title: Stability of archived liquid-based cervical cytologic specimens.
abstract: BACKGROUND
  Exfoliated cervical cell specimens collected in PreservCyt, a methanol-based medium used in ThinPrep liquid-based cytology, have been archived in epidemiologic studies. However, long-term DNA stability and cytologic stability of these biospecimens have not been evaluated.
  
  
  METHODS
  Cervical specimens were collected into PreservCyt from participants in a natural history study of human papillomavirus (HPV) infection and cervical carcinoma in Guanacaste, Costa Rica (1993-2000), and stored at ambient temperatures. Thirty specimens classified as low-grade squamous intraepithelial lesions by liquid-based cytology were randomly chosen from each collection year (except for 1994) and selectively assessed for molecular and cytologic stability. Specimens were tested in 2001 for 1) HPV DNA by the Hybrid Capture 2 test, 2) beta-globin DNA by polymerase chain reaction amplification of multiple length fragments (268, 610, and 1327 bp), and 3) nuclear preservation by visual inspection of newly made liquid-based cytology slides. All testing was done masked to year of collection. Associations of stability and storage time were evaluated using standard contingency tables and chi-square tests for trend.
  
  
  RESULTS
  Human papillomavirus DNA, as detected by the Hybrid Capture 2 test, was unaffected by storage time. Stability of beta-globin DNA (P(Trend) < 0.0001) and nuclear preservation (P(Trend) < 0.0001) declined with increasing storage time. Approximately 15% of specimens could not be amplified for any beta-globin DNA fragment after 5 years of storage (collected in 1996). In addition, cytology slides made from 41% specimens were rated as marginal (32%) or unsatisfactory (9%) after 8 years of storage (collected in 1993).
  
  
  CONCLUSIONS
  Cervical specimens archived in PreservCyt underwent partial DNA and cytologic degradation after several years of storage. Methodologic studies to optimize long-term storage of cervical cells for epidemiologic studies of cervical carcinoma are needed.
authors.affiliation: The National Cancer Institute, Division of Cancer Epidemiology and Genetics, Rockville, Maryland 20892-7234, USA. castlep@mail.nih.gov
authors.forename: Philip E
authors.initials: PE
authors.lastname: Castle
authors.forename: Diane
authors.initials: D
authors.lastname: Solomon
authors.forename: Allan
authors.initials: A
authors.lastname: Hildesheim
authors.forename: Rolando
authors.initials: R
authors.lastname: Herrero
authors.forename: M
authors.initials: M
authors.lastname: Concepcion Bratti
authors.forename: Mark E
authors.initials: ME
authors.lastname: Sherman
authors.forename: Ana
authors.initials: A
authors.lastname: Cecilia Rodriguez
authors.forename: Mario
authors.initials: M
authors.lastname: Alfaro
authors.forename: Martha L
authors.initials: ML
authors.lastname: Hutchinson
authors.forename: S
authors.initials: S
authors.lastname: Terence Dunn
authors.forename: Jane
authors.initials: J
authors.lastname: Kuypers
authors.forename: Mark
authors.initials: M
authors.lastname: Schiffman
mesh_terms: D000328:Adult; D004279:DNA, Viral / Q000032:analysis*; D005260:Female; D006801:Humans; D000432:Methanol; D027383:Papillomaviridae / Q000235:genetics* / Q000472:pathogenicity; D030361:Papillomavirus Infections / Q000175:diagnosis; D016133:Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D012997:Solvents; D013048:Specimen Handling; D013696:Temperature; D013997:Time Factors; D014021:Tissue Preservation / Q000379:methods*; D014412:Tumor Virus Infections / Q000175:diagnosis; D014626:Vaginal Smears; D002578:Uterine Cervical Dysplasia / Q000175:diagnosis* / Q000473:pathology / Q000821:virology
chemical_list: D004279:DNA, Viral; D012997:Solvents; D000432:Methanol