Evaluation of PAPNET-assisted cervical rescreening

Evaluation of PAPNET-assisted cervical rescreening
We have compared the results of targeted manual rescreening of 1211 randomly selected smears with the results of PAPNET-assisted rescreening of 1613 cervical smears, containing at least 6.3% low-grade squamous intraepithelial lesion (SIL). PAPNET diagnosis and the targeted rescreening diagnosis were compared with the initial report, issued on the corresponding smear. Reproducibility scores for inadequacy, presence of endocervical and endometrial cells, specific infections and squamous cell abnormalities were determined. The reproducibility scores for the diagnosis of inadequate smears and specific infections were lower with the PAPNET-assisted rescreening. The detection of squamous cell abnormalities was excellent for both methods (>0.95), with a higher detection rate for false-negative smears with the PAPNET testing system.     

Prospective study of PAPNET: review of 25656 Pap smears negative on manual screening and rapid rescreening

In this prospective study, 27,014 Pap smears were selected for PAPNET review on the request of the referring practitioner or patient. Smears that were negative on routine manual screening were submitted for rapid rescreening. Smears considered normal after these two manual screens (n = 25,656) were reviewed using the PAPNET testing system. Routine manual screening identified 1340 (4.96%) of the smears as abnormal, and a further 18 (0.07%) abnormalities were detected by rapid rescreening. PAPNET review identified an additional 102 (0.4%) abnormal smears, including 10 histologically confirmed high grade lesions. The use of PAPNET testing following routine manual screening and rapid rescreening in tandem, enables cytologists to detect additional diagnostically significant abnormalities and reduce the rate of false-negative smears.     

Computer-assisted primary screening of cervical smears using the PAPNET method: comparison with conventional screening and evaluation of the role of the cytologist

The PAPNET method is an interactive computer-assisted screening procedure. the diagnostician selects the abnormal video tiles out of the 128 and decides which smears need additional light microscopy. the original diagnoses of 1494 archival smears were compared with the PAPNET analysis of the same smears. the general trend observed was that the PAPNET-assisted diagnoses were of a higher grade than those assigned by the primary screener, thus less cases were signed out as negative. In addition, the PAPNET method was used for primary screening of 2971 randomly selected smears, whilst in the same period 5797 smears were conventionally screened. Using the PAPNET method, significantly fewer smears were signed out as negative. Seventy-three percent of the cases were diagnosed on the basis of the information provided by the 128 video tiles, 11% had to be screened completely by the light microscope, and the remaining cases needed additional light microscopy of a part of the smear. As a result, PAPNET-assisted screening was approximately two times faster. the great advantage of the method is that it is much less tiring for the eyes than conventional screening, making fatigue-related errors less likely, and if a smear contains only a few abnormal cells, these are easier to find.     

Cost analysis of PAPNET-assisted vs. conventional Pap smear evaluation in primary screening of cervical smears

OBJECTIVE: To assess the difference in costs between PAPNET-assisted and conventional microscopy of cervical smears when used as a primary screening tool. STUDY DESIGN: We performed time measurements of the initial screening of smears by four cytotechnologists in one laboratory. Time was measured in 816 conventionally screened smears and in 614 smears with PAPNET-assisted screening. Data were collected on the components of initial screening, clerical activities and other activities in the total work time of cytotechnologists in the routine situation and on resource requirements for both techniques. RESULTS: PAPNET saved an average of 22% on initial screening time per smear. Due to costs of processing and additional equipment, the costs of PAPNET-assisted screening were estimated to be $2.85 (and at least $1.79) higher per smear than conventional microscopy. The difference in costs is sensitive to the rate of time saving, the possibility of saving on quality control procedures and the component of the initial screening time in the total work time of cytotechnologists. CONCLUSION: Although PAPNET is time saving as compared with conventional microscopy, the associated reduction in personnel costs is outweighed by the costs of scanning the slides and additional equipment. This conclusion holds under a variety of assumptions. Using PAPNET instead of conventional microscopy as a primary screening tool will make cervical cancer screening less cost-effective unless the costs of PAPNET are considerably reduced and its sensitivity and/or specificity are considerably improved.     

