COCHRANE FOR CLINICIANS: PUTTING EVIDENCE INTO PRACTICE
What Is the Best Collection Device for Screening Cervical Smears?
Am Fam Physician. 2004 Apr 1;69(7):1661-1663.
This clinical content conforms to AAFP criteria for evidence-based continuing medical education (EB CME). EB CME is clinical content presented with practice recommendations supported by evidence that has been systematically reviewed by an AAFP-approved source. The practice recommendations in this activity are available online at http://www.cochrane.org/cochrane/revabstr/AB001036.htm.
A 30-year-old woman comes in for an annual examination and Papanicolaou (Pap) smear. You want to collect the sample in a way that ensures the best possibility of finding any abnormal cells.
What collection device should you choose to get the best sample for detecting any cervical abnormality? Is the presence of endocervical cells important for detection of disease?
The combination of an extended-tip spatula with an endocervical brush (Cytobrush) is the most effective method for obtaining cervical cells. Detection of endocervical cells is a good indication of adequate smears and detection of disease.
Extended-tip spatulas in conjunction with endocervical brushes are most effective in producing adequate smears without blood and inflammatory-cell contamination or insufficient material.1
Background. The large variation in disease detection rates with cervical smears may be partly due to differences in the sampling devices and the techniques of sampling.
Objectives. To assess whether the design of the cervical smear device affects rates of inadequate smears and detection of disease, and whether the presence of endocervical cells in the smear affects disease detection.
Search Strategy. The authors1 searched the Cochrane Gynaecological Cancer Group trials register and MEDLINE up to July 1997. They also hand searched 16 journals.
Selection Criteria. Randomized and quasi-randomized trials and nonrandomized studies comparing cervical smear collection devices in women attending for primary screening, col-poscopy following an abnormal smear, or col-poscopy after treatment.
Data Collection and Analysis. Two reviewers independently abstracted data. Study quality was assessed.
Primary Results. Thirty-six trials and six observational comparative studies were included. In eight trials, the Ayre spatula was shown to be less effective than extended-tip spatulas for collecting endocervical cells (odds ratio [OR], 2.25; 95 percent confidence interval [CI], 2.06 to 2.44).
Use of a spatula with the endocervical brush was more effective than use of a spatula alone at collecting endocervical cells (OR, 3.33; 95 percent CI, 3.05 to 3.63), and the same effect was noted for adequate smear rates (OR, 1.51; 95 percent CI, 1.19 to 1.92). Extended-tip spatulas also were superior in the detection of dyskaryosis in seven trials (OR, 1.21; 95 percent CI, 1.10 to 1.33). Based on data from two trials and three observational studies, smears that contained endocervical cells were more likely to detect dyskaryosis, particularly in women with severe disease. The proportion of smears with endocervical cells increased with increasing severity of disease.
Reviewers' Conclusions. Extended-tip spatulas of various designs appear to be better for collecting endocervical cells than the commonly used Ayre spatula. The most effective combination appears to be the endocervical brush with an extended-tip spatula. The rate of detection of endocervical cells appears to be a valid and convenient surrogate for the ability to detect dyskaryosis and for adequate smear rates. The ability of the extended-tip spatula with the endocervical brush compared with the extended-tip spatula alone to detect disease must be evaluated in a trial.
These summaries have been derived from Cochrane reviews published in the Cochrane Database of Systematic Reviews in the Cochrane Library. Their content has, as far as possible, been checked with the authors of the original reviews, but the summaries should not be regarded as an official product of the Cochrane Collaboration; minor editing changes have been made to the text (http://www.cochrane.org)
Wooden and plastic spatulas perform equally well for conventional Pap smears. Plastic spatulas are recommended for liquid-based Pap smears, because cervical cells wash off of plastic more easily than wood.2 Cotton swabs yield far fewer endocervical cells than do brushes.3 Although the manufacturer does not recommend the use of the brush in pregnant women, no clinical complications have been noted with its use.4 Cervical broom devices are thought to perform similarly to the combination of extended-tip spatula and endocervical brush.2,3
An extended-tip spatula costs virtually the same as the Ayre spatula, and the addition of the endocervical brush adds little to the cost. Both are considerably less expensive than the combination sampling devices and the cervical broom.
