The quantitative interpretation of optical density measurements using PF4-dependent enzyme-immunoassays.

@article{citeulike:2895949, abstract = {Background: Many laboratories test for heparin-induced thrombocytopenia (HIT) using a PF4-dependent enzyme-immunoassay (EIA). An advantage of the EIA is its simplicity; a disadvantage is that it only indirectly detects heparin-dependent, platelet-activating antibodies ("HIT antibodies"). Objectives: To determine whether the magnitude of a positive EIA result, expressed in optical density (od) units, predicts risk of HIT antibodies, defined as a strong-positive platelet serotonin-release assay [SRA] result (>/=50\% serotonin release). Patients/methods: We determined the risk of a strong-positive SRA result for five categories of od reactivity (<0.40; 0.40-<1.00; 1.00-<1.40; 1.40-<2.00; and >/=2.00 od units) using two EIA's (commercial anti-PF4/polyanion IgG/A/M; in-house anti-PF4/heparin-IgG). Results: For patient sera investigated for HIT antibodies, a weak-positive result (0.40-<1.00 od units) in either EIA indicated a low probability (</=5\%) of a strong-positive SRA; the risk increased to approximately 90\% with an od>/=2.00 units. Quantifying the EIA-SRA relationship for 1,553 referred patient sera, we found that for every increase of 0.50 od units in the EIA-IgG, the risk of a strong-positive SRA result increased by OR = 6.39 (95\%CI, 5.13, 7.95; p<0.0001); and for every increase of 1.00 od units in the EIA-IgG, the risk increased by OR = 40.81 (95\%CI, 26.35, 63.20; p<0.0001). Conclusions: The probability of HIT antibodies (strong-positive SRA result) inferred by a positive PF4-dependent EIA varies considerably in relation to the magnitude of the EIA result, expressed as od values. In our laboratory, the probability of HIT antibodies being present reached >/=50\% only when the od level was >/=1.40 units.}, address = {Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.}, author = {Warkentin, T E E. and Sheppard, J I I. and Moore, J C C. and Sigouin, C S S. and Kelton, J G G. }, citeulike-article-id = {2895949}, doi = {http://dx.doi.org/10.1111/j.1538-7836.2008.03025.x}, issn = {1538-7836}, journal = {Journal of thrombosis and haemostasis : JTH}, keywords = {assays, heparin, hit, review}, month = {May}, posted-at = {2008-06-15 09:26:56}, priority = {2}, title = {The quantitative interpretation of optical density measurements using PF4-dependent enzyme-immunoassays.}, url = {http://dx.doi.org/10.1111/j.1538-7836.2008.03025.x}, year = {2008} }

TY - JOUR ID - citeulike:2895949 L3 - citeulike-article-id:2895949 TI - The quantitative interpretation of optical density measurements using PF4-dependent enzyme-immunoassays. JF - Journal of thrombosis and haemostasis : JTH AD - Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada. SN - 1538-7836 N2 - Background: Many laboratories test for heparin-induced thrombocytopenia (HIT) using a PF4-dependent enzyme-immunoassay (EIA). An advantage of the EIA is its simplicity; a disadvantage is that it only indirectly detects heparin-dependent, platelet-activating antibodies ("HIT antibodies"). Objectives: To determine whether the magnitude of a positive EIA result, expressed in optical density (od) units, predicts risk of HIT antibodies, defined as a strong-positive platelet serotonin-release assay [SRA] result (>/=50% serotonin release). Patients/methods: We determined the risk of a strong-positive SRA result for five categories of od reactivity (<0.40; 0.40-<1.00; 1.00-<1.40; 1.40-<2.00; and >/=2.00 od units) using two EIA's (commercial anti-PF4/polyanion IgG/A/M; in-house anti-PF4/heparin-IgG). Results: For patient sera investigated for HIT antibodies, a weak-positive result (0.40-<1.00 od units) in either EIA indicated a low probability (</=5%) of a strong-positive SRA; the risk increased to approximately 90% with an od>/=2.00 units. Quantifying the EIA-SRA relationship for 1,553 referred patient sera, we found that for every increase of 0.50 od units in the EIA-IgG, the risk of a strong-positive SRA result increased by OR = 6.39 (95%CI, 5.13, 7.95; p<0.0001); and for every increase of 1.00 od units in the EIA-IgG, the risk increased by OR = 40.81 (95%CI, 26.35, 63.20; p<0.0001). Conclusions: The probability of HIT antibodies (strong-positive SRA result) inferred by a positive PF4-dependent EIA varies considerably in relation to the magnitude of the EIA result, expressed as od values. In our laboratory, the probability of HIT antibodies being present reached >/=50% only when the od level was >/=1.40 units. KW - assays KW - heparin KW - hit KW - review AU - Warkentin, T E AU - Sheppard, J I AU - Moore, J C AU - Sigouin, C S AU - Kelton, J G PY - 2008/05/17/ UR - http://dx.doi.org/10.1111/j.1538-7836.2008.03025.x ER -