The Diagnostic Pathway
Cervical cancer can be treated if the disease is diagnosed early, particularly at the pre-cancerous or CIN stage. The introduction of screening programmes has significantly reduced the incidence of cervical cancer, however the disease still claims 300,000 lives annually worldwide.
Cervical cancer diagnosis worldwide is a multi-step process based on expert assessment of cervical smears (screening) and then the cervix itself (referral) and involves a significant measure of subjectivity. Initial screening (known as a smear test or Pap test or LBC) involves taking a sample of cells from the cervix at the point of care. This sample is then transported to a cytology laboratory where it is examined by a skilled operator.
HPV molecular tests are laboratory-based assays that can identify the high-risk (hr) strains of the virus. These tests are very sensitive, and therefore a negative test would confirm that hr-HPV is absent and therefore the woman is at very low risk of developing cervical cancer. However the tests are not very specific, and with most HPV infections self-resolving, the challenge is how the hr-HPV positive women should be managed. In 2007 the NCI in the USA reported that around 15% of all women were infected with hr-HPV but only a minority of these will go on to develop HG-CIN or cancer.
Those patients with a positive smear result are then referred to a colposcopy clinic for a magnified visual examination/impression of the cervix by a colposcopist who seeks to discriminate between normal, pre-cancerous, and cancerous cells. The colposcopist’s presumed diagnosis of a pre-cancerous or cancerous lesion is in many cases then tested by a diagnostic biopsy. A biopsy is, today, the only way to confirm a presumed diagnosis of a pre-cancerous or cancerous lesion. Ethical and economic issues mean that it is not practical for every woman to have a diagnostic biopsy as a routine screen.
In 2010, about 3.6 million women between the ages of 25 and 60 were screened in England. 330,000 women had appointments in colposcopy clinics in the same year. In the USA 55 million smear tests are taken annually and of these 3.5 million women are referred for abnormal Pap tests or LBC results. Recent changes to the guidelines in the USA mean that women will have screening tests every three years.