Tuberculin skin test and interferon-gamma release assay use among privately insured persons in the United States

OBJECTIVE: To describe tuberculin skin test (TST) and interferon-gamma release assay (IGRA) (i.e., Quanti-FERON (R)-TB [QFT] and T-SPOT (R).TB [T-SPOT]) use among privately insured persons in the United States over a 15-year period. METHODS: We used current procedural terminology (CPT) codes for the TST and IGRAs to extract outpatient claims (2000-2014) and determined usage (claims/100 000). The chi(2) test for trend in proportions was used to describe usage trends for select periods. RESULTS: The TST was the dominant (>80%) test in each year. Publication of guidelines preceded the assignment of QFT and T-SPOT CPT codes by 1 year (2006 for QFT; 2011 for T-SPOT). QFT usage was higher (P < 0.01) than T-SPOT in each year. The average annual increase in the use of QFT was higher than that of T-SPOT (35 vs. 3.8/100 000), and more so when the analytic period was 2011-2014 (65 vs. 38/100 000). However, during that 4-year period (2011-2014), TST use trended downward, with an average annual decrease of 28/100 000. The annual proportion of enrollees tested ranged from 1.1% to 1.5%. CONCLUSIONS: These results suggest a gradual shift from the use of the TST to the newer IGRAs. Future studies can assess the extent, if any, to which the shift from the use of the TST to IGRAs evolved over time.