Chest Conference4 2009


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Chest Conference4 2009

  1. 1. Chest Conference TB Update Case Presentation Ramin Khashayar, MD April 7, 2009
  2. 2. Presentation of the Case <ul><li>63 y.o. woman with a long standing diagnosis of U.C. treated with moderate to large doses of oral corticosteroid </li></ul><ul><li>Pt developed increasing cough and had a CXR and chest CT scan done as part of the work up </li></ul><ul><li>CXR revealed a new RUL infiltrate </li></ul>
  3. 3. Presentation of the Case <ul><li>Chest CT confirmed the presence of RUL infiltrate without associated LAD or pleural effusions </li></ul><ul><li>She reported 2 week h/o of low grade fevers and mild night sweats but no wt loss </li></ul><ul><li>There was no hemptysis </li></ul>
  4. 4. Presentation of the Case <ul><li>Laboratory testing was otherwise negative </li></ul><ul><li>TST was negative (no controls done) </li></ul><ul><li>Patient lives in W.C but had an extensive travel history in Asia and Africa </li></ul><ul><li>She denies know TB exposure and had not traveled in fungal endemic areas </li></ul>
  5. 5. Presentation of the Case <ul><li>She was seen in the office 3 days ahead of a planned air travel to Hawaii </li></ul>
  6. 6. TB overview <ul><li>Approxiamtely 1/3 of the work population had LTBI </li></ul><ul><li>An estiamted 10 million people worlwide have active TB </li></ul><ul><li>2 million people a year die of tuberculosis </li></ul>
  7. 7. TB overview <ul><li>In the US, foreign-born persons from high TB risk areas have a 10-fold increased risk of developing TB </li></ul><ul><li>The risk of TB is highest in first five years after arrival but continues to be higher throughout their lives </li></ul><ul><li>The risk of TB in immigrant who travel back to the country of origin is higher than their cohort who don’t travel back </li></ul>
  8. 8. TB overview <ul><li>CDC recommend targeted screening for immigrants from high risk countries especially during the first five years after arrival </li></ul><ul><li>Local Health department recommend the use if IGRA (QuantiFERON-TB Gold assay) as this is more specific in people vaccinated with BCG </li></ul>
  9. 9. QuantiFERON-TB Gold assay <ul><li>One of three IGRAs, and one approved by FDA and available at JM (sent out to Sacto county lab) </li></ul><ul><li>It required heparinized fresh whole blood that needs to be tested within 12 hour as it requires viable lymphocytes </li></ul>
  10. 10. QuantiFERON-TB Gold assay <ul><li>Whole blood aliquots are mixed with two MTB (ESAT-6 and CFP-10) antigens, negative control mixture (saline) and a positive control mixture (mitogen) for 16-24 h </li></ul><ul><li>If the lymphocytes react to MTB antigen, they release gamma interferon that can be measures and compared to the negative and positive control samples and resultes as positive, nagative or indeterminate </li></ul>
  11. 11. QuantiFERON-TB Gold assay <ul><li>The major advantage of the test is lack of cross reactivity with BCG, or non-tuberculosis mycobacteria </li></ul><ul><li>It is also a one step test that does not require a second visit </li></ul><ul><li>It requires an expert lab as it is a biological test and can be subject to variability </li></ul>
  12. 12. QuantiFERON-TB Gold assay <ul><li>It requires fresh heparinized blood </li></ul><ul><li>It’s performance in children and immuno-compromized host (HIV/ steroids) is not known </li></ul><ul><li>Hard to study as TST itself is a poorly sensitive and non-specific test </li></ul>
  13. 13. QuantiFERON-TB Gold assay <ul><li>In one study, comparing two types of IGRA with TST, TST was found to be less sensitive than IGRA in HIV, liver transplant and hematologic malignancy patients (15-18% vs 10% positive rates)* </li></ul><ul><li>* Richeldi et al, Chest, April 2, 2009 </li></ul>
  14. 14. QuantiFERON-TB Gold assay <ul><li>A study of 44 suspected pulmonary and 21 extrapulmonary TB pts, found QFT-G to be 75% and 76% sensitive vs 68% and 62% for TST* </li></ul><ul><li>*Ak et al, Jon. J. Infec. Dis., 2009 </li></ul>
  15. 15. QuantiFERON-TB Gold assay <ul><li>In one study, 90 pts underwent bronchoscopic evaluation for TB </li></ul><ul><li>28 had proven TB, 52 did not </li></ul><ul><li>In TB pts QFT-G was positive in 79%, TST in 57% </li></ul><ul><li>*Kobashi et al, Internal Medicine, 2007 </li></ul>
  16. 16. QuantiFERON-TB Gold assay <ul><li>Locally, we quote a 20% false negative rate. </li></ul><ul><li>The sensitivity is probably higher that TST, and it is not complicated by BCG vaccination </li></ul><ul><li>The false negative pts with QFT-g and TST do not overlap </li></ul><ul><li>One study suggested that if both tests are negative, TB is even less likely (?) </li></ul>
  17. 17. TB Review, PT classification <ul><li>TB1: No evidence of TB or LTBI </li></ul><ul><li>TB2: LTBI </li></ul><ul><li>TB3: Active TB </li></ul><ul><li>TB4: Old TB (CXR w/o change for 3 mo, no clinical or microbiologic suspicion for TB </li></ul><ul><li>TB5: TB suspect, high prob or low prob </li></ul>
  18. 18. TB