RESUMO
OBJECTIVE: The objective was to evaluate the clinical and biological factors associated with negative 99mTc-MIBI scanning in patients with primary hyperparathyroidism (PHPT). METHODS: A retrospective observational study was designed in 195 patients (mean age: 59.2⯱â¯13.0 years; 77% woman) with PHPT (calcium: 11,3⯱â¯1,1â¯mg/dl and PTH: 218⯱â¯295â¯pg/ml) studied in endocrinology setting between 2013 and 2020. An univariate and multivariate analysis was made to evaluate the clinical and biological factors associated with negative 99mTc-MIBI scanning. RESULT: 50 patients (26%) with negative 99mTc-MIBI scanning had lower PTH levels (146⯱â¯98 vs. 244⯱â¯334; pâ¯<â¯0,001), adenomas with smaller sonographic dimensions (maximum diameter: 1,2⯱â¯0,4 vs. 1,7⯱â¯0,9â¯cm; pâ¯=â¯0,001 and volume: 0,36⯱â¯0,43 vs. 1,7⯱â¯4,1â¯cm3; pâ¯<â¯0,001), localized more frequently in upper parathyroid glands (37% vs 14%; pâ¯=â¯0,005) and associated more frequently to thyroid nodules (72% vs 57%; pâ¯=â¯0,045) than patients with positive scanning. 116 patients were operated and parathyroid adenomas were smaller (maximum diameter: 1,3⯱â¯0,5 vs. 1,9⯱â¯1,1â¯cm; pâ¯=â¯0,008 and volume: 0,30⯱â¯0,20 vs. 1,2⯱â¯1,1â¯cm3; pâ¯<â¯0,001), less heavy (567⯱â¯282 vs. 1470⯱â¯1374 mgr.; pâ¯=â¯0,030) and were localized more frequently in upper situation (65% vs 16%; pâ¯<â¯0,001) than patients with positive scanning. In the multivariate analysis an independent association between negative 99mTc-MIBI scanning and size of removed adenoma ≤1â¯cm (OR: 5,77; IC 95: 1,46-22,71) and upper adenoma localization were observed (OR: 8,05; IC 95%: 2,22-29,16). CONCLUSIONS: One in four patients studied for PHPT had a negative 99mTc-MIBI scanning and were independent associated with size of adenoma ≤1â¯cm and upper adenoma localization.