Beginning September 8, at approximately 2PM, Spectrum Health Laboratories will go live with their new lot of APTT reagent. This lot change triggered a new therapeutic curve resulting in new heparin nomograms for the system. The standard heparin therapeutic range will change from the current 45-65 seconds to a new range of 37-52 seconds based off the new curve. Reference ranges for the APTT assay will also be updated. Grand Rapids APTT reference range will be 21-27 seconds and the Regional Hospitals will be 21-31 seconds.
APTT specimens that are unable to reach an endpoint (no clot is detected), will reflex to the Unfractionated Heparin (UFH) (Test Code LAB3389) anti-Xa assay. To accommodate this change, UFH values have been added to heparin nomograms. The UFH anti-Xa assay is currently only performed in the Grand Rapids labs and valid only for unfractionated heparin. Any questions concerning these changes may be directed to the Spectrum Health Regional Laboratory Coagulation department at 616-267-2740.