Indeterminate QuantiFERON-TB Gold Increases Likelihood of Inflammatory Bowel Disease Treatment Delay and Hospitalization

Abstract

Background: QuantiFERON-TB Gold (QFTG) is a blood test used to diagnose latent tuberculosis infection (LTBI) prior to TNF-α inhibitor (anti-TNF) initiation. We sought to determine factors associated with indeterminate QFTG results in inflammatory bowel disease (IBD) patients and whether indeterminate results are associated with IBD-related morbidity.

Methods: This nested case-control study included IBD patients who underwent QFTG testing. Cases were patients with indeterminate QFTG and controls were those with negative QFTG. The association of demographic and clinical data with indeterminate QFTG result was assessed using logistic regression. We examined the clinical impact of indeterminate QFTG results on risk of hospitalization and delay in anti-TNF initiation using inverse probability-of-treatment weighting (IPTW) regression.

Results: We identified 411 patients with QFTG testing (320 negative, 80 indeterminate, and 11 positive results). No patient with an indeterminate result subsequently had LTBI. Systemic corticosteroid use (OR, 4.4; 95% CI, 2.0-9.6) and hospitalization at the time of QFTG (OR, 3.8; 95% CI, 1.9-7.7) were associated with indeterminate QFTG, while immunomodulator use was nearly statistically significant (OR, 3.1; 95% CI, 0.9-9.8) and anti-TNF use was not (OR, 0.9; 95% CI, 0.2-4.6). After IPTW adjustment, indeterminate QFTG was associated with a 23.1% (95% CI, 8.2%-37.9%) greater probability of delay in anti-TNF initiation beyond 30 days and an 11.9% (95% CI, 0.6%-23.1%) greater probability of hospitalization within 60 days.

Conclusions: Systemic corticosteroid use and hospitalization were associated with an indeterminate QFTG result. Indeterminate QFTG results were associated with delayed anti-TNF initiation and subsequent hospitalization.

Keywords: QuantiFERON-TB Gold; anti-TNFs; inflammatory bowel disease outcomes; tuberculosis.

Figure 1.

Initial and repeat QFTG results stratified by initial test result

Figure 2.

Kaplan-Meier analysis of days to anti-TNF initiation among subgroup of patients who started an anti-TNF medication within 365 days of QFTG (log-rank test: p = 0.01). Indeterminate QFTG median time to initiation was 30 days. Negative QFTG median time to initiation was 17 days.