- aPTT Reagent Lot Change
At midday on 01/07/02, the laboratory will be changing to a new lot of aPTT reagent. The mean of the reference range with this new reagent is 32 seconds; the reference range will be 26-40 seconds.
Because of the significant variability in response of the aPTT reagent systems to heparin, sixty patient specimens with heparin levels of 0.3-0.7 U/ml were evaluated by an Anti-factor Xa method. The mean of this group of specimens was 78 seconds. The mean of the published therapeutic range for heparinization of 1.5-2.5 times the mean of the reference range yields values of 48-80 seconds with this reagent. Based on our studies of heparin responsiveness, this is a reasonable target range to use with this reagent when treating uncomplicated venous thromboembolism. Regarding the monitoring of heparin therapy, this reagent change does not represent a significant change from our previous lot of reagent.
If you have any questions concerning this change, please contact the Hemostasis & Thrombosis Laboratory at 6-3573.