Estimating Sensitivity of Laboratory Testing for Influenza in Canada through Modelling

Background: The weekly proportion of laboratory tests that are positive for influenza is used in public health surveillance systems to identify periods of influenza activity. We aimed to estimate the sensitivity of influenza testing in Canada based on results of a national respiratory virus surveillance system. Methods and Findings: The weekly number of influenza-negative tests from 1999 to 2006 was modelled as a function of laboratory-confirmed positive tests for influenza, respiratory syncytial virus (RSV), adenovirus and parainfluenza viruses, seasonality, and trend using Poisson regression. Sensitivity was calculated as the number of influenza positive tests divided by the number of influenza positive tests plus the model-estimated number of false negative tests. The sensitivity of influenza testing was estimated to be 33 % (95%CI 32–34%), varying from 30–40 % depending on the season and region. Conclusions: The estimated sensitivity of influenza tests reported to this national laboratory surveillance system is considerably less than reported test characteristics for most laboratory tests. A number of factors may explain this difference, including sample quality and specimen procurement issues as well as test characteristics. Improved diagnosis would permit better estimation of the burden of influenza

Risk Factors for Breakthrough Pneumocystis carinii Pneumonia on Aerosol Pentamidine Prophylaxis

OBJECTIVE: To identify baseline characteristics of human immunodeficiency virus (HIV)-infected individuals on aerosol pentamidine for Pneumocystis carinii prophylaxis that are predictive of subsequent breakthrough Pneumocystis carinii pneumonia (PCP).DESIGN: Nested case-control study assembled from a cohort of patients enrolled in the Toronto aerosol pentamidine program.METHODS: Subjects were selected from a cohort of HIV-infected individuals were enrolled in a community based aerosol pentamidine program between May 1989 and May 1992 in Toronto, Ontario. Cases - individuals who had breakthrough PCP - were matched with up to two controls enrolled in the same week. Risk factors examined for development of PCP for both primary and secondary prophylaxisincluded age, sex, smoking history, evidence of bronchospasm during aerosol pentamidine administration (fall of forced expiratory volume [FEV] 15% or more), administration of salbutamol before aerosol pentamidine, pulmonary function tests including lung volumes, flow rates and diffusing capacity for carbon monoxide. In the primary prophylaxis group, CD4 count at enrolment and in the secondary prophylaxis group, time from the most recent episode of PCP to enrolment for aerosol pentamidine and total time from the most recent episode of PCP to breakthrough PCP were examined as additional risk factors.RESULTS: A total or 1344 patients we re enrolled in the aerosol pentamidine program, 78% for primary prophylaxis and 22% for secondary prophylaxis. At the time of census at the end or 1992 there had been 96 episodes or breakthrough PCP, 5% on primary prophylaxis and 14.5% on secondary prophylaxis. In the primary prophylaxis group, enrolment CD4 count was significantly lower in the cases developing breakthrough PCP: 116±74 compared with 175±85 cells/mm3 in the control group (P=0.001). There was no difference in any other variable. In the secondaryprophylaxis group, time from the most recent episode of PCP to initiation of aerosol pentamidine therapy was longer in the cases developing breakthrough PCP: mean delay 6.1±6.6 months compared with 3.1±2.1 in controls (P=0.02). There was no difference in the other variables examined.CONCLUSIONS: The results of this study support immune augmentation for patients receiving aerosol pentamidine for primary prophylaxis, and aerosol pentamidine should be recommenced as soon as possible following an episode of PCP, for secondary prophylaxis.Peer Reviewe

Risk of End-Stage Renal Disease in HIV-Positive Potential Live Kidney Donors.

New federal regulations allow HIV-positive individuals to be live kidney donors; however, potential candidacy for donation is poorly understood given the increased risk of end-stage renal disease (ESRD) associated with HIV infection. To better understand this risk, we compared the incidence of ESRD among 41 968 HIV-positive participants of North America AIDS Cohort Collaboration on Research and Design followed for a median of 5 years with the incidence of ESRD among comparable HIV-negative participants of National Health and Nutrition Examination III followed for a median of 14 years. We used risk associations from multivariable Cox proportional hazards regression to derive cumulative incidence estimates for selected HIV-positive scenarios (no history of diabetes, hypertension, AIDS, or hepatitis C virus coinfection) and compared these estimates with those from similarly selected HIV-negative scenarios. For 40-year-old HIV-positive individuals with health characteristics that were similar to those of age-matched kidney donors, viral load <400 copies/mL, and CD4+ count ≥500 cells/μL, the 9-year cumulative incidence of ESRD was higher than that of their HIV-negative peers, yet still low: 2.5 versus 1.1 per 10 000 among white women, 3.0 versus 1.3 per 10 000 among white men, 13.2 versus 3.6 per 10 000 among black women, and 15.8 versus 4.4 per 10 000 among black men. HIV-positive individuals with no comorbidities and well-controlled disease may be considered low-risk kidney donor candidates