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

Rapid prescreen of cervical liquid-based cytology preparations: results of a study in an academic medical center

A rapid prescreening or rapid rescreening method for quality assurance in cervical cytology has been used in Europe and in Canada but has not been accepted in the United States. The rapid prescreen method was tested in a cytology laboratory that serves an academic medical center with a high-risk population for cervical cancer. For a period of 3 months, a tray of 20 sequentially numbered Surepath™ liquid-based preparations, randomly selected from the cervical cytology daily workload, were each prescreened in a random fashion for 1 minute. Experienced cytotechnologists performed the rapid prescreen. Results were recorded as negative, further review needed, or epithelial cell abnormality, category specified. The 20 cervical cytology preparations were then replaced in their same position in the daily workload for routine screening performed by another cytotechnologist. Final interpretation was by a cytopathologist as requested or required by Clinical Laboratory Improvement Amendments of 1988. The rapid prescreen data was tabulated and compared with data for a similar time period using the laboratory's normal quality assurance program. Seven hundred and twelve cases underwent rapid prescreen. Six hundred and forty-two were interpreted as negative. Twenty-six cases were interpreted as low-grade squamous intraepithelial lesion (LGSIL) or higher. Forty-four cases were classified as needing further review. For the 642 negative cases by rapid prescreening, routine screening reported 537 as negative and 105 as either abnormal or needed cytopathologist review. The error rate for the rapid prescreen is 50 of 712 (7.0%); for LGSIL and above 19 of 712 (2.6%). Of the 105 abnormal cases or those submitted for cytopathologist review, 31 were interpreted as atypical squamous cells of undermined significance (ASCUS), 41 cases as reactive/repair, 17 as LGSIL, 4 as unsatisfactory, 1 as atypical squamous cells, cannot rule out high-grade squamous intraepithelial lesion (ASC-H), 8 as the presence of endometrial cells in a women aged >40, 1 as malignant melanoma, and 2 as within normal limits with the presence of Actinomyces. The laboratory's routine quality assurance program selects cases, 10% of initially interpreted negative cases plus any gynecologic cytology on patients with a prior abnormal cervical cytology, or history of cervical epithelial cell abnormality. This quality assurance program averages 29% of cases, 4,045 of a total of 13,767, in 2008. Thirty-seven (0.9%) cases were detected in this rescreen (ASCUS, 16 cases; LGSIL, 13 cases; 1 high-grade squamous intraepithelial lesion; 4 ASC-H; and 3 atypical glandular cells of undetermined significance). Eliminating ASCUS cases, eight significant cases were detected, with an error rate of 0.2%. In this cytology laboratory, the rapid prescreen did not prove as reliable as routine quality assurance program for cervical cytology cases.

Assuring the quality of quality assurance: seeding abnormal slides into the negative Papanicolaou smears that will be rapid rescreened

BACKGROUND

Rapid rescreening (RR) of negative Papanicolaou smears (PS) is used in many countries as a quality-assurance measure. Seeding of abnormal slides has been suggested as a way to increase the sensitivity of this procedure. Since 2004, the authors have carried out RR with seeding before issuing reports. In this article, they describe their experience.

METHODS

Abnormal seeds were sourced from the previous day's high-grade cases, both squamous and glandular. Slides were evaluated for the 'degree of difficulty' (which was defined as the number of fields required to find (fields-to-find [FTF]) the abnormality), relabeled, and redotted to make them indistinguishable from the routine RR work. The number of seeds found/missed, the identity of the screener, the type of seeded abnormality, the degree of difficulty of the seed, and the mapping technique used all were recorded. The cytologists also were surveyed about their views on seeding.

