Abstract
The United Kingdom Cyclosporin Assessment Scheme has over eight years experience in the measurement of cyclosporin and has over 176 participants World wide. The scheme provides a source of reference material which has been assayed by many laboratories and, thereby, provides external quality assessment for the clinical measurement of cyclosporin. The results also allow the direct comparison of the available analytical methodologies. The data presented are a summary of the results received during the period July 1990 to July 1991, inclusive.