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Rapid Responses: Rapid Responses published:
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The differential diagnosis list should prioritise what is treatable even though relatively rare
- oscar,m jolobe (10 March 2007)
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"Zebras, not Horses"!
- Anthony H. Knight (13 March 2007)
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Pertussis - An Uncommon Problem In Adults?
- Andrew Johnston, Dr Helen Stone, Dr Chandra Thippanna (20 March 2007)
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The crisis of the clinical method. Our point of view.
- JULIO Y VALDES, JULIO Y. VALDES LISTE,HIRAM MORALES DE AVILA,DAMION R. JOHNSON (3 April 2007)
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Whooping cough – better methods of diagnosis are now available.
- Natasha S Crowcroft, Norman K. Fry, David J. Litt, Timothy G. Harrison, Robert C.George, Muhammad Abid, Philip Monk, Elizabeth Miller (23 April 2007)
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oscar,m jolobe, retired griatrician 1 The Lodge, 842 Wilmslow Road, Didsbury, manchester,M20 2RN
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In relation to this clinical vignette, two issues come to mind, both to do with disease prevalence. The first is that "uncommon presentations of common diseases are more common than (common presentations of)uncommon diseases"(1), hence the importance, in this instance, of entertaining the possibility that, even if the age group is "wrong", if the symptoms are "right", it must be whooping cough(2). The second isuue is that, thanks to slavish adherence to the dictum "common things happen most commonly", many doctors are more prepared to make a provisional diagnosis of a disorder which is highly prevalent, though untreatable, than a provisional diagnosis of a disorder which, though eminently treatable, suffers from the disadvantage of being relatively rare. Witness the example of haemorrhagic pleural effusion in a modern European country where, according to one series, as many as 28 out of 59 instances were attributable to malignancy, as opposed to only two out of the 59 being attributable to tuberculosis(3). No wonder that, in a textbook aimed at English medical students, when blood stained pleural exudates were listed as being commonly attributable to malignancy, this was to the complete exclusion of any mention that tuberculosis might be an alternative underlying cause(4). Likewise, in what is commonly perceived to be an authoritative reference text, the qualification that 50% of malignant pleural effusions might be bloodstained was made without any allusion to the fact that tuberculous pleural effusions might also, on occasion, be bloodstained(5). One of the risks of an inflexible preoccupation with the highly prevalent but untreatable is that, in the event of one such diagnosis being proved wrong, an irretrievable opportunity might have been lost to establish the diagnosis of an eminently curable, though relatively rare disorder. References (1) Montgomery K "Don't Think Zebras": A theory of Clinical Knowing Chapter Eight How Doctors think: Clinical Judgment and the Practice of Medicine 2006 Editor Montgomery K Oxford University Press (2) Levenson R A patient's journey: Whooping cough British Medical Journal 2007:334:532-3 (3)Villena V., Lopez-Encuentra A., Garcia-Lijan R et al Clinical implications of appearance of pleural fluid at thoracocentesis CHEST 2004:125:156-9 (4)Kumar P and Clark M Respiratory Disease: Diseases of the chest wall and pleura Chapter 14 Clinical Medicine 2005 Sixth edition Editors Kumar P and Clark M Elsevier Saunders Edinburgh London New York (5) Benson MK Pleural Disease Chapter 17.12(pages 1513-22) Oxford Textbook of Medicine Volume 2;Fourth Edition Editors:- Warrell DA., Cox TM., Firth JD., Benz EJ Oxford University Press Competing interests: None declared |
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Anthony H. Knight, Retired Consultant Physician Home HP22 5BT
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Ros Levenson's experience of self-diagnosed whooping cough (BMJ 10th March 2007) made allowance for the maxim, "If you hear hoof beats, think horses, not zebras", as she drew attention to the not such rare occurrence of whooping cough in adults. This reminded me of an amusing incident, when the quoting of this equestrian maxim backfired on a visiting lecturer rather splendidly. Some years ago, when I was District Clinical Tutor at Stoke Mandeville Hospital, I invited a friendly orthopaedic surgeon from a neighbouring hospital to give the weekly lunchtime lecture. His topic was "The Diagnosis and Management of Backache" and in making the point that "Common things are common", he used the maxim referred to by Ros Levenson. In doing so he elaborated somewhat declaring that "If you hear clip clop, clip clop outside your surgery window it will probably be a passing horse and not a zebra". At this point, one of our more elderly General Practitioners awoke from his apparent post-prandial slumber to interject that if he heard "Clip clop, clip clop outside his surgery window it would most probably be a zebra and not a horse". This GP's surgery was in nearby Tring, where the eccentricity of the local nobility, in driving about the town in a zebra- drawn carriage, was well known. Competing interests: None declared |
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Andrew Johnston, Specialist Registrar Respiratory Medicine Respiratory Department, University Hospital Birmingham, Birmingham, B15 2TH, Dr Helen Stone, Dr Chandra Thippanna
