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Using ELISPOT to expose false positive skin test conversion in tuberculosis contacts.
- Source :
-
PloS one [PLoS One] 2007 Jan 31; Vol. 2 (1), pp. e183. Date of Electronic Publication: 2007 Jan 31. - Publication Year :
- 2007
-
Abstract
- Background: Repeat tuberculin skin tests may be false positive due to boosting of waned immunity to past mycobacterial exposure. We evaluated whether an ELISPOT test could identify tuberculosis (TB) contacts with boosting of immunity to non-tuberculous mycobacterial exposure.<br />Methodology/principal Findings: We conducted tuberculin and ELISPOT tests in 1665 TB contacts: 799 were tuberculin test negative and were offered a repeat test after three months. Those with tuberculin test conversion had an ELISPOT, chest X-ray and sputum analysis if appropriate. We compared converters with non-converters, assessed the probability of each of four combinations of ELISPOT results over the two time points and estimated boosting with adjustment for ELISPOT sensitivity and specificity. 704 (72%) contacts had a repeat tuberculin test; 176 (25%) had test conversion, which increased with exposure to a case (p = 0.002), increasing age (p = 0.0006) and BCG scar (p = 0.06). 114 tuberculin test converters had ELISPOT results: 16(14%) were recruitment positive/follow-up positive, 9 (8%) positive/negative, 34 (30%) negative/positive, and 55 (48%) were negative/negative. There was a significant non-linear effect of age for ELISPOT results in skin test converters (p = 0.038). Estimates of boosting ranged from 32%-41% of skin test converters with increasing age. Three converters were diagnosed with TB, two had ELISPOT results: both were positive, including one at recruitment.<br />Conclusions/significance: We estimate that approximately one third of tuberculin skin test conversion in Gambian TB case contacts is due to boosting of immunity to non-tuberculous mycobacterial exposure. Further longitudinal studies are required to confirm whether ELISPOT can reliably identify case contacts with tuberculin test conversion that would benefit most from prophylactic treatment.
- Subjects :
- Adolescent
Adult
Aged
Aged, 80 and over
BCG Vaccine immunology
Child
Child, Preschool
Ethnicity
Female
Gambia
Humans
Infant
Male
Middle Aged
Mycobacterium tuberculosis immunology
Sensitivity and Specificity
Sputum microbiology
Tuberculosis microbiology
Tuberculosis prevention & control
Young Adult
Enzyme-Linked Immunosorbent Assay methods
False Positive Reactions
Tuberculin Test
Tuberculosis diagnosis
Subjects
Details
- Language :
- English
- ISSN :
- 1932-6203
- Volume :
- 2
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- PloS one
- Publication Type :
- Academic Journal
- Accession number :
- 17264885
- Full Text :
- https://doi.org/10.1371/journal.pone.0000183