The diagnostic process in general practice: has it a two-phase structure?

The diagnostic process is a complex transition process that begins with the patient’s individual illness history and culminates in a result that can be categorized. A patient consulting the doctor about his symptoms starts an intricate process that may label him, classify his illness, indicate certain specific treatments in preference to others and put him in a prognostic category. The outcome of the process is regarded as important for effective treatment, by both patient and doctor. Various models have been proposed for diagnostic work in clinical practice. Sackett describes four main strategies. 1 Pattern recognition is the instant recognition of a disease, for instance diagnosing Downs syndrome after one look at the patient. In the hypotheticodeductive strategy, one performs some form of test to check a hypothesis, a tentative diagnosis. The two last strategies that he mentions are the algorithm strategy and the ‘complete history’ strategy. The patient’s presentation of his symptoms will be coloured by his experiences and his understanding of his symptoms, and by how articulate he is. In Sackett’s model, the transition from individual clues to a tentative diagnosis suitable for a hypothetico-deductive strategy remains obscure. A string of symptoms merely listed seldom leads to a diagnosis. To a certain degree, a list of symptoms can overlap between diseases. 2 Still, this individual diversity does not usually mislead the doctor, as is seen from the fact that a medical diagnosis in .70% of cases is based on the patient’s history alone. 3 It will be roughly the same whether the patient has a somatic disease or not. In the following discussion, I will, for the sake of simplicity, focus on the diagnostic process when the patient has a somatic disease. The reasoning will be analogous for other illnesses. The patient’s account of his illness will be structured largely by the pathological process taking place in his body, i.e. the pathological process has an impact on how and in what order the patient experiences and describes his symptoms. In the consultation, the doctor works on the way in which the patient has involuntarily clustered the symptoms based on his illness experiences, and at how he lets them develop chronologically in his illness story. These factors give far more information on which to base the diagnosis than a mere listing of symptoms. The clustering of signs and their development over time is, in narrative theory, defined as the plot. 4 It is therefore tempting to draw a parallel between the pathological process constituting a cluster of interrelated events and their development over time, and the plot of the patient’s illness story constituting a cluster of inter-related symptoms developing over time. The doctor works with the plot of the patient’s narrative, and Hunter argues that the plot is the diagnosis, 4 indicating that narrative work is a part of the diagnostic process. This will have a familiar ring to many medical practitioners. We work with the patient’s illness history, starting with few clues on what may be wrong, and then often quite suddenly we recognize which possible diagnoses to pursue further. Sometimes this process is quick, as in Sackett’s category ‘pattern recognition’. At other times, a longer period of non-directive work is required before we suddenly see a few diagnostic possibilities that may be tested further. Diagnostic criteria are valid for groups of patients (with a specific disease), while diagnostic work in practice means working with individual particularities in the process towards the non-individual category of a diagnosis. In this process, the doctor looks for both generalities and for specific and idiosyncratic clues. 5 Ginzburg argues that in an opaque reality, there are certain points—clues, symptoms—that allow us to decipher it. 6 These points are often located ‘on the fringe’ of the picture, and Ginzburg calls the process of