The particle gel immunoassay as a rapid test to rule out heparin-induced thrombocytopenia? (original) (raw)
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Transfusion, 1994
Background: As clinical diagnosis of heparin-associated thrombocytopenia (HAT) is often difficult, confirmation by sensitive laboratory assays is desirable. Stud Design and Methods: The sensitivity of the heparin-induced platelet activation (LIPA) test and the platelet aggregation test (PAT) was prospectively compared by using the sera of 209 patients with the putative diagnosis of HAT. Both assays were performed concomitantly with platelets of the same four donors using a different combination of donors from day to day. Further, all sera were assessed with a platelet factor 4 (PF4)/heparin enzyme-linked immunosorbent assay (ELISA). Results: Positive results were obtained with 33 percent of sera in the PFWheparin ELISA, with 33.5 percent of sera in the HlPA test, and with 11.5 percent of sera in the PAT. The PF4/heparin ELISA and the HlPA test showed no difference in sensitivity (p = 0.27 by McNemar's test) and were more sensitive than PAT (~4 0 " by McNemar's test). However, they recognized different patient cohorts. Nine HIPAindeterminate and 12 HIPA-negative sera were positive in the PFWheparin ELISA. Eight of the nine indeterminate sera caused platelet activation with high he arin concentrations in the HlPA test. Eleven of the 12 negative sera contained no LG, but 9 contained I M and 2 contained IgA HAT antibodies. Four sera that were indeterminate in the bF4,heparin ELISA and 18 sera that were negative were positive in the HlPA test. None of the sera that were positive in the PAT was missed in the HlPA test, but two of those were negative in the PFUheparin ELISA. All sera were assessed with four low-molecular-weight heparins and a low-molecular-weight heparinoid in the HlPA test with platelets from the same four donors. Low-molecular-weight heparin caused platelet activation with positive sera in 98 percent of tests, and the heparinoid did so in 10 percent; in a further 12.8 percent, crossreactivity to the low-molecular-weight heparinoid could not be excluded. Conclusion: The majority of HAT antibodies react with a PFWheparin complex, but there is stron evidence that other antigens are involved in some patients.The HlPA test and the jF4iheparin ELSA are sensitive for diagnosing HAT, and they complement one another. TRANSFUSION 1994;34:381-385. Abbreviations: ELSA = enzyme-linked lmmunosorbent assay; HAT = heparln-assoclated thrombocytopenia; HIPA = heparln-induced platelet activation (test); LMW = low molecular weight; PAT = platelet aggregation test; PF4 = platelet factor 4; SRA = serotonin-release assay.
Thrombosis Research, 2011
Background: The in vitro demonstration of antibodies against platelet factor-4/heparin (PF4/hep) complexes is an important contribution to the diagnosis of heparin-induced thrombocytopenia (HIT). The use of PF4/hep IgG-specific immunoassays enhances the specificity of HIT-investigations without any impairment of the sensitivity. Several IgG-specific immunoassays with different origin and structure of the target antigencomplex are commercially available. Methods: Using a retrospective cohort consisting of 459 patients suspected to have HIT, we compared the performance characteristics of two commercially available IgG-specific immunoassays, GTI-(Genetic Testing Institute) and HIA-IgG-ELISA (Hyphen Biomed Research). Results: PF4/hep antibodies were detected in 85 and 81 sera using GTI-and HIA-IgG-ELISA, respectively. OD values and clinical likelihood of patients who tested positive in one assay only were significantly lower than in those who tested positive in both immunoassays. Both IgG-specific assays showed high negative predictive values (100%) and similar but unsatisfactory positive predictive values, determined by a minimum clinical score of 5 and a positive HIPA result (41% and 43%, respectively). The implementation of a confirmatory step using excessive heparin increased the PPV of both assays, but results in a reduction of NPV in HIA-IgG-ELISA. Conclusions: The detection of IgG antibodies alone improves the clinical usefulness of immunoassays. However, functional assays remain indispensable to avoid the overdiagnosis of HIT caused by the detection of IgG non-platelet activating antibodies. The OD value in IgG immunoassays appears to correlate with the clinical relevance of the antibodies and might be used as a predictive parameter in the assessment of HIT.
Thrombosis and haemostasis, 2010
Heparin-induced thrombocytopenia (HIT) is a life-threatening complication of heparin treatment; the prognosis depends on early and accurate diagnosis, and prompt start of alternative anticoagulants. Because of high sensitivity, the commercially available immunologic assays are widely used, though not suited to be run on single samples and with a turnaround time of 2-3 hours. We evaluated two new, rapid, automated, semi-quantitative chemiluminescent immunoassays in HIT suspected patients: HemosIL AcuStar HIT-IgG(PF4-H) (specific for IgG anti-PF4/heparin antibodies) and HemosIL AcuStar HIT-Ab(PF4-H) (detecting IgG, IgM and IgA anti-PF4/heparin antibodies) (both from Instrumentation Laboratory). A total of 102 patients with suspected HIT were included; HIT was diagnosed in 17 (16.7%). No false negative cases were observed using either the HemosIL AcuStar HIT-IgG(PF4-H) or the HIT-Ab(PF4-H) assay (sensitivity and negative predictive values = 100%; negative likelihood ratios <0.01). T...
