Low intraindividual variability of activated partial thromboplastin time revealed in a population of 10 487 control individuals

Abstract

The activated partial thromboplastin time (aPTT) is a routine coagulation test that reflects the activities of multiple coagulation proteins. Given the known genetic elements underlying the different coagulation factor activities, a low intraindividual variability is expected in aPTT values, but has not been demonstrated in a large population. In this regard, we evaluated the intraindividual variability of aPTT by analyzing serial aPTTs from a large population. The study population consisted of control individuals who had three or more consecutive aPTT values at at least 6-month intervals at a single institution. The coefficient of variation of serial aPTT values was determined in each control individual, and the mean value of the coefficient of variations in the control population was calculated. The aPTT values from a total of 10,487 individuals [mean age 57 years (range 21-93 years); male-to-female ratio 1 : 0.9] were included. The mean value of the coefficient of variation of aPTTs in those individuals was 3.75%, which indicates a very low intraindividual variability. This is the first study to demonstrate a low intraindividual variability of aPTT in a large population. The result supports the previous notion that aPTT is a genetically determined parameter and has potential clinical implications.

Assessment of thrombin generation in horses using a calibrated automated thrombogram

“…In comparison, in one study, the low variability of tissue factor‐activated thromboelastography supported the use of population‐based RIs, but this was not the case for non‐activated thromboelastography 23 . In people, intra and interindividual coefficients of variation of the activated partial thromboplastin time (aPTT) are less than 5% and 10%, respectively 24,25 . This is not surprising since coagulation times are usually activated with high concentrations of a triggering factor (eg, TF or kaolin), which tends to decrease variability.…”

“…23 In people, intra and interindividual coefficients of variation of the activated partial thromboplastin time (aPTT) are less than 5% and 10%, respectively. 24,25 This is not surprising since coagulation times are usually activated with high concentrations of a triggering factor (eg, TF or kaolin), which tends to decrease variability. A larger study with healthy horses from a wide variety of breeds, ages, and sexes would be necessary to define RIs and determine true interindividual variation.…”