On the application of rainfall projections from a convection-permitting climate model to lumped catchment models

Climate change is predicted to increase rainfall intensity in tropical regions. Convection permitting (CP) climate models have been developed to address deficiencies in conventional climate models that use parameterised convection. However, to date, precipitation projections from CP climate models have not been used in conjunction with hydrological models to explore potential impacts of explicit modelling of convective rainfall on river flows in the tropics. Here we apply the outputs of a continental scale CP climate model as inputs to lumped rainfall-runoff models in Africa for the first time. Applied to five catchments in the Lake Victoria Basin, we show that the CP climate model produces greater river flows than an equivalent model using parameterised convection in both the current and future (c. 2100) climate. However, the location of the catchments near to Lake Victoria results in limited changes in extreme rainfall and river flows relative to changes in mean rainfall and river flows. Application of CP model rainfall data from an area where rainfall extremes change more than the change in mean rainfall to the rainfall-runoff model does not result in significant changes in river flows. Instead, this is shown to be a result of the rainfall-runoff model structure and parameterisation, which we posit is due to large-scale storage in the catchments associated with wetland cover, that buffers the impact of rainfall extremes. Based on an assessment of hydrological attributes (wetland coverage, water table depth, topography, precipitation, evapotranspiration and river flow) using global-scale datasets for the catchments in this research, this buffering may be extensive across humid regions. Application of CP climate model data to lumped catchment models in these areas are unlikely to result in significant increases in extreme river flows relative to increases in mean flows

Accuracy of Xpert Ultra in the diagnosis of pulmonary tuberculosis among children in Uganda: a sub-study from the SHINE trial

Background: Childhood tuberculosis presents significant diagnostic challenges associated with paucibacillary disease, and requires a more sensitive test. We evaluated the diagnostic accuracy of XpertMTB/Rif Ultra (Ultra) compared to other microbiological tests using respiratory samples from Ugandan children in the SHINE trial.Design/Methods: SHINE is a randomized trial evaluating shorter treatment in 1204 children with minimal TB disease in Africa/India. Among 352 samples and one cervical lymph node fine needle aspirate, one sample was randomly selected per patient and tested with Xpert MTB/Rif (Xpert), Lowenstein Jensen (LJ) and liquid (MGIT) cultures. We selected only uncontaminated stored sample pellet for Ultra testing. We estimated sensitivity of Xpert and Ultra against culture and a composite microbiological reference standard (any positive result).Results: Of 398 children, 353 (89%) had culture, Xpert and Ultra results. Median age was 2.8-years (IQR 1.3-5.3); 8.5% (30/353) HIV-infected, 54.4% (192/353) male. 31/353 (9%) were positive by LJ and/or MGIT; 36 (10%) by Ultra and 16 (5%) by Xpert. Sensitivities were (%; 95% CI), 58% (39-65% (18/31)) for Ultra and 45% (27-64% (14/31)) for Xpert against any culture-positive, with false-positives of <1% and 5.5% for Xpert and Ultra. Against a composite microbiological reference, sensitives were 72% (58-84% (36/50) for Ultra, and 32% (20-47% (16/50)) for Xpert. However, there were 17 samples that are positive only on Ultra (majority trace).Conclusions: Among children screened for minimal TB in Uganda, Ultra has higher sensitivity than Xpert. This represents an important advance for a condition which has posed a diagnostic challenge for decades