title: New classification of thyroid FNAB results - a three-year observation from one clinic.
abstract: BACKGROUND
  Fine needle aspiration biopsy (FNAB) is the main examination in diagnostics of thyroid nodules. Yet, it does not allow the differentiation of follicular lesions (FL). A new classification of thyroid biopsy results (newC) might improve pre-operative diagnostics mainly due to the introduction of a new subcategory of 'follicular lesion of undetermined significance', as well as the clarification of definitions of other categories. The aim of this study was to analyse the impact of the newC on the distribution of the cytological results among main diagnostic categories and on the values of the parameters describing the effectiveness of FNAB in detecting malignancy.
  
  
  METHODS
  34,371 FNABs outcomes and 3,557 results of surgical follow up were analysed. The frequencies of five main diagnostic categories in two periods: before (years: 2000-2009, 24,271 FNAB) and after the newC had been introduced (years: 2010-2012, 10,100 FNAB) were compared, as well as parameters describing the biopsy effectiveness, with a special focus on FL.
  
  
  RESULTS
  In the second analysed period, the frequency of the 'suspicious for malignancy' results was three times lower, while diagnoses of 'malignant neoplasm' were 33% more frequent and the results corresponding to FL decreased by 10%. In respect to FL, specificity of FNAB increased (22.6% vs. 57.4%), but sensitivity decreased (78.8% vs. 50.0%). In respect to other diagnostic categories considered jointly, the sensitivity of FNAB (61.2% vs. 85.7%) and PPV (57.4% vs. 77.8%) increased, and the specificity was similar (95-97%) for both periods. NPV exceeded 95% irrespective of applied classification.
  
  
  CONCLUSIONS
  Separation of FL with low risk of malignancy affects the values of the parameters describing the effectiveness of FNAB. The improved diagnostic effectiveness of FNAB is also a consequence of epidemiological changes and better selection of thyroid lesions for biopsy.
authors.forename: Ewa
authors.initials: E
authors.lastname: Woźniak-Oseła
authors.forename: Bożena
authors.initials: B
authors.lastname: Popowicz
authors.forename: Stanisław
authors.initials: S
authors.lastname: Sporny
authors.forename: Mariusz
authors.initials: M
authors.lastname: Klencki
authors.affiliation: Department of Morphometry of Endocrine Glands, Chair of Endocrinology, Medical University of Lodz, Poland. dsk@tyreo.am.lodz.pl.
authors.forename: Dorota
authors.initials: D
authors.lastname: Słowińska-Klencka
mesh_terms: D044963:Biopsy, Fine-Needle / Q000145:classification* / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D012680:Sensitivity and Specificity; D013961:Thyroid Gland / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000473:pathology*; D016606:Thyroid Nodule / Q000473:pathology*