Beginning May 1st, the Core Lab will transition from the current ELISA anti-PF4/heparin antibody test to a latex immunoturbidimetric assay (LIA) performed on the TOPS coagulation analyzer. The test will be available 24/7 with an in-lab turnaround time of 1-2 hours.
Laboratory comparisons to SRA send out results show a sensitivity of 100% and a specificity of 68%, consistent with published performance results on over 400 patients with suspected HIT. The results are expressed in arbitrary units ranging from 0.0 to 16 U/mL. A result of >/= 1.0 U/mL is reported as heparin/anti-PF4 antibody positive. A result of < 1.0 U/mL is reported as heparin/anti-PF4 antibody negative. The quantitative result will be reported with the qualitative result. Although a positive result may indicate the presence of Heparin-associated antibodies, IT DOES NOT CONFIRM the diagnosis of Heparin-Induced Thrombocytopenia (HIT). However, the likelihood of a positive SRA result increases with higher LIA positive results.
A reflex Serotonin Release Assay (SRA) will be sent to Blood Center of Wisconsin (BCW) for confirmatory testing on the first positive PF4 antibody test during an admission. No concurrent ordering of SRA will be sent out. Repeat PF4 testing will be available after a 24 hour period. Situations that require testing more frequently or the need to send out an SRA despite a negative PF4 antibody test will require Lab Medicine Resident approval.
If you have questions, please contact the chemistry laboratory medicine resident/fellow at beeper 747-1320, opt. 2.