Diagnostic value of clinical parameters and parathyroid scintigraphy for asymptomatic primary hyperparathyroidism

The purpose of this study was to evaluate the diagnostic value of clinical parameters and parathyroid scintigraphy for asymptomatic primary hyperparathyroidism (aPHPT), including quantitative parameter of laboratory and semiquantitative parameters derived from technetium-99m- metoxyisobutylisonitrile (^99mTc-MIBI) single photon emission computed tomography/computed tomography (SPECT/CT).

Two hundred and fourteen patients who had been diagnosed as PHPT and underwent surgical treatment were enrolled in this study. All patients were divided into two groups: aPHPT and symptomatic PHPT (sPHPT). Dual tracer ^99mTc pertechnetate/^99mTc-MIBI, dual time point and tomography scintigraphy with ^99mTc-MIBI SPECT/CT were performed. Clinical parameters included basic information, serum calcium (Ca), phosphorus (P), parathyroid hormone (PTH) and alkaline phosphatase (ALP) levels. Semiquantitative parameters of parathyroid scintigraphy included the average counts of early parathyroid (PT₁), late parathyroid (PT₂), early thyroid (T₁) and late thyroid (T₂), the ratio of PT₁/ T₁ (R₁), the ratio of PT₂/ T₂ (R₂), parathyroid washout (PTW=(PT₁-PT₂)/PT₁) and retention index (RI=(R₂-R₁)/R₁). P<0.05 was considered as statistically significant.

A total of 167 aPHPT patients (46 males, 121 females) were studied. One hundred and seventy four One hundred and seventy four174 parathyroid glands were removed after operation: 146 (87.4%) lesions were adenoma, 12 (7.2%) lesions were hyperplasia and 1 (0.6%) lesion was adenocarcinoma. There were significant differences in previous history (P=0.000), echo of parathyroid (P=0.004), thyroid function (P=0.029), clinical course (Z=-3.422, P=0.001), ^99mTc-pertechnetat thyroid uptake (TcTU) (Z=-2.126, P=0.033), serum Ca level (t=-2.926, P=0.004) and serum PTH level (Z=-3.028, P=0.002) between aPHPT and sPHPT. For patients with aPHPT, there were significant differences for serum Ca level (t=2.832, P=0.005), R2 (Z=-2.597, P= 0.009) and RI (Z=-2.100, P=0.036) between adenoma and hyperplasia, and serum Ca level in aPHPT patients with adenoma was significantly higher compared with patients with hyperplasia. The areas under the curve (AUC) of clinical course, TcTU, serum Ca and PTH levels were 0.662, 0.399, 0.642 and 0.645 respectively for differential diagnosis of aPHPT and sPHPT. The AUC of R2 and RI were 0.737 and 0.692 respectively for differential diagnosis of adenoma and hyperplasia in patients with aPHPT. The sensitivity, negative predictive value (NPV) and accuracy for diagnosing aPHPT combined ^99mTc-MIBI SPECT/CT with ultrasound (US) were significantly higher than dual tracer, dual time point, ^99mTc-MIBI SPECT/CT and US, which were 97.5%, 95.2% and 55.6% respectively.

Laboratory inspection and semi-quantitative parameters of parathyroid scintigraphy had higher value for differential diagnoses of aPHPT and sPHPT, the same for adenoma and hyperplasia in patients with aPHPT. When combined ^99mTc-MIBI SPECT/CT with US, the diagnostic efficiency would be significantly improved.