uk-drcog MCQ (SBA): HMB Since Menarche - Bleeding Disorder Screen

A 43-year-old woman presents to the GP requesting investigation for heavy menstrual bleeding. Her periods have always been heavy (since menarche), lasting 8 days with flooding and clots. Her mother also had heavy periods. Her FBC shows haemoglobin 96 g/L and MCV 72 fL. Pelvic examination and ultrasound are normal. Which investigation should be specifically considered given her lifelong history?