occur in an approximately equal minority of patients. A leukemoid reaction simulating acute
leukemia can occur (42). Thrombocytopenia and thrombocytosis have been reported.
Pancytopenia due to bone marrow infiltration or a hemophagocytic syndrome has been
described.
Disseminated intravascular coagulation may accompany septic TB and is associated with
a poor outcome. Hyponatremia, the most common biochemical abnormality, often indicates
inappropriate antidiuretic hormone secretion. Hypercalcemia and polyclonal hypergamma-
globulinemia have been reported in several cases. Bronchoalveolar lavage tends to reveal
absolute and relative lymphocytosis, but mostly due to conflicting results no other useful
markers have been identified. As HIV infection is so common in patients with TB, all persons
suspected of having active TB should undergo HIV testing.
Detection of Latent TB Infection
Tuberculin purified protein derivative (PPD) anergy is more common in patients with miliary TB
compared to other TB manifestations. Less than half of all patients with miliary TB will have a
positive PPD. In some patients, tuberculin conversion may occur following successful treatment.
Newer in-vitro assays have become available that detect latent TB infection based on
measurement of interferon-gamma release by T cells following exposure to specific MTB
antigens. These assays are now commercially available and have been automated. Sensitivity
and specificity of these assays appears to be higher than that of the tuberculin skin test, but it is
not at all clear how they will perform in miliary TB. Early case reports appear to indicate that
these tests may not always be able to confirm latent infection in patients with disseminated
disease (43)
Imaging
Chest Radiograph
The diagnosis of miliary TB is often based on the presence of a “classic” miliary pattern on
chest X Ray, which, according to the recommendations of the Nomenclature Committee of the
Fleischner Society, is defined as a collection of tiny, discrete pulmonary opacities that are
generally uniform in size and widespread in distribution, each of which measures 2 mm or less
in diameter (44) Fig. 2. If present, the faint, reticulonodular infiltrate is usually indeed
characteristic enough to alert astute clinicians to consider the diagnosis of miliary TB. There
are, however, several problems with relying too much on the radiologic diagnosis of
disseminated TB. The typical miliary pattern may only become apparent days or weeks after
Figure 2 CT scan with miliary disease pattern.
424 Albrecht