Evaluation of 100% rapid rescreening of negative cervical smears as a quality assurance measure

OBJECTIVE: The objective of this study was to compare the performance of 100% rapid rescreening, 10% random rescreening and the review of smears selected on the basis of clinical criteria, as a method of internal quality control of cervical smears classified as negative during routine screening. METHODS: A total of 3149 smears were analysed, 173 of which were classified as positive and 2887 as negative, while 89 smears were considered unsatisfactory. The smears classified as negative were submitted to 100% rapid rescreening, 10% random rescreening, and rescreening based on clinical criteria. The rescreening stages were blinded and results were classified according to the Bethesda 2001 terminology. Six cytologists participated in this study, two of whom were responsible for routine screening while the other four alternated in carrying out rescreening so that no individual reviewed the same slide more than once. RESULTS: The 100% rapid rescreening method identified 92 suspect smears, of which 42 were considered positive at final diagnosis. Of the 289 smears submitted to the 10% rescreening method, four were considered abnormal but only one was confirmed positive in the final diagnosis. Of the 690 smears rescreened on the basis of clinical criteria, 10 were considered abnormal and eight received a positive final diagnosis. CONCLUSIONS: The 100% rapid rescreening method is more efficient at detecting false-negative results than 10% random rescreening or rescreening on the basis of clinical criteria, and is recommended as an internal quality control method.     

The use of the PAPNET automated cytological screening system for the diagnosis of oral squamous carcinoma

levine t. s., njemenze v., cowpe j. g. and coleman d. v. (1998) Cytopathology 9, 398–405
The use of the PAPNET automated cytological screening system for the diagnosis of oral squamous carcinoma
The automated PAPNET screening system has been developed to recognize abnormal cells in cervical smears. Given that the oral mucosa sheds cells resembling superficial and intermediate cells of the cervix, the aim of this study was to assess whether the PAPNET system could be used to detect dysplastic cells in oral mucosal smears. Sixty-two oral smears from 27 patients were examined by both light microscopy and using the PAPNET system from clinically abnormal and normal areas by two pathologists. The clinically abnormal sites were also biopsied for histological analysis. There was 100% correlation between the manual and PAPNET screening results. Cytological interpretation of oral smears by both manual and PAPNET screening methods correctly diagnosed squamous cell carcinoma in 14/23 (61%) of patients who had all been confirmed by biopsy. The nine patients with false-negative cases could be attributed to poor smear technique and preparation. The PAPNET system can be used to identify abnormal cells in oral smears and, as such, may have an application for screening those populations at high risk of oral cancer—provided that adequate tuition is given in smear technique.     

Quality assurance in cervical smears: 100% rapid rescreening vs. 10% random rescreening

OBJECTIVE: To compare 100% rapid rescreening of cervical smears with 10% random rescreening as a method of quality assurance. STUDY DESIGN: A total of 5215 smears, randomly selected from smears reported as negative by cytotechnologists during routine screening, underwent 100% rapid rescreening by senior cytotechnologists. Ten percent of these smears, selected at random, were rescreened by other senior cytotechnologists. The gold standard was defined by cytopathologists, who rescreened all 5215 smears. After excluding unsatisfactory smears detected by cytopathologists, 4271 were included in the analysis. RESULTS: The 100% rapid rescreening method identified 69.9%, 95.7% and 100%, respectively, of atypical squamous cells of undetermined significance, low grade squamous intraepithelial lesion and high grade squamous intraepithelial lesion cases reported by the cytopathologists. The 100% rapid rescreening method showed a sensitivity of 73.5% and specificity of 98.6%. The 10% rescreening method showed sensitivity of 40.9% and specificity of 98.8%. CONCLUSION: One hundred percent rapid rescreening is an efficient method of internal quality assurance in cervical smear diagnosis. It can reduce the false negative rate and therefore can provide greater certainty to women who have received negative results. Well-trained cytotechnologists are able to identify abnormal smears in 1-minute rapid rescreening.     

Accuracy of liquid-based Pap tests: comparison of concurrent liquid-based tests and cervical biopsies on 782 women with previously abnormal Pap smears

