Essential steps in the measurement of normal circulating levels of calcitonin.

Before interpreting the results of assays which claim to measure circulating levels, one must have full data on the sensitivity, the reproducibility and specificity of the methods and antisera used. Without this information figures are meaningless and may be regarded as fiction rather than science. Secondly, and of equal importance, one must have full details of those physiological and pharmacological factors which are known to affect the circulating levels. It is quite obvious to workers in the field that those laboratories which have paid attention to these matters, have achieved remarkable agreement in practice; those who have neglected these requirements have introduced quite unnecessary confusion in the literature.