Background: Reduction of immunosuppression (IS) upon detection of Polyomavirus (BK) viremia is widely used to prevent BK virus nephropathy. This retrospective casecontrol study assesses the frequency of de novo donor-specific antibodies (dnDSA) in renal transplant recipients with IS modulation due to BK viremia and the associated risk of antibody mediated rejection. Methods: Our cohort included recipients of kidney transplantation between 2007 and 2017 with clinical, HLA antibody, and biopsy data. BK positivity was defined as viremia >10 000 c/ml or biopsy proven BK nephropathy. A total of 190 BK cases matched our inclusion criteria, each case was matched with two controls based on gender, donor type, and transplant within 1 year (N = 396).Results: Despite lower number of HLA antigen mismatches (mean = 3.5 vs. 4.4, p < .001), dnDSA rates were higher in BK cases than in control group (22.1% vs. 13.9%, p = .02), with the majority detected following IS reduction for BK infection, and arising earlier posttransplant compared with no BK infection (294d vs. 434d, p < .001). Antibody mediated rejection rates were similar between cases and controls (8.9% and 8.3%, respectively), but rejection was more likely to occur earlier posttransplant in the BK cases (354d vs. 602d, p = .03). Conclusion:Our data suggest a link between IS reduction and the generation of dnDSA and/or rejection, supporting close monitoring for DSA in patients with reduced IS due to BK infection given their increased risk to develop dnDSA.

Objectives Evaluate the impact on 30-day mortality of early use of corticosteroids in patients with COVID-19 with supplementary oxygen requirements and without invasive mechanical ventilation at the initiation of therapy. Methods Between April 15 th and July 15 th , 2020, all hospitalized patients with COVID-19 and oxygen requirements were prospectively included in a database. Patients who died or required intubation within the first 48 hours were excluded. Patients who received corticoids within the first 5 days of hospitalization and at least 24 hours prior to intubation were considered as in “early corticosteroids group.” To compare both populations and adjust for non-random treatment assignment bias a weight adjusted propensity score model was used. Results 571 patients met the inclusion criteria, 520 had sufficient information for the analysis. Of these, 233 received early corticosteroids and 287 did not. After the analysis, a reduction of 8.5% (p = 0.038) in 30 -day mortality was observed in the early corticosteroid group. The reduction in mortality was nonsignificant when patients with corticosteroid initiation between day 5 and day 8 of hospitalization were included. Conclusion Early corticosteroid use in patients with pneumonia due to COVID-19 and supplementary oxygen requirements without invasive mechanical ventilation reduces mortality.

Introduction: Tuberculosis (TB) is one of the most prevalent respiratory diseases in the world. In 2020 there were at least 9.9 million new infections, with 1.5 million deaths. Approximately 10% of people infected with Mycobacterium tuberculosis (LTBI) develop the disease during the first 2 to 5 years after infection. Currently in South America, the diagnosis of LTBI continues to be per-formed through the Mantoux tuberculin skin test (TST). Objective: The objective of our study was to compare the sensitivity of a new immunofluorescence IGRA test against a widely available IGRA kit on the market. Material and method: Close contact to infectious patients with TB, or HIV patients or immunocompromised for another cause were recruited. Two interferon gamma release assay (IGRA) diagnostic kits were used and compared with TST. Results: 76 patients were recruited. 93.42% were Chilean nationality, 98.68% of the patients did not have immunosuppres-sion. The sensitivity of the new technique was 88.89% and specificity 92.50% in the study popula-tion compared to the IGRA previously used. In the subgroup older than 36 years, the sensitivity was 95.65% and the specificity 89.47%. Conclusion: IGRA techniques are a new resource in clini-cal laboratories to be able to make an accurate diagnosis in LTBI in the region of the Americas. In our population, the greatest benefit of this new IGRA would be observed in people over 36 years of age, where the sensitivity of the technique was like that of the currently available test.

Introduction: Tuberculosis (TB) is one of the most prevalent respiratory diseases in the world. In 2020 there were at least 9.9 million new infections, with 1.5 million deaths. Approximately 10% of people infected with Mycobacterium tuberculosis develop the disease during the first 2 to 5 years after infection. In South America, the diagnosis of Latent Tuberculosis Infections (LTBI) continues to be performed through the Mantoux tuberculin skin test (TST). Objective: The objective of our study was to compare the sensitivity of a new immunofluorescence IGRA test against a widely available IGRA kit on the market. Material and method: Close contact with infectious TB patients, HIV patients, or immunocompromised for another cause were recruited. Two interferon-gamma release assay (IGRA) diagnostic kits were used and compared with TST. Results: 76 patients were recruited, 93.42% were Chilean nationality, and 98.68% of the patients did not have immunosuppression. The sensitivity of the new technique was 88.89%, and the specificity was 92.50% in the study population compared to the IGRA previously used. In the subgroup older than 36 years, the sensitivity was 95.65%, and the specificity was 89.47%. Conclusion: IGRA techniques are a new resource in clinical laboratories to make an accurate diagnosis of LTBI in the region of the Americas. In our population, the greatest benefit of this new IGRA would be observed in people over 36 years of age, where the sensitivity of the technique was like that of the currently available test.