A major challenge facing cytology laboratories is how to implement appropriate quality control measures for the 80-90% of Pap smears that are screened manually and shown to be normal. A small false negative rate is associated with manual screening and quality control procedures need to be put in place to minimise this error rate. One quality control check is to manually review all or a proportion of slides but this places a considerable strain on laboratory resources; AutoPap re-screen of a laboratory’s workload has been demonstrated to be superior.

Prospective clinical trial data on which approval by the US Food and Drug Administration (FDA) was granted for quality control rescreening was summarised in the journal Cancer (Cancer Cytopathology) (Patten et al, 1997; Patten et al, 1997). These studies found that AutoPap rescreening identified 3-5 times more false negative cases than traditional quality control measures. A study conducted at the IMVS further confirmed the value of computerised rescreening for the detection of false negative cases (Stevens et al, 1997).

Optimal performance of the device is dependent on the quality of smears submitted for examination. Presently only conventional smears are suitable for scanning by the device. Recommended guidelines for the collection of samples is as follows:

• Smears prepared in the conventional manner using the combined spatula and brush technique are suitable. No special collection techniques are required.
• Cellular material should be distributed evenly over the smear.
• Prompt fixation is important to minimise air drying artefact.
• Single frosted slides are recommended and can be supplied on request (telephone 82223997).
• Cracked, broken or chipped slides are not suitable.
• The patient details should be written on the frosted end of the slide and before taking the smear to ensure that the cellular material is on the same side as the frosted coating.
• Cellular material should not cover the frosted end of the slide. This area of the slide is reserved for the barcode label and can not be screened manually or by automated means.

Since implementation of the technology in 1996, the device has scanned approximately 215,000 ‘normal’ smears. Manual rescreening of slides rejected for review identified 24 high-grade epithelial lesions confirmed on histology. This represents a very low false negative rate (0.01%) for this screening test and confirms the high quality of cervical screening at the IMVS. Importantly, these women received appropriate treatment preventing progression to an invasive lesion.

In this mode of operation, the instrument score assigned to each slide can be used to identify those smears with a low probability of containing an abnormality. The device can be programmed to identify the 25% of slides with the lowest score, ie completely normal, thus permitting immediate archiving of these slides without further human inspection. The remaining 75% of slides are assigned individual rankings, triaging the slides for manual review and alerting the laboratory to those patient specimens requiring special vigilance. The IMVS is presently considering the implementation of this technology.

Another valuable development is Location Guided Screening (LGS) which may assist the laboratory in prioritising workload. The AutoPap provides ‘maps’ of areas on the slide that have the highest probability of containing abnormal cells thus facilitating prompt manual review. Research is presently being undertaken to examine the benefits of this software development. Finally it is envisaged that the device will be configured to scan monolayer smears that have been prepared from fluid based collection techniques such as ThinPrep.

1. A high speed microscope scans the slide. 2,3. Information about the cells is interpreted by the instruments software. 4. A touch sensors verifies the location of the slide. 5. Barcode reader identifies the slide number. 6. The slides are placed in the input hopper and transported along a conveyor system where they are scanned by the microscope. 7. Following scanning, the slides remain in the output hopper. 8. The instruments interface with the laboratory computer system.

The results of the analysis can be viewed on the AutoPap computer monitor or on printed reports.

If you have any queries regarding the collection of Pap smears for computerised screening or about the technology itself, please contact the Laboratory Manager and Principal Medical Scientist, Mr Mark Stevens on 08 82223622.

Patten SF, Lee JSJ, Wilbur DC, Bonfiglio TA, Colgan TJ, Richart RM, Cramer H, Moinuddin S. The AutoPap 300 QC System Multicenter Clinical Trials for Use in Quality Control Rescreening of Cervical Smears. I. A Prospective Intended Use Study. Cancer (Cancer Cytopathol) 1997;81:337-342.

Stevens MW, Milne AJ, James KA, Brancheau D, Ellison D, Kuan L. Effectiveness of Automated Cervical Cytology Rescreening Using the AutoPap 300 QC System. Diagn Cytopathol 1997;16:505-512.