Spurious hypercalcitoninemia in patients with nodular thyroid disease induced by heterophilic antibodies.
BACKGROUND
Serum calcitonin is the most useful tumor marker for the diagnosis and follow-up of medullary thyroid carcinoma (MTC). Spurious hypercalcitoninemia caused by heterophilic antibody interference (HAI) is rarely found in patients without MTC.


METHODS
We studied 2 patients with hypercalcitoninemia and thyroid nodules, but no evidence of MTC on fine-needle aspiration cytology. We performed calcium stimulation tests, measured serum calcitonin with another calcitonin kit, performed dilution tests, and remeasured serum calcitonin after applying heterophilic blocking tubes.


RESULTS
In a 31-year-old woman with no response to the calcium stimulation test, serum calcitonin was <5 pg/mL using another kit. After we applied heterophilic blocking tubes, the serum calcitonin level decreased to normal range. We concluded that patient had spurious hypercalcitoninemia. In a 63-year-old woman, all tests revealed that the patient had true hypercalcitoninemia. The patient underwent total thyroidectomy that revealed MTC.


CONCLUSIONS
We suggest that patients suspected for spurious hypercalcitoninemia should undergo further investigation due to HAI.
Kim
Jung Min
JM
Research Institute and Hospital, National Cancer Center, Gyeonggi, Korea.
Chung
Ki-Wook
KW
Kim
Seok Won
SW
Choi
Seon Hyeong
SH
Min
Hye Sook
HS
Kim
Ji-na
JN
Won
Woo-jae
WJ
Kim
Seok Ki
SK
Lee
Ji In
JI
Chung
Jae Hoon
JH
Kim
Sun Wook
SW
D000328:Adult; D000465:Algorithms; D000910:Antibodies, Heterophile / Q000097:blood / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000097:blood; D044963:Biopsy, Fine-Needle; D002116:Calcitonin / Q000097:blood*; D018276:Carcinoma, Medullary / Q000175:diagnosis; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D008875:Middle Aged; D011237:Predictive Value of Tests; D011379:Prognosis; D012680:Sensitivity and Specificity; D013964:Thyroid Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000601:surgery; D016606:Thyroid Nodule / Q000097:blood / Q000175:diagnosis* / Q000601:surgery; D013965:Thyroidectomy; D013967:Thyroiditis, Autoimmune / Q000175:diagnosis; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional
D000910:Antibodies, Heterophile; D014408:Biomarkers, Tumor; D002116:Calcitonin