Digital Cytology Could Help Expand Cervical Cancer Screening, New Study Suggests

by Christos Evangelou, MSc, PhD – Medical Writer and Editor

Cervical cancer screening relies heavily on microscopy of Pap smears to detect precancerous cervical lesions. However, widespread access to skilled cytotechnologists able to screen slides is lacking, especially in limited-resource settings.

In a recent study, researchers at the Federal University of Ceará in Brazil evaluated the accuracy of digital whole slide imaging (WSI) compared to traditional light microscopy for cervical cytology screening and diagnosis.1

“Our rationale for undertaking this study was to validate the routine implementation of telepathology within our institution. We sought to validate the integration of technology to optimize our operational processes,” said lead researcher Fábio Távora, MD, PhD, who is an associate professor at the Federal University of Ceará and associate medical director at Argos Laboratory.

The study showed good diagnostic agreement between digital cytology and optical microscopy, particularly for tissues with cellular atypia and inflammation. The authors concluded that although further validation is needed, clinical implementation of digital cytology could significantly accelerate diagnosis and expedite the communication of results to patients.

“The integration of digital pathology in routine cervical cancer screening offers a platform for professionals to collaboratively engage with cases, particularly beneficial for instances presenting cellular atypia that require dual professional assessment,” Dr. Távora said.

The report was published in Diagnostic Cytopathology.

Study Rationale: Overcoming Shortages of Skilled Cytotechnologists

Cervical cancer is one of the most common cancers in women worldwide. The mortality rate of cervical cancer is particularly high in low- and middle-income countries, where tumors are often diagnosed at an advanced stage because access to screening and diagnosis is limited.

Cervical cytology, also known as Pap smear, is a widely used screening method that involves collecting cells from the cervix and examining them under a microscope for signs of abnormality. However, the interpretation of cytology slides is time consuming and requires specialized training, which can limit their availability in resource-limited settings. Although Pap smear screening has helped lower mortality rates in many countries, limitations persist in making screening accessible to all women worldwide.

“Considering the scarcity of qualified cytology professionals, leveraging digital pathology solutions seems like a promising solution,” Dr. Távora noted.

To determine whether new digital microscopy techniques could help overcome the limitations of conventional microscopy and expand screening capacity and access, researchers examined the accuracy of digital microscopy in cervical cancer screening and diagnosis.

Approach: Leveraging Digital Microscopy to Analyze Cervical Cytology Samples

The researchers evaluated the feasibility of using WSI for routine interpretation of cytology samples by retrospectively analyzing 99 Pap smear slides that were prepared using SurePath-based liquid preparation methods.1 The slides were analyzed for diagnostic purposes using standard light microscopy and contained a mix of 50 normal samples and 49 samples exhibiting some degree of cervical dysplasia or cellular atypia.

The fully digitized slide images were assessed independently by three experienced cytotechnologists who were blinded to the original diagnoses. Diagnoses based on digital images were then compared with the original light microscopy diagnoses to evaluate concordance.

“Our study methodology encompassed the selection of a sample reflecting our daily workload, coupled with the involvement of experienced practitioners. Our focus was on validating cytology exams conducted in a liquid-based medium,” said Guilherme de Velozo, the first author of the study.

He added that by aligning analysis parameters across physical and digital slides, they were able to comprehensively compare the diagnostic accuracy of digital cytology to that of traditional light microscopy.

“Upholding diagnostic sensitivity was of paramount importance, with uniform diagnostic criteria serving as the underpinning framework,” de Velozo said.

Diagnostic Accuracy of Digital Cytology

Overall, the study showed good agreement between digital cytology and light microscopy for the identification of cellular atypia and precancerous changes. Two pathologists showed near-perfect agreement with light microscopy for identifying samples without dysplasia (Cohen’s kappa coefficients k = 0.86 and k = 0.84).1 Digital microscopy also demonstrated high sensitivity and specificity for detecting tissues that are negative for intraepithelial lesions and malignancy.

In contrast, low concordance rates between digital microscopy and traditional cytology were observed in discriminating between bacterial species, especially Bacillus, Coccus, and Lactobacillus species.

“Rectifying this limitation necessitates improved image resolution, particularly at the 40x magnification level,” de Velozo said. He further explained that only images at 20x magnification were used in this study.

For atypia of undetermined meaning in squamous cells,  the concordance between digital diagnoses and traditional microscopy was 89%.1 For a few cases, reduced image clarity from cell overlap or lack of z-axis focusing capability also led to missed high-grade lesions being incorrectly labeled as low-grade or borderline changes. This highlights the need for balancing higher-resolution scanning with reasonable image storage size and scanning time.

The evaluators reported that the digital images were reliable and comparable to the physical ones, with no significant differences in the perception of image quality or diagnostic accuracy.

Looking Ahead

One of the limitations of the study is the small sample size, which may limit the generalizability of the findings. The study included only 99 cytology slides from a single laboratory in Northeastern Brazil, which may not be representative of other populations or settings.

Another limitation is the lack of evaluation of the impact of digital slides on the diagnostic accuracy of more complex lesions, such as high-grade squamous intraepithelial lesions or invasive carcinoma.

Future studies are needed to address challenges associated with microbiological analysis of digital images of cervical tissues and to determine the effects of increasing image quality on temporal, storage, and financial resources.

Despite these limitations, the study demonstrates the promising utility of digital cervical cytology for enabling broader screening access, especially in lower-resource settings. With further technological refinement, digital approaches could help expand screening coverage, facilitate AI-assisted automated screening, reduce the need for specialized training, and allow for more equitable cervical cancer prevention.

“The introduction of digital pathology into a resource-constrained environment constitutes an innovative milestone. By meticulously validating digital images, we not only establish procedural consistency but also establish a reliable digital pathology workflow fortified by methodological rigor,” Dr. Távora noted.

References

  1. de Velozo G, Cordeiro J, Sousa J, et al. Comparison of glass and digital slides for cervical cytopathology screening and interpretation. Diagn Cytopathol. August 2023. doi:10.1002/dc.25209

 

 

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