Correct!
5. None of the above
Gold quantiferon is an interferon-γ (IFNγ) release assay used in tuberculosis diagnosis. The patient's lymphocytes are cultured and stimulated with peptides from tuberculosis antigens. A positive result occurs when the lymphocytes release IFNγ. The gold quantiferon test has higher specificity for tuberculosis than the tuberculosis skin test and is not affected by prior BCG vaccination (1).
Our patient's most likely diagnosis is tuberculosis based on his positive gold quantiferon and the clinical situation. Establishing a diagnosis of tuberculous pleuritis can be difficult (2). Tuberculous pleuritis is thought to be a delayed hypersensitivity reaction when a subpleural caseous focus ruptures into the pleural space. Therefore, the organism burden is low and cultures are positive in only 20 to 30% of cases. Furthermore, cultures can require 8-12 weeks before being considered negative.
The pleural fluid is lymphocyte predominant in 60 to 90% with the remaining being neutrophil predominant. The pH < 7.3 in 20%. Our patient's pH was initially 7.33 and 7.09 on repeat. Pleural fluid glucose is usually similar to the serum level and this was the case in our patient. PCR has good specificity, but low sensitivity (46%) and adenosine deaminase (ADA) variable sensitivity (78-99%).
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