Clinical and Applied Thrombosis-hemostasis, 2004
The major complication in the therapeutic or prophylactic use of heparin in medical treatment is type II heparin-induced thrombocytopenia (HIT II), a unique form of drug-induced immune-mediated thrombocytopenia. Due to the extensive use of heparin, this side effect is widespread; up to 3% of patients treated with unfractionated heparin (UFH) develop HIT II (69). Clinically, HIT II is characterized by thrombocytopenia which paradoxically is associated with thrombosis (HIT IIinduced thrombosis [HITTS]) (i.e., deep vein thrombosis, pulmonary embolism, and venous gangrene) in about 50% of the cases.
…, 1994
Background: As clinical diagnosis of heparin-associated thrombocytopenia (HAT) is often difficult, confirmation by sensitive laboratory assays is desirable. Stud Design and Methods: The sensitivity of the heparin-induced platelet activation (LIPA) test and the platelet aggregation test (PAT) was prospectively compared by using the sera of 209 patients with the putative diagnosis of HAT. Both assays were performed concomitantly with platelets of the same four donors using a different combination of donors from day to day. Further, all sera were assessed with a platelet factor 4 (PF4)/heparin enzyme-linked immunosorbent assay (ELISA). Results: Positive results were obtained with 33 percent of sera in the PFWheparin ELISA, with 33.5 percent of sera in the HlPA test, and with 11.5 percent of sera in the PAT. The PF4/heparin ELISA and the HlPA test showed no difference in sensitivity (p = 0.27 by McNemar's test) and were more sensitive than PAT (~4 0 " by McNemar's test). However, they recognized different patient cohorts. Nine HIPAindeterminate and 12 HIPA-negative sera were positive in the PFWheparin ELISA. Eight of the nine indeterminate sera caused platelet activation with high he arin concentrations in the HlPA test. Eleven of the 12 negative sera contained no LG, but 9 contained I M and 2 contained IgA HAT antibodies. Four sera that were indeterminate in the bF4,heparin ELISA and 18 sera that were negative were positive in the HlPA test. None of the sera that were positive in the PAT was missed in the HlPA test, but two of those were negative in the PFUheparin ELISA. All sera were assessed with four low-molecular-weight heparins and a low-molecular-weight heparinoid in the HlPA test with platelets from the same four donors. Low-molecular-weight heparin caused platelet activation with positive sera in 98 percent of tests, and the heparinoid did so in 10 percent; in a further 12.8 percent, crossreactivity to the low-molecular-weight heparinoid could not be excluded. Conclusion: The majority of HAT antibodies react with a PFWheparin complex, but there is stron evidence that other antigens are involved in some patients.The HlPA test and the jF4iheparin ELSA are sensitive for diagnosing HAT, and they complement one another. TRANSFUSION 1994;34:381-385. Abbreviations: ELSA = enzyme-linked lmmunosorbent assay; HAT = heparln-assoclated thrombocytopenia; HIPA = heparln-induced platelet activation (test); LMW = low molecular weight; PAT = platelet aggregation test; PF4 = platelet factor 4; SRA = serotonin-release assay.
Cureus, 2018
Heparin-induced thrombocytopenia (HIT) is an adverse reaction to the administration of heparin due to the activation of the platelets by the immunoglobulin G (IgG) antibody-platelet factor 4 (PF4)/heparin immune complex. Since the clinical outcome is uncertain (as it could be associated with significant morbidity and sometimes death), an early diagnosis and appropriate treatment are necessary. The 4Ts pretest clinical scoring system and testing for all anti-PF4/heparin antibodies can markedly improve the diagnosis and prompt adequate treatment. Our study was undertaken to retrospectively evaluate the appropriateness of ordering the PF4 enzyme-linked immunosorbent assay (ELISA) test by using the 4Ts scoring system in a tertiary institution. We examined a database of 118 patients who had the PF4 ELISA test and calculated their 4Ts scores retrospectively. A total of 107 patients were evaluated; 95 patients (88.79%) had a negative PF4 ELISA assay and 12 patients tested positive (11.21%). Only one patient tested weakly positive in the low probability group (negative predictive value 98%). In the intermediate group, six patients were strongly positive (optical density (OD) > 1.0). In this latter group, further confirmatory testing using serotonin release assays (SRAs) could have been done. We also evaluated the setting where the tests were performed and found that the majority of patients (63.55%) were tested in the intensive care unit (ICU) where thrombocytopenia is multifactorial. We concluded that the large majority of patients were not appropriately evaluated prior to testing, which incurred unnecessary expense and patient distress. For the proper identification of patients suspected of HIT who should undergo PF4/heparin antibody testing, further education of the ordering physicians is recommended.
