ABSTRACT
Strand displacement amplification (SDA) technology has been established in a fully automated system known as BDProbeTec. Target sequences of the insertion sequence IS6110 and the 16S rRNA gene are simultaneously amplified, which thus allows the detection of Mycobacterium tuberculosis complex and, as an additional option, of most Mycobacterium species. Detection occurs via a chemiluminescent microwell assay that employs the simultaneous hybridization and capture of SDA products with a biotinylated capture probe and an alkaline phosphatase detector probe. We have evaluated the performance of the BDProbeTec system in detecting M. tuberculosis complex by testing 799 respiratory specimens and comparing the results to those obtained by conventional diagnostic techniques, i.e. , microscopy and culture (solid and radiometric media). M. tuberculosis was cultivated from 41 specimens, of which 28 (68.4%) were smear positive and 13 (31.6%) were smear negative. The overall sensitivity of the SDA assay was 97.6% (for smear-positive specimens, 100%; for smear-negative specimens, 92.3%), and specificity was 95. 0%. After resolution of the discrepancies by studying the patients' clinical data, sensitivity and specificity were 97.9 and 96.5%, respectively, and positive and negative predictive values were 63.9 and 99.9%, respectively. These preliminary data demonstrate that the BDProbeTec system has promising performance characteristics with respiratory specimens and that it allows the detection of M. tuberculosis complex within hours.
Subject(s)
Mycobacterium tuberculosis/isolation & purification , Reagent Kits, Diagnostic , Respiratory System/microbiology , Adult , Aged , Aged, 80 and over , Bacteriological Techniques , Evaluation Studies as Topic , Female , Humans , Male , Middle Aged , Sensitivity and SpecificityABSTRACT
Atypical, cytoplasmic and perinuclear anti-neutrophil cytoplasmic antibodies (x-, c- and pANCA, respectively) are associated with a variety of inflammatory diseases, including inflammatory bowel disease (IBD). Anti-neutrophil cytoplasmic antibodies are more common in patients with ulcerative colitis (UC) than in patients with Crohn's disease (CD). Most publications only refer to p- and cANCA in relation to IBD. We have prospectively evaluated the reactivity of sera from 58 patients with IBD and 10 healthy controls against human neutrophils with emphasis on the distinction of the ANCA types. The sera were incubated with ethanol- and formaldehyde-fixed granulocytes to differentiate between c-, p- and xANCA. The results showed that 10 of 24 patients with UC were positive for ANCA, whereas only one of 34 patients with CD was ANCA positive. These results correspond to a sensitivity of 42%, a specificity of 97%, a negative predictive value of 91% and a positive predictive value of 75% in UC. Of the 11 ANCA-positive sera, two showed a cytoplasmic staining pattern, three showed a perinuclear and six an atypical staining pattern. The disease activity was not correlated to either the ANCA titre or to the presence of ANCA in the serum. In conclusion, ANCA are of limited value in differentiating between UC and CD. Because the majority of ANCA in patients with IBD are xANCA, these ANCA should be explored by not only incubating on ethanol-fixed granulocytes, but also on formaldehyde-fixed granulocytes.
