Agreement of Parathyroid Hormone Status Measured by Intact and Biointact Parathyroid Hormone Assays among Chronic Kidney Disease Patients and Its Correlation with Bone Turnover Parameters

Saidah Madihah Hashim; Tuan Salwani Tuan Ismail; Noor Azlin Azraini Che Soh; Mahaya Che Mat; Zuad Firdaus Rapiah; Noorazliyana Shafii; Nur Karyatee Kassim; Najib Majdi Yaacob

doi:10.21315/mjms2023.30.2.6

Agreement of Parathyroid Hormone Status Measured by Intact and Biointact Parathyroid Hormone Assays among Chronic Kidney Disease Patients and Its Correlation with Bone Turnover Parameters

Malays J Med Sci. 2023 Apr;30(2):69-82. doi: 10.21315/mjms2023.30.2.6. Epub 2023 Apr 18.

Authors

Saidah Madihah Hashim^{1

2}, Tuan Salwani Tuan Ismail², Noor Azlin Azraini Che Soh², Mahaya Che Mat¹, Zuad Firdaus Rapiah³, Noorazliyana Shafii², Nur Karyatee Kassim^{2

4}, Najib Majdi Yaacob⁵

Affiliations

¹ Chemical Pathology Unit, Hospital Raja Perempuan Zainab II, Kelantan, Malaysia.
² Department of Chemical Pathology, School of Medical Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.
³ Nephrology Unit, Department of Medical, Hospital Raja Perempuan Zainab II, Kelantan, Malaysia.
⁴ School of Dental Sciences, Universiti Sains Malaysia, Kelantan, Malaysia.
⁵ Biostatistics and Research Methodology Unit, Universiti Sains Malaysia, Kelantan, Malaysia.

Abstract

Background: This study aimed to determine the agreement between intact parathyroid hormone (iPTH) and biointact parathyroid hormone (bio-PTH) assays and to correlate them with bone markers.

Methods: This cross-sectional study included 180 patients with chronic kidney disease (CKD) stages 3b, 4 and 5D. We measured their iPTH, bio-PTH, 25-hydroxyvitaminD (25(OH)D), C-terminal telopeptide collagen (CTX), procollagen 1 intact N-terminal propeptide (P1NP), calcium, phosphate and alkaline phosphatase (ALP).

Results: Higher iPTH than bio-PTH concentrations were seen in CKD stages 3b, 4 and 5D (58[62] versus 55[67] pg/mL, 94[85] versus 85[76] pg/mL and 378[481] versus 252[280] pg/mL, respectively). Both PTH assays showed good agreement among all the subjects, with an intraclass correlation coefficient of 0.832 (P-value < 0.001). The Passing-Bablok showed that the equation for the bio-PTH was PTH = 0.64 iPTH + 15.80, with r = 0.99. The Bland-Altman plots showed increased bias with an increasing PTH concentration. Both PTH assays showed a high positive correlation with CTX and P1NP, a moderate correlation with phosphate, a low correlation with ALP and calcium, and a negligible correlation with phosphate and 25(OH)D.

Conclusion: The iPTH and bio-PTH assays were in agreement, but their bias increased with the PTH concentration. The unacceptable large bias indicates that the two assays cannot be used interchangeably. They had a variable correlation with the bone parameters.

Keywords: PTH assays; biointact PTH; bone turnover markers; chronic kidney disease; intact PTH; metabolic bone diseases.