Diagnostic value of different methods for assessing calcemia in primary and secondary hyperparathyroidism

Introduction. Differential diagnosis of primary and secondary hyperparathyroidism is crucial for determining treatment tactics. Diagnosis directly depends on the assessment of calcemia, for which the determination of total, ionized, and albumin-adjusted calcium is used. However, the diagnostic value of various methods for assessing calcemia remains a subject of debate.

Aim. To compare the effectiveness of calcemia assessment methods in the differential diagnosis of primary and secondary hyperparathyroidism.

Materials and methods. The study evaluated the diagnostic informativeness of various methods for determining serum calcium (total; ionized, estimated by calculation; adjusted for albumin level), taking into account their sensitivity, specificity, and predictive value for diagnosing the normocalcemic variant of PHPT (nPHPT) among patients hospitalized at the Department of Parathyroid Pathology and Mineral Metabolism Disorders of the Federal State Budgetary Institution “National Medical Research Center for Endocrinology named after Academician I.I. Dedov” of the Ministry of Health of Russia from 2018 to 2024. An additional analysis of the clinical and laboratory characteristics of nPHPT compared to patients with secondary hyperparathyroidism (SHPT) was conducted. Statistical analysis was performed using the STATISTICA 12 software package (StatSoft, Inc.). ROC analysis was performed to analyze the diagnostic value of the studied methods.

Results. The frequency of the normocalcemic variant of primary hyperparathyroidism was 6.7%. No significant differences from secondary hyperparathyroidism were found in the main clinical and biochemical parameters. Total and albuminadjusted calcium proved to be the most informative for diagnosis, while ionized calcium, estimated by calculation, showed less value.

Conclusions. For the differential diagnosis of primary and secondary hyperparathyroidism, total and albumin-adjusted calcium levels are of the greatest value and can be considered as priority methods for assessing calcemia in clinical practice.

1. Peacock M. Calcium metabolism in health and disease. Clin J Am Soc Nephrol. 2010;5(Suppl. 1):S23–S30. https://doi.org/10.2215/CJN.05910809.

2. Osterhoff G, Morgan EF, Shefelbine SJ, Karim L, McNamara LM, Augat P. Bone mechanical properties and changes with osteoporosis. Injury. 2010;5(Suppl. 1):S23–S30. https://doi.org/10.1016/S0020-1383(16)47003-8.

3. Brown EM. Extracellular Ca2+ sensing, regulation of parathyroid cell function, and role of Ca2+ and other ions as extracellular (first) messengers. Physiol Rev. 1991;71(2):371–411. https://doi.org/10.1152/physrev.1991.71.2.371.

4. Baird GS. Ionized calcium. Clin Chim Acta. 2011;412(9-10):696–701. https://doi.org/10.1016/j.cca.2011.01.004.

5. Flowers KC, Shipman KE, Shipman AR, Gittoes NJL. Investigative algorithms for disorders causing hypercalcaemia and hypocalcaemia: a narrative review. J Lab Prec Med. 2024;9:27. https://doi.org/10.21037/jlpm-24-6.

6. Wang S, McDonnell EH, Sedor FA, Toffaletti JG. pH effects on measurements of ionized calcium and ionized magnesium in blood. Arch Pathol Lab Med. 2002;126(8):947–950. https://doi.org/10.5858/2002-126-0947-PEOMOI.

7. Cheng HP, Wei S, Wei LP, Verkhratsky A. Calcium signaling in physiology and pathophysiology. Acta Pharmacol Sin. 2006;27(7):767–772. https://doi.org/10.1111/j.1745-7254.2006.00399.x.

8. Goltzman D, Mannstadt M, Marcocci C. Physiology of the Calcium-Parathyroid Hormone-Vitamin D Axis. In: GiustinaA, Bilezikian JP (eds.). Vitamin D in Clinical Medicine. Basel, S.Karger AG; 2018, vol. 50, pp. 1–15. https://doi.org/10.1159/000486060.

