Metabolic theory and taxonomic identity predict nutrient recycling in a diverse food web.

Reconciling the degree to which ecological processes are generalizable among taxa and ecosystems, or contingent on the identity of interacting species, remains a critical challenge in ecology. Ecological stoichiometry (EST) and metabolic theory of ecology (MTE) are theoretical approaches used to evaluate how consumers mediate nutrient dynamics and energy flow through ecosystems. Recent theoretical work has explored the utility of these theories, but empirical tests in species-rich ecological communities remain scarce. Here we use an unprecedented dataset collected from fishes and dominant invertebrates (n = 900) in a diverse subtropical coastal marine community (50 families, 72 genera, 102 species; body mass range: 0.04-2,597 g) to test the utility of EST and MTE in predicting excretion rates of nitrogen (E(N)), phosphorus (E(P)), and their ratio (E(NP)). Body mass explained a large amount of the variation in EN and EP but not E(NP). Strong evidence in support of the MTE 3/4 allometric scaling coefficient was found for E(P), and for E(N) only after accounting for variation in excretion rates among taxa. In all cases, including taxonomy in models substantially improved model performance, highlighting the importance of species identity for this ecosystem function. Body nutrient content and trophic position explained little of the variation in E(N), E(P), or E(NP), indicating limited applicability of basic predictors of EST. These results highlight the overriding importance of MTE for predicting nutrient flow through organisms, but emphasize that these relationships still fall short of explaining the unique effects certain species can have on ecological processes.

Peer influence and physical activity behavior in young children: an experimental study.

BACKGROUND: There is evidence that the presence of a friend increases physical activity behavior in school-aged children (≥ 8 years old) and in young adolescents. Little is known about the developmental trajectory of the effects of peer influences on children's physical activity. Therefore, we sought to test the effect of the presence versus absence of a friend on physical activity in young children (≤ 6 years old). METHODS: Physical activity was assessed, via accelerometery, in 3- to 6-year-old children, during 2 social conditions: alone and in the presence of a friend. During each condition, children were taken to a gymnasium and had free access to physical and sedentary activities for 30 minutes. In one condition children were tested alone (solo play), whereas in the other they were tested in the presence of a friend who had access to the same activities. RESULTS: Children exhibited 54% greater (P < .02) average accelerometer counts during the friend condition (mean = 2629, SD = 1080 or 5.7 METs) than during the solo play condition (mean = 1707, SD = 1009 or 4.5 METs). CONCLUSIONS: The presence of a friend contributes to increased physical activity behavior in young children.

Stress myocardial perfusion imaging for the evaluation and triage of chest pain in the emergency department: a randomized controlled trial.

BACKGROUND: Patients with acute coronary syndrome (ACS) often present atypically. In a randomized controlled trial, we studied whether adding stress myocardial perfusion imaging (SMPI) to an evaluation strategy for emergency department (ED) patients presenting with chest pain more effectively identifies patients with ACS. METHODS: Participants were randomized to standard ED chest pain protocol (clinical assessment) or standard protocol supplemented with SMPI results. During 6 hours of electrocardiogram (ECG) monitoring and serial cardiac markers (creatine kinase-MB isoenzyme, troponin), participants developing ST segment changes or elevated cardiac markers were admitted. Those with a negative observation period underwent SMPI (N = 1,004) or clinical assessment (N = 504) based on randomization, and admitted if their SMPI scan was abnormal or senior clinicians found a high or intermediate risk for ACS. RESULTS: SMPI participants had a significantly lower admission rate than clinical assessment participants (10.16% vs 18.45%), with no significant between-group differences in risk of cardiac events (CEs) after 30 days (0.40% vs 0.79%) or 1 year (0.70% vs 0.99%). CONCLUSIONS: When added to a standard triage strategy incorporating clinical evaluation, serial ECGs, and cardiac markers, SMPI improved clinical decision making for chest pain patients, significantly reducing the need for hospitalization without an increase in adverse CE rates at 30 days or 1 year.

Implementing a laboratory automation system: experience of a large clinical laboratory.

Laboratories today face increasing pressure to automate their operations as they are challenged by a continuing increase in workload, need to reduce expenditure, and difficulties in recruitment of experienced technical staff. Was the implementation of a laboratory automation system (LAS) in the Clinical Biochemistry Laboratory at Singapore General Hospital successful? There is no simple answer, so the following topics comparing and contrasting pre- and post-LAS have been explored: turnaround time (TAT), laboratory errors, and staff satisfaction. The benefits and limitations of LAS from the laboratory experience were also reviewed. The mean TAT for both stat and routine samples decreased post-LAS (30% and 13.4%, respectively). In the 90th percentile TAT chart, a 29% reduction was seen in the processing of stat samples on the LAS. However, no significant difference in the 90th percentile TAT was observed with routine samples. It was surprising to note that laboratory errors increased post-LAS. Considerable effort was needed to overcome the initial difficulties associated with adjusting to a new system, new software, and new working procedures. Although some of the known advantages and limitations of LAS have been validated, the claimed benefits such as improvements in TAT, laboratory errors, and staff morale were not evident in the initial months.

