Use of Parathyroid Function Index and Wisconsin Index to Differentiate Primary Hyperparathyroidism From Secondary Hyperparathyroidism: A Case-Control Study

Introduction: Patients with primary hyperparathyroidism (PHPT) can be asymptomatic or have a normal calcium level (NHPT). Patients with 25(OH) vitamin D insufficiency, on the other hand, may present with a similar presentation. In regions where 25(OH) vitamin D deficiency is common, patients are usually diagnosed with secondary hyperparathyroidism (SHPT). Therefore, it is necessary to separate PHPT and NHPT from SHPT. Parathormone and calcium values are used for differentiation in the clinic. The predictive value of the newly developed parathyroid function test (PFindex), which previously had a high diagnostic value, was evaluated in this patient population in our investigation. Methods: The study comprised 163 PHPT and NHPT patients with pathological confirmation and 56 SHPT patients. The PHPT, NHPT, and SHPT properties were defined using PFindex. The diagnostic power of PFindex was investigated using a receiver operating characteristic (ROC) curve of the results assessed in three groups. Results: The PHPT group had the highest PFindex (1365.4±784.6) compared to the other two groups (NHPT: 723.5±509.4; SHPT:227.2±49.9, all p < 0.001). A PFindex threshold of 327.8 yielded 91.9% and 90.9% sensitivity and specificity rates for distinguishing PHPT and NHPT from SHPT, respectively. Conclusion: PFindex gave the outstanding diagnostic capacity to distinguish PHPT from SHPT due to our research. This straightforward tool can assist in making quick decisions about vitamin D therapy or surgery for PHPT.