OBJECTIVE: To evaluate the diagnostic performance of a liquid-based Pap test, the ThinPrep Pap test (TP) (Cytyc Corp., Boxborough, Massachusetts, U.S.A.), by comparing concurrent TP and cervical biopsy results on 782 patients who were referred for colposcopy because of previously abnormal conventional Pap smears (CPs). STUDY DESIGN: The ability of TP diagnoses of atypical cells of undetermined significance (ASC-US) and squamous intraepithelial lesions (SILs) to predict biopsy diagnoses of cervical intraepithelial neoplasia (CIN) was analyzed using chi2 and McNemar tests. RESULTS: The rate of agreement between diagnoses of SIL by TP and CIN by biopsy was 74.7%. ASC-US accounted for 16.0% of TP diagnoses. ASC-US had biopsy diagnoses of CIN 1 in 60% and CIN 2/3 in 12.8% of cases. For TP diagnosis of low grade SIL, biopsy diagnoses of CIN 2/3 were found in 13.5% of cases. For TP diagnoses of ASC-US and higher, the proportions of TP and cervical biopsies in comparable diagnostic categories were statistically significant (p < 0.001), with TP having sensitivity of 89.4% and positive predictive value of 89.7% for the detection of CIN. The false positive rate for TP was 8.1%, but rescreening confirmed the presence of abnormal cells in 51 of 63 (81.0%) cases of ASC-US or higher having negative biopsies. TP had a false negative rate of 8.3% and negative predictive value of 61.3%. Rescreening showed that most (77.6%) of the false negative TP specimens failed to have abnormal cells on the slides. CONCLUSION: For patients having previously detected cervical abnormalities by CP, concurrent TP demonstrated the following: (1) that it has high diagnostic accuracy for SIL, (2) that ASC-US was diagnostically equivalent to LSIL, and (3) that false negative TP for SIL can be attributed primarily to sampling rather than cytotechnologists' screening errors.     

An overview of the College of American Pathologists' programs in surgical pathology and cytopathology. Data summary of diagnostic performance in cervical cytopathology

The survey programs in surgical pathology and cytopathology of the College of American Pathologists are described, along with a summary of the data produced on diagnostic performance in cytopathology. The levels of agreement between individual diagnoses and consensus diagnoses were highest for slides in the "negative" and "positive" categories and somewhat less for slides in the "suspicious" categories. Submission of slides with 70% or less agreement and slides on which a consensus had not been reached to a new group of observers yielded similar levels of agreement, indicating that there is a fairly small percentage of cervical smears that are diagnostic problems. Agreement levels, especially in relation to false negatives and false positives, represent a commendable achievement, especially considering that cervical cytology is a screening procedure and that "suspicious" smears result in further investigations. It is also important to recognize that additional clinical data and studies are often taken into consideration before definitive treatment is begun or additional follow-up smears are taken.     

Intraobserver and interobserver variability in the diagnosis of epithelial abnormalities in cervical smears

In a study of variability in the diagnosis of epithelial abnormalities, cervical smears with abnormalities of different severity were rescreened twice by 19 observers with an interval of six months. The observers focused on grading atypicality of squamous, squamous metaplastic and endocervical columnar epithelial cells; their results were compared (1) for the two screenings to assess intraobserver variability and (2) to "review" (final) diagnoses to assess interobserver variability. When the same observer rescreened a smear, 83.3% of the diagnoses did not differ more than one grade between two screenings; however, average intraobserver variability differed considerably for individual observers. The intraobserver variability was only slightly (not significantly) influenced by the years of experience in cytopathology of the observers. Intraobserver variability proved to be an important factor in incorrect diagnoses: 49.1% of the smears with false-negative and 52.9% with false-positive diagnoses at the first rescreening were correctly assessed at the second rescreening. Of all diagnoses made at rescreening, 80.9% were in agreement with the review diagnosis. The interobserver variability also showed considerable differences between observers; however, there was a strong influence of the experience of the observer on the interobserver variability. Atypicality grading of endocervical columnar epithelium by the observers showed a low correlation with the review diagnoses. The relatively low accuracy in the evaluation of this kind of epithelial abnormality is likely to be attributable to the low incidence of abnormal changes of endocervical columnar epithelium. The results of this study point to intraobserver variability as the main cause of false diagnoses. When wrongly diagnosed, severe epithelial abnormalities are more often underestimated than completely overlooked. Apart from training in cytopathology, the establishment of laboratory protocols for multiple screening of even minor abnormalities seem to be the most effective means of reducing the number of false diagnoses.     

