Accuracy of thin-layer cytology in patients undergoing cervical cone biopsy

Prevention of Cervical Cancer: Guideline of the DGGG and the DKG (S3 Level, AWMF Register Number 015/027OL, December 2017) - Part 1 with Introduction, Screening and the Pathology of Cervical Dysplasia

Aims Annual opportunistic screening for cervical carcinoma has been carried out in Germany since 1971. The creation of this S3 guideline meets an important need, outlined in the National Cancer Plan, with regard to screening for cervical cancer, as the guideline aims to provide important information and support for planned organized screening for cervical cancer in Germany. Methods With the financial support of German Cancer Aid, 21 professional societies developed evidence-based statements and recommendations (classified using the GRADE system) for the screening, management and treatment of precancerous conditions of the cervix. Two independent scientific institutes compiled systematic reviews for this guideline. Recommendations The first part of this short summary presents the pathological basis and considers various questions related to screening for cervical cancer. As also reported in earlier reviews, the meta-analysis by Kleijnen Systematic Reviews showed that HPV-based screening offers better protection against invasive cervical cancer compared to cytology-based screening. The authors of this guideline therefore recommend - in accordance with the guideline of the Joint National Committee of Germany (Gemeinsamer Bundesauschuss, G-BA) - that women aged 35 and above should be examined at regular intervals (at least every 3 years) and undergo HPV-based screening. Co-testing can also be carried out. Women between the ages of 20 and 35 should have cytological screening every 2 years.

The advantages of incorporating liquid-based cytology (TACAS™) in mass screening for cervical cancer

We incorporated liquid-based cytology (LBC) in population-based screening for cervical cancer. The usefulness of using LBC in mass screening for cervical cancer was examined. From 2009 to 2014, 157,061 individuals underwent mass screening for cervical cancer in Aomori Prefecture. From 2009 to 2011, cells were collected from 82,218 individuals and the specimens were conventionally prepared (CP). From 2012 to 2014, cells were collected from 74,843 individuals and the specimens were prepared using LBC (TACAS™). Cytology results for the 2 sets of specimens were compared and differences in cytologic features were examined. ASC-US and more severe lesions were detected at a rate of 1.13 % by CP and 1.44 % by LBC, so LBC had a 1.3-fold higher rate of detection. LBC had a 1.6-fold higher rate of LSIL detection and a 1.2-fold higher rate of HSIL detection. CP detected cancer in 20 cases at a rate of 0.024 % while LBC detected cancer in 18 cases at a rate of 0.024 %. Cytodiagnosis of the 18 cases of SCC that LBC identified revealed that 7 were SCC, 8 were HSIL, and 3 were ASC-H. Atypical cells tended to be smaller with TACAS™. LBC reduced the time needed for microscopic examination of a single specimen by 42 % in comparison to CP. LBC using TACAS™ allowed the detection of slight lesions and slight changes in cells. LBC can lessen the burden on medical personnel and may lead to improved accuracy.

Comparison of conventional and liquid-based cytology, and human papillomavirus testing using SurePath preparation in Japan

We compared the detection rate of cervical neoplasias between a liquid-based cytology (LBC) method using SurePath and the conventional method. We also studied the feasibility of human papillomavirus (HPV) typing by linear array assay. Cytological specimens from 1551 Japanese women were prepared using the conventional and SurePath methods; the cytological and histological results from biopsy samples were compared. HPV typing using an HPV linear array assay was carried out on residual specimens using the SurePath method. The cytodiagnostic results showed a concordance rate of 85.3% (Κ= 0.46) between the two methods. The sensitivity of lesions histopathologically diagnosed as CIN1 or above was not significantly different between the two methods (P = 0.575-1.000). The receiver operating characteristic curve analysis of the detectability in CIN2 or above revealed no significant difference between the two methods (P = 0.096). Among the 44 patients who underwent HPV typing using a linear array assay, 33 samples were eligible for HPV testing and were stored at ambient temperature. In conclusion, the SurePath and conventional methods have equivalent abilities for detecting cervical lesions. After preparation for cytological diagnosis, use of the remaining cells from the SurePath specimens to perform HPV typing using the linear array method could be feasible.

