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Background: Confirmation of pulmonary tuberculosis (PTB) in young children is difficult as they seldom expectorate sputum. Aim: To compare sputa obtained by nasopharyngeal aspiration and by sputum induction for staining and culture of Mycobacterium tuberculosis. Patients and methods: Patients from Mulago Hospital, Kampala with symptoms suggestive of PTB were considered for inclusion in the study. Those with a positive tuberculin test and/or a chest radiograph compatible with tuberculosis were recruited. Infection with human immunodeficiency virus (HIV) was confirmed by duplicate enzyme-labelled immunosorbent assay or in children ,15 months by polymerase chain reaction (PCR). Direct PCR was undertaken on 82 nasopharyngeal aspirates. Results: Of 438 patients referred, 94 were recruited over a period of 5 months. Median (range) age was 48 (4-144) months. Of 63 patients tested, 69.8% were infected with HIV. Paired and uncontaminated culture results were available for 88 patients and smear results for 94 patients. Nasopharyngeal aspirates were smear-positive in 8.5% and culture-positive in 23.9%. Induced sputa were smear-positive in 9.6% and culture positive in 21.6%. Overall, 10.6% were smear-positive, 25.5% were culture-positive and 26.6% had smear and/or culture confirmed tuberculosis. Direct PCR on nasopharyngeal aspirates had a sensitivity of 62% and specificity of 98% for confirmation of culture-positive tuberculosis. Conclusions: Nasopharyngeal aspiration is a useful, safe and low-technology method for confirmation of PTB and, like sputum induction, can be undertaken in outpatient clinics.T he diagnosis of pulmonary tuberculosis (PTB) in young children is usually based on contact history, positive tuberculin test and compatible chest radiography. However, confirmation of tuberculosis by culture is important where, for example, there is difficulty in clinical diagnosis, the contact history is not known or drug sensitivities are not available. In developing countries the diagnosis of PTB is particularly difficult as the contact history is often not clear (especially where tuberculosis/human immunodeficiency virus (HIV) co-infection in the household is common) and the tuberculin test is often falsely negative. Chest radiography may be difficult to interpret, especially when there is HIV-related pulmonary disease such as lymphocytic interstitial pneumonitis (LIP). Obtaining sputum in young children who are unable to expectorate is problematic. Gastric aspiration usually requires a child to be admitted for up to 3 days and has to be undertaken in the early morning while the child is recumbent and fasted overnight.3 Alternative methods include sputum induction (SI), 4 5 laryngeal swab (LS) 6 7 and nasopharyngeal aspiration (NPA).8 9 This study aimed to compare the value of NPA with SI for confirmation of PTB. METHODSThe study was undertaken at Mulago Hospital, Kampala during the period January to June 2004. A diagnostic room was set up for SI, NPA and tuberculin testing, organised by a dedicated paediatrician, a nur...

a b s t r a c t a r t i c l e i n f oMany coastal and estuarine environments are dominated by mixtures of non-cohesive sand and cohesive mud. The migration rate of bedforms, such as ripples and dunes, in these environments is important in determining bed material transport rates to inform and assess numerical models of sediment transport and geomorphology. However, these models tend to ignore parameters describing the physical and biological cohesion (resulting from clay and extracellular polymeric substances, EPS) in natural mixed sediment, largely because of a scarcity of relevant laboratory and field data. To address this gap in knowledge, data were collected on intertidal flats over a spring-neap cycle to determine the bed material transport rates of bedforms in biologically-active mixed sand-mud. Bed cohesive composition changed from below 2 vol% up to 5.4 vol% cohesive clay, as the tide progressed from spring towards neap. The amount of EPS in the bed sediment was found to vary linearly with the clay content. Using multiple linear regression, the transport rate was found to depend on the Shields stress parameter and the bed cohesive clay content. The transport rates decreased with increasing cohesive clay and EPS content, when these contents were below 2.8 vol% and 0.05 wt%, respectively. Above these limits, bedform migration and bed material transport was not detectable by the instruments in the study area. These limits are consistent with recently conducted sand-clay and sand-EPS laboratory experiments on bedform development. This work has important implications for the circumstances under which existing sand-only bedform migration transport formulae may be applied in a mixed sand-clay environment, particularly as 2.8 vol% cohesive clay is well within the commonly adopted definition of "clean sand".