1. Universidad Aut�noma de Nuevo Le�n, Department of Biochemistry and Molecular Medicine, School of Medicine and University Hospital ‘Dr. Jos� E. Gonz�lez’, Monterrey, Nuevo Le�n 64460, M�xico
2. Institutional Core Laboratories, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
3. Universidad Aut�noma de Nuevo Le�n, Service of Rheumatology, School of Medicine and University Hospital ‘Dr. Jos� E. Gonz�lez’, Monterrey, Nuevo Le�n 64460; 4Vitag�nes, SA de CV, Monterrey, Nuevo Le�n 64630, M�xico