**Diagnosis**

**Chapter 9**

**Laboratory Investigations and Immunological Testing in**

Sarcoidosis is a systemic granulomatous disease of unknown aetiology, which can affect virtually any organ and is thus characterised by a variable clinical presentation and course. The disease is generally considered to be a T helper-1 (TH1) type of reaction, although TH2 and TH17 features have also been identified. Approximately 90% of patients demonstrate disease involvement of the lungs and thoracic lymph nodes and although sarcoidosis is usually subacute and self-limiting, progressive inflammation can lead to pulmonary fibrosis and death. Despite these features, there is currently no definitive single laboratory investigation used to identify sarcoidosis, indicating the need for improved understanding of the immuno‐ pathogenesis and identification of disease-specific biomarkers. Currently, sarcoidosis is generally a diagnosis of exclusion that is best confirmed by clinical and radiological findings and tissue biopsies revealing non-caseating granulomas in the absence of known granuloma‐ genic agents. Laboratory testing is nonetheless beneficial in further supporting a diagnosis of

In this chapter, we focus on the laboratory and immunological testing used in sarcoidosis, including biomarkers that have been proposed as measures of the immunological response, as well as cellular markers present in blood and bronchoalveolar lavage. Comparisons will also be made with older immunological investigations including the Kveim-Siltzbach test and recent evidence of potential sarcoid antigens. Novel methods of sampling disease biomarkers, including the technique of exhaled breath analysis will be explored. Immunological testing and measurement of various biomarkers in body tissues has been a useful research tool in understanding sarcoid pathophysiology. There may be a useful role for some of these labora‐

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© 2013 Ahmadzai et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution,

**Sarcoidosis**

Denis Wakefield

**1. Introduction**

http://dx.doi.org/10.5772/55294

Hasib Ahmadzai, Paul S. Thomas and

sarcoidosis and assessing disease severity.

Additional information is available at the end of the chapter
