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We thank Perkins and Collin for their interesting comments on our
needs assessment (1,2). These highlight the difficulties of identifying
the need for a health care intervention when new evidence may accrue which
changes the indications for it. In this case, the final results of the
ECST trial showed that the benefits of carotid endarterectomy may be
restricted to higher degrees of stenosis (80-99% in men and 90-99% in
women) than previously thought (3). This study was published after our
work so could not be taken into account. Both our use:need estimates and
contemporary surgical practice were valid, based on evidence available at
the time. Whilst new evidence suggests that a more selective policy of
intervention should now be followed, and that unmet need and gender
inequality is less than we have shown, it must be remembered that these
indications may change again after the final results of the other large
study NACSET are published.
The estimation of the distribution of carotid stenosis in unselected
population based groups of patients with the underlying conditions (TIA,
amaurosis fugax, minor stroke) and no contraindication to surgery is
complex. Our estimates for TIAs and strokes used hospital TIA series who
had no surgical contraindications (4). More recent hospital series using
duplex scanning show lower percentages with stenosis over 70% (5). However
the trials used angiography, (and to confuse matters different methods of
estimating stenosis), and there is the problem of reconciling
distributions based on duplex scanning. Selective referral, also, might
mean that the distribution of stenosis in hospital case series may not
represent the potential population which may benefit (4). Moreover the
assessment of surgical suitability may be subjective. Perkins and
Collin's implication that need was being met would be unusual within
health services, however, especially for specialist services. It is
possible that our 'use' estimate included some operations for asymptomatic
or lower grade stenosis, but this was not view of vascular surgeons in the
Region.
Evaluation of the epidemiology of evidence based indications for key
health care interventions needs greater priority within the health
service: there are few data for example on the gender specific levels of
80 or 90% carotid stenosis. Our approach to comparing use and need is
important in demonstrating inequity in health care delivery.
1 Perkins JMT and Collin,J. Rate of carotid endarterectomy in Wessex
might already be higher than necessary. BMJ 1999;318:399.
2 Ferris G, Roderick P. Smithies A, George S, Gabbay J, Couper N,
Chant A. A epidemiological needs assessment of carotid endarterectomy in
an English health region. Is need being met? BMJ 1998;317:447-51.
3 European Carotid Surgery Trialists Collaborative Group. Randomised
trial of endarterectomy for recently symptomatic carotid stenosis: final
results of the MRC European carotid Surgery Trial (ECST) Lancet
1998;351:1379-87.
4 Hankey GJ, Slattery JM, Warlow CP. Prognosis of hospital referred
transient ischaemic attacks. J Neurology, Neurosurgery, Psychiatry.
1991;54:793-802.
Implication that need was being met would be unusual within health services
Editor
We thank Perkins and Collin for their interesting comments on our
needs assessment (1,2). These highlight the difficulties of identifying
the need for a health care intervention when new evidence may accrue which
changes the indications for it. In this case, the final results of the
ECST trial showed that the benefits of carotid endarterectomy may be
restricted to higher degrees of stenosis (80-99% in men and 90-99% in
women) than previously thought (3). This study was published after our
work so could not be taken into account. Both our use:need estimates and
contemporary surgical practice were valid, based on evidence available at
the time. Whilst new evidence suggests that a more selective policy of
intervention should now be followed, and that unmet need and gender
inequality is less than we have shown, it must be remembered that these
indications may change again after the final results of the other large
study NACSET are published.
The estimation of the distribution of carotid stenosis in unselected
population based groups of patients with the underlying conditions (TIA,
amaurosis fugax, minor stroke) and no contraindication to surgery is
complex. Our estimates for TIAs and strokes used hospital TIA series who
had no surgical contraindications (4). More recent hospital series using
duplex scanning show lower percentages with stenosis over 70% (5). However
the trials used angiography, (and to confuse matters different methods of
estimating stenosis), and there is the problem of reconciling
distributions based on duplex scanning. Selective referral, also, might
mean that the distribution of stenosis in hospital case series may not
represent the potential population which may benefit (4). Moreover the
assessment of surgical suitability may be subjective. Perkins and
Collin's implication that need was being met would be unusual within
health services, however, especially for specialist services. It is
possible that our 'use' estimate included some operations for asymptomatic
or lower grade stenosis, but this was not view of vascular surgeons in the
Region.
Evaluation of the epidemiology of evidence based indications for key
health care interventions needs greater priority within the health
service: there are few data for example on the gender specific levels of
80 or 90% carotid stenosis. Our approach to comparing use and need is
important in demonstrating inequity in health care delivery.
1 Perkins JMT and Collin,J. Rate of carotid endarterectomy in Wessex
might already be higher than necessary. BMJ 1999;318:399.
2 Ferris G, Roderick P. Smithies A, George S, Gabbay J, Couper N,
Chant A. A epidemiological needs assessment of carotid endarterectomy in
an English health region. Is need being met? BMJ 1998;317:447-51.
3 European Carotid Surgery Trialists Collaborative Group. Randomised
trial of endarterectomy for recently symptomatic carotid stenosis: final
results of the MRC European carotid Surgery Trial (ECST) Lancet
1998;351:1379-87.
4 Hankey GJ, Slattery JM, Warlow CP. Prognosis of hospital referred
transient ischaemic attacks. J Neurology, Neurosurgery, Psychiatry.
1991;54:793-802.
5 Perkins JM, Collin J, Walton J, Hands LJ, Morris PJ. Carotid
duplex scanning: patterns of referral and outcome. Eur J Vasc Endovasc
Surg 1995;10:486- 488.
Paul Roderick
Senior Lecturer
Gill Ferris
Research Fellow
Anthony Chant
Consultant Vascular Surgeon
Steve George
Senior Lecturer
John Gabbay
Professor
Competing interests: No competing interests