9. Cusano NE, Cetani F. Normocalcemic primary hyperparathyroidism. Arch Endocrinol Metab. 2022;66(5):666–677. https://doi.org/10.20945/2359-3997000000556.

10. Baranova IA, Zykova TA. Normocalcemic primary hyperparathyroidism – "new era" in diagnosis of an old disease. Problemy Endokrinologii. 2017;63(4): 236–244. (In Russ.) https://doi.org/10.14341/probl2017634236-244.

11. Mokrysheva NG, Eremkina AK, Elfimova AR, Kovaleva EV, Miliutina AP, Bibik EE et al. The Russian registry of primary hyperparathyroidism, latest update. Front Endocrinol. 2023;14:1203437. https://doi.org/10.3389/fendo.2023.1203437.

12. Vashist SK. Point-of-Care Diagnostics: Recent Advances and Trends. Biosensors. 2017;7(4):62. https://doi.org/10.3390/bios7040062.

13. Lyu Y, Gan S, Bao Y, Zhong L, Xu J, Wang W et al. Solid-Contact Ion-Selective Electrodes: Response Mechanisms, Transducer Materials and Wearable Sensors. Membranes. 2020;10(6):128.https://doi.org/10.3390/membranes10060128.

14. Boink AB, Buckley BM, Christiansen TF, Covington AK, Maas AH, MullerPlathe O et al. IFCC recommendation on sampling, transport and storage for the determination of the concentration of ionized calcium in whole blood, plasma and serum. J Automat Chem. 1991;13(5):235–239. https://doi.org/10.1155/S1463924691000391.

15. Grzych G, Roland E, Beauvais D, Maboudou P, Lippi G. Leukocytosis interference in clinical chemistry: Shall we still interpret test results without hematological data? J Med Biochem. 2020;39(1):66–71. https://doi.org/10.2478/jomb-2019-0005.

16. Toffaletti J, Blosser N, Kirvan K. Effects of storage temperature and time before centrifugation on ionized calcium in blood collected in plain vacutainer tubes and silicone-separator (SST) tubes. Clin Chem. 1984;30(4):553–556. https://doi.org/10.1093/clinchem/30.4.553.

17. Haverstick DM, Brill LB, 2nd, Scott MG, Bruns DE. Preanalytical variables in measurement of free (ionized) calcium in lithium heparin-containing blood collection tubes. Clin Chim Acta. 2009;403(1-2):102–104. https://doi.org/10.1016/j.cca.2009.01.026.

18. Kallner A. Preanalytical procedures in the measurement of ionized calcium in serum and plasma. Eur J Clin Chem Clin Biochem. 1996;34(1):53–58. https://doi.org/10.1515/cclm.1996.34.1.53.

19. Barth JH, Fiddy JB, Payne RB. Adjustment of serum total calcium for albumin concentration: effects of non-linearity and of regression differences between laboratories. Ann Clin Biochem. 1996;33(1):55–58. https://doi.org/ 10.1177/000456329603300108.

20. Phillips P, Pain R. Correcting the calcium. Br Med J. 1977;1(6074):1473. https://doi.org/10.1136/bmj.1.6074.1473-a.

21. Tee MC, Holmes DT, Wiseman SM. Ionized vs serum calcium in the diagnosis and management of primary hyperparathyroidism: which is superior? Am J Surg. 2013;205(5):591–596; d https://doi.org/10.1016/j.amjsurg.2013.01.017.

22. Ridefelt P, Helmersson-Karlqvist J. Albumin adjustment of total calcium does not improve the estimation of calcium status. Scand J Clin Lab Invest. 2017;77(6):442–447. https://doi.org/10.1080/00365513.2017.1336568.

23. Alhenc-Gelas M, Lefevre G, Bachmeyer C, M'Bappe P, Ouahabi S, Grateau G et al. Poor performance of albumin or protein-adjusted plasma calcium to diagnose dyscalcemia in hospitalized patients: A confirmatory study in a general internal medicine department. Rev Med Interne. 2022;43(4):206–211. https://doi.org/10.1016/j.revmed.2021.11.006.

