Heparin-PF4 Antibody (HIT), Serum
Method Description Describes how the test is performed and provides a method-specific reference
The human PF4 (H/PF4) antibody immunoassay is an enzyme-linked immunosorbent assays (ELISA) using microwells precoated with an antigen complex of PF4 and polyanionic heparinoid substitute (polyvinyl sulfonate; PVS). Testing is performed on the Biomek FXP liquid handling system using the GTI PF4 Enhanced test kit. Patient serum is incubated in the wells, and binding of antibodies to this complex is detected by binding of a second phosphatase-conjugated antihuman IgG/IgA/IgM antibody. Color is generated when this bound conjugate cleaves a chromogenic phosphate substrate, and is quantitated by light absorption at 405 nm. Results are calculated as the percent of positive standard (reported as reactivity).
Addition of excess heparin (100 U/mL) to patient serum prior to testing will inhibit the reaction between heparin-dependent antibodies and the PF4:PVS complex, and produces a negative result. This procedure is used to confirm that a positive screening result is caused by heparin-dependent antibodies. Results are calculated as the percent heparin inhibition of the reactivity of the antibody.(Collins JL, et al: Diagnostic testing for heparin-induced thrombocytopenia [HIT]: An enhanced platelet factor 4 complex enzyme linked immunosorbent assay [PF4 ELISA]. Blood 1997 [Suppl 1] 90:461a; Package insert: GTI-PF4 ELISA assay for the detection of antibodies directed against platelet factor 4 [PF4]: polyvinyl sulfonate [PVS] complex. GTI, Inc., Brookfield, WI, Rev 06/07)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; a.m. and p.m. runs
Saturday through Sunday; a.m. run only