Pseudohypocalcemia in Cancer Patients: A Recommendation for the Postanalytical Correction of Serum Calcium in Patients with Hypoalbuminemia

To the Editor:Critical value reporting is a regulatory responsibility of all clinical laboratories. Efforts to reduce the number of calls that are not truly critical could have a significant impact on the clinical laboratory, medical team work flow, and patient care. At Memorial Sloan Kettering Cancer Center (MSKCC), 1 the clinical laboratory makes approximately 30 000 critical value calls a year with only 9 analytes accounting for nearly 75% of these calls. Calcium is one frequently called analyte, responsible for approximately 1000 critical calls a year.We evaluated the findings of critical hypocalcemia [critical value: u003c6.5 mg/dL (u003c1.62 mmol/L); reference interval (RI): 8.5–10.5 mg/dL (2.12–2.62 mmol/L)] in cancer patients with albumin concentrations u003c4.0 g/dL (RI: 4.0–5.2 g/dL). At MSKCC between 2013 and 2015, 38% of albumin results from a comprehensive metabolic panel (CMP) were below 4.0 g/dL. There are several published formulae to correct serum calcium in patients with hypoalbuminemia. The Payne formula {corrected total calcium (mg/dL) = total calcium (mg/dL) + 0.8 × [4.0 − albumin (g/dL)]} is the most widely used and based on the observation that each 1-g/dL reduction in albumin u003c4.0 g/dL …