Tuberculin sensitivity and the BCG scar in tuberculosis contacts.
METHODS
Tuberculosis clinic, St Vincents Hospital, Dublin.


OBJECTIVE
To determine the influence of past BCG vaccination on tuberculin sensitivity in tuberculosis contacts.


METHODS
Prospective cohort study of tuberculin sensitivity using the Mantoux technique (5 TU).


RESULTS
In 1050 contacts of 96 cases of tuberculosis, BCG scars were noted in 76% of the contacts. Approximately 50%, 30% and 20% of the contacts respectively had negative (0-4 mm), positive (5-14 mm) and strongly positive (15+ mm) Mantoux responses. The presence of a BCG scar was not found to significantly influence the degree of tuberculin sensitivity. The degree of tuberculin sensitivity increased after 20 years and decreased after 60 years of age. Contacts of sputum-positive cases of tuberculosis had larger Mantoux responses.


CONCLUSIONS
The study suggests that age of the contact and sputum status of the index case are important determinants of the degree of tuberculin sensitivity. Attributing a 'positive' Mantoux response to past BCG vaccination may be encouraging a false sense of security in contacts recently exposed to an infectious case of tuberculosis. Contact management guidelines may need to be reviewed and perhaps modified to reflect this finding.
Johnson
H
H
Eastern Health Board, Community Care, Dublin, Ireland.
Lee
B
B
Doherty
E
E
Kelly
E
E
McDonnell
T
T
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001500:BCG Vaccine; D002648:Child; D002675:Child, Preschool; D002921:Cicatrix / Q000473:pathology*; D015331:Cohort Studies; D016358:Contact Tracing; D006801:Humans; D007223:Infant; D008875:Middle Aged; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D014374:Tuberculin Test; D014376:Tuberculosis / Q000517:prevention & control* / Q000635:transmission
D001500:BCG Vaccine