Clinical results of a split sample liquid-based cytology (ThinPrep) study of 4,322 patients in a Turkish institution.

Purpose: A prospective study was carried out to compare the efficacy of liquid-based cytology (ThinPrep) with the conventional Pap smear using a split-sample design in a Turkish university hospital outpatient gynecology clinic.
Methods: 4,322 consecutive patients were recruited for the study between 2002 and 2003. All the patients underwent conventional Pap tests followed by a ThinPrep test for screening of cervical cancer. The results were evaluated in terms of the Bethesda III classification. All the patients with abnormal tests underwent colposcopy and directed biopsy.
Results: While 2.3% of the specimens were unsatisfactory for evaluation in the conventional Pap test group, this rate was 1.7% for the ThinPrep group. Epithelial cell abnormalities were observed in 42 (1.0%) patients in the conventional Pap test group and in 36 (0.8%) patients in the ThinPrep group. ASCUS was observed in 26 patients in the conventional Pap test group whereas the ThinPrep group had 20 cases of ASCUS as the leading cause of abnormal cytology. Biopsy of these cases revealed CIN 1 in two CIN 2-3 in three and cervical/endometrial adenocarcinoma in three patients. The ThinPrep application led to diagnoses of one additional case of CIN 2-3 and one case of adenocarcinoma among the negative or unsatisfactory for evaluation categories of the conventional Pap test group.
Conclusion: Despite an adverse bias introduced by the split-sample study design, application of ThinPrep showed an improved rate of specimen adequacy and increased sensitivity for more significant cervical precursor lesions over the conventional Pap test.