Fig 1.
Topography and size of parathyroid glands at parathyroidectomy and ultrasound.
Topography of the right-sided superior and inferior PG after luxation of the thyroid gland (A). Topography and measurement of corresponding PG by US: superior (B+C) and inferior (D+E). Volumes of PG were 479mm3 (PG superior) and 99mm3 (PG inferior) when calculated with US measurements. Documentation of PG size during surgery: superior (F+G) and inferior (H+I). Volumes of PG were 858mm3 (PG superior) and 293mm3 (PG inferior) when calculated with intra-operative measurements. PGs, superior parathyroid gland; PGi, inferior parathyroid gland.
Table 1.
Demographic, clinical and laboratory characteristics of patients.
Table 2.
Characteristics of parathyroid glands.
Table 3.
Variables associated with nodular hyperplasia of individual parathyroid glands (univariable binary logistic regression analysis).
Table 4.
Independent risk factors for nodular hyperplasia of individual parathyroid glands (multivariable binary logistic regression analysis).
Fig 2.
Receiver operating characteristic—curve for the prediction of nodular hyperplasia in individual parathyroid glands by the use of the prognostic model.
The AUROC is 0.857 with a binominal exact 95% confidence interval: 0.773–0.941. The best Youden index determined a predicted probability of 52.9% as the cut-off value with best sensitivity and specificity for prediction of nodular hyperplasia in individual (specificity 86.1%, sensitivity 70.6%, overall correctness 78.3%). Good model fit was demonstrated by use of Pearson (0.75), Deviance (0.49), and Hosmer-Lemeshow tests (0.16).
Table 5.
Internal validation of the developed prognostic score using randomized bootstrapping.
Fig 3.
Probability of nodular hyperplasia of PG depending on values of individual risk-factors.
Values of the duration of dialysis (−∙−∙−), PG volume measured by US (---) and serum levels of PTH (−−−) were categorized and standard units for a 10-step alteration were defined. The duration of dialysis was prolonged from 1 to 10 years by steps of 1 year. The PG volume determined by US was increased from 100 to 1.000 mm3 by steps of 100 mm3. The units of the 10-step alteration are given at the x-axis. The serum level of PTH was decreased from 1.000 to 100 pg/mL by steps of 100 pg/mL. While altering each parameter separately, the others were set to a default reference level with duration of dialysis = 2 years, PG volume determined by US = 400 mm3, and PTH serum level = 600 pg/mL. The calculated probability for nodular hyperplasia of PG is given in percent at the y-axis.