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Ros Levenson’s personal account of her experience with pertussis provides a timely reminder about this condition.[1] We suspect few doctors caring for adult patients include pertussis in their differential diagnosis -as Levenson points out, pertussis is a diagnosis usually considered to affect children, rather than adults. This is due to the misconception that the protection afforded by immunisation is lifelong and the fact that there may be little other than persistent cough to suggest the diagnosis in those previously immunised.[2] As with other immunisations antibody levels decline with time unless the patient is given booster doses or exposed to the disease.[3] Although children are most at risk from the complications of pertussis,[4] adults are also affected by changes in herd immunity. UK Health Protection Agency figures show only a small number of statutory notifications of pertussis, averaging 599 per year over the period 2002-2004, and 67 proven (by serology or PCR) cases,[5] but figures from the US are much higher at around 12000 in one year.[2] Even allowing for differences in the UK and US populations this suggests we are underdiagnosing pertussis. Physicians seeing adults with cough should consider pertussis in their differential diagnosis, as although there is no specific treatment reassurance may be provided and expensive and uncomfortable investigations avoided. 1. Levenson R. A patient's journey: whooping cough. BMJ 2007;334:532- 533 2. Hewlett EL, Edwards KM. Clinical practice. Pertussis--not just for kids. N Engl J Med. 2005;352:1215-22. 3. Crowcroft NS, Britto J. Whooping cough—a continuing problem. BMJ 2002;324:1537-38. 4. Cherry JD. The science and fiction of the "resurgence" of pertussis. Pediatrics. 2003;112:405-6. 5. Health Protection Agency. Epidemiological data – Whooping Cough (Pertussis); [updated 8 May 2006; cited 2007 Mar 15]. Available from: http://www.hpa.org.uk/infections/topics_az/whoopingcough/data.htm Competing interests: None declared |
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JULIO Y VALDES, MEDICAL DOCTOR HOSPITAL UNIVERSITARIO MORON .CIEGO DE AVILA .CUBA.CP67210., JULIO Y. VALDES LISTE,HIRAM MORALES DE AVILA,DAMION R. JOHNSON
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It is extremely productive that works like this are published since it gives us the opportunity to consider how clinical medicine is functioning in the current moment. There are medullar points in the care of this patient that we find opportune to mention in the most synthetic form possible; although it is certain that most of the illnesses are presented to the doctor as typical cases, or like atypical forms of common illnesses , we should have present, possible differential causes to the illnesses that are not so frequent but that some day may present themselves, for example in this patient with cough for more than three weeks of evolution it would be logical to think of illnesses as frequent as later nasal leak, asthma and gastroesophageal reflux(1), never the less if we never think in "zebras" like the whooping cough we will never be able to diagnose it, "what is never thought is never diagnosed." Another important point is the evident violation of the clinical method as showed irrefutable in the crisis in which it happens, any doctor who faces a new patient should carry out a short investigation, apply a clinical method, not directed for experimentation but for the attention of the sick person and then two questions arise. What is the patients illness? How can find out what it is? In this their should be an order, a system, a clinical method that is no more than the application of the experimental method to the attention of the sick individual. There is an order in the method, if a doctor sees a patient, he indicates laboratory exams to see the results and after the results he interrogates and to examine the patient, altering this method, violating it, like in the case that is presented to us is an error that could lead to other errors that could be worst(2). It is evident that many of the medical errors depends not only on scientific knowledge at the hour to interpret the clinical manifestations of a sick person, they also depend on violations in the application of the scientific method in the clinical procedure, that is to say, deficiencies that accumulate from the doctor patient relationship , the gathering of the primary information, the elaboration of the diagnosed hypothesis and the selection and adequate interpretation of the technological investigations of all types to enrich, to contrast this hypothesis and to make a correct confirmation. If we want to avoid or rather to overcome this crisis of the clinical method we should be convinced that the day that the clinical method is respected more and not before we will begin to decrease the so frequent errors in the medical diagnoses, this is the only way possible. Clinical medicine in our times still acquires a value superior to that of the past (3). 1. Diego Damia A. Estudio y tratamiento de la tos crónica. Arch Bronconeumol 2000; 36: 208-220. 2. Moreno Rodriguez MA. El error medico y el método clínico. En: Moreno Rodriguez MA, editores.El arte y la ciencia del diagnostico medico. Editorial Científico Técnica 2001:167-178. 3. Moreno Rodriguez MA.El metodo clinico:recopilacion de articulos.La Habana.Imprenta de las FAR,1998:37. Competing interests: None declared |
