List guidelines for mycobacterial infection prevention in patients who are to receive biologic agents?
• All patients who are to receive biologic agents should undergo MTB (latent and active) and NTM screening.
All patients should have risk factor assessment, physical examination, and a chest radiograph.
Tuberculin skin test only has a sensitivity and specificity of 70%. PPD >5 mm at 48 hours should be considered positive regardless of prior history of BCG vaccination.
Many patients with immune-mediated inflammatory diseases are on prednisone and other immunosuppressants, which can make PPD unreliable. Therefore, IGRA screening is also recommended. Notably, up to 10% of IGRA tests can be indeterminate in patients on immunosuppressants. Consequently, a dual testing strategy (perform one test and, if negative, perform the other) may be used, in which a positive result from either test would be considered positive.
Screening procedures decrease reactivation of MTB by 80%.
In the United States, NTM (especially MAC) is much more common than MTB. There are no skin tests or blood tests to detect NTM infection.
• Biologic therapy: Monoclonal antibodies (especially infliximab) against TNFα have the highest risk, and abatacept and rituximab have the lowest risk for MTB and NTM infection. Reactivation of MTB tends to occur within 6 months of starting anti-TNFα therapy and usually presents as extrapulmonary disease, especially lymphadenitis.
• Patients with latent MTB and normal chest radiograph should delay biologic initiation (especially anti-TNFα agents) until 1 month of latent TB therapy has been administered. Patients should receive a complete course for latent MTB (typically 9 months of isoniazid or 4 months of rifampin).
• Patients with active MTB should have a complete course of anti-tuberculous therapy before starting a biologic (especially anti-TNFα agent).
• Patients with prior history of treated NTM infection should be evaluated by a specialist before a biologic is used. Some NTM are difficult to cure, and anti-TNFα agents should be avoided. Rituximab or abatacept may be safer agents.