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Collection devices for obtaining cervical cytology samples

RHL Commentary by Andrade JM and Ferriani RA

1. EVIDENCE SUMMARY

The review identified randomized trials investigating the performance of sixteen cervical smear collection devices. All the devices capable of collecting endocervical smears were superior to the Ayre spatula in terms of smear quality. The devices that collect a higher proportion of endocervical cells have a better chance of detecting abnormal cytology, particularly in the presence of severe dyskaryosis.

Most of the adequately controlled trials have been included. The study by Germain et al. (1) for example, was not included. The selected trials were carefully analysed.

2. RELEVANCE TO UNDER-RESOURCED SETTINGS

2.1. Magnitude of the problem

Approximately 500 000 cases of invasive cervical cancer are diagnosed each year in developing countries, corresponding to about 80 % of all cases in the world. Invasive cervical cancer is potentially a preventable disease because early detection of cervical intraepithelial neoplasia (CIN) lesions through mass screening programmes of cervical exfoliative cytology can theoretically eliminate invasive disease.

Available data indicate that the extent of coverage, more than the frequency of colpocytologic sampling, is important for reduction of mortality due to invasive cervical cancer (2). In the most developed state in Brazil (state of São Paulo) the latest statistical data available indicate that approximately 1 500 000 tests are performed each year, corresponding to only 20 % of the population at risk. Of concern is the fact that most of these tests involve patients of higher socioeconomic levels, while women from less privileged communities are under-screened. Since collection of material for cytological examination is an almost sporadic occurrence for most of the population, it is of fundamental importance to obtain a smear of high quality, with priority being given to the investigation of techniques that will improve the quality of the collected material. False-negative results, which range from 1.5 %-35 %, are mainly due to collection errors (two thirds of false-negative results). Therefore, attempts at improving the results of screening programmes should focus on reducing collection errors.

2.2. Feasibility of the intervention

The effectiveness of cervical cancer screening programmes depends on how well and accurately the samples of cervical smears are collected. To improve the reliability of different types of cervical smear collection devices, it is possible to use extended-tipped spatulas for mass screening. The incorporation of an additional device increases the costs and collection time, with possibly significant consequences for services that perform a large number of tests. Harrison and associates, (3), noted that a cervical brush was about 100 times more expensive than a cotton swab (brush - US$ 29 per 100 and cotton swab US$ 0.30 per 100). The use of two devices significantly increases the chance of detecting abnormal cytology, but often results in air drying of the sample because of the time needed to transfer the material from each instrument to the glass slide, and its cost is higher.

Despite the higher direct costs, the need to repeat the test due to unsuitability of the material being collected is reduced. Also, even if repetition is not routinely recommended, the reduction in the number of false-negative tests with a corresponding reduction in the number of invasive cancer makes this increase in collection costs irrelevant.

2.3. Applicability of the results of the Cochrane Review

All the studies devoted to the assessment of the effectiveness of different cervical samples were conducted in developed countries. Although the collection of cervical samples should involve an easy-to-learn technique, we can expect some differences in the training of 'collectors' of material for cytology. However, there is no reason to believe that the results of the review would not be applicable to under-resourced settings.

2.4. Implementation of the intervention

The cost of introducing endocervical collection with the use of another device is very low in relation to the total cost of a screening process. The increased screening sensitivity and more effective detection of early cervical disease can easily justify the additional cost. When supported with adequate training, it should be possible to implement the use of the extended tip spatula for routine screening.

2.5. Research

Available studies present the percentage of smears that contain or do not contain endocervical smears. The number of cells, however, is important to define the quality of the smear and its reliability. Thus, it would be interesting if other studies (or reviews, since some studies of this kind are already available) were devoted to the quantification of endocervical cells, using the number of clusters or an estimate of the total as criteria.

References

• Germain M, Heaton R, Erickson D, Henry M, Nash J, O`Connor D. A comparison of the three most common Papanicolaou smear collection techniques. Obstetrics and gynecology 1994;84:168-173.
• Moos SM, Day NE. Screening intervals and identification of high risk groups for cervical cancer. Meeting on prevention and control of cancer of the cervix uteri. Working paper 445. Geneva, World Health Organization 1985 .
• Harrison DD, Hernandez E, Dunton CJ. Endocervical brush versus cotton swab for obtaining cervical smears at a clinic: a cost comparison. Journal of reproductive medicine 1993;38:285.

This document should be cited as: Andrade JM and Ferriani RA. Collection devices for obtaining cervical cytology samples: RHL commentary (last revised: 17 December 2000). The WHO Reproductive Health Library; Geneva: World Health Organization.

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