137 Chapter 7 and/or tranexamic acid to reduce bleeding and improve quality of life. Ultimately, by understanding the types of events that lead to bleeding in OI, medical professionals can take appropriate measures to prevent and treat these bleeding events. Is diagnostic testing for bleeding disorders indicated? The tendency to bleed is complex and can be caused by several factors. Previous studies on the tendency to bleed were not conclusive 64,80, but were also carried out during a period in which the laboratory equipment was less advanced. Several mechanisms have been proposed to explain the bleeding tendency in OI. Our theory is that the defective collagen in OI leads to an abnormal structure and function of the vessel wall, resulting in increased fragility and susceptibility to bleeding (Chapter 5). Another hypothesis is that the altered extracellular matrix in OI affects platelet function and activation, leading to impaired haemostasis. However, these theories could not be confirmed by the studies in Chapters 4 and 6. Diagnostic tests were performed in Chapters 4 and 6. The screening of a random cohort was first performed to objectify the bleeding tendency in Chapter 4, and later on, based on the bleeding questionnaire in the most frequent bleeders, the possible causes were investigated in the laboratory (Chapter 6). The latter was done to maximize the probability of detection. This is also reflected by the fact that we were able to pick out the people with von Willebrand disease who were expected to be found, based on the background incidence in Dutch society 81. However, in addition to these findings (not related to OI), no specific causes were found in the laboratory that could clearly explain the bleeding tendency in OI. There is also no clear evidence in the literature that a specific laboratory test should be used for measuring the bleeding tendency in OI patients. Therefore, we believe that diagnostic testing is for now not possible. What can be learned from therapeutic considerations in other mild bleeding disorders? As explained in Chapter 5, there are several bleeding events that actually carry a significant risk. In surgery, pregnancy and tooth extraction, bleeding has progressed from being inconvenient to potentially life-threatening. There are many therapeutic considerations in general in the literature for controlling the bleeding in these events. However, they are not written specifically for OI, nor are they based on the underlying problems causing the increased bleeding tendency. This makes them potentially inappropriate and perhaps unnecessary. However, interventions that have little to no side effects can well be used in high-risk events for people with OI, such as the use of desmopressin or desmopressin and/or tranexamic acid for heavy menstrual bleeding (Chapter 5).
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