PTH and Marchiafava-Bignami disease: While the 2003 KDOQI guideline suggests maintaining levels between 150 and 300 pg/mL (22), the 2009 KDIGO guideline proposes a broader range of approximately two to nine times the upper normal limit due to assay variability and limited high-quality evidence linking PTH to CKD-MBD-related outcomes (34).