Computation of Foulkes and Davis' nonparametric tracking index using GAUSS

Foulkes and Davis (1981) define tracking as the maintenance of relative rank over a given time span. This paper outlines the development of their statistic, based on a set of individual growth profiles, which estimates the degree of tracking observed in a one-sample longitudinal data set and shows how confidence intervals for the corresponding population parameter may be constructed. An example using a measure of skeletal growth is given and a GAUSS program to do the computations is provided. (Information on obtaining the GAUSS program is provided in the Appendix.) Properties of this statistical approach to tracking are contrasted with another non-parametric method based on Cohen's kappa statistic. © 1992 Wiley-Liss, Inc.     

TRACK: a FORTRAN program for calculating the Foulkes-Davis tracking index

This paper describes a program that calculates the Foulkes-Davis tracking index, the probability that two individuals selected at random will have measurement curves that do not cross.     

Q-tracks: a College of American Pathologists program of continuous laboratory monitoring and longitudinal tracking

CONTEXT: Continuous monitoring of key laboratory indicators of quality by hundreds of laboratories in a standardized measurement program affords an opportunity to document the influence of longitudinal tracking on performance improvement by participants focused on that outcome. OBJECTIVE: To describe the results of the first 2 years of participation in a unique continuous performance assessment program for pathology and laboratory medicine. DESIGN: Participants in any of 6 modules in the 1999 and 2000 College of American Pathologists (CAP) Q-Tracks program collected data according to defined methods and sampling intervals on standardized input forms. Data were submitted quarterly to CAP for statistical analysis. Interinstitutional comparison reports returned in 6 weeks provided each laboratory with its performance profile of key indicators and its percentile ranking compared with all participants in that quarter. This also included longitudinal comparisons of performance during previous cumulative quarters. Control charts graphically displayed data with flags identifying performance points that were out of statistical control. SETTING: Hospital-based laboratories in the United States (98%), Canada, and Australia. PARTICIPANTS: Voluntary subscriber laboratories in the CAP Q-Tracks performance measurement program: roughly 70% from hospitals of 300 occupied beds or fewer, 65% from private, nonprofit institutions, slightly more than half located in cities, one third from teaching hospitals, and 20% with pathology residency training programs. MAIN OUTCOME MEASURES: Each module measured several major and additional minor quality indicators and unbenchmarked individualized data for internal use. RESULTS: Participants in 4 of 6 Q-Tracks continuous monitors demonstrated statistically significant performance improvement trends in 1999 and 2000, which were most marked for laboratories that continued participation throughout both years. These monitors were wristband patient identification, laboratory specimen acceptability, blood product wastage, and intraoperative frozen section consultation. CONCLUSIONS: Key continuous indicators chosen on the basis of a decade's experience in the CAP Q-Probes quality improvement program are useful measurement and benchmarking tools for laboratories to improve performance. In general, measures in which there is a broad range of demonstrable performance initially are most optimal for subsequent improvement using continuous monitoring. These studies have shown that quality is not static, but rather is a moving benchmark of performance as seen in the redefinition of benchmarks over time by participants in the first 2 years of the CAP Q-Tracks program.     

Effects of implementation of an online comprehensive antimicrobial-stewardship program in ICUs: A longitudinal study

Background/purpose

The long-term effects of antimicrobial-stewardship programs in the intensive care units (ICUs) have not been adequately examined. We evaluated the impact of an online comprehensive antimicrobial stewardship program (OCASP) on the outcomes of patients in 200-bed medical/surgical ICUs over the course of 11 years.

A longitudinal evaluation of an educational software program: a case study of Urinalysis-Tutor.

