My patient with rheumatoid arthritis might have been exposed to tuberculosis. Does immunosuppressive therapy affect the results of interferon gamma release assay (IGRA) testing for latent tuberculosis?

The weight of the evidence to date suggests that immunosuppressive therapy, including steroids, other oral immunosuppressants and anti-tumor-necrosis factor (TNF) agents, may negatively impact IGRA results.1

In some ways the finding of false-negative IGRA in the setting of immunosuppression is intuitive since many immunosuppressive agents are potent inhibitors of T cells and interferon-gamma response. 1,2 Despite this, the initial reports have been somewhat conflicting which makes a 2016 meta-analysis of the effect of immunosuppressive therapy on IGRA results in patient with autoimmune diseases (eg, rheumatoid arthritis, lupus, inflammatory bowel disease) particularly timely. 1

This meta-analysis found a significantly lower positive IGRA results among patients on immunosuppressive therapy ( O.R. 0.66, 95% C.I. 0.53-0.83). Breakdown by IGRA test showed a significant association between QuantiFERON-TB Gold In-Tube and lower positive results and a trend toward the same with T-SPOT though the latter did not reach statistical significance with fewer evaluable studies (O.R. 0.81, 95% C.I 0.6-1.1).   Breakdown by type of immunosuppressant showed significantly negative impact of corticossteroids, other oral immunosuppressants, and anti-TNF agents for all. Some studies have reported daily steroid doses as low as 7.5 mg-10 mg may adversely impact T-cell responsiveness in IGRA. 3,4

So, whenever possible, testing for latent TB should be performed before immunosuppressants are initiated.

Bonus Pearl: Did you know that an estimated one-third of the world’s population may have latent TB?

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References

  1. Wong SH, Gao Q, Tsoi KKF, et al. Effect of immunosuppressive therapy on interferon gamma release assay for latent tuberculosis screening in patients with autoimmune diseases: a systematic review and meta-analysis. Thorax 2016;71:64-72. https://thorax.bmj.com/content/thoraxjnl/71/1/64.full.pdf
  2. Sester U, Wilkens H, van Bentum K, et al. Impaired detection of Mycobacterium tuberculosis immunity in patents using high levels of immunosuppressive drugs. Eur Respir J 2009;34:702-10. https://erj.ersjournals.com/content/34/3/702
  3. Kleinert S, Kurzai O, Elias J, et al. Comparison of two interferon-gamma release assays and tuberculin skin test for detecting latent tuberculosis in patients with immune-mediated inflammatory diseases. Ann Rheum Dis 2010;69:782-4. https://ard.bmj.com/content/69/4/782
  4. Ponce de Leon D, Acevedo-Vasquez E, Alvizuri S, et al. Comparison of an interferon-gamma assay with tuberculin skin testing for detection of tuberculosis (TB) infection in patients with rheumatoid arthritis in a TB-endemic population. J Rheumatol 2008;35:776-81. https://www.ncbi.nlm.nih.gov/pubmed/18398944
My patient with rheumatoid arthritis might have been exposed to tuberculosis. Does immunosuppressive therapy affect the results of interferon gamma release assay (IGRA) testing for latent tuberculosis?

How do I interpret an elevated serum C-reactive protein (CRP) and normal erythrocyte sedimentation rate (ESR) or vice-versa?

 

Discordance between serum CRP and ESR is not uncommon (1,2). This phenomenon may be due to a variety of factors including the fact that the kinetics of these two tests is quite different, as discussed under “Should I order C-reactive protein (CRP) or erythrocyte sedimentation (ESR) on patients suspected of having a new infection?” in this blog.

In a study of CRP/ESR discordance (defined as results differing by 2 or 3 quartiles) in adults, a high CRP/low ESR profile was more likely to be associated with  urinary, GI, blood stream, and pulmonary infections, myocardial infarction, and venous thromboembolism and less likely to be associated with bone and joint infections (1).

In the same study, a high ESR/low CRP was associated with connective tissue diseases, such as systemic lupus erythematosus and strokes (1).

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References

1. Feldman M, Aziz B, Kang GN, et al. C-reactive protein and erythrocyte sedimentation rate discordance: frequency and causes in adults. Translational Research 2013;161:37-43. https://www.ncbi.nlm.nih.gov/pubmed/22921838

2. Colombet I, Pouchot J, Kronz V. Agreement between erythrocyte sedimentation rate and C-reactive protein in hospital practice. Am J Med 2010;123:864.e7-863.e13.https://www.ncbi.nlm.nih.gov/pubmed/20800157

How do I interpret an elevated serum C-reactive protein (CRP) and normal erythrocyte sedimentation rate (ESR) or vice-versa?