Session Information
Session Type: Abstract Submissions (ACR)
The Role of Repeating Tuberculin Skin Tests during Biologic Therapy
Background/Purpose: Prior to starting biologic therapy, it is recommended that all patients be screened for tuberculosis (TB).1 However, for patients who screen negative at baseline and then subsequently start biologic therapy, the utility of repeating a tuberculin skin test (TST) is uncertain. This retrospective study was conducted to evaluate the frequency of TST conversion among patients on biologic therapy in a low incidence region for TB (1.4 cases per 100,000).2
Methods: We retrospectively reviewed records from a community rheumatology practice in Boulder County, Colorado, to identify patients screened for TB between March 2005 and August 2010. All patients planning to start biologic therapy were screened with a TST at baseline. Those with negative results were screened annually thereafter while on biologic therapy. We defined ≥5mm induration as a positive TST and “conversion” as induration of ≥5mm after an initial negative TST.
Results: Five hundred eighty-nine patients were screened prior to biologic therapy initiation. Most were female (n=353, 60%) and had rheumatoid arthritis (n=359, 61%) or spondyloarthritis (n=198, 34%). Three hundred twenty-seven patients (56%) underwent a total of 818 repeat TSTs, 9 (1.1%) of which were positive. Five (56%) of the converters had no apparent risk factors for TB exposure. All converters had negative chest radiographs. While continuing biologic therapy, all but 1 completed 8-9 months of isoniazid (INH). None have developed TB during a median follow-up period of 49 months (range 16 to 70).
|
Test |
Patients tested with TST |
Number (%) of +TSTs |
|
TST #1 |
589 |
17 (2.9) |
|
TST #2 |
327 |
5 (1.5) |
|
TST #3 |
220 |
2 (0.9) |
|
TST #4 |
147 |
2 (1.4) |
|
TST #5 |
79 |
0 |
|
TST #6 |
31 |
0 |
|
TST #7 |
10 |
0 |
|
TST #8 |
4 |
0 |
|
TST #2-8 |
818 |
9 (1.1) |
|
Overall |
1407 |
26 (1.8) |
Conclusion: In an area of low TB incidence, annual TST conversion while on biologic therapy was rare. Checking yearly TSTs on all patients being treated with biologic agents is of low yield. A small number of converters were identified, but more than half had no apparent risk factors for TB exposure. It is unclear if these conversions truly represent new infections, but all were started on INH and none have developed TB.
References
1. Singh JA, et al. 2012 Update of the 2008 ACR Recommendations for the Use of DMARDs and Biologic Agents in the Treatment of RA. AC&R 2012;64:625-39.
2. www.cdc.gov/tb/statistics/reports/2010/table20.htm (accessed 6/25/12)
Disclosure:
J. R. Lutt,
None;
K. L. Winthrop,
Oxford Immunotech; Pfizer Inc.,
2,
Abbott; Pfizer Inc; UCB; Amgen; Cellestis,
5.
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