[Can measurement of basal calcitonin replace the pentagastrin test?]

Serum calcitonin is used as a tumour marker in patients with medullary thyroid carcinoma. Traditionally, stimulation of calcitonin secretion with pentagastrin has been used. This may, however, cause significant discomfort for the patient. We studied whether measurements of basal calcitonin could replace the pentagastrin test.

Forty-three patients were consecutively included. Pearson correlation coefficient (r(2)) was used for calculation of calcitonin values.

We performed 104 pentagastrin tests in 43 patients. The squared correlation coefficient (r(2)) between calcitonin values before and after stimulation was between 0.662 and 0.919. One patient had very high and rather divergent calcitonin values. Exclusion of this patient increased r(2) to between 0.923 and 0.999. In 9 of 104 pentagastrin tests (8.7% , 95% CI: 3.3-14.1%), serum calcitonin was higher than the cut-off level in normal subjects after pentagastrin stimulation, but lower before (discrepancy). However, this would have no clinical consequences in any of the cases because serum calcitonin remained measurable, i.e. remnant thyroid tissue had to be present.

In conclusion, good agreement is present between calcitonin values before and after stimulation with pentagastrin. In some cases, the pentagastrin test may be replaced by point measurements of serum calcitonin. However, further studies are necessary.