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Rapid Responses: Rapid Responses published:
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![[Read Rapid Response]](/icons/misc/sectionDOWN.gif)
Diagnosis in General Practice
- David Brooks (24 April 2009)
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Strong argument for routine use of a diagnosis checklist
- Jason R Maude (24 April 2009)
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Look before you leap
- David M Lewis (25 April 2009)
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Diagnosis in general practice and secondary care
- Huw Llewelyn (27 April 2009)
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Caution in over reliance on diagnostic checklists
- David Ruben (7 May 2009)
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Diagnostic strategies in primary healthcare: a simple approach to making a diagnosis
- Terry Kemple (10 May 2009)
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David Brooks, retired GP PR4 5SE
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Dr. Heneghan and his colleagues agree that the hypothetico- deductive method rather than the laborious inductive method is most commonly used by clinicians during the process of making a diagnosis.1 They describe three stages (initiation, refinement and definition) and various strategies used in the diagnostic process. What is less clear from their article is that the history is of prime importance in the genesis of initial hypotheses as is what as general practitioners we know about the patient already from personal knowledge or patient records. Furthermore we must not forget that hypotheses are erected in physical pschological and social terms, the so called triple diagnosis. Initial hypotheses reflect probability, seriousness treatability and novelty. Hypotheses can be revised and re- ranked by further history taking, focussed examination selective further investigation and of course the use of time. Categories such as most likely, less likely and of course rare but important then emerge which can be tested and further refined for management. I would like to emphasise that these ideas are not mine, nor are they exactly new as generations of medical students who have been through the Professorial Department of General Practice at Leicester University will be aware. Indeed others who have been involved in post graduate medical education and have taught clinical reasoning to GP registrars through the years will also be very familiar with them Furthermore those of us who have been concerned about formative and summative assesment in the consultation will have used these ideas clinically in the form of the Leicester Assesment Package both in this country and abroad. May I recommend a text first published in 1987 which describes these ideas in full.2 1. Heneghan C Diagnosis in General Practice BMJ 2009;338: b946 2. Fraser R The Diagnostic Process p36 in Clinical Method, a General Practice Approach (ed Fraser R) Butterworth Heinemann third edition 1999. David Brooks MD FRCGP Competing interests: None declared |
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Jason R Maude, CEO Isabel Healthcare Haslemere, GU27 1AE
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The authors of this paper must be congratulated for this clear analysis and formal recognition of how the first and most important decision is made in the patient's journey. The fact that the Healthcare Commission highlighted that diagnosis has been the leading cause of complaints in primary care for the last 3 years, accounting for around 25% of all complaints, shows that this focus on diagnosis is long overdue. The King's Fund's recent announcement of an 18 month inquiry into the quality of General Practice with a particular focus on the quality of diagnosis and referrals is also to be welcomed. This study highlights that in about 70% of consultations the diagnostic strategy relies on a hypothesis, list or pattern derived from the GP's memory. The stakes are far too high for this vital first step, which determines subsequent treatment and medication, to depend so heavily on one person's memory. Medicine has got much too complex for that. The use of surgical checklists has recently been mandated by the CMO and are being implemented by the NPSA as their use has been shown to dramatically reduce morbidity and mortality. Checklists are particularly useful for processes that rely extensively on memory as the authors of this paper have just shown to be also the case for diagnosis in primary care. Technology has now made it possible to deliver, at the point-of-care, an instant patient specific checklist for the cognitive process of diagnosis decision making and they should now be used routinely. Competing interests: Jason Maude is CEO and Co Founder of Isabel Healthcare which produces the Isabel Diagnosis Checklist system |
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David M Lewis, GP Principal Watford WD24 7PH
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Heneghan et al provide a thoeretical construct for diagnostic reasoning by GPs. However, I submit they have used a cognitive forcing strategy themselves so missing at least one other strategy: 'pattern failure'. Regrettably, a search on google scholar tonight failed to identify any published literature on this phenomenon. I will explain: Consider a LCD monitor screen. Almost all the time there is no problem. However, if a pixel is not working, the eye is drawn to it. It will take time to bring to consciousness what the problem is, but one is aware immediately. Or think of a bobby on the beat. She passes the same houses day in and day out for weeks, months and even years in the past. One day she is on her beat and feels uncomfortable. She turns back and realises a front gate which is usually closed is open. Investigation reveals a crime has taken place. What I am getting to, is that for some GPs the null hypothesis is the patient before them has nothing (seriously)wrong. The decision making process is about refuting this hypothesis by using history and examination to attempt to identify disordered physiology/anatomy. In the absence of such an abnormality, one can be reassured. This is, I believe, a distinguishing feature of first contact doctoring. It is a skill which, I believe, reduces referral to secondary care. General Practice consultations should, in my opinion, conclude with a statement about what is not the problem (often allaying worrying ideas/concerns/fears). Making a diagnosis is rare in unscheduled GP visits; this should be acknowledged. This is at the core of managing uncertainty in general practice and, I believe, should be encouraged and supported. Heneghan et al describe a process which may undermine this principle. Competing interests: None declared |
