scholarly journals Sensitivity of discrete symmetry metrics: implications for metric choice

2021 ◽  
Author(s):  
Allen D Hill ◽  
Julie Nantel
Keyword(s):  
Statistical Power ◽  
Discrete Symmetry ◽  
Absolute Value ◽  
Future Studies ◽  
Group Condition ◽  
Power Simulation ◽  
Asymmetric Data ◽  
Increased Sensitivity ◽  
Low Sensitivity ◽  
Bilateral Difference

Gait asymmetry is present in several pathological populations, including those with Parkinson's disease, Huntington's disease, and stroke survivors. Previous studies suggest that commonly used discrete symmetry metrics, which compare single bilateral variables, may not be equally sensitive to underlying effects of asymmetry, and the use of a metric with low sensitivity could result in unnecessarily low statistical power. The purpose of this study was to provide a comprehensive assessment of the sensitivity of commonly used discrete symmetry metrics to better inform design of future studies. Monte Carlo simulations were used to estimate the statistical power of each symmetry metric at a range of asymmetry magnitudes, group/condition variabilities, and sample sizes. Power was estimated by repeated comparison of simulated symmetric and asymmetric data with a paired t-test, where the proportion of significant results is equivalent to the power. Simulation results confirmed that not all common discrete symmetry metrics are equally sensitive to reference effects of asymmetry. Multiple symmetry metrics exhibit equivalent sensitivities, but the most sensitive discrete symmetry metric in all cases is a bilateral difference (e.g. left - right). A ratio (e.g. left/right) has poor sensitivity when group/condition variability is not small, but a log-transformation produces increased sensitivity. Additionally, two metrics which included an absolute value in their definitions showed increased sensitivity when the absolute value was removed. Future studies should consider metric sensitivity when designing analyses to reduce the possibility of underpowered research.

scholarly journals Detecting Consensus Emergence in Organizational Multilevel Data: Power Simulations

2019 ◽  
pp. 109442811987395
Author(s):  
Jonas W. B. Lang ◽  
Paul D. Bliese ◽  
J. Malte Runge
Keyword(s):  
Sample Size ◽  
Multilevel Model ◽  
Statistical Power ◽  
Field Data ◽  
Multilevel Methods ◽  
Multilevel Data ◽  
Moderating Effects ◽  
Organizational Research ◽  
Future Studies ◽  
Power Simulation

Theories suggest that groups within organizations often develop shared values, beliefs, affect, behaviors, or agreed-on routines; however, researchers rarely study predictors of consensus emergence over time. Recently, a multilevel-methods approach for detecting and studying emergence in organizational field data has been described. This approach—the consensus emergence model—builds on an extended three-level multilevel model. Researchers planning future studies based on the consensus emergence model need to consider (a) sample size characteristics required to detect emergence effects with satisfactory statistical power and (b) how the distribution of the overall sample size across the levels of the multilevel model influences power. We systematically address both issues by conducting a power simulation for detecting main and moderating effects involving consensus emergence under a variety of typical research scenarios and provide an R-based tool that readers can use to estimate power. Our discussion focuses on the future use and development of multilevel methods for studying emergence in organizational research.

The Peguero-Lo Presti criteria has the highest diagnostic accuracy for the diagnosis of left ventricular hypertrophy in the elderly

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
C.A.M Tavares ◽  
N Samesima ◽  
L.A Hajjar ◽  
L.C Godoy ◽  
E.M.P Hirano ◽  
...  
Keyword(s):  
Left Ventricular Hypertrophy ◽  
Diagnostic Accuracy ◽  
Ventricular Hypertrophy ◽  
The Elderly ◽  
Left Ventricular ◽  
Accuracy Score ◽  
Increased Sensitivity ◽  
Low Sensitivity ◽  
Ecg Criteria ◽  
Improved Accuracy