Maltose interference-free test strips for blood glucose testing at point-of-care: a laboratory performance evaluation.

BACKGROUND: Maltose interference is a concern with blood glucose testing at point-of-care. We evaluated a maltose interference-free test strip (with a modified recombinant glucose dehydrogenase-pyrroloquinoline quinone system) for the Accu-Chek(®) Performa glucose meter (Roche Diagnostics, Mannheim, Germany). METHODS: Blood specimens (n = 120) sent for clinical laboratory glucose testing were used in assessing performance characteristics, including imprecision, linearity, clinical impact analysis, and method comparison, of the test strips. To evaluate sugar interference, two heparinized blood specimens were spiked with maltose, xylose, and galactose (up to 500 mg/dL) followed by testing with modified Performa, Accutrend(®) (Roche Diagnostics), and Advantage II (Roche Diagnostics) test strips and by the laboratory method. RESULTS: Test strips demonstrated total laboratory coefficients of variation of <7%; within-run coefficients of variation were 2.7-5.4% for blood glucose at 2.5-19.7 mmol/L. Clarke Error Grid analysis of the 120 results (0.8-27.6 mmol/L) showed all values to be within critical clinical limits. Comparison with laboratory results gave 0.960 correlation (Spearman's r(2)) with a Deming regression y (Performa) = 0.95x (laboratory) - 0.11 mmol/L (SEy|x0.06 mmol/L). A slight negative bias (-0.5 mmol/L) was demonstrated with the Bland-Altman difference plot. Maltose (up to 13.9 mmol/L) and xylose (33.3 mmol/L) had no effect, but galactose (2.2 mmol/L) showed interference. The sugars also affected test strips for Advantage II but not Accutrend glucose meters. With International Organization for Standardization ISO 15197:2003 criteria, 99% of the 120 results determined by the test strips were within the minimal acceptable performance; only one of 106 (5.9 mmol/L) was >20% from the laboratory result. CONCLUSIONS: The modified and improved Performa test strips were not affected by maltose and xylose. They meet ISO 15197:2003 requirements with a slight bias (-0.5 mmol/L) compared to the laboratory method.

Haemoglobin A1c: evaluation of a new HbA1c point-of-care analyser Bio-Rad in2it in comparison with the DCA 2000 and central laboratory analysers.

BACKGROUND: Point-of-care-testing (POCT) of haemoglobin Alc (HbA1c) is popular due to its fast turnaround of results in the outpatient setting. The aim of this project was to evaluate the performance of a new HbA1c POCT analyser, the Bio-Rad in2it, and compare it with the Siemens DCA 2000, Bio-Rad Variant II and Roche Tina-quant HbA1c Gen 2 assay on the cobas c501. METHODS: Imprecision of the four methods were compared by computing total imprecision from within-run and between-run data. A total of 80 samples were also compared and analysed by Deming regression and Altman-Bland difference test. RESULTS: Study of total imprecision of the in2it at HBA1c levels of 6.0% and 10.4% produced a coefficient of variation (%CV) of 3.8% and 3.7%, respectively. These results were more favourable as compared with the DCA 2000 but did not match the low imprecision of the central laboratory methods, the Bio-Rad Variant II and the Roche cobas c501. Comparison between the in2it and the central laboratory analysers, Bio-Rad variant II and cobas c501, revealed positive bias of 12% and 10%, respectively, supported by corresponding Deming regression equation slopes of +1.18 and +1.14. Comparison between the DCA 2000 and the central laboratory analysers revealed a bias that became increasingly positive with rising HbA1c concentrations with Deming regression analysis also revealing proportional and constant differences. CONCLUSIONS: The in2it is a suitable POCT analyser for HbA1c but its less than ideal precision performance and differences with the central laboratory analysers must be communicated to and noted by the users.

Role of procalcitonin in infectious gastroenteritis and inflammatory bowel disease.

BACKGROUND AND AIM: We have evaluated procalcitonin (PCT) as a diagnostic marker for bacterial gastroenteritis (GE) and as a disease activity marker in inflammatory bowel disease (IBD) patients. METHODS: This was a prospective single-center study performed over a 1-year period. Venous blood samples were drawn from hospitalized patients with acute GE and tested for PCT, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and total white cell count (TWC); stools from the same patients were tested for standard pathogens. Venous blood samples from patients with IBD were tested for PCT, CRP, ESR, and platelet count. The PCT level was measured using an immunofluorescent assay, with normal being defined as <0.5 ng/ml. RESULTS: The GE arm of study consisted of 81 patients, 18.5% of whom were diagnosed with bacterial GE. The PCT and CRP levels were good diagnostic markers of bacterial GE, with an area under the curve (AUC) of 0.727 [95% confidence interval (CI) 0.580-0.874] and 0.786 (95% CI 0.627-0.946), respectively. An elevated PCT > or =0.5 ng/ml was associated with a 13-fold increased risk of renal impairment. The IBD arm of study consisted of 72 IBD patients. The PCT levels were not significantly different between active and inactive IBD in this patient cohort. CONCLUSION: Our results indicate that PCT and CRP are comparably good diagnostic markers of bacterial GE but that PCT is not useful as in monitoring disease activity in patients with IBD.