ThinPrep Pap Test: performance and biopsy follow-up in a university hospital

Cancer. 1999 Jun 25;87(3):105-12. doi: 10.1002/(sici)1097-0142(19990625)87:3<105::aid-cncr2>;2-z.


Background: The ThinPrep Pap Test (TP), a liquid-based cervical cytology preparation, was approved for use in the U.S. in 1996. The purpose of this study was to compare TP performance and biopsy follow-up studies with a similar population of high risk patients sampled by conventional Papanicolaou (Pap) smear (CS).

Methods: Diagnostic and specimen adequacy interpretations for 2727 TP direct-to-vial Pap tests from a high risk university hospital practice were compared with 5000 CS preparations from the same physicians taken 1 year previously. Biopsy follow-up studies for the categories of squamous intraepithelial lesion (SIL), carcinoma, and atypical squamous cells of undetermined significance (ASCUS) for each time period and technique were contrasted.

Results: The SIL/carcinoma detection rate increased from 7.7% to 10.5% (P < 0.01) and the ASCUS rate decreased from 12.5% to 6.9% (P < 0.01); the percentage of satisfactory but limited specimens decreased from 19.4% to 10.5% (P < 0.01). Low grade SIL cases increased by 57% (P < 0.01) whereas the 26% increase in high grade SIL cases was not statistically significant. Greater than 90% of ungraded SIL, high grade SIL, and carcinoma cases had abnormal biopsies by both the TP and CS methods. The number of biopsy-confirmed high grade dysplasias and carcinomas was similar in the two groups. A low grade SIL detected by TP was less likely to have an abnormal biopsy (70% vs. 85% for CS). Nevertheless, the 57% increase in low grade SIL diagnoses by TP resulted in more TP patients with dysplastic biopsy diagnoses. Follow-up studies for ASCUS cases diagnosed by either TP or CS were similar, and 21-24% of patients eventually were found to have dysplasia.

Conclusions: The TP technique appears to lead to the increased detection of low grade SIL lesions, decreased satisfactory but limited samples, and fewer equivocal specimens. No increase in biopsy-confirmed high grade dysplasias and carcinomas was found. Follow-up studies for the ASCUS category were nearly identical to those for CS.

MeSH terms

  • Adult
  • Biopsy
  • Carcinoma / diagnosis*
  • Carcinoma / pathology
  • Cervix Uteri / pathology*
  • Female
  • Follow-Up Studies
  • Humans
  • Mass Screening / standards
  • Papanicolaou Test*
  • Reproducibility of Results
  • Uterine Cervical Neoplasms / diagnosis*
  • Uterine Cervical Neoplasms / pathology
  • Vaginal Smears / standards*