The diagnosis of acquired von willebrand disease (VWD) is a challenge for laboratory investigation. Alloantibodies may present different kinetics of FVW neutralization and thus generate inconclusive results. Studies have shown that the sensitivity and specificity of new methodologies applied for the assessment of FVW activity are distinct and confer different interpretations in the investigation of type 1 and type 2 VWD. The guideline for VWD published in collaboration between ASH, ISTH, NHF and WFH published in 2021, recommends that the tests, VWF:GPIbM (Spontaneous FVW binding _Frag GPIbα mutant) and VWF:GPIbR (FVW-Fragment GPIbα) should be used instead of the classical ristocetin cofactor test. More recent methodologies assessing FVW activity by chemiluminescence have not yet been evaluated.

To evaluate the concordance of the VWF:GPIbR test recommended by international guideline (ASH, ISTH, NHF and WFH 2021) with two different tests, ristocetin cofactor and collagen, which assess FVW activity by chemiluminescence methodology in the investigation of congenital and acquired VWD. Material and method: the study was carried out in the hemostasis laboratory of the blood center UNICAMP. Samples from patients under investigation for congenital and acquired VWD were collected between January and August 2023. The clinical data as well as the bleeding score of the patients were evaluated and collected. The VWF:GPIbR (VWF-Fragment GPIbα) test was performed on the TOP 550 coagulometer and the ristocetin cofactor (Cof-Chemil) and collagen (Col-Chemil) tests by chemiluminescence was performed on the Bioflash. All reagents and equipment are Hemosil-Werfen company. Results and discussion: In this study 84 patient samples were included. The results median of the FVW activitywere: 38.7% (0-271%), 52.3% (0.5-200%), 66.5% (0.5-200%) for VWF:GPIbR, Cof-Chemil, Col-Chemil, respectively. In the correlation assessment VWF:GPIbR and Col-Chemil showed better results r 0.8232 (0.7363-0.8833) p < 0.0001. Remarkably, 12 samples from patients diagnosed with Miledysplastic Syndrome, Myelofibrosis and Polycythemia Vera under investigation for acquired von Willebrand disease did not show any concordance between results. The VWF:GPIbR test underestimated the results for FVW activity which led to misinterpretation for possible neutralization of FVW activity by neutralizing antibodies, while the chemiluminescence-based tests showed results at normal levels. Conclusion: Although the VWF:GPIbR test presents adequate results for the investigation of VWD and is recommended by international guidelines, caution should be taken in the investigation of acquired VWD. New chemiluminescence-based tests have been shown to have greater sensitivity and specificity for this type of investigation.