Analysis of false-positive and false-negative results in ^99mTc-MIBI SPECT/CT parathyroid imaging

Exact preoperative localization is desirable to perform minimally invasive parathyroidectomy for hyperparathyroidism (HPT). This study aimed to evaluate the diagnostic values of ^99mTc-methoxyisobutylisonitrile (^99mTc-MIBI) single photon emission computed tomography/computed tomography (SPECT/CT) of parathyroid glands by analyzing the relationship between lesion weight and false-negative (FN) results, as well as to explain the possible reason.

The data from 314 patients with suspected HPT who underwent ^99mTc-MIBI SPECT/CT parathyroid imaging between 2011 and 2022 were retrospectively evaluated. The sensitivity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of parathyroid ^99mTc-MIBI SPECT/CT were calculated, and the false-positive (FP) and FN findings were analyzed.

Accurate localization by ^99mTc-MIBI SPECT/CT was significantly associated with the parathyroid hormone (PTH) level. The ^99mTc-MIBI SPECT/CT for diagnosis/lesion location reached a sensitivity of 84.6%/56.8%, a PPV of 97.3%/98.4%, an NPV of only 23.7%/4.18%, and an accuracy of 83.4%/57.1%, respectively. The largest diameter, shortest diameter, and lesion volume were lower in the FN group than in the TP group. A total of 7 FP cases were found, including 2 cases of thyroid nodules, 4 cases of thyroid tissue, and 1 case of hibernoma. A total of 45 FN patients, including 321 FN lesions, were confirmed, of which parathyroid hyperplasia accounted for 97.8%. Lesion weights greater than 20 µg were able to be detected, but lightweight lesions less than 100 mg were the principal source of FN results, accounting for approximately 39.3%. With lesion weights 0-100, 101-300, 301-1,000, and >1,000 mg, the FN rate was 70.8% (126/178), 51.8% (103/199), 34.6% (81/234), and 8.33% (11/132), respectively.

^99mTc-MIBI SPECT/CT parathyroid imaging provides good sensitivity and high specificity in HPT location. Correct localization by ^99mTc-MIBI SPECT/CT correlates positively with lesion weight and PTH levels. The smaller the lesion, the higher the FN rate in ^99mTc-MIBI SPECT/CT parathyroid imaging, and lesions weighing less than 100 mg are the main source of FN results in ^99mTc-MIBI SPECT/CT parathyroid imaging.