Evidence-based cutoffs for total and adjusted calcium: a major factor in detecting severe hypo- and hypercalcemia

TY - JOUR

T1 - Evidence-based cutoffs for total and adjusted calcium: a major factor in detecting severe hypo- and hypercalcemia

AU - Schmidt, Maria

AU - Steinbach, Daniel

AU - Federbusch, Martin

AU - Tönjes, Anke

AU - Isermann, Berend

AU - Kaiser, Thorsten

AU - Eckelt, Felix

N1 - © 2023 the author(s), published by De Gruyter, Berlin/Boston.

PY - 2024/6/25

Y1 - 2024/6/25

N2 - OBJECTIVES: Severe hypo- and hypercalcemia are common and urgent treatment is recommended. Free calcium (fCa) is the gold standard but needs blood gas tests with challenging preanalytics. Total calcium (tCa) and calculated adjusted calcium (aCa) are readily available, but their interpretation is hampered by identical tCa and aCa cutoffs, laborious local aCa calculation and difficult comparability of calcium biomarkers.METHODS: Laboratory results from University Medicine Leipzig were evaluated over a five-year period (236,274 patients). A local aCa equation was derived by linear least squares regression, the agreement between fCa, tCa and aCa assessed with Cohen's κ and decision thresholds derived by this indirect method.RESULTS: The local aCa equation was created from data of 9,756 patients, each with one paired measurement of tCa, fCa and albumin. Derived aCa cutoffs (1.95/3.15 mmol/L) differ markedly from derived tCa cutoffs (1.6/2.9 mmol/L) and severe hypo- and hypercalcemia can be more accurately assessed by aCa (κ=0.489, 0.812) than by tCa (κ=0.445, 0.744). Comparing our approach to standard care (tCa, literature cutoff), a total 3,250 of 3,680 (88.3 %) misclassified measurements were correctly classified when using aCa with evidence-based cutoffs.CONCLUSIONS: Optimized cutoffs for aCa and tCa hold great potential for improved patient care. Locally derived aCa equations differ mostly in the chosen mean normal calcium and provide minimal overall improvement, but entail a close examination of the used cutoffs before application.

AB - OBJECTIVES: Severe hypo- and hypercalcemia are common and urgent treatment is recommended. Free calcium (fCa) is the gold standard but needs blood gas tests with challenging preanalytics. Total calcium (tCa) and calculated adjusted calcium (aCa) are readily available, but their interpretation is hampered by identical tCa and aCa cutoffs, laborious local aCa calculation and difficult comparability of calcium biomarkers.METHODS: Laboratory results from University Medicine Leipzig were evaluated over a five-year period (236,274 patients). A local aCa equation was derived by linear least squares regression, the agreement between fCa, tCa and aCa assessed with Cohen's κ and decision thresholds derived by this indirect method.RESULTS: The local aCa equation was created from data of 9,756 patients, each with one paired measurement of tCa, fCa and albumin. Derived aCa cutoffs (1.95/3.15 mmol/L) differ markedly from derived tCa cutoffs (1.6/2.9 mmol/L) and severe hypo- and hypercalcemia can be more accurately assessed by aCa (κ=0.489, 0.812) than by tCa (κ=0.445, 0.744). Comparing our approach to standard care (tCa, literature cutoff), a total 3,250 of 3,680 (88.3 %) misclassified measurements were correctly classified when using aCa with evidence-based cutoffs.CONCLUSIONS: Optimized cutoffs for aCa and tCa hold great potential for improved patient care. Locally derived aCa equations differ mostly in the chosen mean normal calcium and provide minimal overall improvement, but entail a close examination of the used cutoffs before application.

KW - Humans

KW - Hypercalcemia/blood

KW - Calcium/blood

KW - Hypocalcemia/diagnosis

KW - Female

KW - Male

KW - Middle Aged

KW - Aged

KW - Biomarkers/blood

KW - Adult

KW - Reference Values

U2 - 10.1515/cclm-2023-0805

DO - 10.1515/cclm-2023-0805

M3 - SCORING: Journal article

C2 - 38095218

VL - 62

SP - 1367

EP - 1375

JO - CLIN CHEM LAB MED

JF - CLIN CHEM LAB MED

SN - 1434-6621

IS - 7

ER -