Altered recognition of reparative changes in ThinPrep specimens in the College of American Pathologists Gynecologic Cytology Program

The Differential Diagnosis of Reparative Changes and Malignancy: Performance in the College of American Pathologists Pap Education and Proficiency Testing Programs

Context.—

Repair is a challenging diagnosis and a significant source of false-positive (FP) interpretations in cervical cytology. No large-scale study of performance of repair in the liquid-based era has been performed.

Objective.—

To evaluate the performance of repair in the College of American Pathologists Pap Education and Proficiency Testing (PT) programs.

Design.—

The FP rate for slides classified as repair was evaluated by preparation type, participant type (cytotechnologist, pathologist, or laboratory), and program. The specific misdiagnosis category and individual slide performance were also evaluated. The rate of misclassification of slides as repair by participants for other diagnostic categories in the Pap Education program was assessed.

Results.—

The overall FP rate was 1700 of 12 715 (13.4%). There was no significant difference by program or preparation type. Within the Education program there was no difference by participant type, but pathologists' FP rate in the PT program (47 of 514, 9.1%) was significantly better than cytotechnologists in the PT program (51 of 380, 13.4%) and pathologists in the Education program (690 of 4900, 14.1%). High-grade squamous intraepithelial lesions/cancers (HSIL+) accounted for 1380 of 1602 FP interpretations (86%) in Education, but 43 of 98 (43.9%) in PT. Most slides had a low rate of misclassification, but a small number were poor performers. False-negative diagnosis of HSIL+ as repair was less common, ranging from 0.7% to 1.8%.

Conclusions.—

Despite initial indications that liquid-based cytology might reduce the rate of misclassification of repair, FP interpretations remain common and are no different by preparation type. Misclassification is most commonly as HSIL or carcinoma, potentially resulting in significant patient harm.

False-positive Papanicolaou (PAP) test rates in the College of American Pathologists PAP education and PAP proficiency test programs: evaluation of false-positive responses of high-grade squamous intraepithelial lesion or cancer to a negative reference diagnosis

CONTEXT

In cytology proficiency testing (PT), participants fail for incorrectly interpreting a high-grade squamous intraepithelial lesion or cancer (HSIL+) Papanicolaou test result as negative. This penalty may lead to a false-positive interpretation of negative slides as HSIL+ to avoid failure.

OBJECTIVE

To investigate factors related to false-positive responses in a PT versus an educational environment.

DESIGN

We analyzed 420,079 responses from 9414 validated negative reference slides in the College of American Pathologists Interlaboratory Comparison Program in Gynecologic Cytopathology (PAP Education) and compared them with responses from the Gynecologic Cytology Proficiency Testing Program for the percentage of false-positive (HSIL+) interpretations in each of 7 negative subcategories. We evaluated the influence of preparation type (ThinPrep, SurePath, and conventional Papanicolaou test), participant type (pathologist or cytotechnologist), and program time interval (preproficiency test or PT) on a false-positive response.

RESULTS

Reference diagnosis and participant type, but not preparation type, were statistically correlated to false-positive responses. The interaction between program time interval and participant type was also significant. Pathologists had higher rates of false-positive results on preproficiency test (1.2% [800 of 68,690]) than they did on PT (0.8% [993 of 129,857]). Cytotechnologists had no differences between program time intervals (preproficiency, 0.9% [515 of 63,281] versus PT, 1.0 [1231 of 121,621]; P = .91). Negative subcategories frequently mistaken for HSIL+ were reparative changes (4.7% [427 of 9069]), atrophic vaginitis (1.8% [18 of 987]), and negative for intraepithelial lesion or malignancy (1.2% [2143 of 178,651]), but during PT, false-positive rates were significantly increased only for the negative for intraepithelial lesion or malignancy and herpes simplex virus (P < .001).

CONCLUSIONS

Pathologists had lower false-positive rates in the Gynecologic Cytology Proficiency Testing Program than they did in PAP Education, but participants were more likely to report a false-positive response (HSIL+) for negative for intraepithelial lesion or malignancy and herpes simplex virus in the Gynecologic Cytology Proficiency Test Program.

