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UBC Theses and Dissertations

Development of an instrument for the early detection of thyroid orbitopathy Linder, Mark

Abstract

Graves' Hyperthyroidism (GH) is an autoimmune disease that affects 1 in every 100 Canadians according to the Thyroid Foundation of Canada. A significant number of these patients go on to develop another closely related autoimmune condition called Thyroid Orbitopathy (TO). In this disease, the extra-ocular muscles become inflamed and enlarged beyond their normal size, leading to a variety of clinical changes that may include (but are not limited to) swelling, pain, exophthalmos, strabismus and double vision. Patients suffering from moderate or serious cases of TO are most often referred to an ophthalmologist at a relatively advanced stage of disease. At that point, major interventions such as surgery or orbital radiotherapy are usually required. Although these treatments are usually quite effective, the patient is rarely restored to the quality of life enjoyed before getting sick. However, if patients are identified early in the disease process, potential therapeutic interventions exist which may lessen or prevent the development of serious disease. The objective of this study was to design and develop a symptom-based self-administered clinical screening rule for the early diagnosis of thyroid orbitopathy. The study took place between September of 1998 and July of2000 and was broken down into two distinct phases. In the first phase, a symptom-based questionnaire was designed, developed and refined through literature search, expert consultation and focus groups. In the second phase, an inception cohort of patients with Graves' Hyperthyroidism was recruited and given a questionnaire as well as a standard TO clinical exam by paricipating ophthalmologists. The resulting data was then analyzed in order to identify symptoms related to presence of disease. Data collection began in January of 1999, and continued until April of 2000. A total of 50 patients with GH, referred from a single endocrinologist practise, participated in the study. The final rule, dubbed the Vancouver Orbitopathy Rule, was designed with a view to maximizing sensitivity. As a result, the final diagnostic analysis yielded a sensitivity of 1.0, a specificty of 0.78 and a positive predicitive value of 0.60. However, these parameters were measured based on the same data that was used to design the rule. In order to calculate the true measure of the test's clinical utility and diagnostic accuracy, a new validation study must be carried out.

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