The false negative technetium-99m-sestamibi scan in patients with primary hyperparathyroidism: correlation with clinical factors and operative findings.

False negative (FN) results limit the efficacy of technetium-99m-sestamibi scanning for parathyroid localization. We determined the incidence of FN results and attempted to correlate it with clinical and operative findings. One hundred forty-six patients underwent parathyroidectomy; 89 had primary hyperparathyroidism (76 single adenoma and 13 multiglandular disease) and underwent sestamibi scanning. The false negative rate was 22 per cent with an overall sensitivity of 77 per cent and a positive predictive value of 99 per cent. Patients with single adenomas were more likely to have a true positive scan than those with multiglandular disease [83% vs 38%; odds ratio (OR) = 7.754, 95% confidence interval (CI) = 2.184-27.524; P < or = 0.0001]. Inferior adenomas (90% vs 59%; OR = 6.261, 95% CI = 2.037-19.243; P < or = 0.0001) and larger adenomas (1422.3 +/- 1576.2 vs 474.6 +/- 193.2 g; P < or = 0.0001) were more likely to be detected by sestamibi imaging. Patients with normal preoperative calcium levels were more likely to have an FN sestamibi scan. Sestamibi parathyroid imaging is limited by a 22 per cent FN rate and is less accurate for detecting abnormal parathyroid tissue in patients with small adenomas, multiglandular disease, superior adenomas, or preoperative normocalcemia.