Conclusions Given an HYP result in an ED blood assay, additional studies must be run regardless of the patient's age, to ﬁnd out it cause, since it can be a potentially serious hidden disorder such as MM. We strongly recommend performance a PE in patients from ED with TP over 9 g/dL. doi:10.1016/j.cca.2019.03.816 ^ W042 Estimation of ﬁbrinogen concentration from activated partial thromboplastine time S. Garcia, V. Ortiz, A. Molina, A. Merino, S. Fumanal, M. Arnau, J.L. Bedini CORE Laboratory, Biomedical Diagnostic Center, Hospital Clinic of Barcelona, Spain Background-aim Fibrinogen is an essential component in the haemostasis process. It is one of the main tests in the screening of the haemostasis function. The technique most used is based on the Clauss method. However, there are some laboratories that use the ﬁbrinogen derived method, which is a low-cost technique estimated from the prothrombin time (PT) results. The objective of this work is to evaluate the possibility of estimating the ﬁbrinogen concentration from the activated partial thromboplastin time (APTT) results. Methods PT, APTT and Clauss ﬁbrinogen were performed over a total of 100 plasma samples from normal control patients. The instrument CS 5100 (Siemens) was used together with the following reagents: Thromborel (PT), Actin FSL (APTT) and Thrombin (ﬁbrinogen). In this study, we performed a linear regression model of the absorbance change (from both PT and APTT) against the Clauss ﬁbrinogen results. From both models we obtained an equation that we used to estimate the concentration of ﬁbrinogen. Results The results of PT, APTT and ﬁbrinogen obtained from the samples analyzed showed an average of 13.6 s; 33.15 s and 2.5 g/L, a minimum value of 12.2 s; 30.3 s and 1.61 g/L; and a maximum value of 15 s; 36 s and 3.58 g/L, respectively. From the regression model performed, we obtained a coefﬁcient of determination (R 2 ) of 0.929 for the estimation based on the APTT, and 0.885 for PT. The sum of the differences between the estimated value of ﬁbrinogen and the measured one was 0.01 for the APTT model and 0.14 for PT. Conclusions The results of this work show that the absorbance change of the APTT is a good estimator for the concentration of ﬁbrinogen, since there is a high correlation between both variables. In addition, APTT results show a better ﬁt to the real ﬁbrinogen concentration than the model based on PT. The estimation of ﬁbrinogen from APTT may have important practical applications, since it provides additional value that complements the derived ﬁbrinogen obtained from PT. Furthermore, it would offer clinically relevant information for those patients to whom only APTT is requested. Therefore, estimating ﬁbrinogen from APTT should be an option to consider in the daily routine of the clinical laboratory. doi:10.1016/j.cca.2019.03.817 ^ W043 Are the platelet indices useful biomarkers of arteriovenous ﬁstula thrombosis in hemodialysis patients? N. Klapuh- Bukvić a , E. Kiseljaković b a Department of Clinical Biochemistry and Immunology, University Clinical Center Sarajevo, Sarajevo, Bosnia and Herzegovina b Department of Medical Biochemistry, Faculty of Medicine, University of Sarajevo, Sarajevo, Bosnia and Herzegovina Background-aim Platelet indices: total platelet count (PLT), mean platelet volume (MPV), platelet distribution width (PDW) and plateletcrit (PCT) are potentially useful biomarkers for the early diagnosis of thrombosis. The native arteriovenous (AV) ﬁstula is the gold standard of access to the blood stream for patients on hemodialysis (HD), and its frequent complication is thrombosis. This study aimed to determine the alterations of platelet indices in hemodialysis patients with AV ﬁstula thrombosis. Methods The clinical cross-sectional, descriptive and comparative study included 100 patients, of both sexes, average age from 20 to 65 years of age, who are admitted to, in the period of four years, the Clinic of Hemodialysis, University Clinical Center Sarajevo (UCCS). Patients were divided in two groups on basis of established AV ﬁstula thrombosis. The study group included 34 patients with conﬁrmed AV ﬁstula thrombosis. The control group included 66 patients without AV ﬁstula thrombosis. The venous blood sample was collected prior to the hemodialysis procedure. Results The mean PLT (185.66 ± 60.26 × 10e9/L vs. 231.62 ± 65.56 × 10e9/L) was signiﬁcantly lower (p = .001), while the mean MPV (8.48 ± 0.72 vs. 6.69 ± fL 0.52 ﬂ) was signiﬁcantly higher (p = .0001) in patients undergoing chronic hemodialysis with thrombosis of AV ﬁstula in relation to the control group. The optimal cut-off value for PLT in differentiating patients on chronic hemodialysis with established thrombosis of AV ﬁstula amounted to 180.0 × 10e9/L with a sensitivity 81.5%, speciﬁcity 55.9%, positive predictive value 77.9%, negative predictive value 61%. By using a cut-off value 7.395 fL for MPV, sensitivity was 97.1%, speciﬁcity was 95%, positive predictive value was 97%, negative predictive value was 98% in differentiating patients on chronic hemodialysis with established thrombosis of AV ﬁstula. Conclusions Platelet counts and mean platelet volume can be used as effective biomarkers of arteriovenous ﬁstula thrombosis in patients undergo- ing chronic hemodialysis treatment, noting that there is a greater Abstracts / Clinica Chimica Acta 493 (2019) S379–S433