practices participating in the vocational training scheme ... innovation without adjusting for practice list size .... sentation and during the course of the disease.'.
gresses more rapidly in this group is in dispute. Although we are unlikely to find premalignant disease in the sexually active girls under 16, we think that cytological screening is useful to educate them about the need for regular cervical smears. These patients are likely to have many sexual partners, have a high prevalence of sexually transmitted diseases (770/o-A J Robinson, unpublished data), and be at high risk of developing cervical intraepithelial neoplasia. ANGELA J ROBINSON J TULLETT J D WILSON
Our definition of innovation is hardly income based, covering as it does participation in the training scheme, employment of a nurse, and participation in the cost rent scheme. None of these decisions add much to income in terms of fees from the family practitioner committee. It would be useful to measure the resources consumed by different practice strategies more precisely, but the qualitv of the data may make this difficult. NICK BOSANQUET Ccntrc for Health Economics, University of York, York YOI 5D1)
Royal Hallamshire Hospital, Sheffield S 10 2JF I Wilson JD, Hill AS, Hicks DA. Value of colposcopy in genitourinary departments. Genttoturin Med 1988;64: 100-2.
Points Measuring faecal fat
Innovation in general practice Mr Nick Bosanquet and Dr Brenda Leese (4 June, p 1576) address an important question relevant to the design and implementation of policies which seek to improve patient care through the reimbursement mechanism. Given the importance of list size and capitation payments in determining practice incomes it is strange that this was not discussed, particularly as it is related to the authors' definition of innovation and practice types. Innovative practices were more likely to be in larger partnerships, where list sizes are known to be larger. On the other hand, practices participating in the vocational training scheme may have had smaller list sizes. Attributing differences in general practitioners' incomes to innovation without adjusting for practice list size obscures the assessment of the income generated by adopting different strategies of practice investment and style. Considering the present remuneration system and the authors' income based definition of innovation it is not surprising that innovative practices enjoy higher gross and net incomes for each partner. One way of avoiding this circularity is to distinguish the income generated from innovative practice activities from the cost of innovation. This would focus on the measurement and valuation of the resources consumed as a consequence of adopting different practice strategies or patterns of investment. If such costs were estimated and set alongside the benefits generated by primary care innovations policy recommendations could proceed on a more informed basis. J F I )RBES
Mr D M MERRINGON (International Laboratories Limited, Alton, Hampshire GU34 2TJ) writes: Drs G K T Holmes and P G Hill (4 June, p 1552) suggest that the fluorescein dilaurate test is inconvenient as an outpatient procedure. It is particularly suitable for outpatient use. Each test kit includes a leaflet addressed to the patient explaining how the test is to be used and a timetable giving details of meals, fluid intake, and urine collections. If patients are given the test kit, two plastic collecting bottles, and an explanation of the test and what they are expected to do they should have little difficulty. There are no special storage requirements for the collected urine. A recent report has emphasised the simplicity of the test for use in outpatients. ' 1 Gould SR, Chinn GL, Nobbs BT, Lewis GA. Evaluation of a tubeless pancreatic ftunction test in patients with steatorrhoea
in a district general hospital. 7 R Soc Med 1988;81:270-3.
Safe limits of drinking Dr M E PURKISS (Tower Hamlets Health Authority, London E I 1BB) writes: Drs Peter Anderson and Paul Wallace (18 June, p 1707) inaccurately paraphrase the royal colleges' reports, and their questionnaire further promotes the mistaken assumption that there is a safe limit for the consumption of alcohol. The Royal College ofGeneral Practitioners' report contains a table which categorises those who drink less than 20 units a week (men) or 14 units a week (women) as being at low risk of harm.' This is not the same as saying that these limits are entirely safe. Individual susceptibility to alcohol and the pattern of consumption-whether evenly spread or consumed on only one or two occasions-are factors that profoundly influence the amount of harm that can occur at these so called safe limits.
Department of General Practicc, University of Edinburgh, Edinburgh EH8 9DX
1 Royal College of General Practitioners. Alcohol-a balatced view. London: Royal College of General lractitioners, 1986:20.
AUTHOR'S REPLY,-Mr J F Forbes asks why the results of our survey did not include more discussion of the effects of list size. Data were available about list size for all the practices in the survey, but the variable did not show many differences by area or practice type. Mr Forbes suggests that larger practices are more likely to have larger list sizes. This was not so in our survey (table). Neither were list sizes smaller in training practices. There has been a considerable success in equalising list sizes between areas, and the more important differences are now in practice size.
