Calcium Phosphate Product and Its Clinical Significance

Definition and Calculation

The calcium-phosphate product is a calculated value obtained by multiplying serum calcium by serum phosphorus, used to assess risk for vascular and soft tissue calcification in chronic kidney disease, with values above 55 mg²/dL² associated with increased mortality and calcification risk, according to the American Journal of Kidney Diseases 1, 2
When using total serum calcium, the traditional threshold values are 55 mg²/dL² and 72 mg²/dL², as recommended by the American Journal of Kidney Diseases 1, 3

The Ca × P product serves as a surrogate marker for the risk of extraskeletal calcification and mortality, particularly in patients with chronic kidney disease, as stated by the American Journal of Kidney Diseases and the National Kidney Foundation 1, 2

Patients with Ca × P product above 72 had a 34% higher relative risk of death compared to those with values between 42-52, according to the American Journal of Kidney Diseases 1, 4
For every 10-unit increase in Ca × P product, there is an 11% increase in relative risk of death, as reported by the American Journal of Kidney Diseases 1, 5

Ca × P values above 55 are associated with increased risk of soft tissue and vascular calcification, as stated by the American Journal of Kidney Diseases and the National Kidney Foundation 1, 2, 3
Hemodialysis patients with Ca × P of 63 ± 13 had significantly higher mitral annular calcification compared to those with 56 ± 13, according to the American Journal of Kidney Diseases 1, 5

The K/DOQI guidelines recommend maintaining Ca × P product below 55 mg²/dL² to minimize calcification risk and potentially reduce mortality, as stated by the National Kidney Foundation and the American Journal of Kidney Diseases 1, 7, 2, 3

Reduce phosphorus intake through dietary restriction and phosphate binders when Ca × P product exceeds 55, as recommended by the National Kidney Foundation and the American Journal of Kidney Diseases 2, 8
Limit calcium-based phosphate binders to under 1,500 mg/day of elemental calcium to avoid excessive calcium load, as stated by the American Journal of Kidney Diseases and the National Kidney Foundation 9, 8
Consider non-calcium phosphate binders when hypercalcemia exists or total calcium intake becomes excessive, as recommended by the American Journal of Kidney Diseases and the National Kidney Foundation 9, 2

Not all patients with elevated Ca × P develop calcification, suggesting other factors play important roles, as stated by the American Journal of Kidney Diseases and the National Kidney Foundation 1, 7
Focusing solely on Ca × P without considering individual calcium and phosphorus levels can lead to suboptimal management, as recommended by the National Kidney Foundation and the American Journal of Kidney Diseases 2