Letter from Dr. D. B. L. McClelland, Edinburgh and South-East Scotland Regional Blood Transfusion Service to Dr. C. Ludlam, Royal Infirmary Edinburgh, cc Dr. R. Perry and Dr. J. D. Cash, re [GRO-A] - Hepatitis B Surface Antigen (HBsAg) Positive, checking of Factor IX batches with urgency and request for names of patients where Hepatitis B is suspected/ proven to be transmitted by Factor IX