Non-invasive ventilation for the treatment of hypercapnic respiratory failure in cystic fibrosis.

92% and those with previously treated tuberculosis would have remained below the diagnostic threshold. In this issue of Thorax, Breen et al 12 take a slightly different approach using tuber-culin testing and flow cytometry (see page 67). BAL fluid was taken from a substantially larger group of patients (n = 250) in whom tuberculosis was suspected but the sputum smear was negative for auramine-positive bacilli, of whom 111 gained a diagnosis of active tuberculosis. The cells were first sorted for CD45 (common leucocyte antigen) and CD4 markers and 50 000 of these cells were cultured with the mixture of anti-gens found in tuberculin-purified protein derivative (PPD). Flow cytometry was then used to measure the percentage of CD4+ cells which expressed interferon-c after stimulation with PPD. Although ESAT-6 was also used in 71 subjects, the specificity was not increased: all those who were positive with PPD but who did not have tuberculosis were also positive after stimulation with ESAT-6. The high false-positive rating in this assay (24%) was a significant problem. Breen et al suggest that many of these should have been treated for tuberculosis as 2 of 34 developed active disease within the period of follow-up. Several could well have had self-healed tuberculosis, as noted by the presence of apical shadowing and/or calcified mediastinal lymphadenopathy, and some had known contact with tuberculosis. The convenience of flow cytometry may have lost out to the specificity of the ELISpot. Should we use the new tests for latent tuberculosis in the examination of BAL fluid? The answer remains unclear, but the excitement is palpable. Many questions remain. Might sputum induction provide a similar sensitivity? Can the ELISA-based tests perform as well as the ELISpot assays? At last the investment made during the last decade may begin to pay dividends in the clinical management of patients with suspected tuberculosis. A, et al. Detection of tuberculostearic acid in serum and other biological fluids from patients with tuberculosis by electron-capture gas chromatography and chemical ionization mass spectrometry. Broad clonal heterogeneity of antigen-specific CD4+ T-cells localizing at the site of disease during tuberculosis. Highly focused T cell responses in latent human pulmonary Mycobacterium tuberculosis infection. Rapid diagnosis of smear-negative tuberculosis by bronchoalveolar lavage enzyme-linked immunospot. Comparison of two interferon-c assays and tuberculin skin test for tracing tuberculosis contacts. Median survival for patients with cystic fibrosis (CF) has improved steadily over the past several decades as a result …