Efficacy of ThinPrep preparation of cervical smears: a 1,000-case, investigator-sponsored study

The diagnoses of 1,000 pairs of conventional Papanicolaou (Pap) smears and ThinPrep preparations were compared. Cervical cells were collected using an Ayre spatula and endocervical brush. The conventional smear was made first, the collection devices were rinsed into PreservCyt solution, and the slides were prepared using the ThinPrep Processor. The diagnoses of the paired smears agreed in 988 of the 1,000 cases (98.8%), including 949 negatives, 28 atypicals, 9 low grade squamous intraepithelial lesions (LGSIL), and 2 high grade squamous intraepithelial lesions (HGSIL). Five cases where LGSIL or HGSIL was found on the ThinPrep slide were negative or atypical on the conventional smear. No conventional smear abnormalities were missed on the ThinPrep slide. Although not statistically significant, this difference indicates that the ThinPrep method gives a better diagnosis of abnormalities than the conventional method. The ThinPrep method was acceptable to participating physicians and ThinPreps were easier and faster to screen than conventional smears.