Tips For Making Good Pap Smears

September 26, 2011

The challenge we face in interpreting Pap smears is to facilitate the assignment of smears into either a low-risk category (including "within normal limits" and "benign cellular changes") or a high-risk category (including "squamous intraepithelial lesion" and higher-grade categories).

The challenge we face in interpreting Pap smears is to facilitate the assignment of smears into either a low-risk category (including "within normal limits" and "benign cellular changes") or a high-risk category (including "squamous intraepithelial lesion" and higher-grade categories). We pathologists, with our partners the cytotechnologists, strive to minimize the number of cases classified as "atypical squamous (or glandular) cells of undetermined significance," as these "ASCUS" or "AGCUS" reports place the patient, clinician, and pathologist into a limbo of uncertainty regarding what should be done for the patient.

It has been my experience that the most frequent preventable cause of "the unnecessary ASCUS" is the suboptimal smear. Accordingly, I have put together a few problems with suggestions for solving them.

  • Problem: Air-drying. This is Pap smear enemy number one. If a cell is dried before it is spray-fixed, the cell enlarges, and nuclear detail is lost. If the pathologist cannot determine if a dried cell is atypical or not, he/she may tend to class the smear as an ASCUS.

Solution: Spray-fix the smear immediately. If you use a two-step technique (brush and spatula both), spray the first part of the smear before collecting the second part of the specimen. When spraying the first part, it is best to use a card or similar object to mask the part of the slide to be used for the second part of the specimen. If this taxes one's dexterity too much, it may be best in the long run to use a two-slide technique.


  • Problem: Blood, mucus, and pus. This unholy triad serves to obscure and distort the epithelial cells, making it difficult to determine if they are atypical.

Solution: Before collecting the specimen, gently remove excess mucus with a ring forceps holding a folded gauze pad. Surface exudate can be removed by placing a 2" x 2" piece of gauze over the cervix and peeling it away after it absorbs the exudate. A dry "proctoswab" or "scopette" can also be used. Do not rinse the cervix with saline, or a hypocellular smear may result. To reduce the amount of blood on the smear, use the spatula first, then the brush (the brush is more likely to induce bleeding). Finally, routine Pap smears should not be taken while the patient is menstruating.


  • Problem: Traumatized cells. These result from excessive manipulation of the delicate epithelial cells, either while being scraped from the cervix or spread on the slide. Traumatized normal cells may impersonate atypical cells.



  • When using the spatula, scrape in one continuous motion for a rotation of no more than 360 degrees. Spread the material collected on the spatula in a single, smooth, continuous stroke, as if buttering a saltine. Use moderate pressure against the slide to avoid producing thick clumps of material.

  • When using the brush, insert it into the os with gentle pressure and rotate it only 90 to 180 degrees. Roll (do not smear) the brush across the glass slide by twirling the handle.


  • Problem: Incomplete clinical information. To gain the greatest amount of useful information from a Pap smear, we need clinical information about the patient.

Solution: Fill out the requisitions completely. Age, date of last menstrual period, pregnancy status, and the history of previous abnormal Pap smears are absolute musts. Any other pertinent information concerning the reproductive system is welcome. Although much of our time is spent in the laboratory, we pathologists are physicians first. We are interested in the whole patient, not just the cells on the slide. You may be surprised at how helpful our reports can be if we have a little more background information.


  • Problem: Dueling laboratories. The Pap report from lab A says "atypical squamous cells of undetermined significance", but the biopsy report from lab B says "chronic cervicitis and squamous metaplasia." Who's right? What do I do now?

Solution: The abnormal Pap and follow-up biopsy MUST be examined simultaneously by the same pathologist. Cytopathological correlation is the cornerstone of cervical pathology. Without it, the clinician cannot determine if the abnormal Pap was significant or not. Did the biopsy recover the abnormal area sampled by the Pap, or was a high-grade dysplasia missed by the biopsy? One never knows unless the Pap and biopsy have been correlated. Remember, studies have shown that a very significant proportion of "ASCUS." Paps are ultimately revealed to be high-grade lesions. Correlation is the key to ferreting out some of these very difficult-to-diagnose cases.

The easiest way around this problem is to send the biopsy to the same lab that did the Pap smear. All reputable labs perform Pap/biopsy correlations routinely. If for some reason it is not possible to use the same lab, then call the Pap lab and ask that the patient's slide be sent to the lab charged with examining the biopsy.

If you are a provider, you should ALWAYS insist that the lab issue a correlation statement with the biopsy report. If you are a patient, you should NEVER accept a "negative" or "reactive" cervical biopsy report from a lab that has not also seen your abnormal Pap smear.

It has come to my attention that some labs are now refusing to send out Pap smears to other labs for cytopathological correlation. The reason given is that Pap slides are one-of-a-kind and are irreplaceable. Loss of such a smear in transit, say risk managers, may subject the lab to liability. While this is certainly true, the potential medical benefit to the patient far outweighs any financial liability to the lab. Accordingly, both clinicians and patients should not accept this no-send policy and should demand that direct visual correlation between Pap and biopsy be carried out in some fashion.


  • Problem: Management. Now that we have a good smear, it still comes back abnormal. Now what?

Solution: Asking how to manage an abnormal Pap is like asking for the correct recipe for potato salad. You will get a variety of answers, all reasonably defendable. 


  • One more question... What about ThinPrep?.

Opinion: ThinPrep is the first of the liquid-based technologies that have been shown to deliver technically superior preparations devoid of drying and other artifacts. Studies funded by ThinPrep's manufacturer, employing labs with a decade of experience with ThinPrep, have shown a slightly increased sensitivity for both high-grade and low-grade squamous intraepithelial lesions. So far, there is no evidence of any superiority in picking up adenocarcinomas and other glandular lesions (the incidence of which is thought to be increasing). Given this evidence, it is hard not to recommend ThinPrep for all Pap tests.

However, having examined these preparations myself, I prefer to be somewhat more cautious. Low grade squamous lesions (LSIL) are clearly easier to recognize on ThinPrep than on conventional Pap smears, but high-grade lesions (HSIL) are another matter. In conventional Paps, the often inconspicuous, small, round cells of HSIL are typically grouped together, where they can be more readily spotted. In ThinPreps, the cells suspension is homogenized, so that HGSIL cells are scattered apart from each other and are much more difficult to spot.

Further, I am bothered by the ThinPrep training materials, which read more like infomercials and soft-pedal the difficulties inherent in this type of preparation, including distinguishing adenocarcinoma cells from normal endometrial cells. Until ThinPrep has proved its superiority in regular, everyday labs that are not funded by grants from ThinPrep's manufacturer or staffed by former ThinPrep employees, I think it is prudent to not abandon the conventional Pap smear altogether. Therefore, my personal recommendation is for women to have annual testing, employing ThinPrep and conventional smears on alternate years.

In summary...

I can't overemphasize how important it is to develop a close working relationship with your pathologists. Otherwise, we all function like the proverbial blind men examining the elephant. The gynecologist has all the clinical information, the pathologist has all the microscopic morphologic information, and without continuously maintained lines of communication between the two, neither may ever appreciate the complete picture.