1. Servei de Medicina Interna de Reus C, St. Llorenc s/n 43201, Reus, Spain
2. Departments of Human Metabolism and Genetics, St. Bartholomew's Hospital, London EC1A 7BE, U.K.
3. Center of Internal Medicine and Biological Chemistry, La Sapienza University, Rome, Italy
4. Clinical Chemistry, Albert Ludwigs Universitat, Freiburg, Germany