RESULTS

Overall, 14.8% of 3082 high-grade seeds were missed during RR. There was no relation between seeds missed and the mapping technique used. However, the difficulty of the seed was relevant to the number missed and ranged from 8.3% when the FTF was <5 to 36% when the FTF was >10 (P = .000). The difference between intraepithelial seeds and invasive seeds was significant for squamous seeds (P = .031) but not for glandular seeds. Glandular seeds also were more likely to be missed than squamous seeds (23.1% vs 14.3%; P = .002). Most cytologists believed that seeding was a good idea and that seeds increased their level of vigilance.

CONCLUSIONS

The authors' experience demonstrated that routine seeding is practicable for both conventional and liquid-based slides. With the advent of the human papillomavirus vaccine, abnormalities will become rarer, and seeding will be necessary to maintain the alertness of cytologists.

Whole, Turret and step methods of rapid rescreening: is there any difference in performance?

We compared the performance of the Whole, Turret and Step techniques of 100% rapid rescreening (RR) in detection of false-negatives in cervical cytology. We tested RR performance with cytologists trained and among those without training. We revised 1,000 consecutive slides from women participating in an ongoing international screening trial. Two teams of experienced cytologists performed the RR techniques: one trained in RR procedures and the other not trained. The sensitivities in the trained group were Whole 46.6%, Turret 47.4% and Step 50.9%; and in the non-trained group were 38.6, 31.6 and 47.4%, respectively. The kappa coefficient showed a weak agreement between the two groups of cytologists and between the three RR techniques. The RR techniques are more valuable if used by trained cytologists. In the trained group, we did not observe significant differences between the RR techniques used, whereas in the non-trained group, the Step technique had the best sensitivity.

Correlation of cytotechnologists' parameters with their performance in rapid prescreening of papanicolaou smears

BACKGROUND

Efficient quality control is essential to ensure high sensitivity of Papanicolaou (Pap) smears. For this purpose, rescreening of 10% random negative smears is increasingly felt to be ineffective. Rapid rescreening (RR) of all negative Pap smears is more practical and has received widespread acceptance, especially in Europe, although its sensitivity is difficult to monitor and its retrospective nature may influence the vigilance of the screeners. The method of rapid prescreening (RPS) overcomes these drawbacks because rapid review of Pap smears precedes full screening.

METHODS

All routine conventional Pap smears (n = 8364) over 2 months underwent RPS by 12 cytotechnologists, followed by full screening. Data were analyzed to determine correlation between the RPS sensitivity of individual cytotechnologists and both their sensitivity in full screening and their years of experience as cytotechnologists.

RESULTS

There was a striking variability in sensitivity (15.4%-72.7%) among the 12 screeners with an atypical squamous cells of undetermined significance (ASCUS) threshold. There was no correlation between RPS sensitivity of individual cytotechnologists with either their sensitivity in full screening or their years of experience as cytotechnologists.

CONCLUSIONS

The skills required of a cytotechnologist for achieving a high sensitivity in RPS are apparently different from those of full screening and are independent of the sensitivity of the screeners at full screening or of the years of experience as cytotechnologists.

Rapid cervicovaginal smear screening: method of quality control and assessing individual cytotechnologist performance

AIM

To validate the method of rapid screening (RS) in the detection of cervical lesions and false-negative results as well as in quality control of cytotechnologist performance.

MATERIAL AND METHODS

The RS method was validated on Papanicolaou-stained and initially conventionally analysed vaginal, cervical and endocervical (VCE) smears collected in an opportunistic programme for the detection of cervical carcinoma. The study included 3680 VCE smears from the Department of Gynaecologic Cytology, University Department of Gynaecology and Obstetrics, Zagreb University Hospital Center, Zagreb and from the Department of Clinical Cytology, Osijek University Hospital, Osijek. Histologically verified abnormal findings accounted for 10% of the study samples. Thirteen cytotechnologists, with no previous experience in RS, performed the test. Each slide was examined using the 'step' technique for 1.5 minutes, the findings were classified as negative or abnormal, and the abnormal ones were also classified according to differential cytological diagnosis. The results were compared with those obtained on initial screening. Abnormal findings from a group of initially negative findings were reanalysed using conventional methods to make definitive cytological diagnosis.

