Reproducibility of Telecytology Diagnosis of Cervical Smears in a Quality Assurance Program: The Georgian Experience

Introduction

Quality assurance programs in cytology are important methods to maintain and improve the diagnostic acumen of cytologists, but there are difficulties in carrying out such programs. A long turnaround time for the circulation of glass slides is a major drawback, particularly when there are many participants and in widely spread institutions.

Telemedicine services are rapidly becoming an integral part in many hospitals and clinics around the world. ^{1 –6} In many programs, telepathology and telecytology account for over 50% of all teleconsultations. Most studies of telepathology and telecytology have focused on usage of robotic microscopes and online microscopy. ^{7 –11} Other studies have evaluated the use of digital images of slides. ^{12 –14} Often diagnostic accuracy tends to be high, but image quality is judged to be poor. Given these equivocal results, the methods of obtaining still images as well as adjustment of images (which usually means improvement of contrast and brightness) need to be investigated. Telepathology as an alternative modality for quality assurance in breast histopathology has been suggested by one study. ¹⁵ However, there is no previous study examining reproducibility of telecytology and its application as an alternative to the conventional microscopic examination of glass slides for quality assurance in cytology.

This is the first study to examine the reproducibility of the telecytology diagnosis of cervical smears in the country of Georgia.

Materials and Methods

We randomly obtained 50 cervical smears (benign, 14; atypical squamous cells of undetermined significance [ASCUS], 14; low-grade squamous intraepithelial lesion [LSIL], 10; high-grade squamous intraepithelial lesion [HSIL], 12) from the files of the laboratory of the general partnership (GP) “Kamkamidze and Partners.” Three cytologists examined these cases, and diagnoses were obtained. The most worrisome cells or groups in each case were selected and marked. The slides of all mentioned 50 cases were photographed with 2.0 universal serial bus (USB) digital eyepiece microscope camera with resolution 3.0. The images had a resolution of 2048×1536 pixels. The mean number of selected fields and digital images for each case were 5 (range 5–7) and 20 (range 18–22), respectively. Each series of images began with a general view, followed by higher magnification of diagnostically interesting areas as directed by the cytologist. The digital images were taken by cytologists. The images were stored in a personal computer and transmitted over the Internet by attachment to electronic mail (e-mail) to cytologists.

The digital images were diagnosed independently by three cytologists in a double-blind manner. Diagnosis of glass slides followed 3 months later in a similar manner. Only marked areas were examined. The sequence was repeated after another 3-month interval. Diagnoses were recorded in four categories: (1) benign, (2) ASCUS, (3) LSIL, and (4) HSIL. Additional information, including comments on adequacy of images, total time required for diagnosing all cases, problems encountered in diagnosing digital images, and whether there was a need for low-magnification digital images, was recorded by each observer.

Interobserver variation was calculated by using an interclass correlation coefficient (ICC), which determines the probability of agreement beyond that occurring by chance. Intraobserver variations in diagnoses between the first and second glass slide and the first and second digital image examinations were assessed by using the weighted kappa statistic.

Results

We captured digital images from the 50 cases in medium compression Joint Photographic Experts Group (JPEG) image files with 2048×1536 pixels resolution. The average number of selected fields per case was 5 (range 5–7). The average number of digital images for each case was 20 (range 18–22). E-mail transmission was done and was 100% successful. There was no image distortion identifiable after the transmission process. Table 1 gives a comparison of individual observer diagnoses in each diagnosis cycle compared with the consensus diagnoses. ICC values revealed that intraobserver agreement was good for the first glass side diagnosis (0.82), first digital image diagnosis (0.80), second glass slide diagnosis (0.68), and second digital image diagnosis (0.66).

Weighted kappa statistics for intraobserver variations between the first and second set of diagnoses made on glass slides and digital images showed values that ranged from moderate to excellent agreement (Table 2). The mean diagnostic time was 141.5 min (range 118–165 min) for glass slides and 60 min (range 50–70 min) for digital images. Under the term “diagnostic time” we mean the time necessary for diagnostic procedure. During this procedure the fields for digital imaging were selected and digital images were captured too. This was the reason for the rather high (141.5 min in average) diagnostic time. Low magnification (×40) of digital images was recorded as not necessary by all observers. The inability to focus at different levels to examine the architectural and cellular details of overlapping cells groups in glandular lesions was recorded as an impediment to diagnosis in digital images.

Discussion

Digital imaging can be used in many areas of anatomic pathology, including the photography of gross and microscopic findings in both surgical and autopsy pathology. It is practical and cost-effective and provide many advantages over traditional pathology practices. Digital imaging also is the first step toward opening the door to many future applications and improved diagnostic, educational, and quality assurance activities.

Most of the studies on telecytology have been confined to the study of breast aspiration biopsies. There is one published study on telecytology using video microscopy in cervical smears. ¹⁶ However, in that study, video microscopy was used without using digitalization and image transmission. Our study is the first to examine the diagnostic accuracy and reproducibility of telecytology in cervical smears after digitalization and image transmission through the Internet.

