Diagnostic and clinical implications of response to tuberculin in two ethnically distinct populations from Peru and Cambodia.
BACKGROUND
Proper interpretation of the tuberculin skin test (TST) requires knowledge about prior vaccination with BCG and the results of epidemiological studies with the test.


METHODS
A TST survey was performed in patients with pulmonary tuberculosis (PTB) in two ethnically distinct populations from Cambodia and the Peruvian Andes. We examined interferon-gamma (IFN-gamma) production in whole blood cultures stimulated by ESAT-6, a Mycobacterium tuberculosis specific antigen in tuberculin-positive BCG-vaccinated Peruvians with no history of PTB.


RESULTS
Of the 81 Peruvian PTB patients tested, none had a skin response to tuberculin that was <10 mm, whereas 98 of 364 Cambodian PTB patients (37%) did. Furthermore, TST skin reaction sizes were significantly larger in Peruvian (21.69+/-5.46 mm) than Cambodian patients (11.42+/-7.74 mm; P < 0.0001). IFN-gamma production in response to ESAT-6 correlated with a TST reaction size >15 mm indicating previous infection with M. tuberculosis (kappa coefficient of agreement 0.66; 95%CI 0.29-1).


CONCLUSIONS
Ethnicity is an important factor in the interpretation of TST results in both BCG-vaccinated and non-vaccinated individuals. A negative TST appears to be a useful indicator to rule out tuberculosis infection in Peruvians of Quechua origin.
Delgado
J C
JC
Center for Blood Research, Institute for Biomedical Research, Boston, Massachusetts 02115, USA.
Quiñones-Berrocal
J
J
Thim
S
S
Miranda
L F
LF
Goldfeld
A E
AE
D000328:Adult; D002160:Cambodia; D006801:Humans; D007371:Interferon-gamma / Q000097:blood; D010568:Peru; D018709:Statistics, Nonparametric; D014374:Tuberculin Test; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis* / Q000208:ethnology
D007371:Interferon-gamma