Comparison of Reagents for Determining the Activated Partial Thromboplastin Time

Abstract

SummarySix commercially available reagents for the determination of the activated partial thromboplastin time have been evaluated and compared with respect to their sensitivity to the coagulation factors VIII, IX and XI and to their response to heparin. Some variation was observed among the reagents regarding their sensitivity to factor XI and even greater differences were obtained with factors VIII and IX. It was also clear that none of the reagents was sensitive to the same extent to the factors tested. The sensitivity to heparin shows considerable variation, in terms of time as well as mode of response to increasing heparin levels. In four reagents this response is linear, it is logarithmic in one and the remaining one is yet again different.It seems unlikely that any standardization of the APTT determination is at present possible with the reagents studied.

Problems In Laboratory Monitoring Of Heparin Dosage

“…There is also evidence of variation between APTT reagents in respect of sensitivity to the levels of clotting factors (Hoffman & Meulendijk, 1978, Hathaway et al, 1979Jennings et al, 1995), particularly factor VIII:C. As factor VIII is an acute-phase reactant, levels probably vary markedly in a group of patients with thromboembolic disease and this may have contributed to the difference in responsiveness of reagents described in some of the above studies.…”

The rare coagulation disorders – review with guidelines for management from the United Kingdom Haemophilia Centre Doctors' Organisation

“…For example, FI Bremen (Aa Gly 17 fi Val) is associated with a bleeding disorder and delayed wound healing. Conversely, the majority of individuals with dysfibrinogenaemia [Aa Arg 16 fi His (Bern IV and Milano XI)] were asymptomatic or associated with only a mild bleeding tendency. Individuals (65%) with FGG mutations are asymptomatic with only 5% having bleeding problems and 30%, thrombosis.…”

“…The sensitivity of PT and APTT to the presence of clotting factor deficiencies is dependant on the test system employed [15][16][17][18]. The degree of prolongation in the presence of a clotting factor deficiency can vary dramatically between reagents.…”

Patientennahe Sofortdiagnostik von H�mostasever�nderungen in der An�sthesie und Intensivmedizin

“…B. Von-WillebrandFaktor [34], D-Dimer [47], Fibrinogen [11], Protein S [49] -zwischen verschiedenen Laboratorien oft nur mäßig über-ein. Seit mehr als 20 Jahren ist die schlechte Standardisierung der aPTT bekannt [32]. Mit der üblichen 1,5-bis 2,5fachen aPTT-Verlängerung werden in verschiedenen Kliniken, je nach verwendetem Reagenz und Analysegerät, bei Patienten erheblich differierende Heparinspiegel erzielt [7,17].…”