Predicting the effect of intravenous calcitriol on parathyroid gland activity using double-phase technetium Tc 99m-sestamibi scintigraphy.

Background: Although intravenous calcitriol is useful for decreasing intact parathyroid hormone (iPTH) blood levels in patients with secondary hyperparathyroidism (SHP) undergoing hemodialysis, approximately half these patients remain refractory to this treatment. The current study measures the diagnostic utility of double-phase technetium Tc 99m-sestamibi (MIBI) scintigraphy in predicting the response to calcitriol treatment.

Methods: Sixty hemodialysis patients with SHP with iPTH blood levels between 240 and 600 pg/mL (ng/L) were selected. Initial intravenous calcitriol pulse therapy was 6 microg/wk (for iPTH levels of 400 to 600 pg/mL [ng/L]) or 3 microg/wk (for iPTH levels of 240 to 400 pg/mL [ng/L]). MIBI scintigraphy was performed before the onset of calcitriol therapy and repeated 1 year later. Patients were injected intravenously with 740 MBq of MIBI. Images were obtained at 15 minutes (thyroid phase) and 2 hours (parathyroid phase) after radiotracer administration. Focal areas of increased MIBI uptake were considered pathological parathyroid glands.

Results: Forty-eight patients completed the study. After 1 year, iPTH levels had decreased significantly in 95.2% (47 patients), whereas good control (iPTH < 240 pg/mL [ng/L]) was reached in 70.8% (34 patients) and only 4 patients had iPTH levels greater than 400 pg/mL (ng/L; all were patients with 3 MIBI-positive areas at baseline determination). At baseline, there were 30 patients (62.5%) with MIBI positive areas (1, 2, or 3 areas), which decreased to 14 patients (29%) at the end of the study period. No patient showed 4 positive areas at any time. The 18 patients (37.5%) with no MIBI-positive area at baseline remained unchanged.

Conclusion: MIBI scintigraphy is a reliable exploratory tool in predicting the response to treatment with intravenous calcitriol in hemodialysis patients with SHP.