title: DNA degradation in liquid-based cytology and its comparison with conventional smear.
abstract: BACKGROUND
  In fine needle aspiration biopsy (FNAB) of thyroid nodules, LBC is adopted in most of the hospitals and clinics in Korea for its convenience. BRAF mutation test has been introduced as an important ancillary test, but its applicability has not been completely proven with LBC samples.
  
  
  METHODS
  Five aspirates from thyroidectomy specimens were simultaneously processed into LBC and CS slides, in which BRAF mutation tests were performed using three primer sets with PCR products of 72, 164, and 226 base pairs (bp) at 6, 9, and 12 months after processing. In addition, BRAF mutation tests were performed in nine clinical samples that had been prepared by LBC or CS and stored for 3-5 years after processing.
  
  
  RESULTS
  At 9 months after processing, LBC failed to provide DNA of sufficient quality for PCR, whereas CS succeeded with primers for amplifying a 226 bp fragment. Furthermore, CS had successful amplification of DNA despite a delay of more than 1 year. The failure of DNA amplification in LBC was overcome by using primers to amplify shorter PCR products, suggesting that DNA degradation occurred in LBC. However, false positive or negative results were observed in primers for amplifying shorter size. The kind of preservative solutions used in LBC did not affect test results.
  
  
  CONCLUSIONS
  LBC may have disadvantages in long-term DNA preservation because of its accelerated DNA degradation compared with alcohol-fixed CS. Using primers to amplify shorter size fragments might be helpful in mitigating loss of signal due to DNA degradation in LBC.
authors.affiliation: Department of Pathology, the Research Institute of Medical Science, Konkuk University School of Medicine, Seoul, Korea.
authors.forename: Wook Youn
authors.initials: WY
authors.lastname: Kim
authors.affiliation: Department of Pathology, Konkuk University Medical Center, Seoul, Korea.
authors.forename: Seo Young
authors.initials: SY
authors.lastname: Oh
authors.affiliation: Department of Pathology, the Research Institute of Medical Science, Konkuk University School of Medicine, Seoul, Korea.
authors.forename: Hyunkyung
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Pathology, the Research Institute of Medical Science, Konkuk University School of Medicine, Seoul, Korea.
authors.forename: Tae Sook
authors.initials: TS
authors.lastname: Hwang
mesh_terms: D004247:DNA / Q000737:chemistry* / Q000235:genetics; D005820:Genetic Testing / Q000379:methods* / Q000592:standards; D006801:Humans; D006868:Hydrolysis; D009154:Mutation; D065006:Papanicolaou Test / Q000009:adverse effects / Q000379:methods*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods; D016606:Thyroid Nodule / Q000235:genetics / Q000473:pathology*
chemical_list: D004247:DNA; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf
keywords: BRAF mutation test; DNA degradation; conventional smear; fine needle aspiration; liquid-based cytology; thyroid