Stabilization of circulating thyroglobulin mRNA transcripts in patients treated for differentiated thyroid carcinoma

Background The clinical utility of serum thyroglobulin in the follow-up of patients with differentiated thyroid carcinoma may be compromised by the presence of endogenous antithyroglobulin antibodies. To prevent interference by antithyroglobulin antibodies several groups have developed real-time PCR-based assays for quantification of blood thyroglobulin mRNA levels. For accurate quantification of thyroglobulin mRNA in blood preanalytical factors must be recognized and controlled. In this study, we evaluate the effect of different blood RNA stabilizing systems - the Tempus Blood RNA system and the PAXgene Blood RNA system - and storage time on RNA yield and quality, and thyroglobulin mRNA stability. Methods Blood samples from 11 patients previously treated for differentiated thyroid carcinoma were collected in K₂-EDTA, Tempus and PAXgene tubes and maintained at room temperature. RNA was isolated following storage for 0 and 72 h, and RNA yield, integrity and purity was determined. Thyroglobulin, GAPDH and ACTB mRNA levels were quantified by semi-quantitative real-time PCR. Results The RNA yield was significantly higher for blood collected in Tempus tubes compared with PAXgene tubes following storage for 72 h at room temperature ( P = 0.0011). High-quality RNA could be extracted from blood collected in PAXgene and Tempus tubes. Blood collected in K₂-EDTA tubes, but not in PAXgene and Tempus tubes, showed significant changes in thyroglobulin mRNA levels following storage for 72 h at room temperature ( P = 0.0263). Conclusions Stabilization of blood in PAXgene and Tempus tubes enables storage at room temperature for up to 72 h, without compromising thyroglobulin mRNA levels.