Comparison of enzyme-linked immunospot assay and tuberculin skin test in healthy children exposed to Mycobacterium tuberculosis.
OBJECTIVE
To compare the enzyme-linked immunospot (ELISPOT) assay with the tuberculin skin test (TST) in children for the diagnosis of Mycobacterium tuberculosis infection in the Gambia.


METHODS
We divided child contacts of sputum smear-positive tuberculosis cases into 3 age categories (<5, 5-9, and 10-14 years) and assessed agreement between the 2 tests plus their relationship to prior Bacille Calmette-Guerin (BCG) vaccination. We categorized a child's level of M tuberculosis exposure according to where he/she slept relative to a case: the same room, same house, or a different house. The relationship between exposure and test result was assessed by multiple logistic regression.


RESULTS
In child contacts of 287 cases, 225 (32.5%) of 693 were positive by TST and 232 (32.3%) of 718 by ELISPOT. The overall agreement between tests was 83% and the discordance was not significant. Both tests responded to the M tuberculosis exposure gradient in each age category. The percentage of those who were TST positive/ELISPOT negative increased with increasing exposure. At the lowest exposure level, the percentage of ELISPOT-positive children who were TST negative was increased compared with the highest exposure level. Neither test had evidence of false positive results because of BCG.


CONCLUSIONS
In Gambian children, the ELISPOT is slightly less sensitive than the TST in the diagnosis of M tuberculosis infection from recent exposure, and neither test is confounded by prior BCG vaccination. Evidence of reduced TST sensitivity in subjects with the lowest known recent M tuberculosis exposure suggests that, when maximal sensitivity is important, the 2 tests may be best used together.
Hill
Philip C
PC
Tuberculosis Division, Mulago Hospital Complex, Kampala, Uganda. phill@mrc.gm
Brookes
Roger H
RH
Adetifa
Ifedayo M O
IM
Fox
Annette
A
Jackson-Sillah
Dolly
D
Lugos
Moses D
MD
Donkor
Simon A
SA
Marshall
Roger J
RJ
Howie
Stephen R C
SR
Corrah
Tumani
T
Jeffries
David J
DJ
Adegbola
Richard A
RA
McAdam
Keith P W J
KP
D000293:Adolescent; D000942:Antigens, Bacterial / Q000276:immunology; D001500:BCG Vaccine; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay; D005192:Family Health; D005714:Gambia; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000276:immunology; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000635:transmission
D000942:Antigens, Bacterial; D001500:BCG Vaccine