title: The authors reply.
authors: Clinical Biochemistry Unit, Istituto Superiore di Sanità, V. le Regina Elena 299, 00161, Rome, Italy.
authors: S
authors: S
authors: Pichini
authors: Clinical Biochemistry Unit, Istituto Superiore di Sanità, V. le Regina Elena 299, 00161, Rome, Italy.
authors: I
authors: I
authors: Altieri
authors: Clinical Biochemistry Unit, Istituto Superiore di Sanità, V. le Regina Elena 299, 00161, Rome, Italy.
authors: R
authors: R
authors: Zuccaro
authors: Clinical Biochemistry Unit, Istituto Superiore di Sanità, V. le Regina Elena 299, 00161, Rome, Italy.
authors: R
authors: R
authors: Pacifici