Table 1.

Classification framework for the CKD-MBD including standard and alternative metrics for assessment, adapted from KDIGO 2006 and 2009 guidelines. Italicized metrics are not discussed specifically in this review.

CKD-MBD Classificationa	Clinical Features	Standard Metrics	Investigational or Alternative Metrics
Laboratory Abnormalities (L)			FGF23
	Hyperphosphatemia	Phosphorus	DKK1
	Secondary Hyperparathyroidism	Intact PTH	Sclerostin
	Hypocalcemia	Calcium (total and ionized)	Soluble klotho
	Vitamin D Deficiency	25- and 1,25-hydroxyvitamin D	Activin-A
	Acidemia	Bicarbonate	Tartrate-resistant acid phosphatase 5b (TRAP-5b)
		Alkaline Phosphatase	Procollagen type 1 N-terminal peptide (P1NP)
			Osteocalcin
Bone Disease (B)	Renal osteodystrophy (based on bone biopsy)	Bone biopsy	Quantitative Ultrasonography
	Osteitis Fibrosa	Turnover (low, normal, high)	High-performance liquid chromatography (HPLC)
	Osteomalacia	Mineralization (normal, abnormal)	Electron microscopy
	Adynamic Done Disease	Volume (low, normal, high)	Micro-CT
	Mild Hyperparathyroid-related Disease	Bone mineral density (DXA) scan	MRI
	Mixed Uremic Osteodystrophy	Bone mineral density (quantitative CT) scan	Radioisotope studies
	Osteoporosis (low bone mineral density)	Plain bone radiographs
	Fractures	Linear growth
	Bone pain
	Bone deformities
	Impaired growth velocity
	Abnormal height
Extraskeletal Calcification (C)	Coronary Artery Calcification	Echocardiography	Multislice or electron beam CT
	Generalized Vascular Calcification	Pulse wave velocity	Cardiac MRI
	Valvular Calcification	Abdominal radiograph
	Vascular Stiffness	Vascular ultrasound
	Systolic/Diastolic Dysfunction
	Joint and Soft Tissue Calcification

^aCKD-MBD categories rarely occur in isolation. The majority of patients with CKD-MBD will be classified as either L, LB, LC, or LBC. For example, a patient with hyperphosphatemia and vascular calcification would be classified as CKD-MBD-LC.