PURPOSE: To examine students' learning before and after revising an educational software program and to explore students' patterns of use of an interactive feature that compares images. METHOD: Study participants were 466 University of Washington School of Medicine students. Two cohorts of students (one in 1996 and one in 1997) used the original version of the software. Following analysis of the students' learning, the software program was modified based on instructional design principles pertaining to visual learning and concept acquisition. A 1998 cohort of students used the revised program and their performance was compared with that of the 1996 cohort. Analyses were based on pre- and post-test scores, data collected from the observation of students, and navigational pathways tracked by the program. RESULTS: There was very little difference in the overall performances of the students who used the original program and those who used the revised program. Error analysis focusing on 11 conceptual areas showed that reductions in errors occurred for six of 11 concepts, with statistically significant reductions of errors for two concepts. Additional navigational data collected in 1998 showed that students used an interactive feature for comparing images in different patterns. The data showed a positive association between performance and the anchored viewing mode of image display. CONCLUSIONS: While this study cannot point to specific design components that facilitated or hindered learning, it demonstrated a potential benefit of linking usage-pattern data and performance. Future studies should evaluate design factors that affect usage patterns and performances based on navigational data collected while students interact with software programs.     

A longitudinal analysis of eye tracking dysfunction and attention in recent-onset schizophrenia

The effect of an attentional manipulation on eye tracking dysfunction (ETD) in the early stages of schizophrenia was examined in 34 recent-onset schizophrenic patients and 24 demographically matched normal subjects over a 1-year period. An attentional enhancement manipulation improved eye tracking performance of recent-onset schizophrenic patients more than that of normal subjects. Eye tracking level also was moderately stable for both groups over the course of 1 year. The possible role of attentional allocation in ETD highlights the need for further examination of the interface between attentional and eye tracking measures of vulnerability to schizophrenia.     

CHI: A contemporaneous health index for degenerative disease monitoring using longitudinal measurements

In this paper, we develop a novel formulation for contemporaneous patient risk monitoring by exploiting the emerging data-rich environment in many healthcare applications, where an abundance of longitudinal data that reflect the degeneration of the health condition can be continuously collected. Our objective, and the developed formulation, is fundamentally different from many existing risk score models for different healthcare applications, which mostly focus on predicting the likelihood of a certain outcome at a pre-specified time. Rather, our formulation translates multivariate longitudinal measurements into a contemporaneous health index (CHI) that captures patient condition changes over the course of progression. Another significant feature of our formulation is that, CHI can be estimated with or without label information, different from other risk score models strictly based on supervised learning. To develop this formulation, we focus on the degenerative disease conditions, for which we could utilize the monotonic progression characteristic (either towards disease or recovery) to learn CHI. Such a domain knowledge leads us to a novel learning formulation, and on top of that, we further generalize this formulation with a capacity to incorporate label information if available. We further develop algorithms to mitigate the challenges associated with the nonsmooth convex optimization problem by first identifying its dual reformulation as a constrained smooth optimization problem, and then, using the block coordinate descent algorithm to iteratively solve the optimization with a derived efficient projection at each iteration. Extensive numerical studies are performed on both synthetic datasets and real-world applications on Alzheimer’s disease and Surgical Site Infection, which demonstrate the utility and efficacy of the proposed method on degenerative conditions that include a wide range of applications.     

PC program for comparing tracking indices in several independent groups

A method for computing a measure of tracking based on Cohen's kappa statistic for one-sample longitudinal data sets was previously described and implemented. This paper shows how one may test the equality of several kappas, each computed from an independent longitudinal sample. Thus, it is possible to formally compare groups of individuals with regard to stability in growth (or adaptive) patterns. Relative assessments of predictability in growth outcomes in different populations can be made with this approach. Also, when a common value of kappa is not contradicted by the data, a method to estimate this value and obtain a confidence interval for it is shown. A menu-driven GAUSS program for carrying out the procedure is described and made available. The method and program are illustrated with three samples of Guatemalan children. © 1992 Wiley-Liss, Inc.     

Project C.A.R.E. substance abuse prevention program for high-risk youth: A longitudinal evaluation of program effectiveness

This article describes and evaluates Project C.A.R.E., a substance abuse prevention program for three cohorts of at-risk fourth graders and their families. Project C.A.R.E. worked intensively with students and their families to increase resiliency factors and decrease risk factors through school, family, and extracurricular activities. The research design was experimental. Project objectives were to decrease substance use, negative behaviors, intent to use substances, school suspensions, and absences; and to increase alternative activities, family communication, academic grades, and consistency of family behavior control and rules. A few positive program effects were found. At posttest, more control students' grades needed improvement, and more program students participated in community activities. Several variables showed differential change over time which favored the program group. Compared to control students, program students increased participation in alternative activities from pretest to posttest and did not increase their school suspensions as much. At the one year follow-up, control students were more willing to use substances than were program students. The program appeared to have the most impact with the third cohort of students and with Black students. Program students with low participation generally had the worst outcomes, often worse than the control students. It was suggested that more research should be done examining differential effectiveness, especially racial and program participation differences, as they could have a profound impact on program development and implementation. © 1997 John Wiley & Sons, Inc.     

