T-SPOT.TB
Background:
It
is estimated that 15 million Americans are infected with Mycobacterium
tuberculosis (1). Each person carrying latent TB
infection (LTBI) has approximately a 10% chance of progression
to active TB disease. Historically, TB infection screening was
performed with the Tuberculin Skin Test but the high rate of false
positive and false negative results indicated the need of more
accurate assays.
T-SPOT.TB
is an FDA approved in vitro diagnostic test based on
an enzyme-linked immunospot (ELISPOT) method that enumerates the
number of effector T-cells responding to stimulation by peptides
simulating ESAT-6 and CFP-10 antigens. These antigens are absent
from all BCG strains and most non-tuberculosis bacteria except
M. kansasii, M. szulgai and M. marinum. In contrast,
individuals infected with M tuberculosis complex organisms
have T-cells in their blood that recognize these mycobacterial
antigens.
T-SPOT.TB
has proven to be the most accurate TB screening test available
with 95% sensitivity in culture positive TB patients and 97% specificity
in low risk healthy individuals (2).
•
Lalvani, A; et.al.; Rapid detection of Mycobacterium tuberculosis
infection by enumeration of antigen-specific T cells. Am.J. Respir.Crit.
Care Med., 2001; 163: 824-828.
•
Meier, T.; et.al.; Sensitivity of a new commercial enzyme-linked
immunospot assay (T SPOT-TB) for diagnosis of tuberculosis in
clinical practice. Eur. J. Clin. Microbiol. Infect. Dis., 2005;
24: 529-536.
Method:
Isolated
lymphocytes are sensitized to M. tuberculosis antigens
and the activated T-cells produce the cytokine Interferon gamma
(IFN- g ). T-SPOT.TB uses
a simplified ELISPOT method to enumerate sensitized T-cells by
capturing IFN- g in the vicinity
of those cells from which it was secreted.
Washed
and counted peripheral blood mononuclear cells (PBMCs) are seeded
into four microtiter wells where they are exposed to phytohemagglutinin,
a mitotic stimulator indicating cell functionality (positive control),
a nil control, and two separate panels of TB specific antigens.
Secreted cytokine is captured by IFN- g
specific antibodies in the base of the well and detected
with a second antibody linked to a color detection agent. Evaluating
the number of spots obtained provides a measure of the abundance
of TB sensitive effector T-cells in the peripheral blood.
Indications
for testing:
•
Patients suspected of active or latent TB infection
•
Recent contacts of TB case patients
•
Residents and employees of high risk congregate settings
•
Immunosuppressed patients including those with HIV infection
•
Patients with chronic renal failure
•
Healthcare workers
•
Immigrants
•
Military
Sample
requirements:
Infants
and children under 2: 2cc lithium heparin vacutainer
Children
2 to 9 years old: 4cc lithium heparin vacutainer
Adults
and children over 10 years old: 6cc lithium heparin vacutainer
Blood
must be stored at room temperature (do not refrigerate or freeze)
and shipped to the laboratory to arrive within 24 hours of blood
draw.
SAMPLE
REPORTS
225
Warren Street
– W420M
Newark
, NJ
07103
973
- 972
- 4480
T-SPOT.TB
INDIRECT TEST FOR M. TUBERCULOSIS INFECTION
Patient
Name: |
|
DOB:
|
|
Lab
ID# |
|
Report
Sent:
«HOSP»
«HOSP2»
«STREET»
«CSZ»
cc:
«COUNSELOR»
cc:
«HID»
|
Date
Sample Received: |
|
Date
of Report: |
|
Type
of Specimen: |
Blood
|
Source
of Referral: |
|
Reference
Ranges
|
Negative
|
0
-
4
spots
|
Equivocal
|
5
-
7
spots
|
Positive
|
>
8
spots
|
RESULTS:
POSITIVE ( >20
spots/well )
INTERPRETATION:
The
results are consistent with TB infection. A positive test result
does not rule-in active TB disease; other tests should be performed
to confirm the diagnosis such as sputum smear and culture and
chest radiography.
ANALYSIS
SUMMARY: T-SPOT.TB is
an FDA approved screening test that detects T cells that respond
to stimulation by TB antigens ESAT- 6 and CFP- 10 . Interferon
gamma (IFN-gamma) secreted by TB infected cells is captured
by anti-IFN- gamma antibodies and visualized by an enzyme linked
immunospot detection method.
Sensitivity:
95 %
in culture positive patients.
Specificity:
97 %
in low risk healthy subjects.
[
1 ]
Lalvani,
A; et.al.; Rapid detection of Mycobacterium tuberculosis infection
by enumeration of antigen-specific T cells. Am.J. Respir.Crit.
Care Med., 2001
; 163
: 824
- 828
.
[
2 ]
Meier,
T.; et.al.; Sensitivity of a new commercial enzyme-linked immunospot
assay (T SPOT-TB) for diagnosis of tuberculosis in clinical
practice. Eur.