Gynecologic cytology on conventional and liquid-based preparations: a comprehensive review of similarities and differences

Liquid-based preparations (LBPs) have largely replaced conventional Papanicolaou smears (CPS) for cervical samples in the United States and in many other industrialized countries. The two FDA-approved LBP currently in use include ThinPrep (TP), (Hologic Inc., Bedford, MA) and SurePath (SP), (BD Diagnostic, Burlington, NC). Split-sample and direct-to-vial studies have shown that LBPs show an overall improvement in sample collection and processing, reduce artifacts that interfere in diagnosis, are more sensitive, can be utilized for ancillary tests and are a cost-effective replacement for CPS. Comparative analyses of diagnostic accuracy indicate that LBPs perform at least as well as CPS. However, the added advantages of standardized, automated preparations and screening, reduced unsatisfactory rate, improved specimen adequacy and ability to perform human papillomavirus (HPV) test, are enough to continue use of LBP. The cytologic features in LBP are similar to CPS with subtle differences, particularly in background information. There are also subtle differences between the two LBPs, SP and TP, which are reflective of different sampling devices, collection media, and processing techniques. Architecturally, LBP shows smaller cell clusters and sheets and more dyscohesion. Cytologically, enhanced nuclear features and smaller cell size are more prominent. Advances in liquid-based Papanicolaou's (Pap) test have lead to well-defined patient management guidelines by the American Society for Colposcopy and Cervical Pathology. Herein, we review these aspects of Pap test including, morphology, automation, ancillary tests (HPV and immunochemistry), pertinent QA/QC monitors, patient management guidelines, and review of pertinent literature.

Papanicolaou Tests With Mixed High-Grade and Low-Grade Squamous Intraepithelial Lesion Features: Distinct Performance in the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytopathology

Context.—Previous studies have shown that in gynecologic cytology, cases of low-grade squamous intraepithelial lesion (LSIL) and high-grade squamous intraepithelial lesion (HSIL) perform differently on interpretive review. The performance of cases with mixed LSIL and HSIL features is unknown.

Objective.—To compare the performance of gynecologic cytology cases of “pure” LSIL and HSIL with cases showing mixed LSIL and HSIL features.

Design.—We compiled performance data from the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytopathology from the years 2003 and 2004, and compared the performance of slides showing relatively pure LSIL and HSIL (≤10% misclassification as HSIL and LSIL, respectively) with slides showing mixed LSIL or HSIL features (cases misclassified as LSIL or HSIL &gt;10% of the time).

Results.—Interpretations from a total of 4508 cases (2452 HSIL and 2056 LSIL) were analyzed. Overall, the sensitivity of participants on slides with a reference diagnosis of HSIL was 97.3%, and of LSIL was 95.9%. Performance trends for pure versus mixed cases varied by slide type and reference diagnosis. For conventional slides, participant sensitivity on pure HSIL cases was greatest (98.0%) and on pure LSIL cases was least (95.2%), while participant performance on cases with mixed features was intermediate (97.0% for mixed HSIL and 96.7% for mixed LSIL). In contrast, participant performance on ThinPrep slides showed the greatest sensitivity for mixed LSIL slides (97.9%), while performance on mixed HSIL slides showed the lowest sensitivity (95.7%); slides with pure features had intermediate sensitivity levels (96.3% for both HSIL and LSIL). Further evaluation demonstrated that conventional pure HSIL slides performed significantly better than mixed HSIL slides (P = .006), whereas mixed LSIL slides performed better than pure LSIL slides (P = .01). For ThinPrep slides, pure HSIL cases performed similarly to mixed HSIL cases (P = .43), while mixed LSIL cases performed better than pure LSIL cases (P = .04).

Conclusion.—Slides with mixed LSIL and HSIL features have measurably distinct performance characteristics in comparison to slides with pure LSIL or HSIL features. Participant performance on conventional mixed cases is distinctly different from performance on ThinPrep mixed cases.