Specimens from APTT assays on nonheparinized patients are kept at room temperature and centrifuged with with plasma remaining on top of cells in an unopened tube should be tested within 4 hours of the collection time.

Specimens from APTT assays suspected to contain unfractionated heparin are kept at room temperature and centrifuged within 1 hour of collection and the plasma tested within 4 hours of the collection time. If agitation is likely after centrifugation the plasma should be removed from the cells.

Tube filled to label marker and mixed by inversion.

Please note updated reference ranges from 28.5.2015 .