Schneiter S Colucci G Sulzer I Barizzi G Lämmle B Alberio L 2009 BACKGROUND Recent studies have shown that a low clinical pretest probability may be adequate for excluding heparin-induced thrombocytopenia. However, for patients with intermediate or high pretest probability, laboratory testing is essential for confirming or refuting the diagnosis. Rapid assessment of anti-PF4/heparin-antibodies may assist clinical decision-making. OBJECTIVES To evaluate the performance of rapid ID-H/PF4-PaGIA. In particular, we verified reproducibility of results between plasma and serum specimens, between fresh and frozen samples, and between different ID-H/PF4-polymer lots (polystyrene beads coated with heparin/PF4-complexes). PATIENTS/METHODS The samples studied were 1376 plasma and 914 corresponding serum samples from patients investigated for suspected heparin-induced thrombocytopenia between January 2000 and October 2008. Anti-PF4/heparin-antibodies were assessed by ID-H/PF4-PaGIA, commercially available ELISAs and heparin-induced platelet aggregation test. RESULTS Among 914 paired plasma/serum samples we noted discordant results (negative vs. low-titre positive) in nine instances (1%; 95%CI, 0.4-1.6%). Overall, agreement between titres assessed in plasma vs. serum was highly significant (Spearman correlation coefficient, 0.975; P < 0.0001). Forty-seven samples tested both fresh and after freezing/thawing showed a good agreement, with one discordant positive/negative result (Spearman correlation coefficient, 0.970; P < 0.0001). Among 1376 plasma samples we noted a strikingly variable incidence of false negative results (none - 82%; 95%CI, 66-98%), depending on the employed ID-H/PF4-polymer lot. Faulty lots can be recognized by titrating commercial positive controls and stored samples of HIT-patients. CONCLUSION Laboratories performing the assay should implement stringent internal quality controls in order to recognize potentially faulty ID-H/PF4-polymer lots, thus avoiding false negative results. application/pdf https://sonar.ch/global/documents/218785 eng info:eu-repo/semantics/altIdentifier/doi/10.1111/j.1538-7836.2009.03507.x info:eu-repo/semantics/altIdentifier/pmid/19515091 info:eu-repo/semantics/openAccess Journal of thrombosis and haemostasis : JTH. - 2009 Antigen-Antibody Reactions Artifacts Autoantibodies Centrifugation Early Diagnosis Enzyme-Linked Immunosorbent Assay Freezing Gels Heparin Humans Immunosorbent Techniques Microspheres Platelet Aggregation Platelet Factor 4 Platelet Function Tests Polystyrenes Purpura, Thrombocytopenic, Idiopathic Reproducibility of Results Sensitivity and Specificity Specimen Handling Variability of anti-PF4/heparin antibody results obtained by the rapid testing system ID-H/PF4-PaGIA. http://purl.org/coar/resource_type/c_6501