The comparison of CS‐2500 and BCS XP coagulation analyzers for Factor VIII and Factor IX one‐stage clotting assays

Abstract

Dear Editors, FVIII and FIX measurements are essential for the diagnosis and classification of patients with hemophilia A and hemophilia B. Today, three assay methodologies including one‐stage, two‐stage, and chromogenic assays are used for measuring plasma FVIII and FIX activities. One‐stage activated partial thromboplastin time (APTT)‐based clotting assays for both factor measurements are widely used in clinical laboratories. The one‐stage clot‐based method measures the ability of a patient sample to shorten the aPTT of factor‐deficient plasma. It has some advantages, such as its easy implementation to automated systems, and disadvantages including interlaboratory variability due to the instability of the aPTT reagent (ellagic acid, silica or kaolin) and type of factor‐deficient plasma. Also differences in the working principles of the analyzers affect interlaboratory variability.1 There are studies reporting that the presence of lipemia or lupus anticoagulants, improper sampling technique, and use of anticoagulant drugs such as heparin, direct thrombin, or direct anti‐Xa inhibitors can affect the test results of the one‐stage clotting method compared with two‐stage and chromogenic methods.2-4 However, report on the comparison of instruments using the same assay principles and reagents are limited. Therefore, we aimed to evaluate the analytical performances of the Sysmex CS‐2500 and Siemens BCS XP analyzers, and compare the results obtained for FVIII and FIX measurements using the same one‐stage clotting assays on each analyzer. One hundred sixty blood samples for FVIII and 98 blood samples for FIX from residual material of the Istanbul Faculty of Medicine Central Laboratory workflow comprised our study group. Consecutive patient samples were collected, and hemolytic, lipemic, or icteric samples were excluded. The venous blood samples were collected into evacuated tubes containing 109 mmol/L (3.2%) sodium citrate (Becton Dickinson). Citrated plasma was obtained by centrifugation of blood samples only once for 10 minutes at 3000g and used for FVIII and FIX assays. Plasma samples were stored at −80°C until required and thawed in a water bath at 37°C for 5 minutes prior to analysis. Assays were performed on a Sysmex CS‐2500 (Siemens Healthcare Diagnostics) and a BCS XP (Siemens Healthcare Diagnostics) in a side‐by‐side study under the same laboratory and workflow conditions within 3 hours, and during a one‐month period. FVIII and FIX activities were measured using the one‐stage clotting assay method on the CS‐2500 and BCS XP coagulation analyzers. The same method and reagents were used on both analyzers for each analyte. Calibration curves were plotted using the same calibrator and stored. On each instrument, a single calibration curve was