Cervical Cytology Practice Guideline
Approved by the ASC Executive Board November 10, 2000
IX. Enhancements to Conventional Cervical Cytology Testing
New technologies are available or are in development that are designed to increase the sensitivity of cervical cytology screening and may enhance other aspects of laboratory performance. Each technological device may have strengths and weaknesses.
IX.A. Liquid Based Methods
Liquid-based processing (LBP) methods are designed to improve cervical cytology specimen adequacy by improved cell harvest and application of the cell sample to the slide, decreased obscuring factors and decreased air drying artifact. A LBP technique can be achieved by a number of methods. Currently, the USA’s Food and Drug Administration (FDA) has approved one filter-transfer method and one density-gradient method.118, 119 Studies from different practice environments may show variable results pertaining to improved adequacy and sensitivity, probably due to differences in pre-analytic and analytic factors (e.g. the patient population served, sample taker proficiency, laboratory conditions, the experience and proficiency of laboratory personnel.) The decision of whether or not to implement LBP methods and which methods to employ should be based on an assessment of the likelihood of improved performance in the particular practice setting.
IX.A.1. Pre-analytic (Sampling and Processing) Considerations
Consideration should be given to using the optimum sampling device for a particular technology. Both current LBP methods have been approved for use with the “broom-type” devices. The plastic spatula and the endocervical brush have also been approved for use with the filter-transfer method. The use of other sampling devices or combinations that are valid for conventional smears should not be presumed to be optimal for LBP in the absence of evidence.
To obtain intended performance, the manufacturer’s recommended processing procedures must be followed. Results are dependent on careful technique.
IX.A.2. Analytic (Screening and Review) Considerations
Only personnel who are trained and certified in these methods should perform the screening and review of the slides. This training may be provided by the manufacturer or accomplished in the laboratory by the manufacturer’s certified personnel.
IX.B. Automated Screening Devices
Automated screening devices rely on computer analysis of digitized images of cells to triage cervical cytology slides for subsequent identification of premalignant and malignant changes. One device has received FDA approval for use both in a quality control rescreening mode, and as a primary screening device.120 The potential benefits from these types of automated screening instruments include reduction of false-negative rates, increased sensitivity, and increased throughput for the laboratory.109
IX.C. Microscope Process control Systems
Microscope process control systems are designed to assist with quality control and quality assurance. By mechanizing and automating certain steps of the screening process, the entire slide or predesignated portion of the slide is presented to the microscopist. The percent overlap during screening, the direction of screening (vertical or horizontal), the mode of screening (continuous or field by field) and the speed of screening can be automatically set to default values or can be adjusted to fit the individual examining the slide. These process control systems are equipped with electronic marking capability that expedites the relocation of cells for review. In addition, some have a mechanical pen that marks the areas of interest on the slide. The cytologic interpretation for each mark can be keyed in by the cytotechnologists for evaluation by the cytopathologists, allowing the pathologists to compare their interpretations with that of the cytotechnologists. The movement and coverage of the slide, the time spent on the stage, the number and location of marks, the interpretation of the cytotechnologist relative to each mark, and the final interpretation, are all available in real time when using a process control system. Thus, statistical data is generated that can be used for quality assurance and quality control.
IX.D. Molecular and Immunologic Techniques
Adjunct testing for low and high-risk HPV subtypes is currently available. HPV testing represents an option in the triage or management of women with a cervical cytology interpretation of ASCUS.86, 121
IX.E. Variability in practice
The decision to implement technologic enhancements to cervical cytology screening is affected by the following:
• Perceptions of current laboratory performance and screening accuracy by laboratory management, pathologists, cytotechnologists, clinicians and patients
Effectiveness of the technology to improve performance and accuracy
Technical limitations (e.g., slide preparation devices may not be compatible with screening devices)
Availability for various sectors of the population
Studies addressing decision analysis and cost-effectiveness of technological enhancements to cervical cytology screening have been published.12, 122, 123, 124 Large scale randomized and blinded clinical studies that compare the new technologies to conventional cervical cytology and to one another would be useful. Rigorous evaluation of these studies will facilitate evidence-based decision-making pertaining to these enhancements.
12 McCrory DC, Matcher DB, Bastian L, Datta S, Hasselblad V, Hickey J, Myers E, Nanda K. Evaluation of Cervical Cytology. Evidence Report/Technology Assessment No.5. (Prepared by Duke University under contract No. 290-97-0014.) AHCPR Publication No. 99-E010. Rockville, Maryland: Agency for Health Care Policy and Research, February 1999.
121 Manos MM, Kinney WK, Hurley LB, Sherman ME, Shieh-Ngai J, Kurman RJ, Ransley JE, Fetterman BJ, Hartinger JS, McIntosh KM, Pawlick GF, Hiatt RA. Identifying women with cervical neoplasia: Using human papillomavirus DNA testing for equivocal Papanicolaou results. JAMA 1999; 281:1645-7.