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Background The completeness of REarranged during Transfection (RET) testing in patients with medullary thyroid carcinoma (MTC) was recently reported as 60%. However, the completeness on a population level is unknown. Similarly, it is unknown if the first Danish guidelines from 2002, recommending RET testing in all MTC patients, improved completeness in Denmark. We conducted a nationwide retrospective cohort study aiming to evaluate the completeness of RET testing in the Danish MTC cohort. Additionally, we aimed to assess the completeness before and after publication of the first Danish guidelines and characterize MTC patients who had not been tested. Methods The study included 200 patients identified from the nationwide Danish MTC cohort 1997-2013. To identify RET tested MTC patients before December 31, 2014, the MTC cohort was cross-checked with the nationwide Danish RET cohort 1994-2014. To characterize MTC patients who had not been RET tested, we reviewed their medical records and compared them with MTC patients who had been tested. Results Completeness of RET testing in the overall MTC cohort was 87% (95% CI: 0.81-0.91; 173/200). In the adjusted MTC cohort, after excluding patients diagnosed with hereditary MTC by screening, completeness was 83% (95% CI: 0.76-0.88; 131/158). Completeness was 88% (95% CI: 0.75-0.95; 42/48) and 81% (95% CI: 0.72-0.88) (89/110) before and after publication of the first Danish guidelines, respectively. Patients not RET tested had a higher median age at diagnosis compared to those RET tested. Median time to death was shorter in those not tested relative to those tested. Conclusion The completeness of RET testing in MTC patients in Denmark seems to be higher than reported in other cohorts. No improvement in completeness was detected after publication of the first Danish guidelines. In addition, data indicate that advanced age and low life expectancy at MTC diagnosis may serve as prognostic indicators to identify patients having a higher likelihood of missing the compulsory RET test.

DNA testing is of great importance in families with multiple endocrine neoplasia (MEN) type 2A to identify non-mutant carrying family members and asymptomatic mutation carriers, and also to confirm the diagnosis in patients who already show clinical or biochemical signs of disease. Several point mutations of the RET proto-oncogene on exons 10 and 11 are associated with the disease, which is characterized by medullary thyroid carcinoma, pheochromocytoma and hyperparathyroidism. The aim of the present study was to develop and evaluate a simple method, which indicates the mutational status of members of families where the site of the point mutation is known. The method is illustrated by the detection of mutation TGC--TAC of codon 611, which is one of the well-known mutations associated with MEN 2A. The method involves the PCR technique with allele-specific primers and detection of the amplified sequences with biotinylated probes. There was a clear-cut difference between the readings from affected and unaffected subjects. The subjects had been evaluated independently and all subjects harboring the mutation also had clinical disease. The method provides a simple and reliable diagnostic tool for DNA screening of members of families with a known mutation of the RET-gene.