Main Line Hospitals Laboratory Services is pleased to announce now
offers in-house testing for QuantiFERON®-TB, a blood test for M.
tuberculosis (TB) infection, effective Tuesday March 2, 2010. This
test is at least as sensitive as the PPD skin test, gives fewer false
positive results, and does not require the patient to return as the skin
QuantiFERON®-TB is unaffected by Bacille Calmette-Guerin (BCG)
vaccination and most environmental non-tuberculous mycobacteria (except M.
kansasii,M. marinum, and M. szulgai). A positive
result is strongly predictive of true infection with M. tuberculosis.
QuantiFERON®-TB is intended for use in conjunction with risk assessment,
radiography, and other medical and diagnostic evaluations. The test may
be ordered as “QuantiFERON-TB”.
The QuantiFERON®-TB assay is a qualitative test of infection. It
measures the production of interferon-gamma by effector T-cells in
response to TB peptide antigens. Effector T-cells are considered to be
present only during current infection, but not in old/cured infection. A
positive result suggests that current M. tuberculosis infection
is likely, whether active disease or latent TB infection. A negative
result suggests that M. tuberculosis is unlikely but cannot be
totally excluded, especially when the illness is consistent with
tuberculosis or the likelihood of progression to disease is increased
(e.g., because of immune suppression). In rare cases results cannot be
interpreted, as the blood cells have not responded to a positive control
stimulant. This indicates the sample may have been mishandled or that
the patient's immune system is not functioning well. These results are
called "indeterminate"; TB infection can neither be excluded nor
The QuantiFERON®-TB assay requires special blood collection tubes
available from hospital storerooms or, for office patients, from Main
Line Hospitals Laboratory Services Client Servicesat 484.580.4200. These
specialized blood collection tubes, one (1) each of Nil Control, TB
Antigen, and Mitogen, are used to collect whole blood via venipuncture,
and contain antigens representing certain M. tuberculosis
proteins or controls. Incubation of the blood occurs in the tubes for 16
to 24 hours, after which plasma is harvested and tested for the presence
To obtain optimal results, the tubes must be shaken vigorously for five
seconds to ensure that the entire inner surface of the tube has
been coated with blood. Proper shaking will lead to frothing of the
blood. The tubes must arrive in the lab as soon as possible after
collection (within 16 hours), and before 3:30 pm Monday through
If you have any questions or concerns please feel free to contact Albert
A. Keshgegian, MD, PhD, Medical Director, at 484.476.3552, or Annemarie
Brewer, Immunology Supervisor, at 484.476.8408.
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