[Comparison of the tuberculin skin test with the interferon-gamma test in the framework of a surroundings investigation in a prison]

Abstract

After the occurrence of a multidrug-resistant tuberculosis in a prison of Lower Saxony (Germany), 223 contact persons (178 inmates, 45 staff members) were identified. To detect latent tuberculosis infections, all contact persons were tested with the tuberculin skin test (TST) and the interferon-gamma release assay (IGRA). An additional standardised questionnaire on anamnestic information and risk factors was completed by the participants. The statistical analysis included 149 male inmates with a mean age of 39 years. 61.1% of the inmates were born in Germany, 14.8% were born in the USSR or, respectively, its follow-up states. With the TST 29.5% of the inmates were tested positive, whereas with the IGRA the positive rate was 18.1%. For 7 inmates there was a positive IGRA despite a negative TST. The positive predictive value of TST with respect to IGRA was 45.5%, agreement was 79.2% (kappa=0.44). The agreement found in this study is comparable to studies within populations with lower incidence. Numerous investigations outside Europe indicate a high risk of tuberculosis infection among inmates.