127 Chapter 6 wall interaction and their control of bleeding time 19. Testing of platelet function comprises a crucial element of haemostasis assessment, particularly for investigations into bleeding and/or bruising. Nowadays, the Platelet Function Assay is the most utilised primary haemostasis-screening test system available 20. It might be useful to monitor PFA-200 results in a larger sample, possibly extended with platelet aggregation tests. Similarly to the study of Leguillier et al.21, we ruled out that bleeding symptoms in patients with OI are associated with VWD based on FVIII and VWF levels, and we confirmed normal levels for VWFag and VWFact in our study population. Although Leguillier et al. 21 recently found a statistical significance for VWFag and VWFact levels between children with a high versus low bleeding score, we could not identify this in our study. Their examination was based on VWF as marker of endothelial dysfunction in vascular disease 21. Despite the thorough patient selection, this study contains several limitations regarding sample size and selection. The study sample was rather small, although the group size of 20 was expected to be sufficient in this explorative study of a rare disease. A more equal male/female distribution between the two opposite groups (low vs. high) would be preferred in future studies. Limiting the self-BAT score of the “low” control group to a maximum of two or three points should be considered. In the current study, two female participants were enrolled in the group with “low” bleeding scores while they scored six on the self-BAT. However, we believe this study still contributes to the sparse knowledge on bleeding tendency in OI patients through the results of extensive performed laboratory tests in 20 OI patients. Conclusion Comparing two opposite OI groups regarding their bleeding scores, both extracted from a large OI population, extensive laboratory testing did not show significant differences between the groups and did not result in finding an underlying mechanism for the reported bleeding problems in OI patients. Interestingly, PFA-200 results were abnormal in 30% of the OI patients. Monitoring PFA-200 results in a larger patient group should be considered in further studies. The results of this study are not conclusive enough to draw up guidelines for clinical practice regarding bleeding tendency in OI patients.
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