CALCIUM, MAGNESIUM, AND PHOSPHORUS - EMERGENCY DEPARTMENT TESTING YIELD

Objectives: To investigate how often the ED ordering of stat serum cal cium (Ca+2), magnesium (Mg+2), and phosphorus (PO4-3) levels affected clinical treatment; to define the diagnoses of patients for whom Ca+2, Mg+2, and PO4-3 measurements did affect clinical therapy; and to sugg est guidelines for more appropriate ordering of these laboratory tests . Methods: A retrospective chart review was performed in an academic t eaching hospital. Ail adult ED patients who had Ca+2, Mg+2, or PO4-3 l aboratory testing during the 9-month study period were included and ev aluated for potential clinical impact of an abnormal Ca+2, Mg+2, or PO 4-3 laboratory test. Results: 1,477 patients had Ca+2, Mg+2, or PO4-3 measured while in the ED during the study period. Of these, 260 patien ts (17.6%) had a total of 312 abnormal Ca+2, Mg+2, or PO4-3 values as defined by results exceeding +/-15% of normal reference values. Of the se, only 5 patients (0.3%) received treatment for abnormal values in t he ED, while 75 patients (5.1%) were treated once admitted to the hosp ital. In this study, the only diagnostic groups to whom significant tr eatment was administered were diabetic patients (Ca+2 and PO4-3); alco holic patients (Mg+2); and renal failure patients (Ca+2, Mg+2, and PO4 -3). Conclusion: These results suggest that stat Ca+2, Mg+2, and PO4-3 levels seldom affect clinical treatment in the ED. The frequency of o rdering these tests may be reduced by obtaining Ca+2, Mg+2, or PO4-3 m easurements only for patients known to be at risk for such abnormaliti es, based on their existing or suspected diagnoses. The authors sugges t obtaining these tests, when indicated, on a ''non-stat'' basis, with the subsequent laboratory results becoming available in-hospital, whe re treatment is more likely to occur.