Case studies, exemplars or tracer conditions

Advice on health categories

The term ‘case study’ is used in a variety of contexts in biomedicine, such as a clinical case study chronicling the treatment of a single patient. However in this context we use ‘case study’ to describe where patients with a particular condition may be used as a proxy / exemplar / tracer condition in studies evaluating models, services or systems that are applicable to other (or a wider range of) conditions.

In these circumstances the specific condition used in the patient group (the ‘case study’) may not be the main aim of carrying out the study, but is used purely to demonstrate a broader argument. Therefore in this specific context the appropriate health category for the condition used as the case study may not be relevant to this wider study aim.

e.g. If the study examines prescriptions for a specified condition, but the wider aim is to assess prescriptions across all areas of health or wellbeing, it would may be more appropriate to ignore the exemplar condition and use the Generic Health Relevance health category instead.

However in many cases the health category of the case study / proxy / exemplar / tracer condition will still be intrinsically linked to the wider study being addressed. In this case, dual coding of both example condition and wider topic would be appropriate.

e.g. Asthma is routinely coded as Respiratory in HRCS, but if it is used as an example of allergenic reactions, it would be appropriate to add the Inflammatory & Immune System health category to the coding of the project.

This approach of when to apply dual coding is similar to the approach taken when considering sequelae (one disease as a consequent of another), studies of cachexia and in co-morbidity research.