Delayed tuberculin reactivity in persons of Indochinese origin: implications for preventive therapy.
OBJECTIVE
To 1) study a variant delayed reaction to tuberculin testing as a way to enhance screening for tuberculosis among high-risk persons and 2) correlate the delayed reaction with lymphocyte blastogenesis.


METHODS
Cross-sectional study.


METHODS
2 public health department clinics in North Carolina.


METHODS
121 adults who had recently emigrated from Vietnam to North Carolina and who were ethnic Vietnamese and ethnic Dega, a minority population group from the central highlands region of Vietnam.


METHODS
Medical history, physical examination, laboratory evaluation, and standard purified protein derivative (PPD) testing (Mantoux method). Skin test results were read at 72 hours and again at 6 days. Variant reactivity was defined as induration of less than 10 mm at 72 hours that, when reassessed at 6 days, had increased in size to 10 mm or greater. Persons with negative (n=54) and variant (n=32) PPD results also had booster testing at 10 to 12 weeks. Serum samples were obtained from 57 participants for lymphocyte blastogenesis studies.


RESULTS
26% of participants had variant tuberculin reactivity. Variant reactivity was strongly associated with booster positivity: Sixty-five percent of persons with variant PPD results had booster positivity compared with 16% of persons with negative PPD results (P<0.001). The lymphocyte blastogenesis response of persons with variant PPD results was between the response of persons with negative PPD results and that of persons with positive PPD results.


CONCLUSIONS
Variant reactivity in this high-risk group was a predictor of booster positivity. Together with the blastogenic response pattern, this association strongly suggests that variant reactivity has a high positive predictive value for tuberculous infection. Clinicians should incorporate these findings into their approach for choosing candidates for preventive therapy.
Robertson
J M
JM
Department of Medicine, University of New Mexico School of Medicine, Albuquerque, NM 87131-5271 USA.
Burtt
D S
DS
Edmonds
K L
KL
Molina
P L
PL
Kiefe
C I
CI
Ellner
J J
JJ
D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D006968:Hypersensitivity, Delayed / Q000208:ethnology* / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D008297:Male; D008875:Middle Aged; D013902:Radiography, Thoracic; D012036:Refugees; D012307:Risk Factors; D014374:Tuberculin Test / Q000379:methods; D014376:Tuberculosis / Q000208:ethnology / Q000276:immunology / Q000517:prevention & control*; D014744:Vietnam