prediction of uniglandular disease in primary hyperparathyroidism

Background: Primary hyperparathyroidism (PHPT) is caused inmost cases by a single adenoma. The development of new techniques – such as intraoperative radioguidance and quick measurement of PTH (qPTH) – prompted ‘focused’ parathyroidectomy. Candidates must be selected by one or more preoperative imaging studies. The success of operation is then confirmed intraoperatively, using serial qPTH determinations. In this study we evaluated the probability that a patient with PHPT, with both MIBI scan and ultrasonography showing one, single abnormal focus, has uniglandular disease. Methods: Among patients with PHPT referred for first operation to theDay Surgery Unit,Department of Surgery, University of Pisa (October 2001 to October 2002), we selected those in whom MIBI scan and ultrasonography were available, and indicated the presence of the same, single lesion. qPTH was used whenever available and early judgement of cure was made according to parathyroid hormone (PTH) and calcium levels obtained the morning after the operation, and it was verified at follow-up. We calculated the positive predictive value (PPV) of MIBI and ultrasonography taken as a single test for the diagnosis of single adenoma by the formulaPPV = a/a + b, with a being the true positives (normocalcaemia at follow-up) and b the false positives (hypercalcaemia at follow-up). Results: Some 103 patients with PHPT underwent first operation during the 13 months. Preoperative MIBI scan and ultrasonography were available for 85 of them, and showed the same abnormality in 52 cases (61 per cent). The image always coincided with a histologically confirmed parathyroid adenoma, and qPTH dropped significantly after its removal. The morning after the operation PTH was normal in 51 subjects. At followup all but one patient were normocalcaemic. The PPV of ultrasonography–scintigraphy (as a single test) for the diagnosis of single-gland disease was 98 per cent. We also registered three cases of slightly elevated PTH in normocalcaemic subjects, in whom a definite judgement of cure was controversial. Conclusion: If we use high-frequency ultrasonography and MIBI scintigraphy as a single test, evidence of a sole abnormality is highly predictive of uniglandular disease; the coupled study is an accurate tool for the selection of candidates in a focused surgical approach for PHPT