Validation of synthetic M-protein materials for external quality assessment: homogeneity, commutability, and stability - Moniek M. Bioch; Theo Rispens; Corrie M. de Kat Angelino; Anke J. ten Haaken-Meijer; Miranda van Berkel; Marc H.M. Thelen; Joannes F.M. Jacobs (Clinical Chemistry and Laboratory Medicine (CCLM), 2026)