A program to compute the sizes and numbers of spherical bodies from observations made on tissue sections

Summary A computer program, written in standard Fortran, is given to facilitate the computation of the sizes and correct distribution of spheres from the number and size of the circular profiles observed in tissue sections. The method is particularly valuable in cases where it is necessary to determine absolute numbers of cells or subcellular fragments where the objects of interest are not of uniform size. The method gives true cell numbers and the distribution of the spherical diameters.     

A system for computing neuromorphometry from magnetic resonance images.

A new technique for the automated measurement of a variety of gross neuroanatomical structures (such as cerebral ventricles) is described. The system exploits the local statistical properties of dual-echo magnetic resonance images of the brain to produce a fully unsupervised classification of these images into a variety of tissue types. Following this, a simple region agglomeration procedure aggregates the segmented regions by class, and submits these regions to a computational-geometric analysis from which a wide variety of measures are derived.     

A method for tracking the locomotion of an isolated microorganism in real time

An inexpensive, real-time recording system ("bug-tracker") for tracking the movements of an isolated microorganism was assembled using a close-up video system, a video memory card, and a personal computer. An isolated organism moving in an almost two-dimensional plane is viewed by the close-up video camera, and a selected video frame is digitized by the video memory card into 256 x 256 pixels (picture points). The pixels of the ith frame are subtracted from those of the i-lth frame to delete images other than that of the image of the moving organism. Windows with an optimized size are generated commonly in the ith and i-lth frame to reduce the number of pixels directly accessed by the computer, and the address of the pixel with the largest value inside the windows identifies the coordinates of the organism on the X and Y axes. By optimizing the size of a window for a given organism, the sampling for the X and Y coordinates can be made at times separated by approximately 0.2 to 2.0 seconds. Data are automatically filed on a floppy disk.     

PC program for obtaining orthogonal polynomial regression coefficients for use in longitudinal data analysis

Much of longitudinal data analysis begins with dimensionality reduction, i.e., the replacement of the T observations x₁, x₂, …, x_T on an individual taken at times t₁, t₂, …, t_T (not necessarily equally spaced) by a smaller number, P, of parameters which are then used to describe and compare growth processes. We focus on the class of polynomial growth curve models for one-sample data matrices in which the P regression coefficients are estimated by an equation of the form $ \hat \tau = ({\rm W'W}) $ ¹W′x and consider the choice of the design matrix W. The case in favor of using orthogonal polynomials to comprise the elements of W and provide a PC program, written in GAUSS, for obtaining them is presented. This program can be used instead of existing tables of orthogonal polynomials in the case of equally spaced time points, and to avoid laborious hand-computation to obtain them when the time points are not equally spaced. The program also computes the corresponding orthogonal polynomial regression coefficients $ \hat \alpha = (\Phi '\Phi)^{ - 1} \Phi '{\rm x} $, where Φ consists of orthogonal polynomials, which may then be input into other programs for subsequent analysis, e.g., to compare the growth profiles of several groups of individuals. Examples of the use of the program are given. Information on obtaining a copy of the program is provided in Appendix A. © 1992 Wiley-Liss, Inc.     