24. Pawade YR, Ghangale SS, Dahake HS. Albumin-adjusted calcium: Are previously published regression equations reliable for your laboratory? – A pilot study. Int J Med Sci Public Health. 2013;2(2):217–222. https://doi.org/10.5455/ijmsph.2013.2.209-214.

25. Dedov II, Melnichenko GA, Mokrysheva NG, Andreeva EN, Antsiferov MB, Beltsevich DG et al. Draft of clinical guidelines for the diagnosis and treatment of primary hyperparathyroidism in adult patients. Endocrine Surgery. 2022;16(4):5–54. (In Russ.) https://doi.org/10.14341/serg12790.

26. Bilezikian JP, Khan AA, Silverberg SJ, Fuleihan GE, Marcocci C, Minisola S et al. Evaluation and Management of Primary Hyperparathyroidism: Summary Statement and Guidelines from the Fifth International Workshop. J Bone Miner Res. 2022;37(11):2293–2314. https://doi.org/10.1002/jbmr.4677.

27. Mamedova EO, Golounina OO, Belaya ZE. Albumin adjustment of total serum calcium – is it worth doing? Problemy Endokrinologii. 2024;70(6):45–61. (In Russ.) https://doi.org/10.14341/probl13503.

28. Kabadi UM. Low 25-Hydroxyvitamin D in Primary Hyperparathyroidism: Enhanced Conversion Into 1,25-Hydroxyvitamin D May Not Be "True" Deficiency. JBMR Plus. 2020;4(11):e10415. https://doi.org/10.1002/jbm4.10415.

29. Meng L, Su C, Shapses SA, Wang X. Total and free vitamin D metabolites in patients with primary hyperparathyroidism. J Endocrinol Invest. 2022;45(2):301–307. https://doi.org/10.1007/s40618-021-01633-1.

30. Clements MR, Davies M, Fraser DR, Lumb GA, Mawer EB, Adams PH. Metabolic inactivation of vitamin D is enhanced in primary hyperparathyroidism. Clin Sci. 1987;73(6):659–664. https://doi.org/10.1042/cs0730659.

31. Walker MD, Bilezikian JP. Vitamin D and primary hyperparathyroidism: more insights into a complex relationship. Endocrine. 2017;55(1):3–5. https://doi.org/10.1007/s12020-016-1169-1.

32. Wang X, Sheng Z, Meng L, Su C, Trooskin S, Shapses SA. 25-Hydroxyvitamin D and Vitamin D Binding Protein Levels in Patients With Primary Hyperparathyroidism Before and After Parathyroidectomy. Front Endocrinol. 2019;10:171. https://doi.org/10.3389/fendo.2019.00171.

33. Desgagnes N, King JA, Kline GA, Seiden-Long I, Leung AA. Use of AlbuminAdjusted Calcium Measurements in Clinical Practice. JAMA Netw Open. 2025;8(1):e2455251. https://doi.org/10.1001/jamanetworkopen.2024.55251.

34. Nordenstrom E, Katzman P, Bergenfelz A. Biochemical diagnosis of primary hyperparathyroidism: Analysis of the sensitivity of total and ionized calcium in combination with PTH. Clin Biochem. 2011;44(10-11):849–852. https://doi.org/10.1016/j.clinbiochem.2011.04.002.

35. Pekar JD, Grzych G, Durand G, Haas J, Lionet A, Brousseau T et al. Calcium state estimation by total calcium: the evidence to end the never-ending story. Clin Chem Lab Med. 2020;58(2):222–231. https://doi.org/10.1515/cclm-2019-0568.

36. Ong GS, Walsh JP, Stuckey BG, Brown SJ, Rossi E, Ng JL et al. The importance of measuring ionized calcium in characterizing calcium status and diagnosing primary hyperparathyroidism. J Clin Endocrinol Metab. 2012;97(9):3138–3145. https://doi.org/10.1210/jc.2012-1429.