What is the role of lab studies in the diagnosis of Pott disease (tuberculous [TB] spondylitis)?

Updated: Aug 08, 2019
  • Author: Jose A Hidalgo, MD; Chief Editor: John L Brusch, MD, FACP  more...
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Answer

Laboratory studies used in the diagnosis of Pott disease include the following:

  • Tuberculin skin test (PPD) - Results are positive in 84-95% of patients with Pott disease who are not infected with HIV
  • Erythrocyte sedimentation rate (ESR) - May be markedly elevated (>100 mm/h)
  • Microbiologic and PCR studies - Used to confirm the diagnosis

With regard to the above-mentioned microbiologic studies, bone tissue or abscess samples are obtained to stain for acid-fast bacilli (AFB), culture and susceptibility, and DNA amplification. Procedures guided by computed tomography (CT) scanning can be used to guide percutaneous sampling of affected bone or soft-tissue structures. These study findings are positive in only about 50% of the cases. A 2015 multicentric, multinational study involving 35 centers and 314 cases reported that the causative agent was identified in 41% of cases. [28] Surgical biopsies can also be considered for tissue sampling.

Nonculture methods (DNA amplification) using skeletal tissue samples offer a high diagnostic yield and high specificity (96%), high sensitivity (95%), and rapid results (2 days). [29, 30, 31] An additional potential advantage is simultaneously identifying drug resistance and improving outcomes. [32]


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