Quality control of cervical cytology in high-risk women. PAPNET system compared with manual rescreening

OBJECTIVE: To compare the effectiveness of the PAPNET System with conventional rescreening of negative cervical smears in a high-risk population. STUDY DESIGN: Three thousand ninety-seven negative cervical smears from women with past history of cervical abnormalities were rescreened manually and with the PAPNET System. There were two reviews of PAPNET images: the first by two cytotechnologists with limited exposure to the instrument, and the second, limited to smears with discrepant diagnoses, by an expert in the use of the system. The remaining discrepant smears were submitted to a blinded microscopic review by a third party. The a priori consensus diagnosis was arbitrarily established when the result of two of the three reviews--manual, PAPNET and the independent third review--were concordant. The results of rescreening were compared with available biopsies. RESULTS: On manual rescreening of the 3,097 smears, 2,901 (93.66%) were reported as negative and 170 (5.49%) as abnormal. On the first PAPNET review, 2,938 (94.87%) were reported as negative and 150 (4.84%) as abnormal. There were 144 smears with discrepant diagnoses. After the second PAPNET review of these discrepant smears, the agreement between manual and PAPNET rescreening rose from 94.27% to 95.58%. A final, blinded review of 89 residual discrepant smears was used to establish consensus diagnoses. The diagnoses made by PAPNET-assisted rescreening agreed much better with the consensus diagnoses than did manual rescreening (Kappa = .61 vs. Kappa = -.32, P < .001). When compared with the results of 50 available biopsies, PAPNET-assisted rescreening also had a somewhat lower false negative rate (sensitivity 58.82% vs. 41.18%, P = .17) and a statistically significant lower false positive rate (specificity 63.64% vs. 36.36%, P = .01). CONCLUSION: PAPNET-assisted rescreening, when carried out by an experienced person, is more efficient than manual rescreening.     

An assessment of partial rescreening as an internal quality control method for cervical smears

Partial screening was performed on 10 800 cervical smears, comprising 8640 filed negative and unsatisfactory smears and 2160 newly received smears prior to conventional screening. Each slide was screened for 30 s and those considered abnormal were reviewed by standard screening. Partial screening led to the detection of 27 additional infections and 44 additional cytological abnormalities. These detection rates are better than those obtained with the traditional method of rescreening only a proportion of smears. Amongst the smears partially screened before conventional screening, partial screening detected 37-66% of infections and 22-71% of cytological abnormalities. We recommend the use of partial rescreening of all negatively reported smears as a method of internal quality control in cervical cytology laboratories.     

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.     

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.     

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.     

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.     

Rapid (partial) prescreening of cervical smears: the quality control method of choice?

Rapid rescreening of all negative and inadequate smears is the quality control method of choice in the UK. The sensitivity of primary screening of laboratory and individual screeners are major indicators of screening quality and are dependent on the number of false negative smears found by rapid screening for their calculation. High sensitivity may indicate good quality primary screening or poor quality rapid review. Quantifiably high quality rapid rescreening is essential if these sensitivity figures are to be meaningful. A 12-month study was undertaken in routine practice using the prescreening mode to ascertain the sensitivity of rapid (partial) screening in our department. The final results of smears were compared with those of rapid prescreening. The calculated sensitivity ranged from 92-54% for high-grade abnormalities and 75-33% for all grades, revealing a wide range of performance between individual prescreeners. Rapid prescreening can identify individuals best suited to rapid screening in routine practice. By using these prescreeners only, the sensitivity of cervical screening could be raised. Rapid (partial) prescreening should be considered as the quality control method of choice.     