It is estimated that at least one third of false-negative Pap smears are related to sampling issues. The American Cancer Society2 recommends that ectocervical cells be collected with an extended-tip spatula before endocervical sampling with an endocervical brush. However, one randomized clinical trial found a higher rate of adequate smears obtained when endocervical sampling was performed first.5
Most studies comparing cytology methods have found that liquid-based cytology is more sensitive and slightly less specific than conventional cytology. Based on these findings, the American Cancer Society2 recommends that routine Pap testing be performed annually if conventional cytology is used but only every two years if liquid-based cytology is used. The American College of Obstetricians and Gynecologists6 states that liquid-based Pap testing is slightly superior to conventional cytology, but it does not recommend any difference in screening based on the cytologic method used. The U.S. Preventive Services Task Force7 found insufficient evidence to recommend for or against the routine use of new technologies to screen for cervical cancer. Another advantage of liquid-based cytology is that it allows for human papillomavirus typing to be performed on the specimen already collected if the Pap smear result is atypical squamous cells of undetermined significance.
Cervical screening is effective in decreasing the incidence of invasive disease. The adequacy of a cervical smear used for screening has long been judged by the presence of endocervical cells in the sample. This suggestion is now confirmed. Cytologic abnormality (particularly severe dyskaryosis) is detected more readily in the presence of endocervical cells. Endocervical cells do ensure adequate sampling of the transformation zone.1
There have been no scientific studies on different management strategies for women whose Pap smear lacked endocervical cells. Some experts recommend that a short (one- to two-week) course of vaginal or systemic estrogen therapy be given before repeat Pap testing in patients whose squamo-columnar junction has regressed into the cervical canal. The Institute for Clinical Systems Improvement8 and others recommend repeating the Pap smear in four to six months. Then, if a “reasonable effort” results in a continued lack of endocervical cells in the cervical sample, “the Pap smear should be considered normal and need not be repeated more frequently than the standard recommendation.”
Michael Schooff, M.D., is associate director of the Clarkson Family Medicine Residency Program in Omaha. He received his medical degree from the Uniformed Services University of the Health Sciences, F. Edward Hébert School of Medicine, Bethesda, Md., and completed a family practice residency at Womack Army Medical Center, Fort Bragg, N.C.
Andrea Lawlor, M.D., is a third-year family practice resident at the Clarkson Family Medicine Residency Program. She received her medical degree from the University of Nebraska College of Medicine in Omaha.
Address correspondence to Michael Schooff, M.D., Clarkson Family Medicine, 4200 Douglas St., Omaha, NE 68131 (e-mail: firstname.lastname@example.org). Reprints are not available from the authors.
1. Martin-Hirsch P, Jarvis G, Kitchener H, Lilford R. Collection devices for obtaining cervical cytology samples. Cochrane Database Syst Rev. 2004:CD001036.
2. Saslow D, Runowicz CD, Solomon D, Moscicki AB, Smith RA, Eyre HJ, et al. American Cancer Society guideline for the early detection of cervical neoplasia and cancer. CA Cancer J Clin. 2002;52:342–62.
3. Martin-Hirsch P, Lilford R, Jarvis G, Kitchener HC. Efficacy of cervical-smear collection devices: a systematic review and meta-analysis [published erratum appears in Lancet 2000;355:414]. Lancet. 1999;354:1763–70.
4. Germain M, Heaton R, Erickson D, Henry M, Nash J, O'Connor D. A comparison of the three most common Papanicolaou smear collection techniques. Obstet Gynecol. 1994;84:168–73.
5. Noel ML, Kazal LA Jr, Glenday MC. Papanicolaou smear adequacy: the effect of the sampling sequence. J Am Board Fam Pract. 1993;6:103–7.
6. American College of Obstetricians and Gynecologists. Guidelines for women's health care. 2d ed. Washington, D.C.: ACOG, 2002: 121–34,40–1.
7. U.S. Preventive Services Task Force. Recommendations and rationale: screening for cervical cancer. Rockville, Md.: Agency for Healthcare Research and Quality. Accessed February 4, 2004, athttp://www.ahrq.gov/clinic/3rduspstf/cervcan/cervcanrr.htm.
8. Institute for Clinical Systems Improvement. Health care guideline: cervical cancer screening. 9th ed. Accessed February 4, 2004, athttp://www.icsi.org/knowledge/detail.asp?catID=29&itemID=156.
The Cochrane Abstract is a summary of a review from the Cochrane Library. It is accompanied by an interpretation that will help clinicians put evidence into practice. Michael Schooff, M.D., and Andrea Lawlor, M.D., present a clinical scenario and question based on the Cochrane Abstract, along with the evidence-based answer and a full critique of the abstract.
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