Is basal ultrasensitive measurement of calcitonin capable of substituting for the pentagastrin-stimulation test?
OBJECTIVE
To evaluate a second-generation assay for basal serum calcitonin (CT) measurements compared with the pentagastrin-stimulation test for the diagnosis of inherited medullary thyroid carcinoma (MTC) and the follow-up of patients with MTC after surgery. Recent American Thyroid Association recommendations suggest the use of basal CT alone to diagnose and assess follow-up of MTC as the pentagastrin (Pg) test is unavailable in many countries.


METHODS
Multicentric prospective study.


METHODS
A total of 162 patients with basal CT <10 ng/l were included: 54 asymptomatic patients harboured noncysteine 'rearranged during transfection' (RET) proto-oncogene mutations and 108 patients had entered follow-up of MTC after surgery.


METHODS
All patients underwent basal and Pg-stimulated CT measurements using a second-generation assay with 5-ng/l functional sensitivity.


RESULTS
Ninety-five per cent of patients with basal CT ≥ 5 ng/l and 25% of patients with basal CT <5 ng/l had a positive Pg-stimulation test (Pg CT >10 ng/l). Compared with the reference Pg test, basal CT ≥ 5 ng/l had 99% specificity, a 95%-positive predictive value but only 35% sensitivity (P < 0.0001). Overall, there were 31% less false-negative results using a 5-ng/l threshold for basal CT instead of the previously used 10-ng/l threshold.


CONCLUSIONS
The ultrasensitive CT assay reduces the false-negative rate of basal CT measurements when diagnosing familial MTC and in postoperative follow-up compared with previously used assays. However, its sensitivity to detect C-cell disease remains lower than that of the Pg-stimulation test.
Hospices Civils de Lyon et Université Lyon 1, Centre de Médecine Nucléaire, Centre d'Investigation Clinique et Fédération d'Endocrinologie, Groupement Hospitalier Est, Centre de Recherche en Neurosciences, Lyon, France. gpina.jomir@gmail.com
Géraldine
G
Pina
Séverine
S
Dubois
Arnaud
A
Murat
Nicole
N
Berger
Patricia
P
Niccoli
Jean-Louis
JL
Peix
Régis
R
Cohen
Claudine
C
Guillausseau
Anne
A
Charrie
Olivier
O
Chabre
Catherine
C
Cornu
Françoise
F
Borson-Chazot
Vincent
V
Rohmer
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002116:Calcitonin / Q000097:blood*; D018276:Carcinoma, Medullary / Q000097:blood / Q000151:congenital* / Q000175:diagnosis / Q000000981:diagnostic imaging; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018813:Multiple Endocrine Neoplasia Type 2a / Q000097:blood* / Q000175:diagnosis* / Q000000981:diagnostic imaging; D010418:Pentagastrin; D011446:Prospective Studies; D000090063:Proto-Oncogene Mas; D011859:Radiography; D013964:Thyroid Neoplasms / Q000097:blood* / Q000175:diagnosis* / Q000000981:diagnostic imaging; D055815:Young Adult
C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D002116:Calcitonin; D010418:Pentagastrin