Page 69 of McCartneys book.
Angela Raffle, a public health doctor in Bristol, has produced some of the most illuminated research about how effective the cervical smear is. She and her colleagues published a paper in the BMJ in 2003, which analysed the effect of cervical screening amongst the 350,000 women in the Bristol area she worked in and organised cervical screening for. The results were disturbing because they rub against the straightforward logic about screening prsents to us by its proponets. I quote:
'For every 10,000 women screen from 1976 to 1996, 1,564 had abnormal cytology, 818 were investigated and 543 had abnormal histology. 176 had persistent abnormality for two years or more. In the absence of screening, 80 women would be expected to develop cancer of the cervix by 2011, of whom 25 would die. With screening ten of these death could be avoided... The lifetime risk for having abnormal cytology detected could be as high as 40% for women born since 1960.
Lets recap. Without screening, over 20 years, 25 out of 10,000 women would die. With screening, taking the same group over the same period of time, 15 would die of cervical cancer. Only ten - the difference between 25 and 15 - out of the 10,000 benefitted from screening by having their lives extended.
Ten women out of every 10,000 over 20 years isn't, of course an unimportant number. But it's not the only number here. To stop these deaths from cervical cancer, you have to do a lot more tests on a lot more women. A total of 818 women had invasive tests, namely a biopsy. A biopsy can be taken using a adapted microscope which examines the cervix, and can treat using an adapted microscope, which examines the cervix, and can treat areas of abnormal cells, in a process called colposcopy. Of these biopsies, 543 had an abnormal result. Two had cancer, 22 had 'micro-invasive' cancer, 361 had high-grade dysplasia, and 158 had low grade abnormalities.
Isn't all this worth it? After all as we are told by the NHS, it could save your life. Perhaps, perhaps not. 'Anxiety' is often mentioned as a 'minor' side-effect of screening. It's said so slightly as though it hardly matters. But anxiety as a side effect does matter. Some women are made ill from worry when a letter arrives on their doorstep telling them that their smear is abnormal and they need further tests. Women can become sleepless, imagining infertility, early death and their children growing up without a mother. Some women manage to put this to one side and get on with their other concerns; some don't. It can be a pervasive worry and a recurrent fear. Anxiety isn't just a minor side effect.
Colposcopy may just involve inspection of the female genitals. It may also involve treatment to the cervix. In the UK, a common treatment is 'large loop exicision of the transformation zone' where the abnormal cells are removed under local anaesthetic. It's popular because its quick, can be done immediately and doesn't need an overnight stay in hospital. But is associated with problems later - namely preterm birth. Women who have had this procedure are more likely to have baby born before full term. One Canadian study found that 2.5% of women who hadn't had a LLETZ procedure gave birth prematurely, as opposed to 7.9% who had.
Is it worth the risk? It might be. It depends on your perspective. A woman may feel that a small chance of stopping a death from a cervical cancer is worth the downsides, such as LLETZ procedures that do not benefit the patient and raise the risk of premature birth. Or she may not. What if she had several anxiety-inducing smears, biopsies and treatment with no benefit to her?
I can't answer that question. But I do feel deep discomfort that these issues are not raised with women routinely before having a smear test. The government may have decided that the smear test is a good thing; but that may not correspond to the woman's own wishes.
With cervical screening, Angela Raffle's study says the potential good is a reduction in cervical screening from 25 to 15, per 10,000 women, per 20 years. The cost of achieving this means that almost 1000 other women get letters telling them they have abnormalities and need repeat tests. More than 500 require colposcopy and biopsy, with the risk that this may lead to premature labour in pregnancies.
Despite the easy lure of government posters, cervical screening is not a simple exercise akin to a visit to the cinema. It isn't a clear cut situation of good versus bad, but a balancing of potential gains and harms. Doctors should not assume that you want to make this trade. Doctors should help you decide what you want to do; explain the risks, not just decide that you value the chance of gain enough to accept the potential harm.
Personally, I think that the overselling and oversimplification of this difficult melange of pros and cons we currently have is a patronising outrage. It's oversexed health advice; overselling of a complex test with many outcomes, not all good. The losers are us, the 'customers' who are simply enticed into screening.