RESULTS

RS yielded a sensitivity of 83.7%, specificity of 93.7%, positive predictive value of 62.4%, negative predictive value of 97.9% and diagnostic accuracy of 92.6%. Relative to the initial abnormal differential cytological diagnosis, the diagnostic value of RS increased with lesion severity [54.8%, 68.0% and 91.3% for cervical intraepithelial neoplasia (CIN) I, CIN II and CIN III respectively]. RS detected 38 additional positive findings; 94.2% of these were atypical squamous cells of undetermined significance (ASCUS)/abnormal glandular cells undetermined significance (AGUS) and CIN I. The rate of additional positive findings was 1.14% (38/3135). The false-negative rate of initial screening was 9.4% (38/406), and individual cytotechnologist sensitivity was 60.0-100.0%.

CONCLUSION

RS could be introduced as an efficient method of quality control to improve the sensitivity of cytological screening as well as for quality control of cytotechnologist performance.

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.

Rapid prescreening of papanicolaou smears

BACKGROUND

Efficient quality control (QC) is essential to ensure high sensitivity of Papanicolaou (Pap) smears. For this purpose, rescreening of 10% random negative smears is ineffective. Rapid rescreening (RR) of all negative Pap smears is more practical and has received widespread acceptance, especially in Europe, although its sensitivity is difficult to monitor and its retrospective nature may influence the vigilance of the screeners. The method of rapid prescreening (RPS) overcomes these drawbacks because rapid review of Pap smears occurs before routine full screening.

METHODS

All routine conventional Pap smears over 2 months underwent RPS by 12 cytotechnologists. Approximately 30 seconds were allowed to prescreen each slide. The presence of abnormal cells (atypical squamous cells of undetermined significance [ASCUS] or above), infection or endometrial cells detected on RPS was documented. All slides subsequently underwent routine full screening. Results of both screening methods were compared.

RESULTS

Of a total of 8364 Pap smears, 310 (3.7%) cases were categorized as abnormal after final diagnosis. Of those, 135 were also detected on RPS (sensitivity of 43.5%). Seventeen abnormal cases were detected only on RPS: these consisted of 13 ASCUS cases, 3 low-grade squamous intraepithelial lesions, and 1 high-grade squamous intraepithelial lesion. The sensitivity of RPS for infections and endometrial cells was 51.6% and 28.3%, respectively. Implementation of RPS did not significantly impact the work flow in our laboratory.

CONCLUSIONS

RPS is an efficient and practical QC tool. It is a reliable method with which to monitor sensitivity and reduce the false-negative rate, and because it is done before finalizing the case, it allows for timely corrections to the diagnosis and avoids the need to amend reports.

Rapid review of liquid-based smears as a quality control measure

The objective of this study was to investigate the effectiveness of a standardized method of rapid review (RR) of monolayer preparations for the identification of abnormalities, the presence of an endocervical component and infectious agents. A total of 200 ThinPrep (Cytyc, Boxborough, MA) slides representing the spectrum of abnormalities commonly encountered in cervical/vaginal cytologic specimens was retrieved from archive. The study set comprised 129 cases within normal limits (WNL); 36 low-grade epithelial abnormalities (LGEA); 28 high-grade epithelial abnormalities (HGEA), including 2 endocervical adenocarcinomas in situ (AIS) and 7 carcinomas. Eighteen false negative (FN) cases were also included for study. Originally missed on initial review, these cases were found to be abnormal on quality control review (17 LGEA; 1 AIS). Commonly encountered infectious agents were represented and included Candida albicans, Trichomonas vaginalis, herpes simplex virus, and Actinomyces. The slides were reviewed using a standardized method of RR (turret technique, for 60 sec) by three experienced screeners masked to the original reference diagnosis. Median sensitivity for LGEA was 70% (range, 67-72%); HGEA, 69% (range, 54-80%); and FN, 65% (range, 56-78%). Specificity remained high, median specificity for LGEA was 95%; HGEA, 97%; and FN, 100%. There was no significant overcalling of any diagnostic category. The chi-square test at P < 0.05 showed no significant difference between RR and full manual rescreen of the ThinPrep smears in this study. While no statistical difference was proven, the sensitivity measurements for all categories of abnormality were moderate due to the high proportion of atypical cases included into the study set. Abnormalities on the monolayer preparations frequently displayed fewer, smaller groups of disaggregated cells with rounded cytoplasmic outlines that were difficult to discern on RR. Interobserver variation was noted. Monolayers with a paucity of diagnostic cells and those displaying subtle nuclear atypia were often overlooked.

