6 Yrs old male child having frequent spontaneous episodic nasal bleeding every 2-3 months, relieved by pressure with adrenaline gauge. No significant birth, family, past history. O/E : Joints are normal, growth normal. Lab.

reports: Hb-11.2, total WBC-7600, Platelets: 4.0 lakhs Bt, ct, pt, aptt, tt normal. At present he is on Vit. C What should be next step? VWF assay?