A-145 Evaluating clinician compliance with laboratory guidance for prolonged aPTT testing

Abstract Background Activated partial thromboplastin time (aPTT) is a test used to evaluate coagulation disorders and is frequently ordered in the preoperative setting. When a patient presents with a prolonged aPTT (=> 40 sec) without documented anticoagulant use, our laboratory performs a mixing study with normal plasma to calculate Rosner*s index. The index is computed by our laboratory informatic system, and a comment is posted on the report to guide clinicians toward further investigation either coagulation factor deficiency or lupus anticoagulant/inhibitor. These supplementary tests are costly in terms of technical time and laboratory resources. Herein, we aimed to assess whether the laboratory recommendations were followed by clinicians and to determine whether the laboratory/clinician strategy could be optimized for prolonged aPTT result. Methods We conducted a retrospective study involving 180 patients who had an aPTT result => 40 seconds when analyzed with the Hemosil Synthasil APTT reagent on the ACL TOP analyzer. First, we analyzed the frequency of follow-up investigations and determined whether clinicians adhered to the recommendations provided on laboratory reports. Next, we assessed whether the patients had coagulation factor deficiencies or lupus anticoagulant, and whether these results were consistent with Rosner*s index calculations (= 10 indicating a coagulation factor deficiency and > 10 indicating a lupus anticoagulant). Results All patients with a Rosner index >10 (n=15), who were investigated a for lupus anticoagulant, tested positive, confirming that the laboratory decision limits for Rosner index are acceptable. Among the 180 patients included in our study, 15 died within a week of the initial request, and only 37 (21%) underwent further investigation. Consequently, clinicians did not follow up on 128 patients (78%) with prolonged aPTT. Of the 37 patients who had a follow-up, only 17 were investigated in accordance with the laboratory’s recommendations. A targeted investigation, either for a coagulation factor deficiency or for lupus anticoagulant, was ordered for 22 of those patients. However, 15 patients underwent both investigations, despite the laboratory recommending only one, suggesting suboptimal use of resources. Conclusion Our results raise concerns about the effectiveness of the current investigation strategy for prolonged aPTT. The low adherence of clinician to laboratory recommendations (21%) and the significant proportion of patients who did not receive the appropriate tests (54% of investigated patients) suggest inefficient use of resources. These findings emphasize the need to optimize the laboratory testing algorithm for prolonged aPTT and encourage improved collaboration between the laboratory and clinicians to ensure more effective patient management.