Advances in the Pap smear and cytology

New techniques have been developed to further enhance specimen collection and interpretation of the Pap test. The ThinPrep method and the LUMA Cervical Imaging System have been introduced and approved by the FDA to improve the quality of specimen collection [6]. These technologies optimize cell preservation and reduce mucus, blood or other debris on the slide that gets in the way discovering pre-cancerous or cancerous cells.

In one study of 251 patients using the ThinPrep method, excellent correlation was shown between the standard Pap smear and the ThinPrep [7]. Slides can be read faster, from a smaller sample area, and with fewer numbers of cells needed to make the correct diagnosis.

Cervical cells are usually collected on a small stick or spatula then smeared on a slide for analysis. A 1994 study found that up 80 per cent of the sample taken from a patient using the conventional Pap smear technique did not make its way onto the slide, but rather stayed collection device [8]. Now instead of smearing the cervical cells onto a slide, a new ‘direct-to-vial’ technique is used. This involves immediately rinsing the collected cells into a vial filled with a special solution. This reduces the likelihood that a patient’s cell sample will be damaged by air, clumping, and so on.

The vial is then taken to the laboratory for slide preparation and screening. In the laboratory, the vial is inserted in a sample preparation device which breaks up blood, mucus, and other debris. The thin layer of cells in then transferred to a slide and deposited into a preservative solution. With newer methods, physicians are now able to conduct multiple analyses using residual cells collected in the vial instead of having to order an additional Pap smear. In a clinical trial of 6,747 patients conducted by Cytyc, the maker of the ThinPrep direct-to-vial technique, researchers found a 65 per cent improvement in the detection of cervical cancer at three screening centers using this new technique and a 6 per cent improvement at three hospitals where the incidence of cervical cancer is historically high [9].

The use of computerized instruments to recognize abnormal cells in Pap smears are now also being used. Typically, technologists and clinicians evaluate all Pap smear samples, but with this technology, a computer re-examines the sample and marks areas of the sample that may indicate abnormal cells. The technologist or physician then takes a closer look at these areas. The added advantage is that it may find pre-cancerous or cancerous cells that a technologist or physician might otherwise miss [10]. However, some critics believe that use of these technologies will increase the number of false positive results or ASCUS (atypical cells of undetermined significance) diagnoses [11], which could lead to patient anxiety and unnecessary follow-up examinations.  

Certain adjuvant tests have also been introduced to improve sensitivity and specificity of cervical cancer screening. These tests include HPV detection, new techniques for visualizing acetic-acid-stained cervical specimens, and molecular markers.  The overall concern for many of these techniques, such as cervicography, speculoscopy, and molecular markers, is maintaining balance between augmenting the effectiveness of the Pap test while keeping it cost-effective [12]. Subsequently, a gap in differentiating between low risk and high risk patients must be filled, so unnecessary surveillance and treatment can be avoided. 

Cervical screening in conjunction with the HPV vaccination

In 2007, the federal allocated $300 million over three years to provinces and territories on a per capita basis to support the launch of a national vaccination program against the HPV virus. All the provinces and the Yukon implemented voluntary vaccination programs targeting various groups of females between the ages of 9 and 17. Gardasil, the first Health Canada approved HPV vaccine, protected against the two high-risk cancer-causing types of HPV (16 and 18) and the two low-risk types (6 and 11) which cause anogenital warts [13].

Over three years, the $300 million on a per capita basis was designed to provide the provinces and territories with the opportunity to create and implement an equal opportunity vaccination program for young females. The execution of the vaccination programs varied wildly across the provinces: certain provinces had a program that only covered a younger group of females, while others covered a second age group in later grades [14]. Eligibility for female participation in the voluntary vaccination program also varied across the provinces, with Quebec estimating 100 per cent coverage and, the lowest, Manitoba, citing 32 per cent [15]. As such, the differences in provincial vaccination programs may result in the levels of cervical cancer incidence across the provinces.

The implementation of provincial and territorial vaccination programs decision bears no relationship to the risk of cervical cancer in the respective jurisdictions. For example, Quebec and BC with the lowest incidence rate of cervical cancer at six per 100,000 females, but have two of the best programs capturing 100 and 65 per cent of females aged 9–17 years, respectively. Provinces with the highest incidence rates such as Nova Scotia with 11 and Prince Edward Island with 10 cases per 100,000 females are only capturing 53 and 41 per cent of females in their programs [16].

Based on existing inconsistencies across the provinces, it remains imperative that cervical cancer screening continues to be offered and promoted as a necessary part of the cervical cancer prevention program [17].

References 

[6] "What Are the Latest Advances with Pap Smear?" Imaginis. Imaginis, 21 Nov. 2007. Web. 14 Aug. 2015.
[7] McMeekin, D. Scott, MD, Kathryn F. McGonigle, MD, and Steven A. Vasilev, MD. "Cervical Cancer Prevention: Cost-Effective Screening." Women's Cancer Information Center. Women's Cancer Center, 2007. Web. 14 Aug. 2015.
[8] "What Are the Latest Advances with Pap Smear?" Imaginis. Imaginis, 21 Nov. 2007. Web. 14 Aug. 2015.
[9] ibid.
[10] ibid.
[11] Fayed, Lisa. "ASCUS Pap Smear Results." ASCUS Pap Smear Results. About Health, 10 Dec. 2014. Web. 14 Aug. 2015.
[12] McMeekin, D. Scott, MD, Kathryn F. McGonigle, MD, and Steven A. Vasilev, MD. "Cervical Cancer Prevention: Cost-Effective Screening." Women's Cancer Information Center. Women's Cancer Center, 2007. Web. 14 Aug. 2015.
[13] Colucci, Rosemary, William Hryniuk, and Colleen Savage. "HPV Vaccination Programs in Canada: ARE WE HITTING THE MARK?" Cancer Advocacy. Cancer Advocacy Coalition, 2008. Web. 14 Aug. 2015.
[14] ibid.
[15] ibid.
[16] ibid.
[17] ibid.