Rapid review in cervical cytology: a retrospective review of cases detected on rapid review within a DGH cytology department and subsequent outcome

We retrospectively reviewed smears detected by rapid review within a district general hospital (DGH) laboratory over a period of 33 months and the subsequent histological or cytological outcome. Sixty-three cases had adequate follow-up data: 32 subsequently had two negative smears and 31 had a histological abnormality on subsequent biopsy. Twenty were high-grade lesions (CIN2, CIN3 or a glandular lesion) and eight of these were preceded by a low-grade smear abnormality. We reviewed and compared the pattern and distribution of smear abnormalities in these 63 cases. Abnormalities were often present within few cells (76%, n = 48 with 50 abnormal cells or less) or in micro-biopsies (27%, n = 17). There was no statistical difference in the pattern and distribution of smear abnormality between the rapid review-detected smears with a biopsy-proven abnormality and those with negative follow-up smears. Overall, the positive predictive value for high-grade CIN detected by rapid review (75%) was within NHSCSP achievable standards targets. This review of rapid review-detected abnormalities and the biopsy and cytological follow-up reiterates the importance of the method in cervical screening.

Rescreening in cervical cytology for quality control. When bad data is worse than no data or what works, what doesn't, and why

The currently mandated methods to measure the sensitivity of Papanicolaou smear interpretation (including the 5-year look back and review of 10% of negative smears) are misleading. They do not allow one to measure the true sensitivity of the test and allow only a small fraction of errors to be detected and corrected. Rapid prescreening and automated screening are the only methods that seem practically feasible, and will allow the sensitivity of the method to be measured on a routine basis, and, thereby allow a reduction in overall errors. Although emerging technologies, such as HPV testing, may allow alternative methods of measuring sensitivity, the most appropriate way to use and interpret these data in this context are not yet fully developed. Unfortunately, at present there seems to be little desire to change the way things are done, and, therefore, to accurately measure sensitivity in cervical cytology. The first task that needs to be undertaken in fixing a problem is to admit that one exists. At present, most laboratory directors believe that their own laboratory is performing satisfactorily. They may well be, although the laboratories lack an analytic method to demonstrate this, and, therefore, the need for better QA methods does not seem to be acute. There is some educational value to the currently practiced and mandated performance measures, the 5-year look back and review of 10% of negative smears. Most laboratory directors seem to be happy with their QA methods and are not concerned that the data that are derived from the 10% review of negative slides does not reflect their actual sensitivity of screening in any meaningful way. Unfortunately, the forces that are currently in place in the United States ensure that accurate measures of the sensitivity of cervical cytology interpretation are unlikely to be implemented beyond the level of individual experimentation. As long as the expectation of cytologists is that the error rates are significantly less than they actually are; as long as there is significant legal and financial risk to actually measuring the true sensitivity; and as long as fictitious measures of performance are not only advocated but mandated; the confluence of incentives will ensure that the true sensitivity of the test will never be measured on a routine basis. Despite all of this, it is possible that cervical cytology screening may, in fact, already be performing at an optimal level. Being able to measure this operating performance may not effect any improvement to the overall process. The ultimate arbiter in this debate will always be the demonstration of a reduction of cervical cancer morbidity and mortality with any new measure implemented. At the present time, there is only one solution to the quality control issue; a force from outside the system must change the balance of the aforementioned incentives. The promise of data from European experiences with rapid rescreening may show that this method is effective and accurate. Such data might make the current methods that are in use in the United States more open to change. So yes, the answer is that "bad" data may be worse than no data at all. The bad data that we have been collecting for more than a decade is as effective a trap as anyone could have devised to ensure that actually measuring the performance of cervical smear interpretation does not happen. The only question that remains is, "How we will be able to escape?"