There are many advantages of using telecytology for quality assurance. Telecytology has the major advantage of rapid turnaround time. Transmission of digital images through the Internet undoubtedly is faster than the conventional method of circulating glass slides, especially when the availability of cytologic smears is limited compared with that of histologic material. Slow turnaround of glass slides during quality assurance exercises is a problem. For the once-a-month assessment meeting of the Georgian Pathologists Association, glass slides were circulated among more than nine institutions throughout the country. This exercise alone took 1 month. Sometimes participants had to attend the meeting without viewing the slides.

The use of digital images also ensures the assessment of identical fields, avoiding the problem posed by differences in field selection. The main aim in quality assurance programs is to test participants' ability to make the correct decision on a specific abnormal finding rather than the ability to screen an entire slide. Thus, telecytology circumvents the problem of field selection and assesses interpretation. It also eliminates the time that would be spent searching the slide for abnormal cells. In the present study, the mean diagnostic time was reduced by more than half for digital images (60 min) compared with glass slides (141.5 min). Cost savings is another advantage. Telecytology reduces the expenses of postal or courier slide circulation. Easy and continuous access to the case material should be achieved through their publishing in Internet. After the quality assurance exercise, the digital images are still available for reference and teaching purposes. Telecytology also makes it possible to share cases beyond the circle of participating members. These advantages, together with the acceptable levels of diagnostic accuracy and reproducibility, strongly support the use of telecytology for quality assurance programs.

Validation of accuracy is the first step in determining the usefulness of telecytology. Intraobserver reproducibility of telecytology diagnoses must be evaluated in addition to other factors such as cost-effectiveness and practicability of use in routine work. There are many reports of telepathology or telecytology that examine diagnostic accuracy. However, there is no previous study that examine the reproducibility of telecytology diagnoses. Our study shows that accuracy and intraobserver reproducibility of telecytology digital image diagnoses are as high as for conventional diagnoses made on glass slides.

Accurate diagnosis of cervical smears is critical to management because treatment protocols differ. It has been reported ¹⁶ that telecytology resulted in a tendency for underdiagnosing cervical smears largely because there is a reluctance to diagnose dysplastic lesions on the video monitor. We did not find that to be the case in our study, which was based on digital images.

There is no single, universally accepted method for assessing agreement and discordance between observations, and we chose two parameters to assess interobserver and intraobserver agreement. The ICC was used to measure interobserver agreement. While closely related to the kappa statistic, which is a common method of measuring interobserver variability and has identical numeric parameters, ICC also has the advantage of analyzing data with multiple response levels when the observer's agreement varies across a number of possible responses. A weighted kappa statistic was used to measure the intraobserver variation between first and second diagnoses for both glass slides and digital images. ¹⁷ ICC and the kappa statistic have been used previously to measure interobserver variance in the diagnosis of ASCUS in cervical samples. ¹⁸

Individual observer performance was variable. All observers had slightly higher diagnostic accuracy and intraobserver reproducibility with glass slides than with digital images (Table 1). Three factors can affect the diagnostic interpretation of digital images: adequate and appropriate sampling (field selection, number, and microscopic magnification of images), image resolution, and color quality. Cytologic diagnosis is based on cytologic features such as nuclear/cytoplasmic ratio, chromatin pattern, nuclear pleomorphism, and cellular arrangement on a limited number of microscopic fields. In telepathology and telecytology, one of the primary problems has been field selection (sampling error). Accuracy for telepathology/telecytology has ranged between 85% and 100%. Insufficient or inadequate sampling of images is the most common reason for low diagnostic accuracy. However, this can be minimized when an experienced pathologist/cytologist who is familiar with the technology and trained to recognize and identify highly informative fields is available for field selection. ¹⁹ With the development of total slide digitalization systems, this problem will be circumvented. ²⁰

In the present study, magnification at ×100 was necessary to identify the background and architecture of cell clusters. However, ×40 magnification was too low a resolution to permit interpretation of the digital images.

Resolution is the ability to show fine details of visual information. The higher the resolution, the more visual information present. Low resolution and color depth were limiting factors in digital images of the past. However, the resolution and color depth of current digital cameras and especially digital eyepiece microscope cameras are more than adequate to make most cytologic diagnoses. ^21,22 Compression of the image file is another important factor that affects the quality of digital image, and lost visual information can never be recovered after image compression. JPEG is by far the most commonly used method of compressing image files. In the present study with high resolution (2048×1536 pixels) JPEG image files, the digital images after Internet transmission could be interpreted accurately and showed excellent cellular details for cytology diagnosis.

Therefore, digital images are a suitable substitute for glass slides in the diagnosis of cervical smears when used in a quality assurance program. Telecytology can be used as an alternative to replace the conventional glass slides used in quality assurance programs and more study is needed to determine what role it can serve for initial diagnosis of cervical neoplasms.