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Medicine
Wednesday, July 4, 2018
Pap smear is used for the early detection of carcinoma of the cervix and its precursors, which are visualized by means of papanicolau staining. / dpa
Vancouver – A viral gene test (HPV) can detect pre-cancerous lesions earlier than conventional cytology (Pap test) in a cervical smear. These are the results of a randomized clinical trial in the American Journal of Physicians (JAMA 2018; 320: 43-52).
Almost all cervical cancers are caused by human papillomaviruses whose genes can now be detected in smears. The test is much more sensitive than the cytological study developed in the 1940s by George Papanicolaou. Since not all infections lead to cancer, switching from Pap testing to HPV testing could lead to a significant increase in unnecessary follow-up. It is also unclear whether the test will reduce the number of women requiring surgery for advanced precancerous conditions. Professional societies are moving from Pap screening to HPV testing based on the results of direct, long-term comparative surveys.
Comparison of Pap smear and HPV genetic test
Such a comparison is in progress in the Canadian HPV FOCAL study. The study is conducted as part of Providence's BC program. It includes more than 25,000 women aged 25 to 65 who had accepted an invitational examination and who had not been diagnosed with cervical intraepithelial neoplasia (CIN2 or higher) in the last 5 years.
The study included 3 groups, In the first group, smears for conventional cytological evaluation were sent to a laboratory where laboratory workers in a Pap smear look for suspicious cells. This was done as usual today in a thin film cytology.
The second group was investigated for oncogenic HPV infection by genetic testing. In the third group, the reliability of the HPV test was verified by early monitoring. This part of the study was discontinued prematurely and is not the purpose of the publication which aims to examine the integration of HPV testing in normal screening (without early monitoring).
The provision provides that women undergo a positive colposcopy test to determine the path to follow. In a negative test, women in the study were re-invited after 24 months (Pap smear) or 48 months (HPV group).
The first screening cycle took place between 2008 and 2012. Due to the higher sensitivity of the HPV test, more smears with a CIN3 or worse were found in the HPV group at that time (Br J Cancer 2012; 107: 1917-1924). Women were therefore more likely to have colposcopy (57% vs. 30.8%).
HPV testing leads to earlier diagnosis of CIN3 lesions
In the period preceding the last 48-month follow-up, it was reversed. A CIN3 or less was diagnosed in the HPV group at 2.3 per 1,000 women versus 5.5 per 1,000 women in the cytology group. Gina Suzanne Ogilvie of BC Women & # 39; s Hospital and Health Center, Vancouver, and her colleagues report a risk ratio of 0.42, which is highly significant with a 95% confidence interval of 0.25 to 0, 69.
Undeniable screening led to an earlier diagnosis of CIN3 lesions (or worse). However, the total number of CIN3 (or less) lesions detected at baseline or at 48 months (9.3 versus 9.8 per 1,000 women) was the same (risk ratio 0.94, 0.71 to 1.26). ).
There was a similar pattern in CIN2 lesions, which may regress spontaneously. On the other hand, they were more frequent at the first examination, but less frequently at the final examination, so that the overall rate (20.4 against 20.2 per 1,000 women) was the same (risk ratio 1, 01, 0.83-1.23).
All things considered, HPV testing could be an improvement, as precancerous lesions requiring treatment (CIN3 or worse) are detected early. However, it remains to be proven that HPV screening also reduces the incidence and mortality of invasive cancer of the cervix of the uterus. In Germany, about 4,500 women become ill each year, of whom 1,500 die from cervical cancer. However, among them, there are many women who did not participate regularly in screening.
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