Precision in gynecologic cytologic interpretation: a study from the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytology

CONTEXT

Numerous studies address the accuracy or positive predictive value of cytologic interpretations for defined histopathologic entities. The reproducibility (precision) of cytologic interpretation is less well defined.

OBJECTIVE

To establish and compare the reproducibility (precision) of cytologic interpretation in gynecologic cytopathology, as reflected in the educational program of the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytology (PAP).

METHODS

The pathologists' interpretations for both validated (25 745 responses) and educational conventional (14 353 responses) slides in the PAP program for 2001 were analyzed. The frequency of exact matches between the reference and pathologists' interpretation for each of the cytologic interpretative categories was identified, and the cumulative distributions of exact match rates were derived. chi2 Tests by reference interpretations were used for cytodiagnostic categories, least and most reproducible groupings, and high-grade (HSIL) versus low-grade (LSIL) squamous intraepithelial lesions.

RESULTS

Pathologists' interpretations of negative, Candida, Trichomonas, herpes, and LSIL were characterized by a high degree of exact matching, while interpretations of repair, HSIL, adenocarcinoma, and squamous cell carcinomas were characterized by a lesser degree of exact matching (reproducibility). Pathologists' cytologic interpretations of HSIL were significantly less reproducible than those of LSIL.

CONCLUSION

The cytologic interpretations of the most significant categories (HSIL, squamous cell carcinoma, and adenocarcinoma) are less precise than those of specific infection (Candida, Trichomonas, and yeast), negative, and LSIL categories. Cytologic interpretations of LSIL are made with greater precision than those of HSIL and may represent a more appropriate endpoint to measure the precision performance of gynecologic cytology laboratories.

Agreement and error rates using blinded review to evaluate surgical pathology of biopsy material

Blinded review has been shown to be an excellent method to detect disagreements and errors and improve performance in gynecologic cytology. Preliminary studies suggest it may be valuable in surgical pathology. We reviewed 5,000 sequential outpatient surgical pathology biopsy cases without knowledge of the original diagnosis or history and compared the results with those of the original diagnosis. Complete agreement was obtained in 91.12% of cases. The technique of blinded review of surgical pathology biopsy material had a sensitivity of more than 99%, failing to identify an abnormality in 19 cases. Although there was a significant level of diagnostic disagreement (444 cases), primarily due to differences in diagnostic thresholds (292 cases), diagnoses that resulted in a change in the original report (true errors) were present in only 5 cases, and only 4 were clinically significant. This clinically significant error rate of 0.08% is significantly lower than previously published error rates. Blinded review is a sensitive (99%) and effective method to identify areas of disagreement and errors in surgical pathology biopsy material. The relatively high rate of disagreement found with blinded review coupled with the very low rate of error highlights the substantial potential for bias in nonblinded reviews.

Metaanalysis of the accuracy of rapid prescreening relative to full screening of pap smears

BACKGROUND

Efficient quality assurance and improvement measures are essential ingredients in a well organized cytology-based program for cervical carcinoma screening. Various pap smear review procedures, aiming for optimization of accuracy, are described throughout the literature. Evaluation and synthesis of those methods are needed. In a previous study, we pooled data on the diagnostic quality of rapid reviewing (RR) of cervical smears initially reported as normal or unsatisfactory. We now focus on rapid prescreening (RPS) of unreported smears.