Liqui-Prep® versus conventional Papanicolaou smear to detect cervical cells abnormality by split-sample technique: a randomized double-blind controlled trial

To assess the diagnostic performances of LiquiPrep® (LP) to detect cervical cellular abnormality in comparison to Papanicolaou (Pap) smear in 194 women with abnormal cervical cytology who were scheduled for colposcopy at the institution between January 2008 and November 2008. The women were randomized to undergo a repeated cervical cytologic evaluation by Pap smear followed by LP, or the two methods in alternating order. The pathologist was blinded to previous cytologic diagnosis and the pair of slides assigned for each woman. Cytologic results from each method were compared to subsequent histopathology. Mean screening time for each LP and Pap slides were 4.3 ± 1.2 minutes and 5.4 ± 1.1 minutes, respectively (P < 0.001). From 194 cases, ASC or AGC were diagnosed in 72 cases (37.1%) from LP and 68 cases (35.1%) from Pap smear. After excluding the ASC/AGC group, the overall cytologic diagnostic agreement between the two tests were 69 of 87 cases (73.6%) while the agreements with histologic diagnoses were 39/87 cases from LP (44.8%) and 41 (47.1%) from Pap smear (P = 0.824). The accuracy of LP was not significantly different from Pap test, 43.4% (95% confidence interval [CI]: 34.8-52.1%) compared to 44.4% (95% CI: 35.7-53.1%). LP did not have superior performance over Pap test to detect high-grade lesions (≥ cervical intraepithelial neoplasia II) using ASC/AGC as the threshold with the sensitivity of 70.5% (95% CI: 64.0-76.9%) versus 77.3% (95% CI: 71.4-83.2%), respectively.

A randomised comparison of SurePath liquid-based cytology and conventional smear cytology in a colposcopy clinic setting

OBJECTIVE

The objective of this study was to compare the sensitivity of cervical cytology using conventional smears and SurePath liquid-based cytology (LBC).

DESIGN

Prospective randomised evaluation of diagnostic test.

SETTING

A single institution colposcopy clinic.

POPULATION

Women attending first visit colposcopy appointments were offered entry into the study.

METHODS

Cervical cytology samples from 913 women of age 16-75 years were randomly processed as SurePath LBC or conventional smears. Conventional smears were taken for 453 women and a SurePath LBC taken for 451 women. Cytology results were correlated with colposcopic findings and histology from colposcopic biopsies, treatment and follow up.

MAIN OUTCOME MEASURES

To compare the sensitivity of SurePath LBC and conventional smears for histologically proven abnormality. Other outcome measures include a comparison of their sensitivity for high-grade abnormalities and their satisfactory rate.

RESULTS

Accounting for all randomised samples, there was a trend towards improved sensitivity for SurePath LBC (79.1 versus 73.7%, P = 0.1). However, excluding unsatisfactory cytology (and samples not taken) eliminated this trend; the sensitivity for both LBC and conventional smears for any epithelial abnormality was 81%. With a threshold of atypical squamous cells of uncertain significance (ASC-US), both SurePath LBC and conventional smears had a sensitivity of 92% for high-grade lesions. SurePath LBC was less likely to be reported as unsatisfactory (2.7 versus 9.1%, P < 0.0001).

CONCLUSIONS

In this context, with a threshold of ASC-US, both SurePath LBC and conventional smears offer high sensitivity for the detection of CIN2/3, but SurePath LBC is less likely to be reported as unsatisfactory.

Liquid compared with conventional cervical cytology: a systematic review and meta-analysis

OBJECTIVE

To compare test performance characteristics of conventional Pap tests and liquid-based cervical cytology samples.

DATA SOURCES

Eligible studies, published between 1991 and 2007, were retrieved through PubMed/EmBase searching and completed by consultation of other sources.

METHODS OF STUDY SELECTION

Studies were selected if a conventional and a liquid-based sample were prepared from the same woman or when one or the other type of sample was taken from a separate but similar cohort. The current systematic review and meta-analysis is restricted to studies where all subjects were submitted to gold standard verification, based on colposcopy and histology of colposcopy-targeted biopsies, allowing computation of absolute and relative test validity for cervical intraepithelial neoplasia grade 2 or worse. Randomized trials were selected as well if all test-positive cases were verified with the same gold standard, allowing computation of the relative sensitivity. Impact of study characteristics on accuracy was assessed by subgroup meta-analyses, meta-regression, and summary receiver operating characteristic curve regression.

