Formula of Levin et al for Predicting Risk of Ischemic Tissue Necrosis (Calciphylaxis)

Parameters:

(1) serum total calcium concentration in mmol/L

(2) serum phosphate concentration in mmol/L

(3) serum alkaline phosphatase concentration in IU/L

(4) serum intact parathyroid hormone (PTH) concentration in ng/L

(5) upper limit to the reference range for intact PTH in ng/L

PTH ratio =

= (serum intact PTH concentration) / (upper limit to the normal reference range)

formula product =

= 2 * (((calcium) * (phosphate)) - 5) * (alkaline phosphatase) * (PTH ratio)

Interpretation:

• A product > 1,000 indicates a high risk for calciphylaxis.

• A value < 1,000 indicates a low risk for calciphylaxis (most patients have values < 0).

Limitations:

• The method and reference range for serum alkaline phosphatase was not stated. There may be considerable variation between institutions for this.