Abstract Background Left Ventricular Hypertrophy (LVH) is an independent predictor of mortality and cardiovascular morbidity and the 12-lead ECG is recommended as a universal screening for patients with hypertension. However, the ECG has low sensitivity and there is limited data in patients 70 years or older. The recently published Peguero-Lo Presti (PLP) criteria had improved accuracy compared with other ECG criteria but with very few patients with age ≥70 years included. Purpose To compare the accuracy of the PLP criteria versus the traditional ECG criteria for detecting LVH in patients ≥70 years. Methods Retrospective single-center study. Patients were included if they were 70 years or older and underwent an ECG and echocardiogram (gold standard) less than 180 days apart from jan/2017 to mar/2018. Patients with left or right bundle branch block, non-sinus rhythm or ventricular paced rhythm were excluded. All tracings were independently reviewed by two cardiologists, blinded to the echocardiogram. The PLP criteria was compared against Cornell voltage (CV), Sokolow-Lyon voltage (SL), and Romhilt-Estes 4 and 5 (RE) criteria. LVH was defined as a left ventricular mass index >115 g/m2 in males and >95 g/m2 in females, according to the echocardiogram. McNemar's test, F1 score, and the area under the Receiver Operating Characteristic curves (AUC) were used to compare the diagnostic performance of the tests Results A total of 592 patients were included (mean age 77.5 years, SD: 5.9; 50.8% were women). The PLP criteria had increased sensitivity compared with both the SL and CV criteria (p<0.0001 for both comparisons) and RE5 (p=0.042). PLP also had better specificity than the RE4 criteria (p<0.0001) and the highest F1 accuracy score (Table 1). The AUC of the PLP was significantly higher than the AUC of the CV and RE criteria (0.70 vs 0.66 vs 0.64, respectively, p<0.05) and numerically higher than the SL criteria (AUC=0.67, p=0.311, Figure 1). Conclusion Compared to the traditional ECG criteria for LVH, the PLP criteria had the highest diagnostic accuracy in elderly patients. Figure 1. AUC of the ECG criteira Funding Acknowledgement Type of funding source: None

scholarly journals The Implications of Regulatory Framework for Topical Semisolid Drug Products: From Critical Quality and Performance Attributes towards Establishing Bioequivalence

Pharmaceutics ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 710
Author(s):  
Tanja Ilić ◽  
Ivana Pantelić ◽  
Snežana Savić
Keyword(s):  
Statistical Power ◽  
Failure Modes ◽  
In Vitro Release ◽  
Optimal Number ◽  
Drug Products ◽  
Pharmaceutical Equivalence ◽  
And Performance ◽  
Low Sensitivity

Due to complex interdependent relationships affecting their microstructure, topical semisolid drug formulations face unique obstacles to the development of generics compared to other drug products. Traditionally, establishing bioequivalence is based on comparative clinical trials, which are expensive and often associated with high degrees of variability and low sensitivity in detecting formulation differences. To address this issue, leading regulatory agencies have aimed to advance guidelines relevant to topical generics, ultimately accepting different non-clinical, in vitro/in vivo surrogate methods for topical bioequivalence assessment. Unfortunately, according to both industry and academia stakeholders, these efforts are far from flawless, and often upsurge the potential for result variability and a number of other failure modes. This paper offers a comprehensive review of the literature focused on amending regulatory positions concerning the demonstration of (i) extended pharmaceutical equivalence and (ii) equivalence with respect to the efficacy of topical semisolids. The proposed corrective measures are disclosed and critically discussed, as they span from mere demands to widen the acceptance range (e.g., from ±10% to ±20%/±25% for rheology and in vitro release parameters highly prone to batch-to-batch variability) or reassess the optimal number of samples required to reach the desired statistical power, but also rely on specific data modeling or novel statistical approaches.

scholarly journals Reversal of Multidrug Resistance by the Chinese Medicine Yiqi Jianpi Huaji Decoction and the Mechanism of Action in Human Gastric Cancer SGC7901/VCR Cells

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Wei-Bing Li ◽  
Yang Li ◽  
Chen Yu ◽  
Yong-Ming He
Keyword(s):  
Gastric Cancer ◽  
Mechanism Of Action ◽  
Low Dose ◽  
Chemotherapeutic Agents ◽  
Human Gastric Cancer ◽  
Gastric Cancer Cells ◽  
Future Studies ◽  
Increased Sensitivity ◽  
Induced Apoptosis