TABULATION, INTEGRATION, AND RESULTS

The relative sensitivity, pooled from eight studies, with complete gold standard verification and from one randomized clinical trial, did not differ significantly from unity. Also, the specificity, considering high-grade and low-grade squamous intraepithelial lesions as cutoff, was similar in conventional and liquid cytology. However, a lower pooled specificity was found for liquid-based cytology when presence of atypical squamous cells of undetermined significance was the cutoff (ratio 0.91, 95% confidence interval 0.84-0.98). Differences in study characteristics did not explain interstudy heterogeneity.

CONCLUSION

Liquid-based cervical cytology is neither more sensitive nor more specific for detection of high-grade cervical intraepithelial neoplasia compared with the conventional Pap test.

Accuracy of liquid based versus conventional cytology: overall results of new technologies for cervical cancer screening: randomised controlled trial

OBJECTIVE

To compare the accuracy of conventional cytology with liquid based cytology for primary screening of cervical cancer.

DESIGN

Randomised controlled trial.

SETTING

Nine screening programmes in Italy.

PARTICIPANTS

Women aged 25-60 attending for a new screening round: 22 466 were assigned to the conventional arm and 22 708 were assigned to the experimental arm.

INTERVENTIONS

Conventional cytology compared with liquid based cytology and testing for human papillomavirus.

MAIN OUTCOME MEASURE

Relative sensitivity for cervical intraepithelial neoplasia of grade 2 or more at blindly reviewed histology, with atypical cells of undetermined significance or more severe cytology considered a positive result.

RESULTS

In an intention to screen analysis liquid based cytology showed no significant increase in sensitivity for cervical intraepithelial neoplasia of grade 2 or more (relative sensitivity 1.17, 95% confidence interval 0.87 to 1.56) whereas the positive predictive value was reduced (relative positive predictive value v conventional cytology 0.58, 0.44 to 0.77). Liquid based cytology detected more lesions of grade 1 or more (relative sensitivity 1.68, 1.40 to 2.02), with a larger increase among women aged 25-34 (P for heterogeneity 0.0006), but did not detect more lesions of grade 3 or more (relative sensitivity 0.84, 0.56 to 1.25). Results were similar when only low grade intraepithelial lesions or more severe cytology were considered a positive result. No evidence was found of heterogeneity between centres or of improvement with increasing time from start of the study. The relative frequency of women with at least one unsatisfactory result was lower with liquid based cytology (0.62, 0.56 to 0.69).

CONCLUSION

Liquid based cytology showed no statistically significant difference in sensitivity to conventional cytology for detection of cervical intraepithelial neoplasia of grade 2 or more. More positive results were found, however, leading to a lower positive predictive value. A large reduction in unsatisfactory smears was evident.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN81678807 [controlled-trials.com].

Accuracy of reading liquid based cytology slides using the ThinPrep Imager compared with conventional cytology: prospective study

OBJECTIVE

To compare the accuracy of liquid based cytology using the computerised ThinPrep Imager with that of manually read conventional cytology.

DESIGN

Prospective study.

SETTING

Pathology laboratory in Sydney, Australia.

PARTICIPANTS

55,164 split sample pairs (liquid based sample collected after conventional sample from one collection) from consecutive samples of women choosing both types of cytology and whose specimens were examined between August 2004 and June 2005.

MAIN OUTCOME MEASURES

Primary outcome was accuracy of slides for detecting squamous lesions. Secondary outcomes were rate of unsatisfactory slides, distribution of squamous cytological classifications, and accuracy of detecting glandular lesions.

RESULTS

Fewer unsatisfactory slides were found for imager read cytology than for conventional cytology (1.8% v 3.1%; P<0.001). More slides were classified as abnormal by imager read cytology (7.4% v 6.0% overall and 2.8% v 2.2% for cervical intraepithelial neoplasia of grade 1 or higher). Among 550 patients in whom imager read cytology was cervical intraepithelial neoplasia grade 1 or higher and conventional cytology was less severe than grade 1, 133 of 380 biopsy samples taken were high grade histology. Among 294 patients in whom imager read cytology was less severe than cervical intraepithelial neoplasia grade 1 and conventional cytology was grade 1 or higher, 62 of 210 biopsy samples taken were high grade histology. Imager read cytology therefore detected 71 more cases of high grade histology than did conventional cytology, resulting from 170 more biopsies. Similar results were found when one pathologist reread the slides, masked to cytology results.

CONCLUSION

The ThinPrep Imager detects 1.29 more cases of histological high grade squamous disease per 1000 women screened than conventional cytology, with cervical intraepithelial neoplasia grade 1 as the threshold for referral to colposcopy. More imager read slides than conventional slides were satisfactory for examination and more contained low grade cytological abnormalities.

