Diagnosis of invasive cervical carcinoma with fluid-based, thin-layer slide preparation method

Objectives: Although the main role of the Papanicolaou smear is to detect precursors of cervical cancer, the detection of invasive disease is important to identify women at the earliest stage of their disease. This study assesses the ability of the ThinPrep Papanicolaou test to identify invasive cervical cancer as compared to the Papanicolaou smear.Methods: A meta-analysis of five studies previously reviewed by the Food and Drug Administration was performed. There were 61 cases of cervical carcinoma processed by both conventional Papanicolaou smear and ThinPrep methods. Each case was reviewed by cytotechnologists and cytopathologists without knowledge of prior diagnoses. In a sub-study, the filtrate resulting from the preparation of the ThinPrep was analyzed to determine if diagnostic cells passed through the filter membrane.Results: With the ThinPrep method, a diagnosis of cancer was made in 54 cases (88.5%) as compared to a diagnosis of cancer in 52 of these cases with the conventional Papanicolaou smear method (85.2%). In those cases where diagnosis of invasive cancer was not made with the ThinPrep method, all cases were classified as abnormal, ranging from atypical glandular cells of undetermined significance to high-grade squamous intraepithelial lesions. The ThinPrep slides contained tumor diathesis and other contextual clues. Analysis of the ThinPrep filtrate demonstrated that cancer cells did not pass through the filter.Conclusions: These studies indicate that the ThinPrep method is at least equivalent to the conventional Papanicolaou smear method for the demonstration of squamous cell carcinoma, adenocarcinoma, and other cervical malignancies. Diagnostically important cells are not lost through the filter membrane during the preparation of the ThinPrep slide, because they are larger than the 8 µm pore size of the filter.