Value of the tuberculin skin testing and of an interferon-gamma release assay in haemodialysis patients after exposure to M. tuberculosis.

BACKGROUND: Patients with end-stage renal disease (ESRD) and Mycobacterium tuberculosis infection pose a high risk of developing active TB disease. It is therefore important to detect latent TB infection (LTBI) to be able to offer treatment and prevent progression to TB disease. We assessed the value of the tuberculin skin test (TST) and of an interferon-gamma release assay (Quantiferon®-TB Gold in-Tube, QFT) for diagnosing LTBI in ESRD patients, after prolonged exposure to a highly contagious TB case in a haemodialysis unit. As a high number of patients presented erythema without induration in the TST response, this type of reaction was also analysed. METHOD: The TST and QFT were simultaneously performed twelve weeks after the last possible exposure to a bacilliferous TB patient. If the first TST (TST-1) was negative, a second TST (TST-2) was performed 15 days later to detect a booster response. A comparison was made between the TST responses (including those cases with erythema without induration) and those for the QFT. The correlation with risk of infection and the concordance between tests were both analysed. RESULTS: A total of 52 patients fulfilled the inclusion criteria. Overall, 11 patients (21.2%) had a positive TST response: 3 for TST-1 and 8 for TST-2, and 18 patients (34.6%) showed a positive QFT response (p = 0.065). Erythema without induration was found in 3 patients at TST-1 and in a further 9 patients at TST-2. The three patients with erythema without induration in TST-1 had a positive TST-2 response. Concordance between TST and QFT was weak for TST-1 (κ = 0.21); it was moderate for overall TST (κ = 0.49); and it was strong if both induration and erythema (κ = 0.67) were considered. CONCLUSIONS: In patients with ESRD, erythema without induration in the TST response could potentially be an indicator of M. tuberculosis infection. The QFT shows better accuracy for LTBI diagnosis than the TST.

Ultrapure dialysate and inflammatory response in haemodialysis evaluated by darbepoetin requirements--a randomized study.

BACKGROUND: Dialysate quality has been suggested to influence inflammation status in patients subject to haemodialysis (HD). The aim of this study was to compare ultrapure dialysate (UPD) vs conventional dialysate (CD) with respect to darbepoetin requirements and other inflammation markers. METHODS: A controlled prospective randomized study was carried out on 78 patients from two HD units who were treated with low-flux polyamide dialysers. Patients were assigned to two groups by using different sized blocks per unit and dialysis session. One group received CD treatment while the other was treated with UPD over 12 months. From the groups, 37 patients started treatment with CD and 41 with UPD while 31 patients ended with CD and 30 with UPD. The main variables analysed were haemoglobin (Hb) and darbepoetin dose; other variables studied were C-reactive protein (CRP), albumin, interleukin-6 (IL-6) and interleukin-1 receptor antagonist (IL-1Ra). RESULTS: No significant differences were observed between the two groups for the variables analysed. At the beginning of the study the following values of CD and UPD were assessed: Hb 11.3 and 11.3 (g/dl); darbepoetin dose: 0.49 and 0.44 (microg/kg/week); CRP: 13 and 24 (mg/l); albumin: 3.8 and 3.7 (g/dl); IL-6: 5.94 and 4.18; and IL-1Ra: 345 and 420 (ng/l), respectively. At the end of the study the values of CD and UPD were: Hb 12 and 11.9 (g/dl); darbepoetin dose: 0.47 and 0.48 (microg/kg/week); CRP: 14 and 14 (mg/l); albumin: 3.8 and 3.7 (g/dl); IL-6: 14.03 and 12.93 and IL-1Ra: 322 and 340 (ng/l). CONCLUSIONS: UPD does not improve the inflammatory status evaluated by darbepoetin requirements in conventional HD patients treated with low-flux polyamide dialyser. Further controlled studies are required to evaluate the clinical influence of UPD in HD with other low- and high-flux membranes.