J. Clin. Microbiol. Infect. Dis., 2005
; 24
: 529
- 536
.
__________________________________________
James
J. Dermody, Ph.D.
Laboratory
Director, Institute of Genomic Medicine
ABMG
Certified, Clinical Molecular Genetics
225
Warren Street
– W420M
Newark
, NJ
07103
973
- 972
- 4480
T-SPOT.TB
INDIRECT TEST FOR M. TUBERCULOSIS INFECTION
Patient
Name: |
|
DOB:
|
|
Lab
ID# |
|
Report
Sent:
«HOSP»
«HOSP2»
«STREET»
«CSZ»
cc:
«COUNSELOR»
cc:
«HID»
|
Date
Sample Received: |
|
Date
of Report: |
|
Type
of Specimen: |
Blood
|
Source
of Referral: |
|
Reference
Ranges
|
Negative
|
0
-
4
spots
|
Equivocal
|
5
-
7
spots
|
Positive
|
>
8
spots
|
RESULTS:
NEGATIVE ( 0 spots/well )
INTERPRETATION:
No evidence
of TB infection. A negative test does not exclude the possibility
of TB infection. T-SPOT.TB negative patients with recent exposure
to TB infected individuals should consider retesting within
2-3 months or if other clinically relevant symptoms indicate
possible infection.
ANALYSIS
SUMMARY: T-SPOT.TB is
an FDA approved screening test that detects T cells that respond
to stimulation by TB antigens ESAT- 6 and CFP- 10 . Interferon
gamma (IFN-gamma) secreted by TB infected cells is captured
by anti-IFN- gamma antibodies and visualized by an enzyme linked
immunospot detection method.
Sensitivity:
95 %
in culture positive patients.
Specificity:
97 %
in low risk healthy subjects.
[
1 ]
Lalvani,
A; et.al.; Rapid detection of Mycobacterium tuberculosis infection
by enumeration of antigen-specific T cells. Am.J. Respir.Crit.
Care Med., 2001
; 163
: 824
- 828
.
[
2 ]
Meier,
T.; et.al.; Sensitivity of a new commercial enzyme-linked immunospot
assay (T SPOT-TB) for diagnosis of tuberculosis in clinical
practice. Eur.
J. Clin. Microbiol. Infect. Dis., 2005
; 24
: 529
- 536
.
__________________________________________
James
J. Dermody, Ph.D.
Laboratory
Director, Institute of Genomic Medicine
ABMG Certified, Clinical Molecular
Genetics
225
Warren Street
– W420M
Newark
, NJ
07103
973
- 972
- 4480
T-SPOT.TB
INDIRECT TEST FOR M. TUBERCULOSIS INFECTION
Patient
Name: |
|
DOB:
|
|
Lab
ID# |
|
Report
Sent:
«HOSP»
«HOSP2»
«STREET»
«CSZ»
cc:
«COUNSELOR»
cc:
«HID»
|
Date
Sample Received: |
|
Date
of Report: |
|
Type
of Specimen: |
Blood
|
Source
of Referral: |
|
Reference
Ranges
|
Negative
|
0
-
4
spots
|
Equivocal
|
5
-
7
spots
|
Positive
|
>
8
spots
|
RESULTS:
BORDERLINE/EQUIVOCAL
( 6 spots/well )
INTERPRETATION:
Borderline/Equivocal
results are valid but unable to indicate a positive or negative
result. Retesting a new sample is recommended to get a more
definitive result. If the result on retesting is still borderline/equivocal,
then other diagnostic tests and/or epidemiological information
should be used to help determine TB infection status in the
patient.
ANALYSIS
SUMMARY: T-SPOT.TB is
an FDA approved screening test that detects T cells that respond
to stimulation by TB antigens ESAT- 6 and CFP- 10 . Interferon
gamma (IFN-gamma) secreted by TB infected cells is captured
by anti-IFN- gamma antibodies and visualized by an enzyme linked
immunospot detection method.
Sensitivity:
95 %
in culture positive patients.
Specificity:
97 %
in low risk healthy subjects .
[
1 ]
Lalvani,
A; et.al.; Rapid detection of Mycobacterium tuberculosis infection
by enumeration of antigen-specific T cells. Am.J. Respir.Crit.
Care Med., 2001
; 163
: 824
- 828
.
[
2 ]
Meier,
T.; et.al.; Sensitivity of a new commercial enzyme-linked immunospot
assay (T SPOT-TB) for diagnosis of tuberculosis in clinical
practice. Eur.
J. Clin. Microbiol. Infect. Dis., 2005
; 24
: 529
- 536
.
__________________________________________
James
J. Dermody, Ph.D.
Laboratory
Director, Institute of Genomic Medicine ABMG Certified, Clinical
Molecular Genetics