Implementation of Hills' growth curve analysis for unequal-time intervals using GAUSS

Longitudinal data are widely regarded as the most efficient and informative type of data with which to investigate growth. Paradoxically, appropriate statistical methods for analyzing longitudinal data have been unavailable; with the exception of a computer program for executing Rao's (Biometrika 46:49–58, 1959) one-sample polynomial growth curve analysis (Schneiderman and Kowalski, Am. J. Phys. Anthropol. 67:323–333, 1985) and another applying the Preece-Baines function (Brown and Townsend, Ann. Hum. Biol. 9:495–505, 1982), no programs for analyzing longitudinal data are generally available to the scientific community. Whereas much of the pediatrically oriented work has involved fitting growth curves for individual children, the concern here is the estimation of growth trends for populations. An Adequate understanding of average tendencies is a prerequisite to understanding the growth of individuals. The present paper implements Hills' (Biometrics 24:189–196, 1968) analysis, which is formally equivalent to Rao's but uses finite differences instead of orthogonal polynomials. This method is suitable for data collected at unequal time points and generates explicit measures of velocity and acceleration. The polynomial specification of the curve that best fits the data is also determined with this method. An additional advantage of this approach is that it is conceptually simpler than the classic model of Rao. An application of this method is given using the same craniofacial growth data as in our earlier (1985) paper for comparability. We provide an easy to use program written in GAU's (Edlefson and Jones, Kent, WA; Applied Technical Systems, 1985), a matrix programming language that runs on PC-compatible microcomputers. This implementation for PCs extends the accessibility to investigators who may not have access to mainframe computers.     

The development of two-dimensional tracking: a longitudinal study of circular pursuit

We investigated 6- to 12-month-old infants' ability to track an object moving on circular trajectories, using a longitudinal design. Consistent predictive gaze tracking was not found before 8 months of age. These results indicate that infants' horizontal and vertical components of circular tracking are less mature than expected from previous studies of one-dimensional horizontal tracking. Vertical components are especially immature, particularly during high velocity tracking (approximately 20 degrees /s). The results also suggest that horizontal and vertical tracking are mutually dependent during early development. Saccades were predictive (average lag >-125 ms) from 6 months onwards.     

Correlation between antibiotic consumption and resistance of Pseudomonas aeruginosa in a teaching hospital implementing an antimicrobial stewardship program: A longitudinal observational study

Background/purposeThe rapid emergence of Pseudomonas aeruginosa resistance made selecting antibiotics more challenge. Antimicrobial stewardship programs (ASPs) are urging to implant to control the P. aeruginosa resistance. The purpose of this study is to evaluate the relationship between antimicrobial consumption and P. aeruginosa resistance, the impact of ASPs implemented during the 14-year study period.MethodsA total 14,852 P. aeruginosa isolates were included in our study. The resistant rate and antimicrobial consumption were investigated every six months. Linear regression analysis was conducted to examine the trends in antibiotics consumption and antimicrobial resistance over time. The relationship between P. aeruginosa resistance and antimicrobial consumption were using Pearson correlation coefficient to analysis. The trend of resistance before and after ASPs implanted is evaluated by segment regression analysis.ResultsP. aeruginosa resistance to ceftazidime, gentamicin, amikacin, ciprofloxacin and levofloxacin significantly decreased during the study period; piperacillin/tazobactam (PTZ), cefepime, imipenem/cilastatin and meropenem remained stable. The P. aeruginosa resistance to ciprofloxacin and levofloxacin increasing initial then decreased after strictly controlled the use of levofloxacin since 2007. As the first choice antibiotic to treat P. aeruginosa, the consumption and resistance to PTZ increase yearly and resistance became stable since extended-infusion therapy policy implant in 2009.ConclusionOur ASP intervention strategy, which included extended infusion of PTZ and restrict use of levofloxacin, may be used to control antimicrobial resistance of P. aeruginosa in medical practice.     

A seven step approach to starting an exercise program for older adults

There is strong experimental evidence to indicate that regular aerobic exercise can prevent disease, decrease the risk of failing, reduce physical disability, improve sleep, and enhance mood and general well being. Despite these benefits, approximately 50% of sedentary adults who start an exercise program stop them within the first 6 months of involvement. To help older adults initiate and adhere to a regular exercise program, a seven step approach was developed and implemented in a continuing care retirement community (CCRC). The seven steps include: (1) education; (2) exercise pre-screening; (3) setting goals; (4) exposure to exercise; (5) role models; (6) verbal encouragement; and (7) verbal reinforcement/rewards. Following implementation of the seven step approach, 40 (19%) of the 212 residents living in the CCRC exercise regularly.