Fig. 1.
Evaluation of FNA sample adequacy before mutational analysis using the expression of the GAPDH and KRT7 genes detected by RT-PCR. A, KRT7 and GAPDH were expressed at similar levels in normal thyroid tissues (NT) (n = 10), follicular carcinomas (FC) (n = 10), and papillary carcinomas (PC) (n = 40) (mean ΔCt = −0.41, where ΔCt is CtGAPDH − CtKRT7; P = 0.90). However, KRT7 was expressed at a significantly lower level in white blood cells (WBC), which are a frequent contaminant of thyroid FNA samples (mean ΔCt = 13; P < 0.001). B, Serial dilution of RNA from thyroid papillary carcinoma tissue in RNA derived from normal WBC demonstrated a linear decrease in KRT7 expression compared with stable GAPDH expression, with the ΔCt of 3.5 corresponding to approximately 10% of thyroid epithelial cells within the sample. The ΔCt of 3.5 was used as a cutoff for sample adequacy.