DG4: DySIS and colposcopy
Dr Pierre Martin-Hirsch discusses the latest diagnostics guidance on DySIS and colposcopy, and Lucy Hammerton-Barry from NICE talks about the cost implications of the guidance.
This podcast was added on 1 Aug 2012
Hello and welcome to this podcast from NICE on the DySIS diagnostics technology guidance. I’m with Dr Pierre Martin-Hirsch, specialist committee member of the Diagnostics Advisory Committee for the topic and part of the lead team.
Dr Martin-Hirsch, can I start by asking what are the current screening arrangements for cervical cancer?
The current screening arrangements are that we take cervical smears of women between the ages of 24 and 64 in England – we start screening at 20 in Scotland and Wales – and the aim is to detect pre-invasive disease, that’s precancerous cells in the cervix. And if we can detect precancerous changes, and treat them, then we reduce the risk of developing invasive cancer in women.
So we currently screen in England between 24 and 64. Between 24 and 50 the screening intervals are three-yearly and after that if all smears are negative, five yearly until the age of 64.
Could you explain what low grade and high grade cervical smears are?
Women who have a cervical smear in general practice, the vast majority of smears are negative – 90% plus are negative. So for the 10% that are abnormal, the vast majority of those are borderline, equivocal or low grade. So borderline means there’s only slight abnormalities with the cervical cells on a cervical smear. But nevertheless, there’s a 10-20% risk of having a high grade lesion on the cervix. And what I mean by a high grade lesion on the cervix is that the actual tissue on the cervix has got precancerous cells, and those precancerous cells are high grade, and we know that high grade precancerous cells over time might lead onto cervical cancer.
With a high grade cervical smear, in the quality assured laboratories that we have in the UK nowadays, we know there’s an 80-90% risk of having high grade lesions on the cervix. We have to remember that a cervical smear is a screening test, and not a diagnostic test. So a screening test just detects women who are potentially at risk, a colposcopy with or without a biopsy is a definitive diagnostic test to rule disease out or to detect cancerous or precancerous cells in the cervix.
What is colposcopy, and how does it fit into screening for cervical cancer?
Women who are diagnosed as having abnormal cervical cells on a cervical smear are referred to colposcopy if they have a high grade smear or if they have a low grade or borderline smear, and are HPV high-risk positive – that’s the virus that can cause cervical cancer.
Colposcopy takes place usually in a hospital setting, and either a nurse or a doctor performs the colposcopy. The colposcopy is performed, hopefully, in a nice surrounding, and the lady has to get on the couch, and we place the speculum to visualise the cervix. And colposcopy is simply a technique of looking at the cervix under lower power magnification.
We look at the cervix initially without any special dyes, and then we put acetic acid, which is mild vinegar solution, onto the cervix, and that helps us to see abnormal cells on the cervix, and occasionally we use diluted iodine as well.
The whole process takes between 5 and 10 minutes, and if a clinician sees an abnormality of any significance at colposcopy, we generally take a biopsy and send that biopsy to the pathologist, and the pathologist takes sections of the biopsy and has a look at it under the microscope, and they report to us if there are any abnormal cells or not in the grading of the abnormal cells.
Thank you, and what are the advantages and disadvantages of colposcopy as a method for identifying cancerous tumours?
Colposcopy has been used for over 80 years in the management of pre-cevical cancer, and we’ve had a dramatic reduction in the incidence of cervical cancer by cervical smears and managing women with abnormalities within a colposcopy clinic. So we know the combination of organised cervical screening and organised colposcopy practice, which is quality assured, has dramatically reduced the incidences of cervical cancer in the UK and other countries that have got organised cervical screening programmes. So there’s no doubt that colposcopy is effective.
The main drawback of colposcopy is that it’s very subjective, and we’re all aware that every different clinician has got a different opinion on what they see, and sometimes there can be a wide variation in peoples’ opinion about colposcopic images and the interpretation of colposcopic images.
So colposcopy is subjective. From the evidence from published reports, the sensitivity of colposcopy is between 50 and 60%. So that means that occasionally you will miss disease because it’s subjective, and that’s the drawback of colposcopy.
So, following from that, what is the DySIS system?
The DySIS system aims to be more objective in the interpretation of colposcopic images. So the DySIS system has been evolved over the last ten years. The modern DySIS system is an integrated colposcope and DySIS interpretation of the colposcopic image.
The process relies on applying acetic acid, and objectively measuring the blanching effect of the acetic acid on the epithelium, and rate of decay of the blanching effect. And this is interpreted by a computer, and gives us an objective measurement and an estimate of the degree of abnormality present on the cervix.