European Journal of Haematology, 2019
Objectives: Reliable diagnosis of HIT is mandatory for patient management, yet prompt determination of pathogenic antibodies remains an unmet clinical challenge. Common immunoassays carry inherent limitations and functional assays which detect antibodymediated platelet activation are not usually readily available to routine laboratories, especially the serotonin-release assay (SRA), being technically demanding, time consuming, and requires high level expertise. To overcome some of these limitations, we have developed a practical functional flow cytometric assay (FCA) for routine clinical use. Methods: A simple, FCA is described which avoids platelet manipulation, is highly specific and sensitive compared to SRA, and provides rapid results. Results: Of the 650 consecutive samples, from HIT-suspected patients, 99 (15.3%) were positive by the PaGIA-Heparin/PF4 immunoassay and 31 (4.8%) by FCA. Average platelet activation was 11-fold higher in PaGIA+/FCA+ vs. PaGIA-/FCA-samples. Of 21 Accepted Article This article is protected by copyright. All rights reserved. SRA-positive samples, 19 were FCA-positive (relative sensitivity 90.5%), and of 42 SRAnegative samples, 40 were FCA-negative (relative specificity 95.2%). The FCA showed significantly higher correlation with the clinical presentation of HIT (4Ts score) performed on 182 patients, compared to PaGIA-Heparin/PF4 (ROC-plot analysis, AUC 0.93 vs. 0.63, p<0.001). At a 92% sensitivity, the assay specificity was 96%. Conclusions: The present FCA is practical for routine testing, providing prompt reliable results for initial diagnosis and confirmation, to effectively assist in HIT patient management.
Thrombosis Research, 2002
Antibodies to heparin -platelet factor 4 (PF4) complexes have been observed in patients with heparin-induced thrombocytopenia (HIT) syndrome. These antibodies may be of various isotypes and differ with respect to their ability to activate platelets/endothelial cells. This study determined the isotypes and functionality of antiheparin -platelet factor 4 (AHPF4) antibodies in 111 patients treated with heparin and clinically suspected for HIT. In this patient population, 50% had detectable AHPF4 cumulative IgA, IgG, and IgM (determined by enzyme-linked immunosorbent assay, ELISA), but only 35% was positive when tested with the 14 C-serotonin release assay (SRA). Using antihuman Ig specific for different isotypes, we found that 50% of the 111 samples was positive for IgG, 45% for IgM, and 37% for IgA. In 50 normal human serum (NHS) samples, only two were positive for IgG, but 33 were positive for IgM, indicating a potential humoral response to the heparin -PF4 complex prior to heparin administration. Patients that were ELISA + for AHPF4 antibody titer were subdivided into SRA-positive (+) and SRA-negative ( À ) groups. The SRA + group had a mean ELISA optical density (OD) for AHPF4 IgA/IgG/IgM of 2.1, while the SRA À group had a mean OD of 0.8 ( P < .001). The SRA + group had greater mean OD values for all three individual isotypes. Using flow cytometry, we determined the ability of different patient samples to activate platelets. Samples that contained IgG and were SRA + activated platelets (as measured by microparticle generation and P-selectin expression) in the presence of therapeutic concentrations of heparin. NHS and samples containing IgA and/or IgM that were SRA À were not able to produce microparticles nor were they able to increase expression of P-selectin. Together, these data indicate that IgG is the principal mediator of platelet activation in patients with HIT, with IgA and IgM playing a less significant role in the pathophysiology of this syndrome. D
Positive Heparin/PF4 Antibodies and High Mortality Rate: a Retrospective Case-Series Analysis
Brazilian Journal of Cardiovascular Surgery, 2020
Introduction Heparin-induced thrombocytopenia (HIT) is a potentially lethal complication of unfractionated or low-molecular weight heparin therapy. We aimed to determine the incidence and mortality rate of patients with positive heparin/platelet factor 4 (PF4) antibodies, which is a rapid detection test of HIT. Methods Coronary artery bypass grafting and mitral and aortic valve surgeries were evaluated. Cardiopulmonary bypass was employed in all patients. The diagnosis of HIT was based on immunological assays. Postoperative complications, mortality rates, and the causes of death were specified in patients with positive heparin/PF4 antibodies. Results Postoperative thrombocytopenia was detected in 257 patients. Twenty of these patients undergoing open heart surgery were included in the final analysis. Antibodies against heparin/PF4 complex were positive in 20 patients. The mean body mass index was 28.8±2.3 kg/m2, mean value of left ventricular ejection fraction was 48.3±6.7%, cardiop...