Endocrine Abstracts

The wide variability of analysis obtained from the fine needle aspiration cytology (FNAC) of thyroid nodules is attributed to experience differences in their interpretation. It is known that reproducibility is a critical parameter for the clinical usefulness of a diagnostic test. However, interobserver and intraobserver reproducibility of cytological examinations of the thyroid has been very little investigated. We studied 74 patients who underwent FNAC and a thyroidectomy. The examinations were reviewed by two pathologists, one experienced and one novice. Interpretations of the smears occurred on two separate occasions, with a time interval of six months between the first and second. The results revealed consistent intraobserver reproducibility after a lapse of six months, both for the experienced pathologist (K=0.82 [0.71 to 0.94], Kw =0.79, P=0.988) and for the novice (K=0.78 [0.64 to 0.91], Kw =0.71, P=0.291). There was no difference for the experienced and novice pathologist, respectively, in terms of rate for insufficient material, follicular neoplasm (FN), false-positive, false-negative and proportion of malignant tumors identified. The analysis of interobserver reproducibility showed a significant difference in both the first analysis (K=0.55 [0.38 to 0.72], Kw =0.50, P=0.011) and the second (K=0.54 [0.37 to 0.71], Kw =0.44, P=0.021). There was also a difference in the number of unsatisfactory results in both the first (P=0.001) and second (P=0.021) examination and FN in the second analysis (P=0.015). However, there was no difference in the first and the second analysis, respectively, in terms of proportion of malignant tumors identified, false-positive and false-negative. The intraobserver reproducibility in the interpretation of FNAC is consistent and independent of experience to the examination, however, interobserver reliability is influenced. Examiner experience significantly influences the proportion of unsatisfactory results and cases compatible with FN. Surgical thyroidectomy should take into account the high rate of false-negative results, which occurs even when performed by an experienced pathologist, as well as the high rate of unsatisfactory results, mainly due to the high rate of malignancy observed in these samples.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.