Liquid-based cytology for cervical cancer screening

In multiple studies during the last decade, liquid-based cytology for cervical cancer screening has been shown to increase the detection rate for preneoplastic squamous intraepithelial lesions equal to or greater than the conventional Papanicolaou (Pap) smear method. Liquid-based collection and processing provide more representative cervical sampling than conventional smearing of the specimen on a glass slide. Currently, there are two test methodologies that are widely marketed and available to clinical laboratories, health systems and clinicians that undertake cervical cytology. The purpose of this article is to provide an overview of the methodology and performance of SurePath Liquid-Based Pap Test in cervical cytology screening. The SurePath liquid-based Pap test significantly reduces the unsatisfactory rate of Pap test slides, and detects a significantly higher number of low- and high-grade squamous lesions when compared with the conventional Pap smear technique. Biopsy confirmation shows that this increased detection does not come at a cost of decreasing specificity, and sensitivity for histologic dysplasia is equal to or greater than the best available data for the conventional Pap method. The SurePath collection vial provides residual cellular material for adjunctive out-of-the-vial molecular testing, including sexually transmitted diseases and oncologic biomarkers associated with cervical carcinoma. Finally, SurePath slides can be placed on an automated cervical cytology screening device (FocalPoint), thus providing improved disease detection and enhanced laboratory productivity.

Effect of study design and quality on unsatisfactory rates, cytology classifications, and accuracy in liquid-based versus conventional cervical cytology: a systematic review

BACKGROUND

Liquid-based cytology is reported to increase the sensitivity of cervical cytology and the proportion of slides that are satisfactory for assessment, in comparison with conventional cytology. Although some countries have changed to liquid-based cytology for cervical screening, controversy remains. We reviewed the published work to assess the performance of liquid-based cytology relative to conventional cytology in primary studies assessed to be of low, medium, or high methodological quality.

METHODS

56 primary studies were reviewed and assessed with strict methodological criteria. Liquid-based cytology and conventional cytology were compared in terms of the percentage of slides classified as unsatisfactory, the percentage of slides classified in each cytology category, and the accuracy of detection of high-grade disease. Data were examined for studies overall and in strata to examine the effect of study quality on results.

FINDINGS

The median difference in the percentage of unsatisfactory slides between liquid-based cytology and conventional cytology was 0.17%. Only one small study was a randomised controlled trial. The classification of high-grade squamous epithelial lesion varied according to study quality (p=0.04), with conventional cytology classifying more slides in this category than did liquid-based cytology in high-quality studies (n=3) only. In medium-quality (n=30) and high-quality studies, liquid-based cytology classified more slides as atypical squamous cells of unknown significance than did conventional cytology when compared with low-quality studies (n=17; p=0.05). Only four studies provided sufficient verified data to allow estimation of sensitivity and specificity and comparison of test accuracy.

INTERPRETATION

We saw no evidence that liquid-based cytology reduced the proportion of unsatisfactory slides, or detected more high-grade lesions in high-quality studies, than conventional cytology. This review does not lend support to claims of better performance by liquid-based cytology. Large randomised controlled trials are needed.

Efficiency of an inexpensive liquid-based cytology performed by cytocentrifugations: a comparative study using the histology as reference standard

BACKGROUND

Although liquid-based cytology (LBC) is now recommended for cervical cancer screening, it requires expensive automated devices and materials. To evaluate the efficiency of inexpensive LBC methods relying on an inexpensive fixative liquid, Easyfix, we compared the results obtained by the liquid-based cytology (LBC) diagnoses performed by cytocentrifugations (Papspin and Turbitec) with those obtained by histology. Furthermore, we evaluated the efficiency of the fixative liquid, Easyfix, to preserve HPV DNA in the collected samples.

METHOD

266 LBC were compared with 174 colposcopies and 91 Loop Electrosurgical Excision Procedure (LEEP). Among the LBC, 51 were performed using the Papspin system and 215 were performed using the Turbitec system. To control the quality of the preservation liquid, Easyfix, we correlated the results of HCII assays with those of HPV PCR.

