Clinical evaluation of a new sensitive calcitonin assay: study of specificity.
BACKGROUND
Calcitonin (CT) is the most sensitive marker available for medullary thyroid carcinoma, but it lacks specificity. Procalcitonin is the precursor protein of calcitonin. Infections are known to be associated with elevations of procalcitonin. The aim of this study was to evaluate a new sensitive calcitonin assay in a large population and to study the assay specificity in two particular populations: patients with renal failure and patients hospitalized in intensive care units with a high procalcitonin level.


METHODS
Using two immunometric assays (A and B) to detect only mature calcitonin, we evaluated the calcitonin level in 488 sera (46 stimulation tests) from 340 subjects.


RESULTS
The clinical evaluation showed that the calcitonin concentrations obtained with the two assays were similar for all patients except those with high procalcitonin levels. Among the patients, 12% (n=13) had basal calcitonin concentrations greater than 10 pg/ml with method A and 25.7% (n=25) with kit B. No correlation was found between calcitonin and procalcitonin concentrations.


CONCLUSIONS
The new sensitive calcitonin assay tested is very efficient especially for the low concentrations. The cross-reaction for high procalcitonin levels exists and is variable according to the kits used. The procalcitonin evaluation can help the interpretation of ambiguous calcitonin levels.
d'Herbomez
M
M
Institut de Médecine Nucléaire, Centre Hospitalier Régional Universitaire, 59037 Lille Cedex, France. m-dherbomez@chru-lille.fr
Leclerc
L
L
Vantyghem
M C
MC
Fourrier
F
F
Proye
C
C
Wemeau
J L
JL
D000293:Adolescent; D000328:Adult; D000911:Antibodies, Monoclonal; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D003429:Cross Reactions; D005260:Female; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D011498:Protein Precursors / Q000097:blood; D006435:Renal Dialysis; D013959:Thyroid Diseases / Q000097:blood; D013965:Thyroidectomy
D000911:Antibodies, Monoclonal; C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide