Letter from Alison Smithies to Ms Coker re 'Safety of Factor VIII and Factor IX Produced at the Blood Products Laboratory (BPL), Elstree'. The letter sets out the process of heated Factor products and the that there might be partially screened factor products from unscreened donors at BPL and the potential risk to still transmit NANB Hepatitis in heat treated products, whilst it appears to be safe from HIV.