Latent and subclinical tuberculosis in HIV infected patients: a cross-sectional study.

BACKGROUND: HIV and tuberculosis (TB) are commonly associated. Identifying latent and asymptomatic tuberculosis infection in HIV-positive patients is important in preventing death and morbidity associated with active TB. METHODS: Cross-sectional study of one time use of an interferon-gamma release assay (T-SPOT.TB - immunospot) to detect tuberculosis infection in patients in a UK inner city HIV clinic with a large sub-Saharan population. RESULTS: 542 patient samples from 520 patients who disclosed their symptoms of TB were tested. Median follow-up was 35 months (range 27-69). More than half (55%) originated from countries with medium or high tuberculosis burden and 57% were women. Antiretroviral therapy was used by 67%; median CD4 count at test was 458 cells/µl. A negative test was found in 452 samples and an indeterminate results in 40 (7.4%) but neither were associated with a low CD4 count. A positive test was found in 10% (50/502) individuals. All patients with positive tests were referred to the TB specialist, 47 (94%) had a chest radiograph and 46 (92%) attended the TB clinic. Two had culture-positive TB and a third individual with features of active TB was treated. 40 started and 38 completed preventive treatment. One patient who completed preventive treatment with isoniazid monotherapy subsequently developed isoniazid-resistant pulmonary tuberculosis. No patient with a negative test has developed TB. CONCLUSIONS: We found an overall prevalence of latent TB infection of 10% through screening for TB in those with HIV infection and without symptoms, and a further 1% with active disease, a yield greater than typically found in contact tracing. Acceptability of preventive treatment was high with 85% of those with latent TB infection eventually completing their TB chemotherapy regimens. IGRA-based TB screening among HIV-infected individuals was feasible in the clinical setting and assisted with appropriate management (including preventive treatment and therapy for active disease). Follow-up of TB incidence in this group is needed to assess the long-term effects of preventive treatment.

Limited added value of T-SPOT.TB blood test in diagnosing active TB: a prospective bayesian analysis.

OBJECTIVES: To determine the diagnostic value of a blood interferon-gamma release assay in suspected active tuberculosis (TB). METHODS: 136 subjects with suspected pulmonary TB (pTB) at a single London centre with intermediate TB incidence, were clinically graded into low (<25%), medium, or high (>75%) likelihood of active pTB and then tested by T-SPOT®.TB assay. The diagnosis was confirmed by culture (n = 33), treatment response (n = 13) or a firm alternative diagnosis (n = 90). RESULTS: Overall, the T-SPOT.TB sensitivity was 74% (95% confidence intervals 60-84%), positive predictive value (PPV) 56% (43-68%), negative predictive value (NPV) 83% (71-90%), positive likelihood ratio (PLR) 1.75 and negative likelihood ratio (NLR) 0.45. Results for high pTB likelihood subjects: PPV 100%, NPV 25% (7-60%), PLR >69, NLR 0.31. Results for intermediate pTB likelihood subjects: PPV 67% (41-85%), NPV 88% (65-96%), PLR 2.39, NLR 0.26. Results for low pTB likelihood subjects: PPV 15% (6-34%), NPV 92% (79-97%), PLR 1.23, NLR 0.80. False negatives occurred in 24% of cases of active tuberculosis (4 smear and culture-positive, 3 smear negative and culture-positive, and 4 culture negative). CONCLUSIONS: The predictive values and likelihood ratios show the T-SPOT.TB test does not assist in confidently confirming or excluding active TB, regardless of the pre-test probability of disease.

Adverse reactions to voriconazole.

Voriconazole is a new antifungal agent effective in the treatment of invasive aspergillosis. Interpatient variation in plasma concentrations is considerable--more than 100-fold. We describe 3 patients with diverse manifestations of toxicity (e.g., hallucinations, hypoglycemia, electrolyte disturbance, and pneumonitis) possibly attributable to high voriconazole concentrations. Measurement of plasma concentrations could be helpful in optimizing voriconazole dosages.

Nanosecond dynamics of acetylcholinesterase near the active center gorge.

To delineate the role of peptide backbone flexibility and rapid molecular motion in acetylcholinesterase catalysis and inhibitor association, we investigated the decay of fluorescence anisotropy at three sites of fluorescein conjugation to cysteine-substitution mutants of the enzyme. One cysteine was placed in a loop at the peripheral site near the rim of the active center gorge (H287C); a second was in a helical region outside of the active center gorge (T249C); a third was at the tip of a small, flexible omega loop well separated from the gorge (A262C). Mutation and fluorophore conjugation did not appreciably alter catalytic or inhibitor binding parameters of the enzyme. The results show that each site examined was associated with a high degree of segmental motion; however, the A262C and H287C sites were significantly more flexible than the T249C site. Association of the active center inhibitor, tacrine, and the peripheral site peptide inhibitor, fasciculin, had no effect on the anisotropy decay of fluorophores at positions 249 and 262. Fasciculin, but not tacrine, on the other hand, dramatically altered the decay profile of the fluorophore at the 287 position, in a manner consistent with fasciculin reducing the segmental motion of the peptide chain in this local region. The results suggest that the motions of residues near the active center gorge and across from the Cys(69)-Cys(96) omega loop are uncoupled and that ligand binding at the active center or the peripheral site does not influence acetylcholinesterase conformational dynamics globally, but induces primarily domain localized decreases in flexibility proximal to the bound ligand.

Hypotonicity induces TRPV4-mediated nociception in rat.

We hypothesized that TRPV4, a member of the transient receptor family of ion channels, functions as a sensory transducer for osmotic stimulus-induced nociception. We found that, as expected for a transducer molecule, TRPV4 protein is transported in sensory nerve distally toward the peripheral nerve endings. In vivo single-fiber recordings in rat showed that hypotonic solution activated 54% of C-fibers, an effect enhanced by the hyperalgesic inflammatory mediator prostaglandin E2. This osmotransduction causes nociception, since administration of a small osmotic stimulus into skin sensitized by PGE2 produced pain-related behavior. Antisense-induced decrease in expression of TRPV4 confirmed that the channel is required for hypotonic stimulus-induced nociception. Thus, we conclude that TRPV4 can function as an osmo-transducer in primary afferent nociceptive nerve fibers. Because this action is enhanced by an inflammatory mediator, TRPV4 may be important in pathological states and may be an attractive pharmacological target for the development of novel analgesics.