Browsing by Author "Crampin, Amelia C."

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    Age-Specific Mortality Patterns in HIV-Infected Individuals: A Comparative Analysis of African Community Study Data
    (Aids, 2007) Zaba, Basia; Marston, Milly; Crampin, Amelia C.; Isingo, Raphael; Biraro, Sam; Ba¨rnighausen, Till; Lopman, Ben; Lutalo, Tom; Glynn, Judith R.; Todd, Jim
    Describe age-specific mortality patterns of HIV-infected adults in African communities before introduction of HAART.Mortality data (deaths and person-years observed) for HIV-positive subjects aged 15–65 from six African community studies in five different countries were pooled, combining information from 1793 seroconverters and 8534 HIV positive when first tested. Age-specific mortality hazards were modelled using parametric regression based on the Weibull distribution, to investigate effects of sex, and site-specific measures of mean age at incidence, crude mortality rate of uninfected, and measures of epidemic maturity.The combined studies yielded a total of 31 777 person-years of observation for HIV-positive subjects, during which time 2602 deaths were recorded. Mortality rates rose almost linearly with age, from below 50/1000 at ages < 20 years, up to 150/1000 at 50 years +. There was no significant difference between men and women in level or age pattern of mortality. Weibull regression analysis suggested that intersite variation could be explained by HIV prevalence trend, and by the ratio of HIV proportional mortality to current HIV prevalence. A model representation was constructed with a common age pattern of mortality, but allowing the level to be adjusted by specifying HIV prevalence indicators.The linear age trend of mortality in HIV-infected populations was satisfactorily represented by a Weibull function providing a parametric model adaptable for representing different levels of HIV-related mortality. This model might be simpler to use in demographic projections of HIV-affected populations than models based on survival post-infection.
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    Evaluation of cytokine responses against novel Mtb antigens as diagnostic markers for TB disease
    (Journal of Infection, 2016) Awoniyi, Dolapo O.; Teuchert, Andrea; Sutherland, Jayne S.; Mayanja-Kizza, Harriet; Howe, Rawleigh; Mihret, Adane; Loxton, Andre G.; Sheehama, Jacob; Kassa, Desta; Crampin, Amelia C.; Dockrell, Hazel M.; Kidd, Martin; Rosenkrands, Ida; Geluk, Annemieke; Ottenhoff, Tom H.M.; Chegou, Novel N.; Walzl, Gerhard
    We investigated the accuracy of host markers detected in Mtb antigenstimulated whole blood culture supernatant in the diagnosis of TB. Methods: Prospectively, blood from 322 individuals with presumed TB disease from six African sites was stimulated with four different Mtb antigens (Rv0081, Rv1284, ESAT-6/CFP-10, and Rv2034) in a 24 h whole blood stimulation assay (WBA). The concentrations of 42 host markers in the supernatants were measured using the Luminex multiplex platform. Diagnostic biosignatures were investigated through the use of multivariate analysis techniques. Results: 17% of the participants were HIV infected, 106 had active TB disease and in 216 TB was excluded. Unstimulated concentrations of CRP, SAA, ferritin and IP-10 had better discriminating ability than markers from stimulated samples. Accuracy of marker combinations by general discriminant analysis (GDA) identified a six analyte model with 77% accuracy for TB cases and 84% for non TB cases, with a better performance in HIV uninfected patients. Conclusions: A biosignature of 6 cytokines obtained after stimulation with four Mtb antigens has moderate potential as a diagnostic tool for pulmonary TB disease individuals and stimulated marker expression had no added value to unstimulated marker performance.