RESULTS

For Papspin and Turbitec systems, the sensitivities were respectively 82.6% (95% CI: 61.2-95.0%, p < 0.001) and 75.0% (95% CI: 64.4-89.8%, p < 0.001) and the specificities were 92.6% (95%CI: 76.5-99.1%, p < 0.001) and 96.2% (95% CI: 91.3-98.7%, p < 0.001). We find no statistical difference between the results of the both systems (p = ns). The sensitivity of the HCII was 86.4% (95% IC: 77.4-92.8%, p < 0.001) and the specificity was 39.4% (95% CI: 31.2-48.1%, p < 0.001). The comparison between HCII and HPV-PCR shows a good correlation: the kappa was 0.89.

CONCLUSION

LBC performed by cytocentrifugations are inexpensive, reduce inadequate smears, show excellent efficiency and allow HPV detection by molecular biology.

Can we substitute brush cytology for biopsy in the evaluation of cervical lesions under the guidance of colposcopy?

In cervical cancer screening, colposcopically directed biopsy is the gold standard method for identifying intraepithelial and occult invasive lesions of the uterine cervix. As biopsy needs special expertise and the procedure is not convenient for the patients, we sought to evaluate colposcopically directed brush cytology as a substitute for biopsy of cervical lesions. We studied a series of 150 women who were referred for colposcopic evaluation. Colposcopically directed brush cytology and biopsy were performed for all patients with abnormal colposcopic findings. A total of 40 samples were excluded due to unsatisfactory report of brush cytology. Of the remaining 110 samples, 34 abnormal pathologies were reported in biopsy evaluations, while only 9 abnormal cytologies were reported in brush cytology specimens. Brush cytology sensitivity and specificity were 26% and 97%, respectively. We conclude that colposcopically directed brush cytology is not a safe substitute for biopsy in the evaluation of cervical lesions.

Liquid-based cervical cytology

BACKGROUND

The objective of the current study was to evaluate the applicability of liquid-based cytology in the Netherlands population screening program for cervical cancer.

METHODS

A special committee performed an evaluation of all the available literature. Two methods were investigated: the AutoCytePrep system (currently known as ShurePath-system; TriPath Imaging, Burlington, NC) and the ThinPrep system (Cytyc, Boxborough, MA) for the detection of squamous epithelial abnormalities. All literature up to May 2000 was evaluated.

RESULTS

For the AutoCytePrep system, there were indications that the detection rate for atypical squamous cells of undetermined significance (ASCUS) or higher had lower sensitivity compared with conventional screening. No definitive statement could be made concerning the value of the AutoCytePrep system for the detection rate of low-grade squamous intraepithelial lesions (LSIL) or higher and high-grade squamous intraepithelial lesions (HSIL) or higher because of conflicting results. For the ThinPrep system, there were indications that the detection rate of ASCUS or higher had a higher detection rate compared with conventional screening, with slightly lower specificity. It is likely that the detection rate of LSIL or higher with the ThinPrep system had greater sensitivity compared with conventional screening with almost unchanged specificity. In addition, it is likely that the detection rate of HSIL or higher with the ThinPrep system had a higher detection rate and greater absolute sensitivity compared with conventional screening with almost unchanged relative and absolute specificity.

CONCLUSIONS

Further research that complies with the standards stated in the current study will be necessary to evaluate the applicability of the AutoCytePrep method. Further evaluation of the costs and benefits of the ThinPrep method should be undertaken to decide definitively whether to implement this method in the Netherlands population screening program.

Positive predictive value of liquid-based and conventional cervical Papanicolaou smears reported as malignant

OBJECTIVES

The predictive value of cervical Papanicolaou (Pap) smears reported as "positive for malignancy," especially those obtained by the liquid-based method, has not been adequately assessed. The objectives of this study are to determine the positive predictive value of Papanicolaou smears with features of malignancy, to compare the accuracy of Papanicolaou smears obtained by the liquid-based method to those obtained by the conventional technique in this setting, and to study the factors influencing a false-positive cytologic diagnosis of malignancy.

MATERIALS AND METHODS

Pap smears significant for malignant cytology were identified at Fletcher Allen Health Care Hospital in Burlington, VT, from May 1, 1995, to April 30, 2001. A retrospective review of the hospital records and pathology reports was performed documenting patient characteristics, the collection technique, and the final histology. An independent review of the cytology and histology was performed. The positive predictive value and false-positive rate of malignant cytology were calculated for the liquid-based and conventional Pap smear techniques.

