Abstract
I read with interest the review by Daniels (1) on the utility of screening thyroid nodules with serum calcitonin (CT) measurement in the September 2011 issue of Thyroid. While I have to congratulate Dr. Daniels for the extremely careful review of the literature and the appropriateness of the still controversial aspects of the matter, I have some disagreement with the conclusion against the use of serum CT screening in United States. The conclusion of the author seems to be based mainly on three arguments: nonthyroidal conditions associated with increased serum CT levels, detection of “cryptic” medullary thyroid cancer (MTC), unavailability of pentagastrin in the United States, and increased patient and physician anxiety in observing minimal elevation of serum CT. I will try to explain the reason why I believe that these arguments should not be advocated against routine screening of thyroid nodules with serum CT measurement.
As pointed out by the author, several nonthyroidal conditions maybe associated with elevated serum CT levels. It is true, but all of them are very easily ruled out by a careful history of the patient's affections and drug use. In my experience this issue has never been a problem.
When we first proposed the use of serum CT in thyroid nodules (2), the MTCs we detected were clinical MTCs in almost all cases (only one was a micro-MTC coexisting with a functioning follicular adenoma), “clinical” meaning that the nodules were not detected by ultrasound screening but were the presenting symptom of the disease. The same is true in most of the other European series published up to now. Thus, the word “cryptic” should not be used for such nodules. It is true that nowadays many additional thyroid nodules are discovered during neck ultrasound examination performed for indications other than thyroid diseases, but CT screening is diagnostic of MTC in both incidentalomas and clinical thyroid nodules.
Regarding the issue of pentagastrin, I understand that the lack of pentagastrin in United States may be a problem; however, the calcium test was the first to be proposed for the diagnosis of MTC and for many years it was the standard test before the advent of pentagastrin. Usually, there is a good correlation between the results of pentagastrin and calcium stimulation, although I agree that modern cutoff should be determined, which I do not think it should be difficult. I want also to note that in my country (Italy) too pentagastrin is not available, but we can get pentagastrin from France without any problem and at very low cost. Why should American institutions not do the same?
Patient and physician anxiety is something that exists and will exist in any aspect of medical practice. The most frequent example is the decision to perform or not perform fine-needle aspiration in thyroid incidentalomas: would the patient or the physician not be anxious about the presence of microcarcinoma whenever (very often) the test is not performed?
Based on these considerations, I think that the only concrete argument against routine use of serum CT in thyroid nodules remains the issue of the cutoff. In my opinion this should be addressed by individual institutions trying to set its own cutoff, but in general this maybe overcome applying the algorithm reported in Figure 1 by the author (1).
I want to finish by quoting an editorial by Deftos (3), whose title is self-explanatory: “Should serum calcitonin be routinely measured in patients with thyroid nodules—will the law answer before endocrinologists do?”