1. NYC Health . https://www1.nyc.gov/site/doh/covid/covid-19-main.page. https://www1.nyc.gov/site/doh/covid/covid-19-main.page (accessed April 2021)
Google Scholar2. Di Filippo, L, Formenti, AM, Rovere-Querini, P, et al. Hypocalcemia is highly prevalent and predicts hospitalization in patients with COVID-19. Endocrine 2020; 68: 475–478. DOI: 10.1007/s12020-020-02383-5.
Google Scholar | Crossref | Medline3. Elezagic, D, Johannis, W, Burst, V, et al. Venous blood gas analysis in patients with COVID-19 symptoms in the early assessment of virus positivity. J Lab Med 2021; 45: 27–30. DOI: 10.1515/labmed-2020-0126.
Google Scholar | Crossref4. Cappellini, F, Brivio, R, Casati, M, et al. Low levels of total and ionized calcium in blood of COVID-19 patients. Clin Chem Lab Med (Cclm) 2020; 58: e171–e173. DOI: 10.1515/cclm-2020-0611.
Google Scholar | Crossref | Medline5. Calvi, LM, Bushinsky, DA. When is it appropriate to order an ionized calcium? J Am Soc Nephrol. 2008; 19: 1257–1260. DOI: 10.1681/asn.2007121327.
Google Scholar | Crossref | Medline | ISI6. Anonymous. Reducing high cost ionized calcium testing. J Hosp Med 2014; 9 (suppl. 2): 254. https://shmabstracts.org/abstract/reducing-high-cost-ionized-calcium-testing/ (accessed April 2021).
Google Scholar7. Farmer, R . Costs and stewardship of laboratory tests in the capital health district. Dalhousie Med J 2015; 42: 3–7.
Google Scholar | Crossref8. Hamroun, A, Pekar, J-D, Lionet, A, et al. Ionized calcium: analytical challenges and clinical relevance. J Lab Precision Med 2020; 5: 22. DOI: 10.21037/jlpm-20-60.
Google Scholar | Crossref9. Anonymous . Correcting the calcium. Br Med J 1977; 1: 326.
Google Scholar10. Dickerson, R, Alexander, K, Minard, G, et al. Accuracy of methods to estimate ionized and “corrected” serum calcium concentrations in critically ill multiple trauma patients receiving specialized nutrition support. J Parenter Enteral Nutr 2004; 28: 133–141. DOI: 10.1177/0148607104028003133.
Google Scholar | Crossref | Medline11. Ladenson, JH, Lewis, JW, Boyd, JC. Failure of total calcium corrected for protein, albumin, and pH to correctly assess free calcium status. J Clin Endocrinol Metab 1978; 46: 986–993. DOI: 10.1210/jcem-46-6-986.
Google Scholar | Crossref | Medline | ISI12. Pekar, J-D, Grzych, G, Durand, G, et al. Calcium state estimation by total calcium: the evidence to end the never-ending story. Clin Chem Lab Med 2020; 58: 222–231. DOI: 10.1515/cclm-2019-0568.
Google Scholar | Crossref | Medline13. Yap, E, Roche-Recinos, A, Goldwasser, P. Predicting ionized hypocalcemia in critical care: an improved method based on the anion gap. J Appl Lab Med 2020; 5: 4–14. DOI: 10.1373/jalm.2019.029314.
Google Scholar | Crossref | Medline14. Jassam, N, Thomas, A, Hayden, K, et al. The impact of the analytical performance specifications of calcium and albumin on adjusted calcium. Ann Clin Biochem 2020; 57: 382–388. DOI: 10.1177/0004563220944426.
Google Scholar | SAGE Journals | ISI15. Nordin, BE, Need, AG, Hartley, TF, et al. Improved method for calculating calcium fractions in plasma: reference values and effect of menopause. Clin Chem 1989; 35: 14–17.
Google Scholar | Crossref | Medline | ISI16. Takano, S, Kaji, H, Hayashi, F, et al. A calculation model for serum ionized calcium based on an equilibrium equation for complexation. Anal Chem Insights 2012; 7: ACI.S9681. DOI: 10.4137/aci.S9681.
Google Scholar | SAGE Journals17. Danner, J, Ridgway, MD, Rubin, SI, et al. Development of a multivariate predictive model to estimate ionized calcium concentration from serum biochemical profile results in dogs. J Vet Intern Med 2017; 31: 1392–1402. DOI: 10.1111/jvim.14800.
Google Scholar | Crossref | Medline18. Moons, KGM, Kengne, AP, Grobbee, DE, et al. Risk prediction models: II. External validation, model updating, and impact assessment. Heart 2012; 98: 691–698. DOI: 10.1136/heartjnl-2011-301247.
Google Scholar | Crossref | Medline | ISI19. DeJesus, J . Cuomo designates university hospital of Brooklyn as a COVID-19 only facility, 2020. https://brooklynreporter.com/2020/03/cuomo-designates-university-hospital/ (accessed April 2021)
Google Scholar20. https://qxmd.com/calculate/calculator_704/predicting-ionized-hypocalcemia-in-critical-care.
Google Scholar21. Hanley, JA, McNeil, BJ. A method of comparing the areas under receiver operating characteristic curves derived from the same cases. Radiology 1983; 148: 839–843. DOI: 10.1148/radiology.148.3.6878708.
Google Scholar | Crossref | Medline | ISI22. Collins, GS, Reitsma, JB, Altman, DG, et al. Transparent reporting of a multivariable prediction model for individual prognosis or diagnosis (TRIPOD): the TRIPOD Statement. BMC Med 2015; 13: 1. DOI: 10.1186/s12916-014-0241-z.
Google Scholar | Crossref | Medline23. Weaving, G . Calcium — An adjustment too far or not far enough? Ann Clin Biochem 2020; 57: 401–403. DOI: 10.1177/0004563220961751.
Google Scholar | SAGE Journals24. Altman, DG, Gardner, MJ. Calculating confidence intervals for regression and correlation. Br Med J (Clin Res Ed 1988; 296: 1238–1242. DOI: 10.1136/bmj.296.6631.1238.
Google Scholar | Crossref | Medline25. Roth, JV . Prediction interval analysis is underutilized and can be more helpful than just confidence interval analysis. J Clin Monit Comput 2009; 23: 181–183. DOI: 10.1007/s10877-009-9165-0.
Google Scholar | Crossref | Medline26. Sehgal, AR . Race and the false precision of glomerular filtration rate estimates. Ann Intern Med 2020; 173: 1008–1009. DOI: 10.7326/m20-4951.
Google Scholar | Crossref | Medline