Yiqi Jianpi Huaji Decoction (YJHD), a traditional Chinese medicinal formula composed of twelve ingredients, has recently been reported to have a good clinical curative effect. The purpose of the present study was to evaluate the effects of YJHD on SGC7901/VCR gastric cancer cells and to elucidate the possible mechanism of action. First, the effects of a low dose of YJHD in combination with chemotherapeutic agents on SGC7901/VCR cells were assessed using the CCK-8 assay and flow cytometry, and the effects of YJHD on genes and proteins involved in drug resistance (MDR1, MRP, TUBB3, STMN1, and TS) were evaluated. Furthermore, transfection of SGC7901/VCR cells with siRNAs targeting these genes inhibited their expression, and the efficacy of vincristine against the cells was dramatically improved in vitro when these genes were silenced. These results demonstrate that low-dose YJHD inhibited cell proliferation, induced apoptosis, reversed MDR, and increased sensitivity to chemotherapeutic agents in vitro by downregulating P-gp, MRP, TUBB3, and STMN1 expression. MDR can be reversed by siRNAs targeting genes involved in MDR, and this strategy for cancer treatment should be evaluated in future studies.

scholarly journals How do we construct and operate experimental streams? An overview of facilities, protocols, and studied questions

Hydrobiologia ◽  
2019 ◽  
Vol 847 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Noémi Menczelesz ◽  
Ildikó Szivák ◽  
Dénes Schmera
Keyword(s):  
Statistical Power ◽  
Current Knowledge ◽  
Global Scale ◽  
Future Research ◽  
Future Studies ◽  
Natural Stream ◽  
Experimental Protocols ◽  
Organism Group ◽  
Experimental Stream ◽  
Over Time

Abstract Experimental streams are bounded and partly enclosed lotic units that facilitate the simulation of certain aspects of natural stream ecosystems under controlled conditions. We summarized the current knowledge regarding experimental streams in order to support researchers in designing and undertaking future studies using experimental streams. We observed an increase in the number of such studies since 1975. The geographically uneven distribution of studies suggests that the generalization of findings to global scale may not be straightforward. Our results indicate that macroinvertebrates, fish, and algae are the most frequently studied organisms and that the size of the experimental streams was related to the focal organism group(s) studied. The size of the units decreased over time, while the number of treatments, interpreted as the combination of the levels of factors, increased. These results suggest that biologically complex studies have gradually been replaced by biologically less complex ones. In contrast, the experimental complexity (the number of treatments) and the statistical power (number of replication) increased. Finally, we identified a number of important, but poorly documented pieces of information regarding experimental stream systems and experimental protocols and made recommendations for future research.

scholarly journals Correlations between the functional integrity of the endoplasmic reticulum and polarized Ca2+ signalling in mouse lacrimal acinar cells: a role for inositol 1,3,4,5-tetrakisphosphate

2002 ◽  
Vol 367 (1) ◽  
pp. 137-143 ◽  
Author(s):  
Alexander R. HARMER ◽  
David V. GALLACHER ◽  
Peter M. SMITH
Keyword(s):  
Endoplasmic Reticulum ◽  
Acinar Cells ◽  
Cell Types ◽  
Half Time ◽  
Fluorescent Marker ◽  
Functional Integrity ◽  
Physiological Regulator ◽  
Increased Sensitivity ◽  
Lacrimal Acinar Cells ◽  
Low Sensitivity

Ca2+ signalling in exocrine acinar cells has been shown to be both polarized and pulsatile in all cell types tested, except acutely isolated mouse lacrimal acinar cells. Lacrimal cells are also unusual in that they display a very low sensitivity to Ins(1,4,5)P3 (InsP3) that may be enhanced by placing the cells in primary culture for 12—72h or by intracellular infusion of a low concentration of Ins(1,3,4,5)P4 (InsP4). We have proposed previously that this atypical behaviour stemmed from vesiculation of the endoplasmic reticulum (ER) incurred during isolation of the cells and, furthermore, that time in culture or InsP4 increased sensitivity to InsP3 by increasing ER integrity [Smith, Harmer, Letcher and Irvine (2000) Biochem. J. 347, 77—82]. We have measured the half time for fluorescence recovery after photobleaching (FRAP) of a fluorescent marker (Mag-fluo 4) loaded into the ER lumen in order to determine directly the functional integrity of the ER in lacrimal cells. The half-time for FRAP was increased (indicating a reduction in the functional integrity of the ER) following exposure to anti-microtubule agents (taxol and nocodazole) known to perturb ER structure and decreased (indicating an increase in the functional integrity of the ER) by time in culture and exposure to InsP4. The action of InsP4 was particularly pronounced because it occurred under patch-clamp whole-cell conditions that were themselves found to reduce ER functional integrity. These data show that ER remodelling could be a physiological regulator of Ca2+ signalling and indicate a role for InsP4 in control of this process.

