Approaches to the nonparametric analysis of limited longitudinal data sets

Dawson, Deborah V.; Siegler, Ilene C.

doi:10.1080/03610739608253996

Cited by 7 publications

(3 citation statements)

References 26 publications

(24 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Trapezoidal area under the curve (AUC) was used as a summary measure of bacterial variability over the treatment time course 37,38 where larger AUC values correspond to greater viability. Comparisons were made with and without the inclusion of AUCs from the control sample.…”

Section: Methodsmentioning

confidence: 99%

Oral mucosal lipids are antibacterial against Porphyromonas gingivalis, induce ultrastructural damage, and alter bacterial lipid and protein compositions

et al. 2013

View full text Add to dashboard Cite

Oral mucosal and salivary lipids exhibit potent antimicrobial activity for a variety of Gram-positive and Gram-negative bacteria; however, little is known about their spectrum of antimicrobial activity or mechanisms of action against oral bacteria. In this study, we examine the activity of two fatty acids and three sphingoid bases against Porphyromonas gingivalis, an important colonizer of the oral cavity implicated in periodontitis. Minimal inhibitory concentrations, minimal bactericidal concentrations, and kill kinetics revealed variable, but potent, activity of oral mucosal and salivary lipids against P. gingivalis, indicating that lipid structure may be an important determinant in lipid mechanisms of activity against bacteria, although specific components of bacterial membranes are also likely important. Electron micrographs showed ultrastructural damage induced by sapienic acid and phytosphingosine and confirmed disruption of the bacterial plasma membrane. This information, coupled with the association of treatment lipids with P. gingivalis lipids revealed via thin layer chromatography, suggests that the plasma membrane is a likely target of lipid antibacterial activity. Utilizing a combination of two-dimensional in-gel electrophoresis and Western blot followed by mass spectroscopy and N-terminus degradation sequencing we also show that treatment with sapienic acid induces upregulation of a set of proteins comprising a unique P. gingivalis stress response, including proteins important in fatty acid biosynthesis, metabolism and energy production, protein processing, cell adhesion and virulence. Prophylactic or therapeutic lipid treatments may be beneficial for intervention of infection by supplementing the natural immune function of endogenous lipids on mucosal surfaces.

show abstract

Section: Methodsmentioning

confidence: 99%

Oral mucosal lipids are antibacterial against Porphyromonas gingivalis, induce ultrastructural damage, and alter bacterial lipid and protein compositions

et al. 2013

View full text Add to dashboard Cite

show abstract

“…Correlation analysis at the start of treatment was calculated using the Spearman rank‐order correlation coefficients. Individual longitudinal developments were analysed using the Spearman rank‐order correlation following the methodology outlined by Dawson and Siegler (1996). The longitudinal analysis was based on 12 patients responding to the questionnaires twice or more.…”

Section: Methodsmentioning

confidence: 99%

Acute leukaemia or highly malignant lymphoma patients’ quality of life over two years: a pilot study

Persson

Larsson²,

Ohlsson³

et al. 2001

European Journal of Cancer Care

View full text Add to dashboard Cite

The aim of this study was, first, to investigate the quality of life and sense of coherence for acute leukaemia and malignant lymphoma patients at the start of treatment and over 2 years. A second aim was to compare questionnaire responses with patients' statements in open-ended interviews. A consecutive sample of 16 patients responded to the Quality of Life Questionnaire (QLQ-C30), Lund Gerontological Centre questionnaire and the Sense of Coherence Scale at the start of treatment and after 12 and 24 months. The QLQ-C30 questionnaire was administered also after 4, 8, 16 and 20 months. Tape-recorded open-ended interviews were conducted every 4 months before the patients responded to the questionnaires. Quality of life (QoL) and sense of coherence were scored more highly at the beginning of treatment for patients who did not relapse, than for those who relapsed. This difference remained throughout the study period. There was no correspondence in responses between questionnaire and personal interviews, although the results from the interviews, in some aspects, validated the result from the QLQ-C30. Those patients who relapsed may have had different prerequisites or been in a worse position at the onset of the disease and, reasonably, they needed more compensatory nursing care. More knowledge about the correspondence between a person's perceived QoL when discussed in personal interviews compared with responses given in standardised QoL questionnaires is needed before any assumption about clinical relevance can be made.

show abstract

“…Section 3 defines summary statistics for change over time based upon area-under-the-curve computations, and the univariate and multivariate rank tests used to assess them (Ghosh, Grizzle, and Sen 1973; Dawson and Siegler 1996). Multiple testing procedures are also outlined.…”

Section: Introductionmentioning

confidence: 99%

Multiple Hypothesis Testing for Experimental Gingivitis Based on Wilcoxon Signed Rank Statistics

Preisser

Sen²,

Offenbacher

2011

Statistics in Biopharmaceutical Research

View full text Add to dashboard Cite

Dental research often involves repeated multivariate outcomes on a small number of subjects for which there is interest in identifying outcomes that exhibit change in their levels over time as well as to characterize the nature of that change. In particular, periodontal research often involves the analysis of molecular mediators of inflammation for which multivariate parametric methods are highly sensitive to outliers and deviations from Gaussian assumptions. In such settings, nonparametric methods may be favored over parametric ones. Additionally, there is a need for statistical methods that control an overall error rate for multiple hypothesis testing. We review univariate and multivariate nonparametric hypothesis tests and apply them to longitudinal data to assess changes over time in 31 biomarkers measured from the gingival crevicular fluid in 22 subjects whereby gingivitis was induced by temporarily withholding tooth brushing. To identify biomarkers that can be induced to change, multivariate Wilcoxon signed rank tests for a set of four summary measures based upon area under the curve are applied for each biomarker and compared to their univariate counterparts. Multiple hypothesis testing methods with choice of control of the false discovery rate or strong control of the family-wise error rate are examined.

show abstract

Approaches to the nonparametric analysis of limited longitudinal data sets

Cited by 7 publications

References 26 publications

Oral mucosal lipids are antibacterial against Porphyromonas gingivalis, induce ultrastructural damage, and alter bacterial lipid and protein compositions

Oral mucosal lipids are antibacterial against Porphyromonas gingivalis, induce ultrastructural damage, and alter bacterial lipid and protein compositions

Acute leukaemia or highly malignant lymphoma patients’ quality of life over two years: a pilot study

Multiple Hypothesis Testing for Experimental Gingivitis Based on Wilcoxon Signed Rank Statistics

Contact Info

Product

Resources

About