Rapid rescreening of cervical smears as a quality control method in a high-risk population

OBJECTIVE: Cancer of the cervix is one of the commonest cancers in South Africa. Accurate cytological diagnosis is one of the prerequisites for an effective cervical screening programme and requires the implementation of appropriate quality assurance modalities. This study was undertaken to determine if rapid review of reportedly negative cervical smears is a useful internal quality assurance modality in an unscreened population with very high rates of cervical carcinoma. METHOD: Approximately 26% of all cervical smears received at the study institution between 1 January 1998 and 31 December 2003, and initially reported as negative or inadequate, underwent rapid review. RESULTS: A total of 62,866 (26%) cervical smears out of 241,796 reportedly negative or inadequate cervical smears underwent rapid review. An amended report was sent out in 373 (0.59%) of these 62,866 cervical smears. This included 101 cases of high-grade squamous intraepithelial lesion (HSIL) and high-grade atypical squamous cells (ASC-H), 143 low-grade squamous intraepithelial lesions, 54 atypical squamous cells of undetermined significance (ASC-US) and 33 atypical glandular cells that were not reported initially. The false-negative proportion for HSIL and ASC-H (combined) in this study was 5.76%. No squamous cell carcinomas were diagnosed on rapid review but one patient with HSIL/ASC-H on review had squamous cell carcinoma on biopsy. Three cytotechnologists had a lower sensitivity of primary screening and required retraining. CONCLUSIONS: Rapid review is beneficial as an internal quality assurance modality in an unscreened high-risk population and increases the detection of women with significant cervical lesions requiring treatment. The relatively low cost of rapid review compared with other rescreening modalities makes this an attractive option in low resource settings.     

Characteristics of high grade dyskaryotic cervical smears likely to be missed on rapid rescreening

OBJECTIVE: To determine if there is a type of high grade dyskaryotic cervical smear that is likely to be missed on rapid rescreening. STUDY DESIGN: Fifty high grade dyskaryotic smears that had originally been incorrectly reported as negative (FN) were admixed with 100 true negative smears. Each smear in the set was rapidly reviewed at least 40 times. The FN smears that were picked out on > 50% of screenings were compared with those that were passed as unremarkable on > 50% of screenings for features of the dyskaryotic cell population. RESULTS: Significant differences between the two types of FN smear were present in five aspects of the dyskaryotic cell population. A FN smear is more likely to be missed on rapid rescreening than to be selected for review if it has few dyskaryotic cells; if the dyskaryotic cells are small, with pale nuclei; and if they are scattered singly rather than in groups or syncytia. CONCLUSION: A type of severely dyskaryotic smear is likely to evade rapid rescreening as well as routine screening. This suggests that even when rapid rescreening is used as a quality assurance measure, the "zero-error standard" is unlikely to be attained.     

Reproducibility in double scanning of cervical smears with the PAPNET system

OBJECTIVE: To determine the reproducibility of the PAPNET scanning station (Neuromedical Systems, Inc., Suffern, New York, U.S.A.) in selecting cells from a cervical smear. STUDY DESIGN: We compared the images of 196 smears that were scanned on two occasions by the PAPNET scanning station on two monitors simultaneously and compared the cellular contents and technical records provided by the scanning station. The sample consisted of 62 positive smears (mild dysplasia and more) and 134 negative smears. RESULTS: Although differences were found in the technical information provided by the scanning station (kappa = .65, 95% confidence interval [CI] = .51-0.79) and in the reported percentages of air bubbles (kappa = .60, 95% CI = .51-.68), the detection of abnormal cases was not affected. Furthermore, the agreement on microscopic review was excellent (kappa = .92, 95% CI = .88-.96). In nine cases that did not differ in tech code or percentage of air bubbles, however, differences were found in the cellular content of the tiles that would have led to different advice for additional microscopic review. This would have had important clinical consequences in two cases because a serious abnormality would have been missed. CONCLUSION: The consistency of the PAPNET scanning system is somewhat on the low side in providing technical information, although this did not affect the clinical outcome. In nine cases, for example, we found differences in the demonstration of cells in the tiles on the screen; two would have had clinical consequences. It is important to set goals for the performance of the machine and to incorporate them in the procedures to be used as standard practice. This is especially true when the scanning stations are going to be operated on site in the cytology laboratory.     

100% rapid rescreening for quality assurance in a quality control program in a public health cytologic laboratory

