Fundamentals of clinical methodology. 4. Diagnosis

Nosological Diagnosis, Theories of Categorization, and Argumentations by Analogy

The nosological diagnosis is a particular type of nontheoretical diagnosis consisting of identifying the disease that afflicts the patient without explaining the underlying etiopathological mechanisms. Its origins are within the essentialist point of view on the nature of diseases, which dates back at least to 18th-century taxonomy studies. In this article, we propose a model of nosological diagnosis as a two-phase process composed of the categorization of inductive inferences and argumentations by analogy. In the inductive phase, disease entities are identified by means of typicality-based categorization processes, and meaningful clinical samples are learned (abstract clinical cases, i.e., syndromes and actual cases); in the subsequent phase, those samples are used as the bases of argumentations by analogy to obtain a diagnosis for a given patient. This model extends the prototype resemblance theory of disease including also the exemplar theory proposed in cognitive science and, moreover, it frames the clinical activity of nosological diagnosis and how it can be explained within the theory of argumentation. According to it, diagnosis based on the recognition of a typical syndrome is explained in terms of the prototype theory of categorization and the antisymmetrical argumentation by analogy, while diagnosis based on a comparison with a previous clinical case is explained by the exemplar theory of categorization and by the symmetrical argumentation by analogy.

How should we diagnose disease in palaeopathology? Some epistemological considerations

This paper analyses some of the epistemological frameworks that underpin diagnosis in palaeopathology. Currently, the dominant approach is comparative: relationships between skeletal lesions and disease in a reference group in which there is independent evidence of the diseases present in individuals are used to identify disease in unknown archaeological skeletons on the basis of the lesions present. This is essentially a reference sample - target sample approach, analogous to that used to develop methodology in other areas of biological anthropology (e.g. age estimation in palaeodemography). As well as considerable strengths, this approach also has significant weaknesses. Many of these arise from the nature of the reference material (mainly pathology museum and other skeletal collections, and published collations of medical imaging data) used to develop diagnostic criteria. There may also be a tendency toward over-emphasis on pattern-matching between reference and target material, and an under-emphasis on developing our understanding of the biology of bone lesions. Despite its shortcomings, the comparative approach is likely to remain the foundation of most palaeopathological work, but we should increasingly augment it with other diagnostic approaches, especially those grounded in the pathophysiology of bony responses to disease.

The reliability of experts' opinions in constructing a composite environmental index: the case of ESI 2005

The complexity of the environment demands a well-constructed composite environmental index (CEI) to provide a useful tool to draw attention to environmental conditions and trends for policy purposes. Among the common difficulties in constructing a proper CEI are uncertainties due to the selection of the most representative underlying variables or indicators. A degree of uncertainty accompanies experts' judgments, and to deal with vague, subjective or inconsistent information, logic other than classic is required. This study analyzes a procedure that uses different experts' opinions in constructing a CEI, with the use of paraconsistent annotated logic. For this, a sensitivity analysis of the Environmental Sustainability Index (ESI 2005) was used as an example to assess the reliability of experts' opinions. The uncertainty due to the disagreement in experts' opinions clearly indicates that the forms we presently use to measure and monitor the actual environment are insufficient, that is, there is a lack of a "science of sustainability".

Differential diagnosis of rheumatic diseases using conventional radiography

The approach to the differential diagnosis of rheumatic diseases using conventional radiography is systematic and module-oriented, which, with respect to future developments, forms the basis for computer-assisted diagnosis (CAD). The indications follow consensus-based referral criteria and attempts should be made to raise the evidence level of the recommendations. Investigation techniques have been improved in the last few years with the use of digital radiography. New imaging technologies may be available in the future that will achieve at least the same quality of images, while exposing patients to a significantly lower radiation dose. The interpretation of radiographical signs could be enhanced through a correlation with other imaging modalities. Computer-assisted techniques with image processing tools for automated measurements, lesion detection and in the form of expert systems are under development. With conventional radiography embedded in CAD systems, promising options will be available to enhance the differential diagnosis of rheumatic diseases.

ISABEL: a web-based differential diagnostic aid for paediatrics: results from an initial performance evaluation

AIMS

To test the clinical accuracy of a web based differential diagnostic tool (ISABEL) for a set of case histories collected during a two stage evaluation.

SETTING

acute paediatric units in two teaching and two district general hospitals in the southeast of England.

MATERIALS

sets of summary clinical features from both stages, and the diagnoses expected for these features from stage I (hypothetical cases provided by participating clinicians in August 2000) and final diagnoses for cases in stage II (children presenting to participating acute paediatric units between October and December 2000).

MAIN OUTCOME MEASURE

presence of the expected or final diagnosis in the ISABEL output list.

RESULTS

A total of 99 hypothetical cases from stage I and 100 real life cases from stage II were included in the study. Cases from stage II covered a range of paediatric specialties (n = 14) and final diagnoses (n = 55). ISABEL displayed the diagnosis expected by the clinician in 90/99 hypothetical cases (91%). In stage II evaluation, ISABEL displayed the final diagnosis in 83/87 real cases (95%).

CONCLUSION

ISABEL showed acceptable clinical accuracy in producing the final diagnosis for a variety of real as well as hypothetical case scenarios.

Fundamentals of clinical methodology: 3. Nosology

Intelligent clinical judgement is one of the main goals of medical artificial intelligence. To achieve that goal requires a reliable nosological language. Such a language is not yet available, however. In this paper the notions of health, disease, and nosology are analyzed. It is shown that health and disease as generic concepts, and also individual disease entities are best understood as fuzzy sets. Clinical language and linguistics, nosology and diagnosis may thus become directly amenable to fuzzy theory.