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Huw Llewelyn, Consultant Physician Queens Hospital, Burton, DE13 0RB
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The diagnostic steps described by Henegan et al [1] are also used by hospital doctors. The detailed history and examination model is useful to beginners but is also useful when a doctor sees a patient with multiple problems and no detailed past records. If the patient’s background and other diagnoses are already well known, in hospital or general practice, the process can be focussed more easily on a single problem. The basic aim of diagnosis is to show that the patient is a member of a group with findings, within which it is helpful and safe to take some action (e.g. reassuring, admitting to hospital, prescribing some medication or operating). A probable or definitive diagnosis becomes final when the outcome is accepted by the patient and advising team. In many cases the final diagnosis is ‘some unknown process that has resolved with no active intervention’. Until the diagnosis is final, in primary or secondary care, a differential diagnosis has to be kept in mind in order to avoid a diagnostic error due to premature closure. It is always important to start with the presenting complaint (a correct spot diagnosis of eczema would be silly in a patient wanting help because of chest pain). The appropriate model for all this is not Bayes theorem alone. Another ‘theorem’ is also needed to explain how differential diagnoses are formed from presenting complaints or other triggers (also called ‘diagnostic leads’ [2]) and how other information are used to differentiate between them (also called ‘differentiators’ [2]). The arithmetic of this process needs to be understood in order to practice evidence-based medicine properly [2]. All this can be taught to students and trainees so that the diagnostic process can be practiced in an evidence-based, cost-effective way and the reasoning explained to patients and other members of the team in writing. [1] C Heneghan, P Glasziou, M Thompson, P Rose, J Balla, D Lasserson, C Scott, and R Perera. Diagnostic strategies used in primary care. BMJ 2009; 338: b946 [2] H Llewelyn, H Ang, K Lewis and A Al Abdullah. The Oxford Handbook of Clinical Diagnosis, 2nd edition. Oxford University Press, Oxford 2009. Competing interests: Huw Llewelyn is an author of the Oxford handbook of Clinical Diagnosis |
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David Ruben, Associate GP Mill Hill, London NW7 1GR
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Maude's response of diagnostic checklists may be of value, but a surgical pre-op checklist is quite different from diagnosing in the real world the presentation of uncertainty. Indeed straw-poll arguement that diagnosis is major problem in primary care - something must always be "the leading cause of complaints". Diagnostic checklists can only take us only so far - eventually the generalising processes of EBM must be applied to the one specific patient in front of us, and with checklists never giving absolute diagnostic certainty, so there will remain doubt as to the correct action for that specific patient. Perhaps Maude meant to suggest a Consultation checklist (eg of whether diagnosis given, reassurance of conditions ruled out, of treatment options and what realistically to expect of them and of contingency action). A checklist is not the right medium for addressing cost-benefit of a wrong diagnosis and what is a wise/prudent clinical approach, rather than what a well programmed robot can tick off from a checklist. I have on rare occasions encountered patients relieved of their chest pain by GTN spray, despite subsequent normal coronary angiogram, for it may also relieve oesophageal spasm in GORD. Similarly in patients presenting with onset of headache, neck stiffness is an unhelpful sign if they have pre-existing neck arthritis and pain. Competing interests: None declared |
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Terry Kemple, General Practitioner Horfield Health Centre, Bristol BS7 9RR
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Michael Porter, Professor at Harvard Business School, says ‘The essence of strategy is choosing what not to do.’ Diagnosing what disease a patient has is important but observing and making sense of the different ways our patients minds work is one of the keystones of general practice. Hence (as Osler observed) we need to know what sort of patient has a disease more than what sort of disease a patient has and that whilst a good physician treats the disease; the great physician treats the patient who has the disease. Perhaps doctors do decide to use fourteen formal strategies in three different stages of diagnosis (reference 1) but perhaps it’s simpler than that, and all we need to do is decide what not to do. James Reason describes a model (reference 2) of how the mind works. We all live in the immediate world of our ‘conscious workplace’. This is what you are aware is in your mind right now. Constantly and automatically our conscious workplace accesses our long-term memory store for additional information. Long-term memory is searched for the missing information using one of two processes either similarity matching or frequency gambling. Similarity matching produces more robust results. For instance, search your mind for a pet that has four legs and barks and you are likely to think of a dog. Frequency gambling produces less reliable results. Search your mind for a furry brown animal and some furry brown answer will immediately pop into your consciousness. What it is depends on your own experience of furry brown animals. Frequency gambling is the process that results in us misdiagnosing meningitis as flu in a flu epidemic. You may get a strong but wrong answer. A simple approach to diagnostic strategy is to be aware if you used similarity matching or frequency gambling in making the diagnosis. If it is similarity matching you can proceed with confidence, if its frequency gambling you must choose not rely on it and instead get more information so that similarity matching can provide the answer. William Osler’s advice: ‘No human being is constituted to know the truth, the whole truth, and nothing but the truth; and even the best of men must be content with fragments, with partial glimpses, never the full fruition’. References 1. C Heneghan, P Glasziou, M Thompson, P Rose, J Balla, D Lasserson, C Scott, and R Perera. Diagnostic strategies used in primary care. BMJ 2009; 338: b946 2. The Human Contribution: Unsafe Acts, Accidents and Heroic Recoveries by James Reason. Ashgate Publishing Ltd 2008 Competing interests: None declared |
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