OBJECTIVE: To verij5 the efficacy of the quality control (QC) program in a cytologic laboratwy with a rapid rescreening (RR) protocol. STUDY DESIGN: RR, according to the Turret RR method, of all samples initially screened as negative at the Laboratory of Cytology, Adolfo Lutz Institute, was performed. The slides were reviewed for 60 seconds. Suspect smears were fully checked by 2 reviewers to determine the final diagnoses. A total of 2954 sequential cytologic results were considered in this study. Of the 2954, 2568 (86.9%) were considered initially negative according to our internal QC, and these cases underwent RR. Also, 10% were randomly selected from these negative cases for full reviewing. The internal QC in our laboratory includes review of cases selected according to clinical and cytomorphologic criteria. RESULTS: Among the 2954 total cases, QC detected 386 (13%) atypias with final diagnoses reported according to The Bethesda System 2001 as follows: 82 (2.18%) low grade squamous intraepithelial lesions (LSILs), 35 (1.18%) high grade squamous intraepithelial lesions (HSILs), 2 (0.06%) squamous cell carcinomas, 105 (3.5%) atypical cells of undetermined significance (ASC-US), 4 (0.12%) atypical endocervical cells (AECs) and 158 (5.3%) unsatisfactory samples. RR of 2568 smears initially considered negative selected 194 (7.5%) slides. Of the 194, 146 (75.3%) were negative, 28 (14.4%) ASC-US, 5 (2.6%) AEC, 1 (0.5%) LSIL and 14 (7.2%) unsatisfactory. Full review of a 10% random fraction of the 2568 cases interpreted as negative did not detect lesions but did detect 5 (1.95%) unsatisfactory samples. CONCLUSION: Internal QC used in our laboratory based on clinical and cytomorphologic criteria to select cases for review proved to be an efficient method of detecting HSIL and cervical cancer. The consensus basis of this program strongly limits the false positive and false negative rates and also provides subjects with continuing education. One hundred percent RR is more efficient than 10% full reviewing in detecting cervical abnormalities.     

Partial Rescreening of All Negative Smears: an Improved Method of Quality Assurance In Laboratories Undertaking Cervical Screening

Partial rescreening was carried out on 9633 cervical smears reported as negative by standard screening. Each slide was ‘step-screened’ at normal speed for 30 s. Thirteen false negative smears were detected by this method. No false negatives were revealed by conventionally rescreening 10% of the same study group. the sensitivity of the method was assessed by ‘step-screening’ 100 known positive smears. of this group 92 were detected. the results indicate that partial rescreening is a sensitive method of quality assurance and should replace conventional 10% proportional rescreening, which is ineffective.     

Rapid rescreening of cervical smears: an improved method of quality control

Rapid rescreening of approximately 30% of all negative and inadequate consecutive smears was carried out over a 26-month period. Smears (n = 24012) were rescreened using a × 6.3 objective only. Two minutes were allowed for each slide. Thirty-nine smears were found to have been incorrectly diagnosed as negative, a rate of 0.16%. This can be compared with the previous 26 months during which the traditional 1 in 10 random rescreening of unsatisfactory and negative smears had been carried out at a routine pace and with an objective of × 10. A total of 6866 smears were rescreened. Eleven were found to have been incorrectly diagnosed as negative, a rate of 0.16%. Rapid rescreening is as sensitive as 1 in 10 rescreening, and allows a greater proportion of smears to be rescreened. We propose rapid rescreening should replace the traditional 1 in 10 rescreening methods.     

Detection of false negative Pap smears by rapid reviewing. A metaanalysis

OBJECTIVE: To explore the diagnostic validity of rapid reviewing (RR) as a quality control method in cytologic laboratories. STUDY DESIGN: Fourteen studies dealing with the detection of false negative Pap smears by RR were included in a metaanalysis. RESULTS: The overall additional yield of positive slides, expressed as the percentage of all reviewed slides, is: 0.18% (95% confidence interval [CI]: .14-.21) for all cytologic abnormalities; 0.07% (CI: .05-.09) for squamous intraepithelial lesions (SIL) and 0.02% (CI: .01-.03) for high grade SIL. The false negative rate of primary screening, evaluated by RR, was 2.0% (CI: 1.5-2.6) for all cytologic abnormalities and 1.4% (CI: .8-2.1) for high grade SIL. The specificity of rapid rescreening was estimated as 97.2% (CI: 96.4-98.1). The positive predictive value of suspicion at RR is about 8.8%. Seven references contained historical data on full rescreening of a random sample of slides reported originally as negative. The results were also pooled and compared with RR. Complete rescreening is more sensitive, but if applied on only 10% of the negative workload, it would yield, on average, 4.7 times fewer extra positives, 5.6 times fewer SIL and 7.9 times fewer high grade SIL in comparison with RR of all sides. CONCLUSION: RR of all smears initially reported as nonpositive is a more effective and a fortiori a more cost effective quality control method in comparison with full rescreening of a 10% random sample.     

