Stability of archived liquid-based cervical cytologic specimens.
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cervical cell specimens collected in PreservCyt, a methanol-based medium used in ThinPrep liquid-based cytology, have been archived in epidemiologic studies.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.
Castle
Philip E
PE
The National Cancer Institute, Division of Cancer Epidemiology and Genetics, Rockville, Maryland 20892-7234, USA. castlep@mail.nih.gov
Solomon
Diane
D
Hildesheim
Allan
A
Herrero
Rolando
R
Concepcion Bratti
M
M
Sherman
Mark E
ME
Cecilia Rodriguez
Ana
A
Alfaro
Mario
M
Hutchinson
Martha L
ML
Terence Dunn
S
S
Kuypers
Jane
J
Schiffman
Mark
M
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
D004279:DNA, Viral; D012997:Solvents; D000432:Methanol