Ultrasound screening and abdominal aortic aneurysm
List sizes for different partnership sizes No of partners
List size
2 3 4 5
2940 2209 2198 2339 2203
6
360
Mr JACK COLLIN (Nuffield Department of Surgery, John Radcliffe Hospital, Oxford OX3 9DU) writes: Mr R A P Scott and others (18 June, p 1709) do less
than justice to the value of screening for abdominal aortic aneurysm as they seem to be still screening both men and women. Abdominal aortic aneurysm is overwhelmingly a disease of men, particularly in those of an age at which prophylactic aortic operation is likely to be considered. In Oxford over the past 31 months only 13 of the 121 emergency admissions for ruptured or symptomatic abdominal aortic aneurysms were women under 80. During the same time only two out of 99 patients undergoing elective surgery for abdominal aortic aneurysm were women. It is an essential requirement of any screening programme to screen the right group. If Mr Scott and others had presented their data separately for men and women we should no doubt see that the prevalence of abdominal aortic aneurysms over 3 5 cm in diameter was about double their value of 288% in men and uncommon in women.
Apparent haematuria Drs N R RowELL (Leeds General Infirmary, Leeds LS1 3EX) and G M FAIRRIS (Royal South Hampshire Hospital, Southampton S09 4PE) write: In their paper on apparent haematuria as an early sign in poliomyositis (18 June, p 1725) Drs Richard Lim and John L W Parker state that serum enzyme activity is the most reliable diagnostic test, creatine phosphokinase activity being raised in nearly all cases of acute or subacute myositis. Our observations have shown that the 24 hour urinary creatinine excretion is a better index of muscle activitv than creatine phosphokinase, being more commonly raised at presentation and during the course of the disease.' Rowell NR, Fairris GM. Biochemical markers ot- nivositis ill dcrmatomvositis. Clin Exp D)ernatiol 1986;1 1:69-72.
Treating the discharging ear Mr GEORGE G BROWNING (Department of Otolaryngology, Royal Infirmary, Glasgow G4 OSF) writes: As a hospital doctor I found it instructional to read Professor John Bain's and Dr Ian Wiliamson's critical appraisal of the management in general practice of a symptom such as otorrhoea (4 June, p 1617) with the realisation that there are many patients and conditions that we do not see as regularly in hospital. It is, however, important that the appropriate patients are referred to otolaryngologists for investigation and management. In their leading article Professor Bain and Dr Williamson suggested that in active chronic otitis media general practitioners should be able to identify ears with a cholesteatoma. My experience is that this can be extremely difficult and, indeed, is a common reason why candidates fail their final fellowship in otolaryngology. It is suggested that in most instances an experienced eye is necessary to make the distinction between ears with and without a cholesteatoma. But how important is it to identify what many consider to be more dangerous because of an increased likelihood of developing complications such as intracranial abscesses? The risk of this happening in the United Kingdom, however, is low, for it occurs in about six out of 100 000 cases a year (D A Nunez and G G Browning, unpublished observations). In addition, the risks are virtually the same when there is mucosal disease with granulation tissue but without cholesteatoma.' 1 Browning GG.Ihe unsafeiiess of "safe" ears. .7 Lanlgol Otol 1984;98:23-6.
Managing flying phobia Drs RICHARD F CRELLIN and LYNNE M DRUMMOND (Department of Psychiatry, St George's Hospital, London SW17 ORE) write: Dr Andrew Steptoe (25 June, p 1756) discusses the treatment of flving phobia. Although in these cases real life exposure may seem to be costly and difficult to arrange, one of the major British airlines offers inexpensive day return "fun" flights which are ideal for this purpose and well within the price range of most patients. These flights are cheaper than those offered by many airlines for anxious flyers. It is the practice on many of thcse flights for the anxious to offer alcohol before and during the flight. Using alcohol as an anxiolvtic is contrary to the exposure principle of treatment. In our experience a woman with a severe phobia was successfully treated by four and a half hours of exposure in fantasy with the help of a therapist and in the airport environment, followed by a day return "fun" flight. These patients may also be suitable for treatment by some psychiatrists. The Royal College of Psychiatrists has emphasised the importance to trainee psychiatrists of behavioural psychotherapy experience.' Flying phobia is usually treated with a modest investment of the therapist's time and can acquaint inexperienced trainee psychiatrists with the basic principles of exposure treatment. I Royal College of Psychiatrists. Guidelines for the traininig of general psychiatrists in psychotherapy. Br .7 I'.svchatrv 1971;
119:555-7. 2 Royal Collegc of Psychiatrists. Guidelines for the training of general psychiatrists in psychotherapy. Bulletit, of the Roal
College oJfPsvchiatrists 1986;10:286-9.
BMJ VOLUME 297
30 JULY 1988
