Albumin-Corrected Calcium and the Prevalence and Categories of Hypercalcemia in Hospitalized Patients With 1-Year Follow-Up of Undiagnosed Cases

Objective To assess the impact of using corrected calcium versus total calcium on hypercalcemia case detection in hospitalized patients. Methods Patients hospitalized from June 2012 to June 2017 with a corrected calcium level of ≥10.5 mg/dL were identified by medical record review. One-year follow-up data through June 2018 were acquired. Albumin-corrected calcium level was calculated: (4 − albumin concentration in g/dL) × 0.8 + total serum calcium in mg/dL. Results A group of 1067 patients had a corrected calcium level of ≥10.5 mg/dL. The prevalence of hypercalcemia was 0.73% with total calcium and 1.09% with corrected calcium, respectively, with a 49% relative increase. Most patients (62%) had mild hypercalcemia (10.5-11.9 mg/dL); 3.7% had severe hypercalcemia (>14 mg/dL). With corrected calcium, the most common categories of hypercalcemia were malignancy (35.4%), hypercalcemia that was not further evaluated (31.1%), and hyperparathyroidism (22.4%). All patients in the unidentified category had albumin levels <2.8 g/dL. At the 1-year follow–up, 63% of the unidentified cases had normal calcium levels, and 26.8% had mild persistent hypercalcemia. Of those with persisting hypercalcemia at 1 year, 16.8% were diagnosed with hyperparathyroidism. Conclusion Using albumin-corrected calcium resulted in an ∼50% increase in the detection of hypercalcemia cases. Although hypercalcemia resolved in majority of the undiagnosed cases at 1 year, a number of these remained abnormal. Detecting hypercalcemic disorders by correcting for low albumin level can help identify conditions such as hyperparathyroidism. Adding auto-calculated albumin-corrected calcium to routine laboratory tests could be a cost-effective intervention to improve the detection of hypercalcemic disorders.