Rapid pre-screening of cervical smears as a method of internal quality control in a cervical screening programme

Objective:  To evaluate the performance of rapid pre-screening (RPS) as a method of internal quality control in the cytopathological examination of cervical smears for cervical cancer screening.
Methods:  The sample consisted of 6135 cervical smears submitted to RPS and routine screening (RS) methods. The smears classified as negative in RPS and RS were considered final diagnoses, and were not, therefore, submitted to any additional review. The smears identified as suspect or unsatisfactory according to RPS were analysed separately by two different cytologists irrespective of the diagnosis reached in RS. Smears considered abnormal or unsatisfactory at RS were also reviewed. When both cytologists issued concordant diagnoses, this was considered the final diagnosis. Discordant results were analysed by a third cytologist and a consensus meeting was held to define the final diagnosis.
Results:  Taking abnormalities detected by RS as the denominator, RPS had a sensitivity of 63.0% for the detection of all abnormal smears and 96.7% for high grade squamous intraepithelial lesion (HSIL). When compared with the final diagnosis, sensitivity of RPS for all abnormal smears was 74.9% and for HSIL 95.0%. Of the 529 abnormal smears confirmed in the final diagnosis, 2.15% were detected only by the RPS.
Conclusion:  RPS is an effective alternative method of internal quality control with high sensitivity for the detection of more severe lesions. It also permits monitoring of the laboratory rate of false-negative results, and allows constant evaluation of the performance both of the pre-screening and RS cytologists.     

Potentially difficult smears of women with squamous cell carcinoma pose fewer problems when PAPNET is used for primary screening

The diagnosis of squamous cell carcinoma (SCC) on a cervical smear is often far from easy. This study reports the analysis of 40 true-positive SCC smears detected in primary PAPNET screening and eight false-negative (FN) conventionally screened smears. All FN cases contained sparse abnormal material (< 10% of the slide). In these potentially difficult cases the diagnosis on the PAPNET images was not hard. Statistical analysis of the quantitative data indicated that the PAPNET images of the FN cases and the true-positive cases differed in some aspects. PAPNET highlighted the importance of background information (old blood, fibrin and necrosis). In addition, all FN smears contained cancer cells in the PAPNET images, allowing a correct diagnosis.     

Expression of p16INK4A in Pap smears containing atypical glandular cells from the uterine cervix

OBJECTIVE: To verify one of the diagnostic dilemmas concerning atypical glandular cells (AGC) by immunocytochemical detection of p16INK4A (p16) applied to routine Pap smears with correlation of follow-up biopsies for improvement of cytologic diagnoses. STUDY DESIGN: The study included 36 Pap smears in AGC diagnostic categories, all of which were correlated histologically. The cytologic diagnoses of AGC were further classified according to the 2001 Bethesda System. All Pap smears were decolorized and immunostained with the primary anti-p16 antibody, clone E6H4. Immunoreactivity for p16 was correlated with histologic sections in a semiblind fashion. RESULTS: Of the 36 smears containing AGC, 22 (61%) were reclassified as general AGC and 14 (39%) as AGC--favor neoplasia. Follow-up biopsies revealed that 15 (42%) cervixes had no obvious abnormalities and that 21 (58%) cases had different cervical lesions. More than half the cases (19/36, 53%) of follow-up biopsies concerning AGC-containing smears represented significant lesions. There was a much higher proportion of significant lesions (13/14, 93%) in AGC--favor neoplasia than those (6/22, 27%) in general AGC cases. Fifteen of 36 (36%) AGC-containing cases were actually squamous abnormalities on follow-up biopsies. p16 Immunocytochemical stain was reactive in 22 (61%) of 36 smears, either weakly/sporadically (2 cases, 6%) or strongly positively (20 cases, 55%). Conversely, 14 (39%) of the smears were negative for p16 and displayed predominantly reactive changes. However, there was 1 case of high grade squamous intraepithelial lesion showing negative immunostaining for p16. From the view-point of clinical significance, this analysis was highly sensitive (sensitivity, 95%) and specific (specificity, 88%) and had favorable positive (90%) and negative (94%) predictive values. CONCLUSION: On the basis of both morphologic and immunostaining patterns, there was a clear association between strong p16 immunostaining of atypical cells in smears and the presence of significant lesions in the cervix except in 1 patient. Similarly, there was a clear association between lack of p16 expression and absence of cervical lesions. p16 Immunocytochemical stain can be applied successfully to conventional Pap smears and may serve as a useful biomarker in diagnoses of AGC-containing smears. This may offer a more objective parameter to help clarify this ambiguous area of gynecologic cytopathology.