Global Tuberculosis Report -- 2012.pdf

sputum specimens and TB isolates from culture – conventionalphenotypic testing remains the reference standardfor detecting extensively drug-resistant TB (XDR-TB)until more data become available. Further details aboutthe evaluation of these tests is provided in Chapter 6.Consistent challenges in developing new TB diagnosticshave been the sophisticated and costly laboratoryinfrastructure and specialized human resources requiredfor the range of tests needed to diagnose TB in its variousforms, and test utility being restricted to increasinglysophisticated levels of laboratory services. Only oneDST technology – based on a rapid colorimetric methodsuitable for use at the intermediate laboratory level – iscurrently at the stage of being tested for feasibility. Second-generationXpert assays and possible alternativemolecular technologies are in the early or conceptualstages of development and are not expected to reach themarket before the end of 2015.TB remains unique among the major infectious diseasesin lacking accurate and rapid point-of-care (POC)tests. Insufficient progress in biomarker research, technicaldifficulties in transforming sophisticated laboratorytechnologies into robust yet accurate POC platforms, anda lack of interest from industry have resulted in slow andsuboptimal progress. The era of “omics” has seen largescalesearches for biological markers of disease and theapplication of emerging technologies to identify novelmarkers of disease, particularly from blood and urine.These have traditionally been directed at finding reliablesurrogates for culture to assess and/or predict treatmentprognosis and have only recently become a focus for thedevelopment of TB diagnostics.Non-sputum based tests remain an attractive avenueto explore for POC development. Commercially availableantigen detection assays can identify Mycobacteriumtuberculosis lipoarabinomannan (LAM) in urine; however,their accuracy in routine clinical use has beensuboptimal. 1 Two recent studies evaluating a low-cost,POC version of a commercial TB-LAM test (Determine®TBLAM, Alere Inc., Waltham, MA, USA) showed moderatesensitivity and high specificity in a subgroup of TBpatients living with HIV who had advanced immunosuppression(CD4 cell-counts