Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (45 page)

   
Chest CT and MRI
detect effusions with high sensitivity and specificity and may provide useful information pertinent to performing pericardiocentesis (hematocrit of effusion, loculations, pericardial thickening). Often, concern of tamponade makes echocardiography the imaging modality of choice for clinically tenuous patients due to its mobility.

   
Tuberculin skin test or interferon-gamma release assay
: Evaluation to rule out TB is recommended for all patients. Additional diagnostic testing for TB, like AFB cultures, should be performed on patients at increased risk on the basis of epidemiologic and clinical factors.

   
Cultures
: Cultures of blood and other potentially infected specimens should be submitted for patients with significant fever, signs of sepsis, or systemic or local infection.

   
Histology
: Pericardiocentesis (and occasionally pericardial biopsy) should be performed for patients with clinically significant tamponade or persistent effusions. Pericardiocentesis is recommended for patients in whom pyogenic, tuberculous, or malignant pericardial disease is suspected. As most forms of pericarditis are viral in etiology, the diagnostic yield of routine pericardiocentesis has a low diagnostic yield (7%).

   Recommended tests for pericardial fluid include

   Histopathologic and cytologic examination of tissue and fluid.

   Bacterial and mycobacterial stains and culture.

   Triglyceride concentration for chylous fluid.

   Adenosine deaminase and
M. tuberculosis
PCR, if tuberculous pericarditis is suspected.

   Other specific diagnostic tests, like fungal cultures or PCR, are performed based on clinical suspicion.

   Core laboratory: CBC, electrolytes, tests of renal function and thyroid function, and plasma troponin concentration. ANA titers, anti-dsDNA, and serum complement are recommended for patients when an autoimmune cause is suspected. Note: protein, glucose, LDH, RBC count, and WBC count cannot distinguish exudative from transudative effusions and are usually noncontributory in establishing a diagnosis.

   Serology: HIV should be considered. Pericardial disease is relatively common in HIV-infected patients. Furthermore, HIV infection predisposes patients to mycobacterial infections. Viral diagnostic testing, including serology, has low diagnostic yield and is not routinely recommended.