Background The use of direct oral anticoagulants (DOACs) is a convenient therapeutic option for patients at risk of thrombosis. DOACs interfere with clot‐based testing for the identification of lupus anticoagulant antibodies (LACs) in patients with antiphospholipid syndrome (APS), a common cause of acquired thrombotic disease. Objectives To evaluate a commercially available reagent DOAC‐Stop for the removal of DOAC interference encountered in LAC testing. Patients/Methods We collected a cohort of 73 test samples from patients on DOAC therapy identified at a large institutional coagulation laboratory from March to December 2019, along with samples from 40 LAC positive and negative control patients not on therapy. Samples were treated with DOAC‐Stop and tested for anti‐Xa activity and thrombin time for the removal of apixaban, rivaroxaban, argatroban, and dabigatran activity from patient samples. Treated and untreated samples were tested using the activated partial thromboplastin time, silica clotting time, and dilute Russell’s viper venom time to evaluate the reliability and utility of DOAC‐Stop. Results DOAC‐Stop markedly reduced DOAC interference from test samples (P < .05). DOAC‐Stop had no effect on LAC testing in the absence of DOAC therapy, permitting the identification of all LAC positive and negative controls. DOAC‐Stop removed false positives and false negatives resulting from DOAC interference and allows the identification of patients meeting criteria for the diagnosis of APS by LAC testing, as well as the detection of patients on rivaroxaban who are triple positive for APS. Conclusions DOAC‐Stop is an effective adjunct for the clinical laboratory faced with DOAC interference in LAC testing.

Background: Cerebrospinal fluid (CSF) leak is typically diagnosed by detecting a protein marker β2-transferrin (β2-Tf) in secretion samples. β2-Tf and β1-transferrin (β1-Tf) are glycoforms of human transferrin (Tf). A novel affinity capture technique for sample preparation, called microprobe-capture in-emitter elution (MPIE), was incorporated with high-resolution mass spectrometry (HR-MS) to analyze the Tf glycoforms and elucidate the structures of β1-Tf and β2-Tf. Methods: To implement MPIE, an analyte is first captured on the surface of a microprobe, and subsequently eluted from the microprobe inside an electrospray emitter. The capture process is monitored in real-time via next-generation biolayer interferometry (BLI). When electrospray is established from the emitter to a mass spectrometer, the analyte is immediately ionized via electrospray ionization (ESI) for HR-MS analysis. Serum, CSF, and secretion samples were analyzed using MPIE-ESI-MS. Results: Based on the MPIE-ESI-MS results, the structures of β1-Tf and β2-Tf were solved. As Tf glycoforms, β1-Tf and β2-Tf share the amino acid sequence but have varying N-glycans. β1-Tf, the major serum-type Tf, has two G2S2 N-glycans on Asn413 and Asn611. β2-Tf, the major brain-type Tf, has an M5 N-glycan on Asn413 and a G0FB N-glycan on Asn611. Conclusions: The structures of β1-Tf and β2-Tf were successfully elucidated by MPIE-ESI-MS analysis. The resolving power of the novel MPIE-ESI-MS method was demonstrated in this study. On the other hand, knowing the N-glycan structures on β2-Tf allows for the design of other novel test methods for β2-Tf in the future.