Intraoperative Parathyroid Hormone Assay Remains Predictive of Cure in Renal Impairment in Patients with Single Parathyroid Adenomas.

BACKGROUND: Parathyroid hormone (PTH) has a short half-life and is cleared by the liver and kidneys. This study examined whether declining estimated glomerular filtration rate (eGFR) affects application of the Miami criterion for intraoperative PTH (ioPTH) decline during parathyroidectomy for primary hyperparathyroidism (pHPT).

METHODS: A retrospective review of consecutive patients undergoes parathyroidectomy for pHPT. Patients with multi-gland disease, without ioPTH, failure-to-cure and those <18 years were excluded. Baseline demographics, pre-operative PTH, ioPTH and 6-month follow-up data were available. Patients were categorised into normal or chronic kidney disease (CKD stage 2-5) based on pre-operative eGFR. Nonparametric data were compared using Mann-Whitney U test/Kruskal-Wallis test. The primary outcome measure was to assess whether CKD-affected ioPTH decline in parathyroidectomy for pHPT.

RESULTS: A total of 476 patients were included [75.4% women; median age 63.8 years (18-92)]. CKD was present in 362 (76%) (CKD2:289; CKD3:66; CKD4/5:7). Increasing CKD stage was associated with advancing age [normal 53 years (41-61); CKD2 65 (57-73); CKD3 73.5 (66-78); CKD4/5 74(63-81); p < 0.001] and higher pre-operative PTH [16.6 pmol/L (11.1-22.9); 13.1 (10.4-17.7); 22.6 (13.8-33.7); 33.8(12.4-41.7); p < 0.001]. Baseline and post-excision ioPTH were significantly higher in those with CKD4/5 (p < 0.05). The Miami criterion was met in all patients, but median fall in ioPTH at 10-min varied between groups [normal:0.78 (0.71-0.82); CKD2:0.76 (0.69-0.83); CKD3:0.75 (0.69-0.82); CKD4/5:0.69 (0.61-0.70); p = 0.048)]. It was significantly lower in those with CKD4/5 compared with the remainder of patients [0.69 (0.61-0.70) vs. 0.76 (0.70-0.82); p = 0.008].

CONCLUSIONS: Although the reduction in ioPTH after successful parathyroidectomy is lower in severe CKD, the Miami criterion remains predictive of cure. Differences in absolute levels of PTH and tumour weight suggest that renal HPT may be a confounding factor.