Delayed Tuberculin Reactivity in Persons of Indochinese Origin: Implications for Preventive Therapy

1 May 1996 | Volume 124 Issue 9 | Pages 779-784

Objectives: 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.

Design: Cross-sectional study.

Setting: 2 public health department clinics in North Carolina.

Participants: 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.

Measurements: 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.

Author and Article Information

From the University of New Mexico, Albuquerque, New Mexico; Case Western Reserve University School of Medicine, Cleveland, Ohio; the University of North Carolina School of Medicine, Chapel Hill, North Carolina; and the University of Alabama at Birmingham, Birmingham, Alabama.
Acknowledgments: The authors thank John Bass, MD, Carla J. Herman, MD, MPH, and Gary Simpson, MD, PhD, for their helpful suggestions and the dedicated nursing, medical, and support staff of the Guilford and Wake County Health Departments.
Grant Support: During the study, Dr. Robertson was a Fellow in Preventive Medicine at the University of North Carolina, Chapel Hill, funded through the Department of Social Medicine.
Requests for Reprints: John M. Robertson, MD, MPH, Department of Medicine, ACC 5th Floor, University of New Mexico School of Medicine, 2211 Lomas NE, Albuquerque, NM 87131-5271.
Current Author Addresses: Dr. Robertson: Department of Medicine, ACC 5th Floor, University of New Mexico School of Medicine, 2211 Lomas NE, Albuquerque, NM 87131-5271.