Community assembly history is increasingly recognized as a fundamental determinant of community structure. However, little is known as to how assembly history may affect ecosystem functioning via its effect on community structure. Using wood-decaying fungi as a model system, we provide experimental evidence that large differences in ecosystem functioning can be caused by small differences in species immigration history during community assembly. Direct manipulation of early immigration history resulted in three-fold differences in fungal species richness and composition and, as a consequence, differences of the same magnitude in the rate of decomposition and carbon release from wood. These effects - which were attributable to the history-dependent outcome of competitive and facilitative interactions - were significant across a range of nitrogen availabilities observed in natural forests. Our results highlight the importance of considering assembly history in explaining ecosystem functioning.

et al. Ultrasound screening in pregnancy: a systematic review of the clinical effectiveness, cost-effectiveness and women's views. Health Technol Assess 2000;4(16). Health Technology Assessment is indexed in Index Medicus/MEDLINE and Excerpta Medica/EMBASE. Copies of the Executive Summaries are available from the NCCHTA website (see overleaf). NHS R&D HTA Programme T he overall aim of the NHS R&D Health Technology Assessment (HTA) programme is to ensure that high-quality research information on the costs, effectiveness and broader impact of health technologies is produced in the most efficient way for those who use, manage and work in the NHS. Research is undertaken in those areas where the evidence will lead to the greatest benefits to patients, either through improved patient outcomes or the most efficient use of NHS resources. The Standing Group on Health Technology advises on national priorities for health technology assessment. Six advisory panels assist the Standing Group in identifying and prioritising projects. These priorities are then considered by the HTA Commissioning Board supported by the National Coordinating Centre for HTA (NCCHTA). This report is one of a series covering acute care, diagnostics and imaging, methodology, pharmaceuticals, population screening, and primary and community care. It was identified as a priority by the Population Screening Panel and funded as project number 93/30/03. The views expressed in this publication are those of the authors and not necessarily those of the Standing Group, the Commissioning Board, the Panel members or the Department of Health. The editors wish to emphasise that funding and publication of this research by the NHS should not be taken as implicit support for the recommendations for policy contained herein. In particular, policy options in the area of screening will be considered by the National Screening Committee. This Committee, chaired by the Chief Medical Officer, will take into account the views expressed here, further available evidence and other relevant considerations. Reviews in Health Technology Assessment are termed 'systematic' when the account of the search, appraisal and synthesis methods (to minimise biases and random errors) would, in theory, permit the replication of the review by others. Criteria for inclusion in the HTA monograph series Reports are published in the HTA monograph series if (1) they have resulted from work either prioritised by the Standing Group on Health Technology, or otherwise commissioned for the HTA Programme, and (2) they are of a sufficiently high scientific quality as assessed by the referees and editors.

Background As those with HIV infection live longer, ‘non-AIDS’ condition associated with immunodeficiency and chronic inflammation are more common. We ask whether ‘non-HIV’ biomarkers improve differentiation of mortality risk among individuals initiating combination antiretroviral therapy (cART). Methods Using Poisson models, we analysed data from the Veterans Aging Cohort Study (VACS) on HIV-infected veterans initiating cART between 1 January 1997 and 1 August 2002. Measurements included: HIV biomarkers (CD4 cell count, HIV RNA and AIDS-defining conditions); ‘non-HIV’ biomarkers (haemoglobin, transaminases, platelets, creatinine, and hepatitis B and C serology); substance abuse or dependence (alcohol or drug); and age. Outcome was all cause mortality. We tested the discrimination (C statistics) of each biomarker group alone and in combination in development and validation data sets, over a range of survival intervals, and adjusting for missing data. Results Of veterans initiating cART, 9784 (72%) had complete data. Of these, 2566 died. Subjects were middle-aged (median age 45 years), mainly male (98%) and predominantly black (51%). HIV and ‘non-HIV’ markers were associated with each other (P<0.0001) and discriminated mortality (C statistics 0.68–0.73); when combined, discrimination improved (P<0.0001). Discrimination for the VACS Index was greater for shorter survival intervals [30-day C statistic 0.86, 95% confidence interval (CI) 0.80–0.91], but good for intervals of up to 8 years (C statistic 0.73, 95% CI 0.72–0.74). Results were robust to adjustment for missing data. Conclusions When added to HIV biomarkers, ‘non-HIV’ biomarkers improve differentiation of mortality. When evaluated over similar intervals, the VACS Index discriminates as well as other established indices. After further validation, the VACS Index may provide a useful, integrated risk assessment for management and research.

Summary.We investigated the impact of maternal and fetal variables on cord blood (CB) haemopoietic stem/progenitor cell content. These included maternal age, ethnic origin, parity, ABO and Rhesus D blood group, antenatal haemoglobin, alcohol and cigarette consumption at time of registration, mode of delivery, duration of the first and second stages of labour, gestational age, birth weight, cord pH and cord erythrocyte mean cell volume (MCV). Cord volumes and total nucleated cellularities (TNC) were recorded, the colony assay for granulocyte-macrophage colony-forming-cells (CFU-GM) was used to quantify the progenitor cells and the potential of CFU-GM to produce secondary colonies on replating was used as a measure of progenitor cell quality. We found: (1) significantly greater ( P ¼ 0·04) volumes were collected from babies who weighed у 2·5 kg versus babies with a birth weight < 2·5 kg; (2) significantly greater numbers of mononuclear cells (MNC) from mothers who drank 0-3 units versus those who drank у 4 units of alcohol weekly ( P ¼ 0·03), and in babies with a cord pH р 7·1 v > 7·1 ( P ¼ 0·02); (3) Significantly greater numbers of cord CFU-GM in mothers who drank 0-3 v у 4 units weekly ( P ¼ 0·004) and smokers of у 10 v 0-9 cigarettes daily ( P ¼ 0·02) and in spontaneous vaginal deliveries than assisted vaginal and caesarean deliveries ( P ¼ 0·04), and (4) the potential of CFU-GM to produce secondary colonies was significantly greater in CB derived from Caucasians than from non-Caucasians ( P ¼ 0·02); in assisted vaginal delivery v spontaneous vaginal ( P ¼ 0·02) and in deliveries with prolonged first stage of labour v short first stage of labour ( P ¼ 0·04). We conclude that antenatal and perinatal variables may influence the CB stem/ progenitor cell yield available for transplantation.Keywords: maternal factors, fetal factors, progenitor assays, AUC.Human cord blood (CB) is an alternative source of haemopoietic stem cells for clinical transplantation. Over 500 related and unrelated CB transplants have been undertaken, mostly in children. The availability of CB may shorten the period needed to search for an unrelated donor in the case of recipients who have no sibling donor. Rubinstein et al (1993) found that unrelated cord blood was available at a median of 69 d versus > 2·5 months for bone marrow. More recently, during a search for unrelated CB for 85 high-risk leukaemic patients (Gluckman, personal communication), potential donations were identified for 65/ 85 patients (76%) at a median of 4 d (range 0-586); of these 59 donations fully eligible for transplantation were identified for 34 patients (40%) after a median of 47 d (1-449).The contribution of CB to adult transplantation remains limited due to the restricted number of stem/ progenitor cells available in CB donations (Wagner et al,