Enhanced Tuberculosis Infection Treatment Outcomes after Implementation of QuantiFERON®-Gold Testing

Use of the tuberculin skin test (TST) for diagnosis of latent tuberculosis infection (LTBI) among individuals who received the Bacille Calmette-Guérin (BCG) vaccine is complicated by its potential cross-reaction with TST antigens which may cause false-positive results and lead to patient and physician reluctance to initiate LTBI treatment. QuantiFERON®-TB Gold (QFT-G) lacks this cross-reaction. We sought to study the impact of implementing QFT-G testing in 2006 on LTBI treatment initiation and completion at NYC chest clinics.

QFT-G results from 10/2006-12/2008 in NYC Department of Health and Mental Hygiene chest clinics were obtained from the electronic medical record system. The proportions of patients who initiated and completed treatment among patients tested with QFT-G were compared to those tested with TST from 10/2004-9/2006.

Among 36,167 patients tested with QFT-G, 2,300 (6%) tested positive, 33,327 (93%) tested negative, and 540 (1%) had an indeterminate result. Among those who had a positive QFT-G test and deemed eligible, 985 (80%) initiated LTBI treatment and 490 (40%) completed treatment. Historically, among patients tested with TST, 7,073 (19%) tested positive (p<0.0001 compared to QFT-G); 3,182 (79%) of those eligible initiated LTBI treatment and 1,210 (30%) completed treatment (p<0.0001 compared to QFT-G).

QFT-G implementation increased the proportion of patients completing LTBI treatment. Additional studies are needed in more settings to determine whether using QFT-G leads to a sustained increase in treatment completion.