1. Department of Medicine, University of Hull, Hull HU16 5JQ, United Kingdom
2. Department of Clinical Biochemistry, Wythenshawe Hospital, Manchester M23 9LT, United Kingdom
3. Department of Medicine, York District General Hospital, York YO31 8HE, United Kingdom
4. Department of Clinical Biochemistry, Hull Royal Infirmary, Anlaby Road, Hull HU3 2JZ, United Kingdom