Abstract
BackgroundPatients with primary hyperparathyroidism (PHPT) may be asymptomatic, and some may present with normocalcemic PHPT (NPHPT). Patients with vitamin D deficiency may also be asymptomatic, with normal calcium and elevated PTH concentrations. These latter patients are usually diagnosed with vitamin D deficiency-induced secondary hyperparathyroidism (VD-SHPT). Therefore, it is very difficult to distinguish PHPT and NPHPT from VD-SHPT based on calcium or PTH concentrations in clinical settings. In this case-control study, we aimed to verify the diagnostic power of a new parathyroid function index (PFindex = Ca*PTH/P).MethodsThis study enrolled 128 patients with surgically and pathologically confirmed PHPT, including 36 with NPHPT, at a hospital in West China between January 2009 and September 2017. Thirty-seven patients with VD-SHPT and 45 healthy controls were selected from the population of a cross-sectional epidemiological study as the SHPT and healthy groups, respectively. We used the PFindex to describe the characteristics of PHPT, NPHPT, and VD-SHPT.. Differences between the four groups were compared, and a receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic power of PFindex.ResultsThe PHPT group had the highest PFindex (454 ± 430), compared to the other three groups (NPHPT: 101 ± 111; SHPT: 21.7 ± 6.38; healthy: 12.2 ± 2.98, all p < 0.001). A PFindex cut-off value of 34 yielded sensitivity and specificity rates of 96.9 and 97.6% and of 94.4 and 94.6% for the diagnoses of PHPT and NPHPT, respectively. The use of a PFindex > 34 to differentiate NPHPT from VD-SHPT yielded the highest positive likelihood ratio and lowest negative likelihood ratio.ConclusionThe PFindex provided excellent diagnostic power for the differentiation of NPHPT from VD-SHPT. This simple tool may be useful for guiding timely decision-making processes regarding the initiation of vitamin D treatment or surgery for PHPT.
Highlights
Patients with primary hyperparathyroidism (PHPT) may be asymptomatic, and some may present with normocalcemic PHPT (NPHPT)
Patients diagnosed with either vitamin D deficiency-induced secondary hyperparathyroidism (VD-secondary hyperparathyroidism (SHPT)) or PHPT would have an elevated Parathyroid hormone (PTH) concentration [5], and many presented with vitamin D deficiency as well as a normal serum calcium concentration [6,7,8]
We created a parathyroid function index (PFindex) to magnify the biochemical differences between these diseases. This equation multiplies the serum PTH by the albumincorrected serum calcium concentration, and divides this value by the serum phosphate concentration. In this case-control study, we aimed to verify the diagnostic power of the PFindex in subjects with confirmed PHPT and SHPT, as well as healthy subjects
Summary
Patients with primary hyperparathyroidism (PHPT) may be asymptomatic, and some may present with normocalcemic PHPT (NPHPT). Patients with vitamin D deficiency may be asymptomatic, with normal calcium and elevated PTH concentrations. These latter patients are usually diagnosed with vitamin D deficiency-induced secondary hyperparathyroidism (VD-SHPT). It is very difficult to distinguish PHPT and NPHPT from VDSHPT based on calcium or PTH concentrations in clinical settings. Chronic renal insufficiency and vitamin D deficiency are the most common causes of secondary hyperparathyroidism (SHPT) The former can be distinguished from the medical history and laboratory tests. Patients diagnosed with either VD-SHPT or PHPT would have an elevated PTH concentration [5], and many presented with vitamin D deficiency as well as a normal serum calcium concentration [6,7,8]. A convenient clinical tool to differentiate PHPT from VD-SHPT
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