scholarly journals Testing the behaviour of Australian brushtail possums (Trichosurus vulpecula) to candidate semiochemicals from conspecifics’ urine

2021 ◽  
Author(s):  
◽  
Lauren Mockett
Keyword(s):  
Statistical Power ◽  
Brushtail Possum ◽  
Control Methods ◽  
Trichosurus Vulpecula ◽  
Observer Effect ◽  
Future Studies ◽  
Testing Protocol ◽  
Significant Difference ◽  
Chemical Groups

<p>The Australian brushtail possum (Trichosurus vulpecula) is a prolific introduced mammalian pest. Current pest control methods involve traps and poisons, but are proving to be ineffective long term solutions. As semiochemical lures are thought to be more attractive than food-based lures at low densities, researchers are attempting to utilize semiochemicals for kill traps. The objectives of this thesis were to create a testing protocol for use in a research colony of possums and use that protocol to test the attractiveness of semiochemicals found in possum urine that had been positively associated with possum attraction and interest in urine.. I hypothesised that there would be an observer effect present in the colony due to the nature of the colony husbandry protocols. There was no statistically significant observer effect present in the colony for eating, interaction, sitting, grooming or enclosure use (front or back). However, there was a trend (across the colony) that sitting and grooming increased in the presence of an observer. From these results, I designed an active presentation protocol for testing semiochemicals. I predicted that the most attractive compounds would belong to the acids and alcohol chemical groups. Overall there was no statistically significant difference between the semiochemicals. However, when taken individually there was clear evidence that five of the semiochemicals (belonging to the ketone, alcohol and phenol chemical groups) were more attractive than their control and the standard lure. It has been shown in this thesis that the attractiveness of semiochemicals can be tested in a small research colony. However, limits on colony size greatly reduce statistical power. For future studies, I would recommend increasing the sample size or instead developing field-based bioassays capable of being repeated across a greater number of sites, populations and therefore, individual possums.</p>

scholarly journals Xpert MTB/RIF Ultra is highly sensitive for the diagnosis of tuberculosis lymphadenitis in an HIV-endemic setting

2021 ◽  
Author(s):  
Stephanie Minnies ◽  
Byron W.P. Reeve ◽  
Loren Rockman ◽  
Georgina Nyawo ◽  
Charissa C. Naidoo ◽  
...  
Keyword(s):  
Clinical Investigation ◽  
False Negative ◽  
Needle Aspiration ◽  
World Health ◽  
Number Of Patients ◽  
Highly Sensitive ◽  
Specimen Processing ◽  
Increased Sensitivity ◽  
Health Organization ◽  
Low Sensitivity

