Decision Analysis for Use of Platelet Aggregation Test, Carbon 14–Serotonin Release Assay, and Heparin–Platelet Factor 4 Enzyme-Linked Immunosorbent Assay for Diagnosis of Heparin-lnduced Thrombocytopenia (original) (raw)
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American journal of clinical pathology, 1999
The value of the platelet aggregation test, carbon 14-labeled serotonin release assay (SRA), and heparin-platelet factor 4 enzyme-linked immunosorbent assay (H-PF4 ELISA) for the diagnosis of heparin-induced thrombocytopenia was evaluated by studying blood samples from 100 patients with suspected heparin-induced thrombocytopenia, and categorized into 4 clinical groups: unlikely (n = 22), possible (34), probable (36), and definite (8) thrombocytopenia. Results of the platelet aggregation test were positive in 40 of 44 patients with probable or definite heparin-induced thrombocytopenia (sensitivity 91%) and in 5 of 22 unlikely to have heparin-induced thrombocytopenia (specificity 77%). The SRA exhibited sensitivity of 88% and negative predictive value of 81%, close to those values for the platelet aggregation test; specificity and positive predictive value were 100%. The sensitivity of the heparin-PF4 ELISA was 97%, with specificity 86%, and a positive correlation was recorded between...
…, 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.
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.
American Journal of Hematology, 1979
Eleven patients with heparin-induced thrombocytopenia were studied. Thrombocytopenia appeared 3-16 days following the initiation of prophylactic or therapeutic doses of heparin. The mean lowest platelet count recorded was 48,000/mm3. When heparin was stopped, recovery from thrombocytopenia began within 24 hours and was complete by ten days. Two patients developed fatal thromboses, and two others had myocardial infarctions while thrombocytopenic. In the serum of seven patients, including three of the four with arterial thrombosis, a heparin-dependent platelet aggregating factor was present. The factor caused release of platelet 14C serotonin but did not lyse platelets. It was present in the globulin fraction of all positive sera, and in one serum studied it was isolated in the IgG/IgA immunoglobulin fraction. The factor was not present in 16 normal sera or in the sera of 1 5 nonthrombocytopenic patients receiving heparin. Our observations suggest that heparin-induced thrombocytopenia is common and that, in some patients it may be accompanied by severe arterial thrombosis. In vivo platelet aggregation is a possible explanation for the thrombocytopenia and the thrombosis in this disorder.
Clinical and Applied Thrombosis/Hemostasis
Heparin-induced thrombocytopenia (HIT) remains diagnostically challenging. Immunoassays including PF4/heparin enzyme-linked immunosorbent assay (ELISA) have high sensitivity but low specificity. Whether the heparin neutralization assay (HNA) improves the diagnostic accuracy of the PF4/heparin ELISA for HIT is uncertain. In this study, to assess its clinical utility and evaluate whether it improves the diagnostic accuracy for HIT, we implemented HNA in conjunction with PF4/heparin ELISA over a 1-year period. A total of 1194 patient samples were submitted to the laboratory for testing from December 2015 to November 2016. Heparin neutralization assay alone is a poor predictor for HIT, but it has high negative predictive value (NPV): Cases with %inhibition <70% are always negative for serotonin release assay. It improves the diagnostic positive predictive value (PPV) of ELISA without compromising sensitivity: ELISA optical density (OD) ≥1.4 alone has a sensitivity of 88% (14/16) and ...
American journal of clinical pathology, 2001
We studied whether laboratory confirmation of heparin-induced thrombocytopenia (HIT) can be improved after antigen clearance by determining free antibody and combining the results of an antigenic and a biologic assay. Blood samples taken over 40 days in 14 patients with HIT with thromboembolism underwent fluorescence-linked immunofiltration and the carbon 14-serotonin release assays. Of the 14 patients, 11 showed positive results in both assays at day 1 after stopping heparin. The 3 patients with negative results seroconverted in one or both assays during the subsequent 7 days. Combining the positive results of the assays increased the sensitivity from 85% at day 1 to 100% at day 7. Assay results became negative in all patients within 40 days. The platelet count normalized between days 2 and 9 after withdrawal of heparin. It is assumed that the free antibody can be detected after withdrawal of heparin and after clearance of the platelet factor 4-heparin complex in patients with HIT.
Cytometry, 2001
Background: Heparin-induced thrombocytopenia (HIT) is a possible complication of heparin therapy that can evolve with life-threatening thromboembolism, for which early diagnosis is essential. However, the specific laboratory approach to the diagnosis of HIT is still controversial. Methods: Sera from 13 patients with HIT, from 15 patients with non-HIT thrombocytopenia, and from 10 normal subjects were used to compare nonfunctional and functional methods to detect anti-heparin:PF-4 antibodies and platelet activation. We used three enzyme-linked immunosorbent assays (ELISAs) and the particle gel immunoassay as nonfunctional tests, and platelet aggregometry, CD62p (p-selectin) phenotypical expression, and Annexin V binding as functional assays. Results: CD62p expression was positive in 85% of the cases and Annexin V was positive in 40% of the HIT cases examined. Aggregometry gave variable results that depend strongly on the donor. Conclusion: Functional tests for platelet activation are more reliable for HIT diagnosis than the nonfunctional tests. We conclude that the phenotypical expression of p-selectin detected by flow cytometry on activated platelets appears to be a good functional marker for the diagnosis of HIT and its possible thromboembolic complications. Cytometry (Comm. Clin. Cytometry) 46:290–295, 2001. © 2001 Wiley-Liss, Inc.
Heparin‐Induced Thrombocytopenia: Pathophysiology, Diagnosis, and Treatment Monitoring
Drug Development Research, 2013
Heparin-induced thrombocytopenia (HIT) without or with thrombosis (HIT-T) constitutes an acquired immune prothrombotic state, occurring in patients under unfractionated heparin or rarely low molecular weight heparin treatment. Heparin binding to secreted platelet factor-4 (PF4) generates PF4 neo-epitopes, against which polyclonal IgG-antibodies are produced. IgG-Hep/PF4 complexes bind on specific platelet, monocyte and endothelial cell Fcγ surface receptors, causing platelet consumption (thrombocytopenia), cell activation, release of prothrombotic tissue factor-bearing microparticles and thrombin generation. Mild to moderate thrombocytopenia and venous or arterial thrombosis are the two hallmarks of HIT. "4T" scoring-system predicts HIT-probability, while diagnosis is further confirmed via specific laboratory assays, which reveal either the presence of IgG antibodies against Hep/PF4 complex (immunological assays), or whether patient's serum can activate donor platelets in the presence of heparin (functional assays). HIT-treatment imposes immediate heparin cessation and initial parenteral anticoagulation with alternative anticoagulants, such as direct thrombin inhibitors (DTIs: lepirudin, argatroban, bivalirudin, desirudin) or indirect FXa inhibitors (IXaIs: danaparoid, fondaparinux). Monitoring of DTIs and IXaIs (via activated partial thromboplastin time or modern assays such as hemoclot thrombin inhibitor and anti-Xa activity, respectively) is essential especially in patients with renal or hepatic failure or in patients with HIT-related consumptive coagulopathy, in order to avoid serious bleeding events or anticoagulant underdosing. Vitamin K antagonists, which are contraindicated during acute phase, are permitted only after platelet count has substantially recovered and must be continued for at least 30 days and 3 months in isolated HIT and HIT-T, respectively, with target international normalized ratio (INR) between 2.0 and 3.0. Drug Dev Res 74 : 558-567, 2013.