A patient has total calcium 7.6 mg/dL, albumin 2.0 g/dL, and ionized calcium within the reference interval. Which explanation best accounts for the results?
1The patient has severe ionized hypocalcemia due to parathyroid hormone deficiency
2Low albumin decreased the protein-bound fraction and produced a low total calcium result✓ 정답
3EDTA contamination in the sample tube selectively increased ionized calcium measurement
4Hyperalbuminemia caused calcium to shift into cells, lowering total serum calcium levels
해설
A substantial portion of total calcium is albumin-bound. Hypoalbuminemia can lower total calcium while biologically active ionized calcium remains normal; ionized measurement or an appropriate correction is used to confirm true hypocalcemia.