Background: Tuberculosis lymphadenitis (TBL) is the most common extrapulmonary TB (EPTB) manifestation. Xpert MTB/RIF Ultra (Ultra) is a World Health Organization-endorsed diagnostic test, but performance data for TBL, including on non-invasive specimens, are limited. Methods: Fine needle aspiration biopsies (FNABs) from outpatients (≥18 years) with presumptive TBL (n=135) underwent: 1) routine Xpert (later Ultra once programmatically available), 2) a MGIT 960 culture (if Xpert- or Ultra-negative, or rifampicin-resistant), and 3) study Ultra. Concentrated paired urine underwent Ultra. Primary analyses used a microbiological reference standard (MRS). Results: In a head-to-head comparison (n=92) of FNAB study Ultra and Xpert, Ultra had increased sensitivity [91% (95% confidence interval 79, 98) vs. 72% (57, 84); p=0.016] and decreased specificity [76% (61, 87) vs. 93% (82, 99); p=0.020], and detected patients not on treatment. HIV nor alternative reference standards affected sensitivity and specificity. In patients with both routine and study Ultras, the latter detected more cases [+20% (0, 42); p=0.034] and, further indicative of potential laboratory-based room-for-improvement (e.g., specimen processing optimisation), false-negative study Ultras were more inhibited than true-positives. Study Ultra false-positives had less mycobacterial DNA than true-positives [trace-positive proportions 59% (13/22) vs. 12% (5/51); p<0.001]. “Trace” exclusion or recategorization removed potential benefits offered over Xpert. Urine Ultra had low sensitivity [18% (7, 35)]. Conclusions: Ultra on FNABs is highly sensitive and detects more TBL than Xpert. Patients with FNAB Ultra-positive “trace” results, most of whom will be culture-negative, may require additional clinical investigation. Urine Ultra could reduce the number of patients needing invasive sampling.

scholarly journals A Pilot Observational Study Comparing Wet Bulb Globe Temperature (WBGT) Parameter Measurements Between Three Commercial Kitchen Configurations

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Madison Ellis ◽  
Rod Handy ◽  
Darrah Sleeth ◽  
Leon Pahler ◽  
Camie Schaefer
Keyword(s):  
Heat Stress ◽  
Observational Study ◽  
Statistical Power ◽  
Occupational Injury ◽  
High Stress ◽  
Descriptive Statistics ◽  
Future Studies ◽  
Wet Bulb Globe Temperature ◽  
Test Of Significance ◽  
Globe Temperature

Line cooks in commercial restaurants work intense, high-stress shifts during near sources of heat, rendering them vulnerable to heat stress and occupational injury. However, there is a dearth of literature on heat stress among this population. This study investigated three common commercial kitchen configurations—zone, island, and assembly—to determine which design experiences the highest temperatures and if temperatures were in excess of recommended levels. A total of 11 restaurants were sampled for temperature using a Wet Bulb Globe Thermometer (WBGT). Descriptive statistics indicated that, on average, zone configurations are hotter than other kitchens and could pose a risk of heat stress; however, a Kruskal-Wallis test of significance revealed that this distinction was not statistically significant. Two measurements for zone kitchens were borderline significant, suggesting that future studies with greater statistical power would find significant differences between the kitchen types and further illuminate the risk of heat stress.

scholarly journals Diagnostic Algorithm Using a Sensitive Broth Culture Method for Detection ofClostridium difficileToxin from Stool Samples

2009 ◽  
Vol 20 (4) ◽  
pp. e135-e138
Author(s):  
Paul Bayardelle
Keyword(s):  
Screening Method ◽  
Diagnostic Algorithm ◽  
High Sensitivity ◽  
Culture Method ◽  
Neutralization Assay ◽  
Broth Culture ◽  
Increased Sensitivity ◽  
Stool Samples ◽  
Step Algorithm ◽  
Low Sensitivity

BACKGROUND: The two-step glutamate dehydrogenase antigencytotoxicity neutralization assay algorithm has been found to be reliable for the diagnosis of toxigenicClostridium difficile. However, the high sensitivity of the screening method is compromised by the relative low sensitivity of the second step, the direct cytotoxin neutralization assay (DCNA) using a fecal filtrate. The objective of the present study was to compare the DCNA with an indirect cytotoxin neutralization assay (ICNA).METHODS: For ICNA, the cytotoxin B ofC difficilewas obtained from a broth culture of the stools and neutralized according to a standard cytotoxin assay using MRC-5 fibroblast cells.RESULTS: A total of 923 stool specimens from adults were tested during a three-month period from June to August 2008. The prevalence of toxigenicC difficilewas 13.5%. The sensitivity of the two-step algorithm was 88%. With the ICNA, 12% toxigenicC difficilewere detected that were missed by DCNA.CONCLUSIONS: The use of broth for the ICNA is convenient, and results in increased sensitivity of detection of toxigenicC difficile. It can be implemented in routine diagnosis.

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