After carefully reading this article and other related references, weagree that detection of M tuberculosis using interferon gamma release assays (IGRA) is more sensitive and specific than the classic Tuberculin Skin Test (TST) for the detection of Latent TB Infection (LTBI) in
patients receiving immunosuppressive therapy. As the authors indicate, there are two commercially available IGRAs, an Enzyme Link...
After carefully reading this article and other related references, weagree that detection of M tuberculosis using interferon gamma release assays (IGRA) is more sensitive and specific than the classic Tuberculin Skin Test (TST) for the detection of Latent TB Infection (LTBI) in
patients receiving immunosuppressive therapy. As the authors indicate, there are two commercially available IGRAs, an Enzyme Linked Immunosorbent Assay (ELISA), QuantiFeron TB-Gold, and an Enzyme Linked Immunospot
(ELISPOT) assay, T-SPOT.TB.
It has been shown that the ELISPOT methodology can be up to 200 times more sensitive than ELISA. T-SPOT.TB requires just a few spots to give a positive result (one spot = one effector T cell), so just a few activated
T cells in a sample can provide a positive result. Many more T cells are required to provide a measurable change in cytokine concentration by ELISA.
In addition to the methodological advantages of ELISPOT over ELISA, the T-SPOT.TB protocol has some procedural differences that produce a more reliable result. T-SPOT.TB has a washing step that removes the source of interfering background signals, which reduces sensitivity and produces
indeterminate results. This washing step is absent in the ELISA based QuantiFeron TB-Gold.
In the T-SPOT.TB procedure, the Peripheral Blood Mononuclear Cells (PBMCs) are counted. This step ensures there are an adequate number of cells and that each time the assay is performed there is the same number of cells present, which standardizes the assay. This step maintains the high sensitivity in immunocompromised and immunosuppressed patients. This step is also absent in the ELISA based QuantiFeron TB-Gold.
In conclusion, we believe that T-SPOT.TB is a novel in vitro diagnostic test that uniquely identifies the number of T cells specific to Mycobacterium tuberculosis antigens and therefore is better equipped to identify LTBI, particularly in immunosuppressed populations.
References
1. Tanguay and Killion. Direct comparison of ELISPOT and ELISA-based assays for detection of individual cytokine-secreting cells. Lymphokine and Cytokine Research 1994;13:259–263.
2. G Matulis, P Jüni, P M Villiger, S D Gadola. Detection of latent tuberculosis in immunosuppressed patients with autoimmune diseases: performance of a Mycobacterium tuberculosis antigen-specific interferon assay. Ann Rheum Dis 2008;67:84-90.
We applaud Kang et al in their efforts to study the clinical features and risk factors of postsurgical gout [1]. They recommend prophylactic
administration of colchicine prior to surgery to prevent postsurgical gout [1]. However, we should not forget that the dose of colchicine in the management of acute gout remains controversial [2-6], and caution should be exercised in deciding the prophylactic dose for s...
We applaud Kang et al in their efforts to study the clinical features and risk factors of postsurgical gout [1]. They recommend prophylactic
administration of colchicine prior to surgery to prevent postsurgical gout [1]. However, we should not forget that the dose of colchicine in the management of acute gout remains controversial [2-6], and caution should be exercised in deciding the prophylactic dose for surgical patients as well.
Interestingly, there has been only one randomised controlled trial done a couple of decades ago looking into this matter, where gastrointestinal side effects had occured before the relief of pain [7].
We would like to highlight the caveats to be aware of with regard to dosing colchicine and it is prudent for the non-specialist to be aware of the high dose of colchicine that is generally recommended as lesser doses have been found to be effective and less toxic [2-6].
This becomes more pertinent in postsurgical patients who could potentially be at a higher risk of side effects too.
References
1. Kang EH, Lee EY, Lee YJ, Song YW, Lee EB. Clinical features and risk factors of postsurgical gout. Ann Rheum Dis 2007 Nov 12; [Epub ahead of print] PMID: 17998214
2. Varughese GI, Jammalamadaka D, Varghese AI, Babu S, Reddy M. Colchicine in acute gout: the need for a reappraisal. Int J Clin Pract 2007;61(12):2132-3. PMID: 17997813
3. Varughese GI, Varghese AI, Tahrani AA. A caveat in the management of acute gout. Am J Med 2007;120(11):e31. PMID: 17976406
4. Varughese GI, Varghese AI, Tahrani AA. Colchicine: time to rethink. N Z Med J 2007;120(1249):U2429. PMID: 17308565
5. Varughese GI, Varghese AI. Colchicine in acute gouty arthritis: the optimum dose? Arthritis Res Ther 2006;8(5):405. PMID: 17005028
6. Morris I, Varughese G, Mattingly P. Colchicine in acute gout. BMJ 2003;327(7426):1275-6. PMID: 14644973
7. Ahern MJ, Reid C, Gordon TP, McCredie M, Brooks PM, Jones M. Does colchicine work? The results of the first controlled study in acute gout. Aust N Z J Med 1987;17(3):301-4. PMID: 3314832
Dear Editor,
After carefully reading this article and other related references, weagree that detection of M tuberculosis using interferon gamma release assays (IGRA) is more sensitive and specific than the classic Tuberculin Skin Test (TST) for the detection of Latent TB Infection (LTBI) in patients receiving immunosuppressive therapy. As the authors indicate, there are two commercially available IGRAs, an Enzyme Link...
Dear Editor,
We applaud Kang et al in their efforts to study the clinical features and risk factors of postsurgical gout [1]. They recommend prophylactic administration of colchicine prior to surgery to prevent postsurgical gout [1]. However, we should not forget that the dose of colchicine in the management of acute gout remains controversial [2-6], and caution should be exercised in deciding the prophylactic dose for s...
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