Relação entre os níveis séricos de cálcio e paratormônio e a positividade da cintilografia das paratiróides com sestamibi: análise de 194 pacientes

To correlate PTH and calcium serum levels with the percentages of positive results on the parathyroid scintigraphy, we retrospectively analyzed 194 patients who performed parathyroid scintigraphy. The distribution of the parathyroid scintigraphy results was visually analyzed in a scatter plot, being calcium (Y axis) and PTH (X axis) serum levels the axes. Six groups of patients were defined: 1) calcium > 12mg/dL; 2) 11mg/dL ¾ calcium 120pg/mL; 4) 9.9mg/dL < calcium < 11mg/dL with 65pg/mL < PTH < 120pg/mL; 5) 9.9mg/dL < calcium < 11mg/dL with PTH < 65pg/mL; and 6) calcium < 9.9mg/dL. The percentage of positive scintigraphy in these groups were respectively: 10/10 (100%), 18/29 (62%), 7/9 (78%), 18/45 (40%), 2/21 (10%) and 1/80 (1%). We conclude that in patients with suspected primary hyperparathyroidism, parathyroid scintigraphies performed before surgery on those with calcium level above 11mg/dL are frequently positive. In patients with calcium levels between 9.9mg/dL and 11mg/dL the pertinence of performing the scintigraphy will depend on the PTH levels, and it will be high for patients with PTH serum level above 120pg/mL and very low for patients with PTH level below 65pg/mL. Patients with calcium level below 9.9mg/dL rarely present positive results on parathyroid scintigraphies.