Hexagonal Phospholipid Neutralization assay (STACLOT-LA). Hexagonal Phospholipid Neutralization assay (STACLOT-LA). Patient plasma plus normal plasma are incubated in the absence of HPE tube 1) and in the presence HPE (tube 2). An APTT is performed using a LAC sensitive reagent. The clotting time of tube 1 is compared to tube 2. If a LAC is present, tube 1 minus tube 2 should be ≥ to the established cut-off. Larry J. Smith Clin Lab Sci 2017;30:7-14 © Copyright 2016 American Society for Clinical Laboratory Science Inc. All rights reserved.