RESULTS

A total of 472,743 Pap smears were performed during the period specified. One hundred four Pap smears were reported as positive for malignancy, yielding a prevalence rate of 0.02%. A total of 68 patients had paired cytology and histology specimens. Malignant cytology was identified in 36 smears obtained by the liquid-based technique and 32 smears obtained by the conventional technique. A true-positive result, meaning malignant cytology confirmed by the presence of invasive carcinoma on histology, was obtained in 61 of 68 (89.7%) patients. A false-positive result, meaning malignant cytology not confirmed by histology, was obtained in 7 of the 68 (10.3%) patients. The false-positive rate of malignant cytology was 8.4% for the liquid-based technique and 12.5% for the conventional technique. All 7 false-positive smears were diagnosed with high-grade dysplasia by histology. Three of the 7 patients with high-grade dysplasia had previous treatment for dysplasia, one of whom was also pregnant at the time of the smear.

CONCLUSIONS

Malignant cervical Papanicolaou smear cytology has a high positive predictive value in the setting of gynecologic and nongynecologic malignancies. Previous treatment for cervical dysplasia or pregnancy may influence the false-positive rate of malignant cytology.

Cross sectional study of conventional cervical smear, monolayer cytology, and human papillomavirus DNA testing for cervical cancer screening

OBJECTIVES

To compare the sensitivity, specificity, and interobserver reliability of conventional cervical smear tests, monolayer cytology, and human papillomavirus testing for screening for cervical cancer.

DESIGN

Cross sectional study in which the three techniques were performed simultaneously with a reference standard (colposcopy and histology).

SETTING

Public university and private practices in France, with complete independence from the suppliers.

PARTICIPANTS

828 women referred for colposcopy because of previously detected cytological abnormalities and 1757 women attending for routine smears.

MAIN OUTCOME MEASURES

Clinical readings and optimised interpretation (two blind readings followed, if necessary, by consensus). Sensitivity, specificity, and weighted kappa computed for various thresholds of abnormalities.

RESULTS

Conventional cervical smear tests were more often satisfactory (91% v 87%) according to the Bethesda system, more reliable (weighted kappa 0.70 v 0.57), and had consistently better sensitivity and specificity than monolayer cytology. These findings applied to clinical readings and optimised interpretations, low and high grade lesions, and populations with low and high incidence of abnormalities. Human papillomavirus testing associated with monolayer cytology, whether systematic or for atypical cells of undetermined significance, performed no better than conventional smear tests.

CONCLUSIONS

Monolayer cytology is less reliable and more likely to give false positive and false negative results than conventional cervical smear tests for screening for cervical cancer.

Cell block findings from residual PreservCyt samples in unsatisfactory ThinPrep Paps: no additional benefit

Our objective was to determine whether cell blocks (CB) performed on unsatisfactory ThinPrep Pap Test residual samples rendered additional clinically significant pathologic findings not detected in the original ThinPrep Pap smears. One hundred consecutive ThinPrep Paps categorized as unsatisfactory were selected for this study. The cytologic diagnosis of unsatisfactory was based on lack of cellularity (squamous) or complete obscuring blood or inflammation. Residual PreservCyt samples from these consecutive unsatisfactory ThinPrepPaps were used to prepare a cell block, using the inverted filter technique. One hematoxylin-eosin (H&E)-stained slide was prepared and evaluated. The amount and the cellular changes were noted for all smear constituents and compared with the original slides. The average patient age was 32 +/- 11 yr. The ThinPrepPap was performed as a follow-up on a previous abnormal smear (12%), pregnancy (25%), abnormal bleeding (22%), or previous unsatisfactory ThinPrepPap (5%), or as routine screening (36%). Variable amounts of endocervical cells, endometrial cells, and metaplastic cells, as well as a variable number of squamous epithelial cells, were present in 89%, 9%, 50%, and 35% in the CB method vs. ThinPrep, respectively. Abnormal cellular changes were noted in 15% of patients (9% with LSIL, and 6% with atypia of undetermined significance); 9 patients with squamous dysplasia had a previous abnormal ThinPrep Pap. A follow-up Pap smear and/or cervical biopsy were performed in 10 of the 15 patients with abnormal cytology detected on CB method revealing: LSIL (1 patient), HSIL (1 patient), ASCUS (1 patient), and within normal limits (7 patients). The findings indicate that the preparation of a CB does not contribute significantly. Importantly, no carcinomas or HSILs were identified on CB preparations. Since a large majority of lesions identified were LSILs, a repeat Pap smear in these cases represented a more cost-effective strategy than cell block preparation, although a cell block preparation may be useful in selected cases.