The sensitivity of rapid (partial) review of cervical smears

SHIELD P. W. AND COX N. C. (1998) Cytopathology 9, 84–92 The sensitivity of rapid (partial) review of cervical smears Rapid review involves a daily rapid (e.g. 30 s) review of all smears not normally double-screened. It has been suggested that the method may increase the sensitivity of cervical cytology by identifying abnormalities not reported on initial screening, true false negatives (TFN). Rapid screening is reported to have high sensitivity for cervical neoplasia when used as a preview tool. To be effective, however, in a review mode it must be able to detect TFN. Several studies have found that many TFN result from factors such as low numbers of abnormal cells or subtle expression of diagnostic criteria. Studies on the sensitivity of rapid screening for detecting TFN would therefore provide a more reliable estimate of its value as a review tool. The sensitivity of rapid re-screening was evaluated using a test set of 200 cases. Each of 15 screeners rapidly reviewed (30 s partial screen) the set over a 2-week period. The set consisted of 129 normal, 28 low-grade squamous lesions (CIN I), 37 high-grade lesions (CIN II, III and adenocarcinoma in situ (AIS)) and six invasive carcinomas. The abnormals included 20 TFN cases. The median sensitivity for abnormalities was 62%. Rapid review was more sensitive for CIN II and CIN III (67%) and invasive carcinoma (66.7%) than for CIN I (53%). Great variation was apparent in the sensitivity for individual screeners, with a range of 41–86% for all abnormalities. The sensitivity for TFN cases varied even more (10–75%, median 35%) and for most screeners was significantly (P < 0.05) lower than for cases which were detected on initial screen (53–90%, median 70.6%). Following this trial rapid review was used routinely for a period of 3 months. In this time 11 413 cases were rapidly reviewed. This led to the full review of 415 slides (3.5%) and the identification of 16 cases of undetected CIN (12 CIN I, three CIN II, one CIN III). Based on current estimates of our laboratory false-negative rate this represents between a quarter and half of the TFN cases of CIN that probably occurred in this period. In conclusion, rapid screening is likely to be significantly less sensitive when used in a review rather than a preview mode. In routine practice the method requires a daily commitment of screener time, but does provide a higher yield of TFN smears than does random review, and allows amendment of these results prior to reporting.     

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 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.     

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.     

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.     

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.     

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.     

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.     

False negative rate of cervical cytologic smear screening as determined by rapid rescreening.

OBJECTIVE: To determine the reliability of the false negative rate (FNR) of cervical cytologic smear screening by rapid rescreening. STUDY DESIGN: A test set of 401 cases (311 originally diagnosed as negative, 74 as atypical squamous cells of undetermined significance [ASCUS], 14 as low grade squamous intraepithelial lesion [LSIL] and 2 as high grade squamous intraepithelial lesion [HSIL]) were rapidly (30 seconds each) rescreened by five cytotechnologists with no prior experience in rapid rescreening, and the FNRs of rapid rescreening and primary screening were determined. These results were compared with each other and with the FNR of primary screening as determined by routine rescreening of all cases with no time limit. RESULTS: All five observers detected a different group of abnormal cases; only 9% of all cases originally diagnosed as ASCUS or worse and 43% of all cases diagnosed as LSIL or worse were detected by all five observers. Nevertheless, using ASCUS as the threshold for an abnormal result, the FNR of rapid rescreening fell into a relatively narrow range, 61-74% (mean, 68.2 +/- 5.0); using LSIL as the threshold resulted in FNRs of rapid rescreening between 25% and 38% (30.0 +/- 4.7). Each observer, using rapid rescreening, detected between one and three false negative cases; routine rescreening of all cases without a time limit detected five cases. The FNR of cervical cytologic smear screening, as determined by rapid rescreening, was 18.4 +/- 6.1% as compared with 14.8% by routine rescreening without a time limit. CONCLUSION: The FNR of rapid rescreening is relatively reproducible even though the individual cases identified varied between reviewers. The FNR of rapid rescreening is similar to that of routine rescreening. Rapid prescreening may be the most logistically simple method to determine the true FNR of a laboratory.     

