Albumin-Corrected Calcium
Serum calcium corrected for albumin concentration.
About this calculator
Albumin-corrected calcium estimates true calcium when albumin is low. About 40% of total calcium is albumin-bound; the remaining 60% is ionized (active) calcium and calcium bound to other proteins and anions. When albumin drops, total calcium falls but ionized stays normal. Payne formula (Br Med J, 1973). Corrected Ca = measured Ca + 0.8 × (4 – albumin in g/dL). In mmol/L units: Ca + 0.02 × (40 – albumin in g/L). Clinical use. In hypoalbuminemia (nephrotic syndrome, cirrhosis, severe infection, burns, malabsorption) total calcium is falsely low. Without correction hypocalcemia is misdiagnosed and calcium supplements lead to hypercalciuria and nephrocalcinosis. The corrected value is a rough approximation of ionized calcium. Interpretation (adult reference). 2.15-2.55 mmol/L (8.5-10.2 mg/dL). <2.1 – hypocalcemia (tetany, paresthesias, Chvostek and Trousseau signs, QT prolongation). >2.7 – hypercalcemia (nephrolithiasis, bone pain, nausea, psychosis, coma in severe cases). Limitations. Payne is inaccurate in severe hypoalbuminemia (<20 g/L), critical illness, acidosis and alkalosis. Gold standard – direct ionized calcium (normal 1.15-1.33 mmol/L). KDIGO 2017 and EASL 2018 recommend measuring ionized Ca in significant hypoalbuminemia and ICU, not relying on calculated formulas.
Source
Formula version: payne-1973-v1
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