The diagnostic pathway

Diagnostic tests for food allergy, as with all medical tests, cannot be discussed in isolation. They are only one part of the whole diagnostic pathway. When an individual presents a particular problem to a health professional, a diagnostic pathway is embarked upon. This pathway starts with the professional taking the individual's medical history, the story of their particular problem. This is often complemented by an examination. The pathway may or may not conclude with particular tests. All diagnostic tests should be seen within the context of this pathway. Tests only serve to add further pieces of information to that already gleaned from the history and examination. They very rarely alone give a definitive answer.

Using the term 'pathway' makes the process sound linear. It is in fact a cyclical process. Just as the history and examination help the clinician to select relevant tests, information gleaned from diagnostic tests may make the clinician return to the patient, and seek further information from the history or examination.

This chapter will start with an explanation of how to judge any test's 'worth'. It will then describe particular aspects of the history and examination relevant to the diagnosis of food allergies and intolerance. There will then follow an introduction to the wide range of tests used by the clinician in the diagnosis of food allergy, their scientific basis, and evidence of efficacy or utility in the diagnosis of food allergies. Some of these tests are readily available, for example, to general practitioners; others are used only by practising allergists within specialist clinics or even only within research departments. Some of the tests have good evidence to back up their use, whereas others do not. They include tests that depend upon studying the patient's physiological reactions to particular stimuli. These are often referred to as in vivo tests and include skin prick tests, patch tests and bronchial provocation tests. Other tests are laboratory-based, in vitro tests. These look for specific biochemical markers within the patient's serum, or changes within biopsies of the patient's tissue. There follows a discussion of food challenges and the various outcome measures used to assess whether a food challenge can be defined as positive.

Many 'mainstream' health professionals are involved in the diagnosis of food allergies and intolerances. These include medical doctors from many disciplines. All branches of nursing will encounter at some stage a patient with a food allergy. The chief allied profession involved is the dietician, whose role is essential in both the diagnosis and ongoing management of people with food allergies.

The complementary or alternative healthcare system has another group of workers involved in the diagnosis and treatment of those who may have food allergies. Many therapists are members of bodies that ensure careful control of training and practice. Some of their diagnostic tests, however, lack evidence to support their use. There are also individuals with little or no training, however, and with less transparent credentials selling schemes purporting to diagnose food allergy, either by mail or through high street healthfood shops.

Food Allergies

Food Allergies

Peanuts can leave you breathless. Cat dander can lead to itchy eyes, a stuffy nose, coughing and sneezing. And most of us have suffered through those seasonal allergies with horrible pollen counts. Learn more...

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