And how would a clinician use the DySIS system?
The client/lady would get on the same colposcopy couch as in any colposcopy clinic, and the DySIS system, as I say is an integrated colposcopy system. A disposable speculum is inserted into the vagina, just like in any colposcopy, and the distance between the speculum and the colposcope has to be fixed.
Acetic acid is sprayed onto the cervix. And the colposcopist sets the DySIS machine and that estimates the degree of abnormality. At the same time, the colposcopist makes an interpretation of the cervix in his/her own right, and in combination with the DySIS estimation of abnormality, or normality, and the colposcopist’s judgement, you take a biopsy of what appears to be the most abnormal area on the cervix.
The whole process takes 15 minutes from start to finish, so it’s only slightly longer than a traditional colposcopy by 2 or 3 minutes.
Thanks, and how does DySIS compare with conventional colposcopy in terms of clinical effectiveness?
When we’re using the colposcope it very much depends on the severity of the referral cervical smear. If a woman has a high grade cervical smear, generally because we have quality assured laboratories now, there’s a high chance of the woman having a high grade lesion – an 80-90% chance.
So, when a colposcopist looks at the cervix under that scenario and sees an abnormality, almost certainly a colposcopist is going to take a biopsy. The DySIS product, will almost certainly match the colposcopist’s objective opinion, but probably will improve the accuracy of taking a biopsy from the worst area on the cervix. So it probably improves the accuracy of taking a biopsy in that scenario. I think the major advantage of the DySIS product is in low-grade cervical smear referrals. So if you have a low-grade cervical smear, there’s only a 20% risk of having a high grade lesion on the cervix. So those are easily missed, because a colposcopist might not be expecting a high grade lesion and the lesions might be very small. So a system that improves the diagnostic sensitivity, that’s the ability to pick up disease, is very useful in that scenario. And the DySIS system will increase the colposcopist’s sensitivity/ability to detect disease in that scenario.
And what’s the difference in sensitivity between the DySIS system and conventional colposcopy?
Well the evidence we have so far are from one publication in the UK from that was performed in the Hammersmith hospital, and two Dutch studies, which are more recent studies. The initial UK study used an earlier version of DySIS and that was just using DySIS alone without colposcopy. So when they compared colposcopy to DySIS in that first scenario, the sensitivity of colposcopy was 52%, and the sensitivity of DySIS was 65%.
Now the subsequent two Dutch studies have demonstrated that a similar rate of sensitivity of colposcopy in Holland to the UK, so 52% and 55%, but the combination of DySIS and colposcopy – so that’s dynamic DySIS examination is around 80%. So that’s a significant difference between 52% and 80% in sensitivity.
The combination of DySIS and colposcopy is slightly less specific than colposcopy alone, so that means you’ll end up with false positives, but the overriding advantage is the improved sensitivity of diagnosing disease.
And what are the cost implications of DySIS in comparison with conventional colposcopy?
The main difference is the initial purchase price. The average colposcope varies between £10-15,000. Where DySIS colposcope is between £18-22,000. Obviously, the DySIS machine has an integrated colposcope. So not only does it function as DySIS analysis equipment, but it also functions as a ordinary colposcope so it has that dual function.
To find out more about the cost implications of DySIS in comparison with conventional colposcopy, I spoke to Lucy Hammerton-Barry, Costing and Commissioning Coordinator at NICE.
What are the cost implications of DySIS in comparison with conventional colposcopy?
We’ve prepared cost impact estimates on the basis of incremental resource impact. This is an assessment of the change in activity and costs that may arise as a result of implementing the guidance. The costing work has identified three main areas of costs and savings.
Firstly, DySIS is estimated to generate annual national cost savings of £4.1 million for the NHS. This is around £8000 per 100,000 population.
The second is a cost impact for the additional purchase cost of the DySIS equipment. This would be a non-recurring cost that would impact on capital programmes and is estimated to be around £2 million for England.
The third area of costs and savings, which is also identified in the economic analysi,s is the potential future years’ savings arising from progressions to cancer avoided. These are estimated to be £5.4 million from the cohort of patients treated each year. However, because the rate of progression is variable, these savings will be achieved across a range of future times.
And what tools has NICE produced to help with estimating the costs of DySIS?
NICE has produced a costing template to assist with estimating the local cost impact of the guidance. The tool can be amended so that users can enter their local estimates and produce a report that can be used to aid decision making.
Lucy, thank you very much.
This resource should be used alongside the published guidance. The information does not supersede or replace the guidance itself.
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This page was last updated: 19 September 2012