Abstract
Background The purpose of the current study is to determine PTH reference values in vitamin-D-replete Lebanese adults using 2nd and 3rd generation PTH assays and to look at the factors that affect PTH variations. Methods Fasting PTH was measured using 2nd and 3rd generation Diasorin PTH assays in 339 vitamin-D-replete healthy subjects aged 18 to 63 years (230 men and 109 women) who have normal calcium levels and an eGFR ≥60 ml/mn. 25-OH vitamin D (25(OH)D) was measured using the Diasorin assay. Results For the 2nd PTH generation, median (IQR) levels were 48.9 (34.9–66.0) pg/ml, and its 2.5th–97.5th percentile values were 19.7–110.5 pg/ml for 25(OH)D values between 20 and 30 ng/ml, and 19.7–110.7 pg/ml for 25(OH)D values ≥30 ng/ml. For the 3rd PTH generation, the median (IQR) values were 23.9 (17.7–30.5) pg/ml, and its 2.5th–97.5th percentile values were, respectively, 9.2 and 50.2 pg/ml for 25(OH)D values between 20 and 30 ng/ml, and 8.4 and 45.4 pg/ml for 25(OH)D values ≥30 ng/ml. The median (IQR) serum 25(OH)D levels were 27.5 (23.8–32.7) ng/ml. 2nd and 3rd generation PTH values are strongly correlated (r = 0.96, p < 0.0001), but poorly concordant (Lin's concordance coefficient 0.365, 95% CI: 0.328–0.401) with observations beyond the 95% Bland–Altman limits of agreement. 2nd and 3rd generation PTH levels did not differ according to gender and were significantly correlated with age but not with 25(OH)D and serum calcium levels. Conclusion Lebanese adult healthy subjects have higher 2nd and 3rd generation PTH levels compared with the reference range provided by the manufacturer. The reference range was not influenced by changing the 25(OH)D cutoff. The clinical significance of the higher PTH levels in our population should be investigated.
Highlights
In clinical practice, assessing parathormone (PTH) concentration is important in exploring calcium/phosphorus metabolism disorders and in monitoring patients suffering from chronic kidney disease
Establishing a normal reference range for PTH is usually based on the values measured in 95% of healthy individuals after ruling out potential confounding factors since the PTH level is affected by multiple factors, such as vitamin D status, age, and renal function [1, 8,9,10]. erefore, vitamin D deficiency as well as renal failure, both conditions leading to International Journal of Endocrinology secondary hyperparathyroidism, should be ruled out or taken into consideration when establishing a reference range of PTH [11]
We established the reference ranges for PTH in 339 Lebanese subjects using the Diasorin 2nd and 3rd generation PTH assays. ese reference ranges were established in vitamin-D-replete subjects (25(OH)D ≥20 ng/ml) after excluding subjects with abnormal calcium levels and low estimated glomerular filtration rate (eGFR)
Summary
In clinical practice, assessing parathormone (PTH) concentration is important in exploring calcium/phosphorus metabolism disorders and in monitoring patients suffering from chronic kidney disease. Erefore, vitamin D deficiency as well as renal failure, both conditions leading to International Journal of Endocrinology secondary hyperparathyroidism, should be ruled out or taken into consideration when establishing a reference range of PTH [11]. Other interfering factors such as calcium/ phosphorus disorders should be excluded [12]. Reference values were mainly established using either 2nd or 3rd generation PTH assays Few studies compared both assays in healthy adults [4, 5, 19] and included only a small number of subjects [4, 19]. The concordance between both assays has only been studied in one study with a good concordance in healthy patients [4]
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