Department of Internal Medicine, University of Pisa, Italy.

Correspondence and requests for reprints to Stefano Taddei, Department of Internal Medicine, University of Pisa, Via Roma, 67, 56100 Pisa, Italy. Tel: +39 50 551110; fax: +39 50 553407; e-mail: [email protected]

Received 6 March 2002

Revised 7 May 2002

Accepted 8 May 2002