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Natasha S Crowcroft, Consultant Medical Epidemiologist HPA Centre for Infections, 61 Colindale Avenue, London NW9 5EQ, Norman K. Fry, David J. Litt, Timothy G. Harrison, Robert C.George, Muhammad Abid, Philip Monk, Elizabeth Miller
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We welcome Ros Levenson’s account of her experience of whooping cough and sympathise with her experience (1). She illustrates perfectly the challenges faced by patients because clinicians don’t recognise the infection, especially in adults, or often don’t know how to make the diagnosis. But does it need to be so difficult? It may be helpful to update clinicians about the diagnostic methods which are now available. This is important because, although pertussis is at historically low levels in the UK (2), it is still one of the most frequently reported infections of all vaccine preventable diseases included in the routine childhood immunisation programme. Fewer than five cases of diphtheria, tetanus, polio and rubella per year are reported in children, and frequently there are no cases at all. The number of cases of Haemophilus influenzae type b (Hib), group C meningococcal infection (MenC), and measles in children are less than 200. In contrast, only cases of mumps currently exceed the number of reported cases of pertussis. As under- reporting of pertussis is greater than most other diseases, the numbers of severe cases and deaths are even greater than that shown by routine surveillance (3, 4, 5). The more we look, the more we find (6). Even if pertussis is suspected, many clinicians don't investigate, perhaps because they think this requires pernasal swabs, which they don’t like to take, or know that culture is a relatively insensitive test, particularly in the later stages of illness. Paediatricians should be aware that the HPA has been providing polymerase chain reaction (PCR) diagnostics for infants since 2001, which is much more sensitive than culture (7). Sero-diagnosis by detection of raised serum IgG antibodies to pertussis toxin (PT) is available to GPs and is provided for those who have been coughing for 2 weeks or more. Clinicians who are aware of these methods may still be reluctant to take blood in this patient group, so they may content themselves with notifying the infection but not confirming it by laboratory testing. Notifying is important as it triggers important public health interventions, including considerations as to the use of prophylactic agents for household contacts. But a group of patients are left without laboratory confirmation. To address this last group, HPA is proposing to make available oral fluid testing (for anti-PT IgG) to diagnose those who have been coughing for >2 weeks (8). Taking the specimen for this test involves using a simple device already used successfully for diagnosis and surveillance of measles, mumps and rubella. It is suitable for parents to use at home, and to post to the Centre for Infections Respiratory and Systemic Infection Laboratory. A pilot study of testing oral fluid from notified cases of pertussis has been carried out in two areas of the country (Thames Valley and Leicestershire). Follow up of notified cases by oral fluid was acceptable to Health Protection Units, clinicians (mainly G.P.s) and patients. Laboratory confirmation of notified cases was obtained in 46% of oral fluid specimens submitted. This represented confirmation of 22% of all notified cases in the two areas. Total ascertainment of cases by enhanced surveillance in England and Wales increased by 2% nationally as result of this small pilot study. This new diagnostic service is not currently available anywhere else in the world. The HPA is leading the way in innovative methods of simultaneously improving the quality of laboratory diagnostic methods for the benefit of patients, and enhancing surveillance for the benefit of vaccine policy development and public health. We hope to be rolling this service out nationally in the near future. For further information please contact: The HPA Centre for Infections Respiratory and Systemic Infections Laboratory (telephone 020 8327 7330). References 1. Levenson R. A patient’s journey. Whooping cough. BMJ 2007;334:532- 3 2. http://www.hpa.org.uk/infections/topics_az/whoopingcough/data_not_region.htm 3. Van Buynder,P.G.; Owen,D.; Vurdien,J.E.; Andrews,N.J.; Matthews,R.C.; Miller,E. Bordetella pertussis surveillance in England and Wales: 1995-7 Epidemiology.& Infection. 1999;123:403-11 4. Crowcroft NS, Andrews N, Rooney C, Brisson M, Miller E. Deaths from pertussis are underestimated in England. Arch Dis Child 2002;86: 336-338 5. Crowcroft NS, Booy R, Harrison T, Spicer L, Britto J, Mok Q, Heath P, Murdoch I, Zambon M, George R, Miller E. Severe and unrecognised: pertussis in UK infants. Arch Dis Child. 2003 Sep;88(9):802-6. 6. Harnden A, Grant C, Harrison T, Perera R, Brueggemann AB, Mayon-White R, Mant D. Whooping cough in school age children with persistent cough: prospective cohort study in primary care. BMJ. 2006 Jul 22;333(7560):174-7 7. Epub 2006 Jul 7. http://www.hpa.org.uk/cfi/rsil/bordetella.htm 8. Litt DJ, Samuel D, Duncan J, Harnden A, George RC, Harrison TG. Detection of anti-pertussis toxin IgG in oral fluids for use in diagnosis and surveillance of Bordetella pertussis infection in children and young adults. J Med Microbiol. 2006 Sep;55(Pt 9):1223-8. Competing interests: None declared |
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