GYN Atlas - Specimen Adequacy

Specimen Adequacy
James Linder, MD

In order for a Pap sample to be properly interpreted, it must contain adequate numbers of squamous epithelial cells. The terminology from the Bethesda 2014 conference recommends that Pap tests be categorized either as “satisfactory for evaluation” or “unsatisfactory for evaluation”. The “satisfactory but limited by” category that was a component of previous Bethesda schemes was eliminated. A description of the presence or absence of endocervical/transformation zone component and any other quality factors may be included as a descriptive component of “Satisfactory”, but not “limit” the adequacy. At least 10 well-preserved endocervical or squamous metaplastic cells should be observed to report that a transformation zone component is present. If the specimen shows a high-grade lesion or cancer, it is not necessary to report the presence/absence of transformation component.


Generally, a minimum of 5,000 well-visualized/preserved squamous cells are needed for a specimen to be considered satisfactory, with the following caveats:

  • It is recognized that strict objective criteria are not applicable in every case. For example, slides with cell clustering, atrophy, or cytolysis are technically difficult to count, and laboratories should apply professional judgment and employ hierarchical review when evaluating these slides.
  • Not every specimen requires a count to be employed to assess cellularity. If the cytotechnologist feels there may be less than 5000 well-visualized/ preserved squamous cells present a counting scheme as follows may be utilized.

Any specimen with abnormal cells is by definition satisfactory for evaluation.
If it is necessary to count squamous cells in a ThinPrep slide: 1. A minimum of 10 fields should be counted along a diameter that includes the center of the preparation. The average cell number per microscopic field to achieve 5000 cells is shown in the following table:

FN20 eyepiece/10X objective # Fields@FN20 10X
# Cells/field for 5K Total
FN20 eyepiece/40x objective # Fields@FN20 40X
# Cells/field for 5K Total
FN22 eyepiece/10x objective # Fields@FN22 10X
# Cells/field for 5K Total
FN22 eyepiece/40x objective # Fields@FN22 40X
# Cells/field for 5K Total

For individuals using oculars not shown, the formula is:
Number of Cells Required per Field =5000 / (Area of Circle / Area of Ocular)

The diameter of an ocular or microscopic field in millimeters is the field number of the eyepiece divided by the magnification of the objective. The area of the field can then be determined by the formula for the area of a circle [pi X (Radius squared)].

For slides processed with the ThinPrep® Imaging System, adequacy should be determined as outlined in the Operator’s Manual.

According to Bethesda 2014, additional information on the meaning of adequacy qualifiers and any implications for patient follow-up may be provided optionally in an educational note. Unsatisfactory Paps that are processed and evaluated require considerable time and effort. While such specimens cannot exclude an epithelial lesion, some helpful information (presence of infectious organisms, etc) may be provided that can help direct further patient management. Suggested wording from Bethesda 2014 to clarify reports is as follows:

A) Rejected Pap:
Specimen rejected (not processed) because ____ (specimen not labeled, slide broken, etc.)

B) Fully evaluated unsatisfactory Pap:
Specimen processed and examined, but unsatisfactory for evaluation of epithelial abnormality because of ____ (insufficient squamous epithelium due to blood, etc.) Additional comments/recommendations, as appropriate

Specimens with >75% of cells obscured should be termed unsatisfactory (assuming no abnormal cells are present). When 50-75% of cells are obscured, a statement describing the specimen as partially obscured should follow the satisfactory term.

The photomicrographs contained in this atlas will display a wide variety of cellular specimens containing adequate squamous and glandular material. For the purpose of this topic, photomicrographs containing the minimum number of cells for adequacy are included as well as examples of transformation zone components.