College of American Pathologists
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  PAP/NGC Program Review





cap today

August 2002
Feature Story

Where do Pap program
slides come from?

Ann Moriarty, MD
Karen Nomiya, CT(ASCP)

Every quarter, subscribers to the CAP Interlaboratory Comparison Program in Cervicovaginal Cytopathology receive a set of slides. They have them for a week, and the slides then pass out of their labs, never to return. While a lab's encounter with the slides may be fleeting, it is just one stop in the life cycle of a slide. Here's how slides get into the Pap program—and how eventually they fall out.

Gestation. A donor recognizes that a slide is educationally valuable and sets it aside. Demographic information is then obtained, including age, pertinent history, and date of last menstrual period. For epithelial cell abnormalities, the donor needs to await a confirmatory biopsy. After all information is gathered and recorded, the slide is packaged for delivery.

Delivery. Once the slides reach the CAP, they are assigned an accession number in the CAP Scores computer system. The following demographic information is entered for each case: donor ID, donor accession number, patient age, LMP, clinical history, reference interpretation, biopsy confirmation for LSIL or higher, type of slide (conventional, ThinPrep, Sure-Path), and amount of reimbursement.

A standard review sheet and CAP slide labels are printed. The review sheet is attached to the donor sheet. The slides, labels, and original donor forms are scrutinized in a quality control step. The slide labels are matched to the slide and placed over the original donor's label. The status of the slides is "pending initial review." The slide has now been successfully delivered into the early stages of life as a slide in the CAP program.

Perinatal period. This is an unstable time in the life of a slide. It comes under layers of scrutiny before it is allowed to grow and thrive in the program. The CAP staff cytotechnologists prescreen the slides, rejecting slides that do not meet standards for physical as well as interpretive quality. Slides are rejected if they are chipped or broken, have a chipped or broken coverslip, have a plastic coverslip (these retain marks and tend to separate from the slide over time), if there are faded stains or other staining problems, if cells are not representative of the original interpretation, if two interpretive elements are on the slide (that is, organisms and an intraepithelial lesion), and if biopsy confirmation of an intraepithelial lesion is not provided.

Infancy. Once the slide has survived early scrutiny, the slide proceeds to a CAP Cytopathology Committee session. There, three pathologists review the slide, and all three must agree on the interpretation, that it is a good representation of the disease process, and that it will perform well in the program. Once it has passed this scrutiny, the slide must wait for coming of age in a process called "kit configuration."

Early development. The donor receives a letter, after reimbursement is authorized, that identifies which slides were accepted and which were rejected. The rejected slides are return-ed to the donor. A slide that is accepted undergoes a randomization and is configured into an educational slide set (ungraded slide set). Once it has been "configured" into a set with four others, it is sent to a participating laboratory with an accompanying test response form, instructions, and continuing education forms.

Early education. Educational (ungraded) slides are circulated. The participants' responses are collected each time a slide set is returned to the CAP. Validation criteria are matched to the slide's data. When the slide has fulfilled the validation criteria, it is considered peer validated and becomes "graded." The criteria for validation are as follows:

  • At least 20 participants must submit correct responses on the slide.
  • The participants must have placed it into the same "selection series" at least 90 percent of the time. There must be exact matching of the interpretation in 50 percent of the participants for all negative responses (100 series). And an LSIL slide must have 70 percent concordance.
  • The standard error of the participant responses is calculated for the slide, and it must be at most 0.05. If p = the proportion of correct responses and n = the total number of responses, then the standard of error is the square root of (p*(1-p)/n).

Matriculation. Once the slide has met the validation criteria, it is randomized again and placed into a graded slide set. It then circulates as a "mature" slide to participants as a graded challenge. Some slides never progress to a graded set. If a slide demonstrates a rare entity, is not a "classic" case, or may have limited numbers of diagnostic cells, it is less likely to be validated. While these slides are important educational assets, they are not validated because of a lack of concordant peer diagnoses.

Middle age. Whether graded or ungraded, the slide is sent to participants, responses are received, and the data collection resumes in a predictable cycle. All slide sets are reviewed routinely every six months. The slide is assessed physically before it is cleaned and re-circulated; slides that do not meet the physical criteria are pulled and retired. A slide is also subject to review and retirement if it undergoes a change in performance (validation criteria).

Senescence and retirement. Even with the best care and nurturing, slides ultimately are removed from the slide pool. Stains fade, slides break, performance drops. When statistics indicate that a slide isn't performing well, members of the Cytopathology Committee review it. The slide is retired if a committee member confirms that the character of the slide causes the discordance. The slides are stored or returned to their donor if they are less than five years old. Over time, a slide in the CAP program usually lives a full life and provides each of us with a valuable educational assessment.

Dr. Moriarty, of AmeriPath—Indiana in Indianapolis, is a member of the CAP Cytopathology Committee. Karen Nomiya is a cytology technical specialist at the College of American Pathologists.