Are new assays useful for detecting TB?
Investigators retrospectively evaluated the routine use of an interferon-γ release assay, one of two that are currently available,
for detecting infection with Mycobacterium tuberculosis. They analyzed data for 237 children younger than 18 years in a pediatric tertiary care center in whom the assay had been
used as a routine diagnostic test because of suspected active or latent tuberculosis (TB). About a quarter of these children
were immunocompromised.
The test was positive in 17% of the study group, negative in 48%, and indeterminate in 35%. Analysis showed that age younger
than 5 years and being immunocompromised were both independently associated with a higher probability of an indeterminate
result. In children who were not immunocompromised, the likelihood of an indeterminate test result was inversely correlated
with age, decreasing by 13% for each additional year of age (Haustein T et al: Pediatr Infect Dis J 2009;28:669).
COMMENTARYThese tests are based on detection of interferon gamma production by mononuclear cells after exposure to antigens produced
by M tuberculosis. They offer a potentially useful tool for making the often confusing diagnosis of both tuberculosis infection
and disease.
One advantage of these tests over the traditional tuberculin skin test is that bacille Calmette-Guérin and most nontuberculous
mycobacteria do not generate the antigens necessary to cause a positive test. The tests now available include a positive control:
In other words, if the control is not positive, the tested sample may be inadequate, or the patient may not be able to mount
the appropriate response even in the presence of these TB antigens. These authors show that indeterminant tests such as these
are more common in the youngest patients and in those with immune deficiency, the very patients who are most likely to develop
TB disease after infection.
The 2009 Red Book offers a clear explanation of the current role of these assays in detection of TB. As more information is
obtained, that role will likely increase. —MB
PARENTS EXPECT TO BE GREETED BY NAME
According to a study conducted in a pediatric clinic at a hospital in Michigan, parents expect basic courtesies from their
children's doctors and often are disappointed. The authors interviewed 100 parents or caretakers, mostly African American,
after a medical encounter with a resident or an attending at the clinic to determine their expectations for being greeted
by their doctor—and whether they were met.
Overall, 83% of the adults wanted the doctor to shake hands, and most did (70% of residents, 66% of attendings). Even more
parents, 87%, wanted their physicians to address them by name, but only 14% of residents and 24% of attendings did so. Physicians
did best in meeting expectations by introducing themselves at encounters, with 84% of residents and 93% of attendings extending
this courtesy (Amer A et al Clin Pediatr 2009;48:720).
COMMENTARY
Name tags for everyone. In 9% of encounters, physicians incorrectly addressed the parent by using the child's last name. I
wonder how often physicians fail to call the parent by name so as to avoid this error. If that's the case, we need to display
parents' names prominently on patient charts, on appointment lists, and in the hospitalized child's room. —MB
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