METHODS

Six published studies on the accuracy of RPS relative to subsequent full screening were pooled using metaanalytic methods. Individual and pooled sensitivity, specificity, and predictive values were assessed using forest plots. Random effect pooling methods were used for interstudy heterogeneity. Variation in sensitivity according to influencing factors was explored by metaregression.

RESULTS

The pooled average sensitivity of RPS was 64.9% (95% confidence interval [CI] 50.7-79.1%) for all abnormalities, 72.6% (95% CI 60.6-85.2%) for low-grade lesions or more severe, and 85.7% (95% CI 77.8-93.6%) for high-grade lesions or more severe. The pooled specificity was estimated at 96.8% (CI 95.8-97.8%). The sensitivity increased significantly with duration of screening and decreased with workload. Almost 3% of all abnormal slides were detected only by RPS (2.8%; CI 0.0-5.8%). This is comparable to the proportion of false-negative smears detectable by RR.

CONCLUSIONS

Rapid prescreening has a high yield for severe dysplasia and shows diagnostic properties that support its use as a quality control procedure in cytologic laboratories. We showed previously that RR is superior to full reviewing of a 10% random sample of negative slides (10% FR). Because the yield of additional abnormalities found by RR and RPS is comparable, we expect RPS to be more efficient than 10% FR as well.

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.

Blinded review as a method for quality improvement in surgical pathology

CONTEXT

Several studies have shown that blinded review, because it is less biased and may improve vigilance, is an excellent method for detecting errors and improving performance in gynecologic cytology. The value of blinded review in surgical pathology is not known.

OBJECTIVE

To determine the value of blinded review in surgical pathology.

METHODS

Five hundred ninety-two biopsy cases were reviewed without knowledge of the original diagnosis or history, and the results were compared with those of the original diagnosis.

RESULTS

Complete agreement was obtained in 567 (96%) of 592 cases. The technique of blinded review of biopsy material had a sensitivity of 98%, failing to identify a lesion in 7 cases; no cases of malignancy were missed. The specificity was 100%. Differences in diagnostic threshold were the most common source of disagreement. False-negative cases were identified by the technique and were clinically significant. Power studies show that the number of cases requiring review to identify significant errors are large, but potentially achievable by blinded review.

CONCLUSION

Blinded review is a sensitive and effective method for identifying areas of disagreement, including false-negative cases, and for decreasing errors in surgical pathology biopsy material.

Rapid screening: a comparative study

Although rapid screening of negative and inadequate cervical smears is a quality assurance requirement for all UK laboratories, there has been little attempt to standardize the method and laboratories make use of a number of different techniques and times. The aim of this study was to assess the sensitivity of these various techniques by measuring their ability to pick out known false-negative smears. Completed questionnaires from 123 laboratories across England revealed that 52% of laboratories use a "step" technique, 19% use "turret", 15% use random paths and 34% attempt to rescreen the whole slide quickly. Twenty-two percent of laboratories use a mixture of techniques. Timings are also variable, with the majority of laboratories allowing screeners to review slides at a pace decided by themselves but usually between 1 and 2 min. The study involved 120 participants who performed a total of 24 000 rapid screens. The results showed that, of the 90 abnormal slides used in the study, 62 cases (69%) were identified as abnormal or needing review by more than 50% of participants. Overall rapid screening picked out 58% of high-grade squamous abnormalities, 59% of low-grade abnormalities and 72% of glandular lesions. Step screening performed best, followed by whole slide/random and then turret. One minute was the optimum time and there was a significant fall in performance once individuals attempted to rescreen large numbers (>50). The most significant finding was the marked variation in the performance of individuals using the same slide sets.

The human false-negative rate of rescreening Pap tests. Measured in a two-arm prospective clinical trial

BACKGROUND

Routine quality control rescreening often is used to calculate the false-negative rate (FNR) of gynecologic cytology. Theoretic analysis suggests that this is not appropriate, due to the high FNR of rescreening and the inability to actually measure it. The authors sought to determine the FNR of manual rescreening in a large, prospective, two-arm clinical trial using an analytic instrument in the evaluation.

