Using ELISPOT to Expose False Positive Skin Test Conversion in Tuberculosis Contacts

Download
Author
Hill, PC; Jeffries, DJ; Brookes, RH; Fox, A; Jackson-Sillah, D; Lugos, MD; Donkor, SA; de Jong, BC; Corrah, T; Adegbola, RA; ...Date
2007-01-31Source Title
PLoS OnePublisher
PUBLIC LIBRARY SCIENCEAffiliation
Doherty InstituteMicrobiology and Immunology
Metadata
Show full item recordDocument Type
Journal ArticleCitations
Hill, P. C., Jeffries, D. J., Brookes, R. H., Fox, A., Jackson-Sillah, D., Lugos, M. D., Donkor, S. A., de Jong, B. C., Corrah, T., Adegbola, R. A. & McAdam, K. P. (2007). Using ELISPOT to Expose False Positive Skin Test Conversion in Tuberculosis Contacts. PLOS ONE, 2 (1), https://doi.org/10.1371/journal.pone.0000183.Access Status
Open AccessAbstract
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. 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. 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.
Export Reference in RIS Format
Endnote
- Click on "Export Reference in RIS Format" and choose "open with... Endnote".
Refworks
- Click on "Export Reference in RIS Format". Login to Refworks, go to References => Import References