אילמ"ר - האיגוד הישראלי למדעי המעבדה הרפואית

אילמ"ר - האיגוד הישראלי למדעי המעבדה הרפואית

כינוס שנתי ה-46 | 2012

פוסטרים להצגה בכינוס

IMPROVING TUBERCULOSUS DIAGNOSIS IN THE COMMUNITY

Miriam Parizade1, Irena Goichman1, Samy Rezonzew1, Rachel Preiss2, Diana Taran1 & Bracha Shainbrerg1
Central Laboratory1 & TB clinic2, Maccabi Health Services, Rechovot

 

Backround: Israel, as an industrialized country, attracts many immigrants and foreign workers coming from endemic tuberculosis (TB) countries. The awareness of community physicians to this disease has since arisen and as a consequence, the workload in our community based TB Laboratory increased as well. In this abstract we describe two new tests introduced recently into our routine TB diagnosis setup: The QuantiFERON TB Gold In-Tube assay (QFT) used for aiding the diagnosis of latent-TB and the BD MGIT-TBc test (TBc-ID) for rapid identification of TB-complex positive cultures.


Methods: Thirty three blood samples from health care workers and patients were drawn at the TB clinic, Rehovot and incubated over night in three pre- coated (Nill, TB Antigen and Mitogen) tubes at 37°C. The next morning plasma was separated and tested for γ-interferon (γ-INF) by an ELISA method according to manufacturer's instructions (Cellestis, Australia). The TBc-ID device (Becton Dickinson, USA) was tested with 47 positive liquid based Mycobacteria cultures, confirmed by acid fast microscopy. All TBc-ID results were compared to molecular based identification (PCR, Hain Lifescience, Germany).


Results: γ-INF release from T cells incubated with TB specific antigens indicates previous exposure to TB bacteria. We compared the γ-INF measured by QFT in 28 blood samples, to Mantoux results. Agreement between both tests was found in 68% (19/28). QFT gave fewer positives (39% ;11/28) than the Mantoux test (64%; 18/28), indicating higher specificity. Percent cv was measured in 4 independent assays between the duplicates of the 4 and 1 IU/ml standards. Within run and in-between run cv% resulted 1.1-4.1% and 2.5-3%, respectively. Assay linearity was tested in serial dilutions of 2 high QFT samples. In one of the samples linearity was obtained while the other remained high in spite of diluting factor.
The TBc-ID immunochromatographic device was evaluated for rapid identification of positive TB-complex cultures in comparison to molecular based PCR identification. The device correctly identified 18/19 positive TB-complex strains. One TB-complex positive strain was identified by PCR as a mutated BCG strain lacking the MPT 64 protein, which is the protein target in the TBc-ID test. The TBc-ID test resulted negative when testing 28 non-tuberculosis Mycobacteria (NTM) strains, but positive in 2/5 Staphylococcus aureus strains. Sensitivity and specificity were 95% and 91%, respectively.


Conclusions:  Utilizing these new technologies in our TB Laboratory aids in the early identification of LTBI patients and positive TB-complex cultures, thus enabling rapid, cost-effective treatment. The QFT assay eliminates the problem of false positive Mantoux results due to past BCG immunization. The TBc-ID test is an easy 15 minute, accurate laboratory solution for shortening positive culture results by at least 10 days. Using this test provides an excellent alternative for expensive PCR TB-complex identification.

 

לתכנית הכנס     חזרה לריכוז הפוסטרים 2012
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