount of factor in the patient sample can be interpreted. Two or more points must be plotted against the standard curve, which enhances accuracy and allows for the recognition of inhibitors in the patient sample. These points must fall within the acceptable range of the standard curve to be considered valid.
Two or more assayed reference plasmas that validate the standard curve should also be tested at least every 8 hours of patient testing to ensure the accuracy of patient results.