Evaluation of the AutoCyte SCREEN system in a clinical cytopathology laboratory

OBJECTIVE: To compare the AutoCyte SCREEN (AutoCyte, Burlington, North Carolina, U.S.A.) system with manual screening by experienced cytotechnologists using thin-layer preparations that had been previously extensively studied and their cytologic abnormalities well defined. STUDY DESIGN: AutoCyte PREP (AutoCyte) samples prepared for a previous split-sample study comparing thin-layer preparations to conventional smears were used. These 1,992 AutoCyte PREP samples were in a cohort the abnormal findings of which had been confirmed via independent review by two sets of pathologists. For the current study, these samples were remasked and evaluated by the AutoCyte SCREEN system in a clinical laboratory. The instrument scanned each slide and selected six overview fields and 120 single objects for storage and display. The computer classified each slide in one of the following categories: abnormal, uncertain, normal or unsatisfactory. Independently for each case, a cytotechnologist evaluated the six fields and 120 objects selected by the instrument as abnormal, normal or unsatisfactory. For those cases classified as uncertain by AutoCyte, the technologist then reexamined the cellular displays and entered a consensus classification. These results were then compared to those of an independent review by cytotechnologists of the identical set of slides using routine manual screening. RESULTS: The AutoCyte SCREEN selected 35% of slides for manual review. Technologist and computer rendered equivalent classifications in 79%. Of the total slides screened by the AutoCyte SCREEN, 57% were classified as "uncertain," and 88% of these were subsequently classified as normal by consensus. Using the well-defined abnormal values of the cellular sample as a basis for calculation, the AutoCyte SCREEN-assisted practice had a diagnostic sensitivity of 85% and diagnostic specificity of 97.6%. Comparable values for manual screening of the identical cellular sample were a diagnostic sensitivity of 80% and specificity of 97.4%. CONCLUSION: The AutoCyte SCREEN achieves comparable or greater sensitivity in detecting cervical abnormalities in comparison with manual screening. When combined with the substantial advantage of thin-layer preparations over conventional smears, the AutoCyte SCREEN provides a screening system of superior sensitivity over conventionally prepared and examined cervical smears.     

Rapid rescreening of cervical smears as a quality control method

Rapid rescreening of cervical smears as a quality control method The use of a rapid rescreening method as part of an internal quality control programme is reported. During a 12-month period 33 976 smears were reviewed (90.9% of total workload). Two-hundred and nineteen reports were altered, with 23 dyskaryotic smears identified, a false-negative rate of 0.07%, a false-negative dyskaryotic rate of 1.7%. Smears reported as dyskaryotic were also subjected to the rapid screening method (with 86.8% correctly identified) as well as using the method to assess smears before the usual primary screen (with 67.2% of dyskaryotic smears correctly identified). Rapid rescreening as a quality control method is effective, and although it has limitations, should replace 10% proportional rescreening as the preferred daily quality control method of choice. La relecture rapide des frottis cervico-utérins comme méthode de contrôle de qualité Ce travail décrit l'utilisation de la méthode de relecture rapide dans le cadre d'un programme de contrôle de qualité interne. Pendant une période de 12 mois, 33 976 frottis ont été revus (90,9% du recrutement). Deux cent dix neuf comptes-rendus ont été modifiés dont 23 concernant des frottis avec dyscaryoses, ce qui donne un taux de faux négatifs de 0,07% et un taux de faux négatifs pour les dyscaryoses de 1,7%. La méthode rapide a été appliquée à la relecture des frottis initialement classés comme dyscaryotiques (86,8% ont été correctement identifiés) ainsi qu'a la lecture de frottis avant le screening primaire (avec 67,2% de frottis dyscaryotiques correctement identifiés). La méthode de relecture rapide utilisée comme méthode de contrôle de qualité est efficace et, malgré ses limitations, elle devrait remplacer la relecture de 10% comme méthode de contrôle de qualité de routine. Rasches Nachscreenen als Methode der Qualitätskontrolle Während 12 Monaten wurden 33.976 Abstriche durch rasches Nachscreenen überprüft (90,9% aller Abstriche). 219 Befunde wurden abgeädert darunter 23 neue Dyskariosen, Dies entspricht einer Rate falsch negativer von 0,07% und falsch negativer Dyskariosen von 1,7%. Sämtliche Dyskariosen wurden ebenfalls überprüft mit einer Ausbeute von 86,8%, während die Methode als Vorlauf vor dem normalen Screening 67,2% erfasste. Trotz ihrer Einschränkungen ist die Methode wirkungsvoll und sollte die übliche Überprüfung von 10% der negativen Abstriche ersetzen.     

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.     

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.