METHODS

The results of the Autopap System Clinical Trial, encompassing 25,124 analyzed slides, were reviewed. The false-negative and false-positive rates at various thresholds were determined for routine primary screening, routine rescreening, Autopap primary screening, and Autopap rescreening by using a simple, standard methodology.

RESULTS

The FNR of routine manual rescreening at the level of atypical squamous cells of undetermined significance (ASCUS) was 73%, more than 3 times the FNR of primary screening; 11 cases were detected. The FNR of Autopap rescreening was 34%; 80 cases were detected. Routine manual rescreening decreased the laboratory FNR by less than 1%; Autopap rescreening reduced the overall laboratory FNR by 5.7%. At the same time, the false-positive rate for Autopap screening was significantly less than that of routine manual screening at the ASCUS level (4.7% vs. 5.6%; P < 0.0001). Rescreening with the Autopap system remained more sensitive than manual rescreening at the low grade squamous intraepithelial lesions threshold (FNR of 58.8% vs. 100%, respectively), although the number of cases rescreened was low.

CONCLUSIONS

Routine manual rescreening cannot be used to calculate the FNR of primary screening. Routine rescreening is an extremely ineffective method to detect error and thereby decrease a laboratory's FNR. The Autopap system is a much more effective way of detecting errors within a laboratory and reduces the laboratory's FNR by greater than 25%.

Rapid rescreen: a viable alternative to 1:10?

A rapid screen of those Pap smears designated as within normal limits is a quality control requirement of all UK laboratories. However in the United States standard QC involves a combination of 1:10 and selective rescreening procedures. Forty participants at the joint ASCT/ACP meeting in Las Vegas rapid screened 50 slides as part of a rapid screening workshop. They used different patterns of screening but were allowed only 60 seconds for each slide. Thirty of the slides contained abnormal cells but all had originally been called negative or unsatisfactory and as such were "false negatives". Ability to identify the abnormal smears varied considerably between individuals but overall rapid screening correctly identified 54% of the ascus or LGSIL cases and 61% of the HGSIL cases. The results demonstrate the superiority of such a rapid screen over 1:10 and question what if any role this outdated practice should have.

Detection of false-negative Papanicolaou smears by rapid rescreening in a large routine cervical cytology laboratory

Rapid rescreening was established in our laboratory in 1995, following the publication of several studies indicating improved sensitivity for the detection of abnormalities in cervical smears. During the study period, 285,841 negative smears (representing 89.09% of the total workload) were rapidly rescreened. A total of 7,650 (2.68%) were identified as abnormal or suspicious and selected for full rescreening. Of these, 228 cases were considered abnormal following pathologist review and resulted in the issue of an amended report. This represents an increased detection rate for all abnormalities of 0.08%. Of the cases with histological follow-up, a high grade epithelial abnormality (HGEA) was confirmed in 31% of cases and a low grade epithelial abnormality (LGEA) in 42%. We conclude that rapid rescreening is easily incorporated into the daily workflow of a large routine cervical cytology laboratory, Our results support conclusions from previous studies that rapid rescreening is an effective quality control technique resulting in the detection of increased numbers of abnormal smears.

Prospective study of PAPNET: review of 25,656 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.

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.

Is cervical screening working? A cytopathologist's view from the United Kingdom

This article considers the NHS cervical screening program and the controversies which have attended the introduction of comprehensive screening in a partially screened population of women in whom the underlying risk of disease was unknown. The increase in screening coverage which has taken place since 1988 has coincided with a period of high prevalence of cervical cancer and its precursors among women in the screening age group, against which background the recent fall in mortality and incidence of the disease has been a far greater achievement than generally recognized. The success of the program is considered in the context of the expectations and limitations of the test itself, and the high standards required for screening to be effective.