Possible roles of MIBI parathyroid scan in assessment of dialysis patients with hyperparathyroidism

AbstractWe investigated the relationship between the result of technetium-99m-methoxyisobutylisonitrile (MIBI) parathyroid scanning and the subsequent biochemical outcome following calcitriol treatment. Twenty-two patients on dialysis with serum intact parathyroid hormone (PTH) level (iPTH) more than 500 pg/mL on annual checkup were selected. Around 20 weeks later, baseline iPTH were repeated at the time of performing MIBI scan and assayed again another 20 weeks later, while patients had intensification of treatment with oral calcitriol. Ten had positive MIBI parathyroid scans (MIBI+) while 12 had negative MIBI parathyroid scans (MIBI-). Although there was no statistically significant difference between both groups concerning baseline iPTH, phosphate, calcium × phosphate product and aluminum level, the MIBI+ group had higher serum calcium level and a tendency toward longer duration of dialysis. At 20 weeks, the MIBI- group showed a significantly lower iPTH of 413.2 ±335.7 pg/mL as compared to the MIBI+ group of 884.6 ±706.6 pg/mL (p = 0.03). The MIBI-group also had a higher proportion of patients showing decrease in iPTH (p = 0.05). Despite more profound iPTH suppression, the MIBI- group was actually given a lower mean maximum weekly calcitriol dosage of 2.20 ±1.82 μg as compared to 4.33 ±2.15 μg in the MIBI+ group (p = 0.025). Excessive suppression of iPTH below 100 pg/mL was evident in two patients of the MIBI- group and none in the MIBI+ group. We concluded that for patients on dialysis with grossly elevated baseline iPTH, the biochemical response to calcitriol is more profound in the MIBI- group. MIBI parathyroid scan may provide supplementary hints concerning the outcome of the medical treatment for uremic hyperparathyroidism