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PubMed1995

Validity of the Computer Science and Applications, Inc. (CSA) activity monitor.

The validity of the Computer Science and Applications, Inc. (CSA) accelerometer in assessing physical activity was assessed during treadmill walking and running at three different grades. Energy expenditure (EE) served as the criterion measure. CSA data were compared to data collected with the Caltrac accelerometer. Both accelerometers were sensitive to changes in treadmill speed, but neither discriminated changes in treadmill grade. Caltrac and CSA activity counts were significantly and similarly correlated with EE (r = 0.66-0.82), relative VO2 (r = 0.77-0.89), heart rate (r = 0.66-0.80), treadmill speed (r = 0.82-0.92), and with each other (r = 0.77-0.82). CSA data were used to develop models to predict EE (kcal.min-1). Cross-validation resulted in a mean difference between actual and predicted EE of 0.02 kcal.min-1 (SEE = 0.85 kcal.min-1). The range of individual differences in the validation group was large for both the CSA model (-2.86 to +3.86 kcal.min-1) and Caltrac (-4.17 to +2.04 kcal.min-1). It is concluded that the CSA and Caltrac accelerometers have similar validity and that either instrument can be used to estimate EE of groups.

Adult↗

PubMed1995

Anthropometric estimation of thigh muscle cross-sectional area.

The purpose of this investigation was to derive and validate circumference and skinfold equations for estimating the anatomical cross-sectional area (CSA) of the quadriceps, hamstrings, and total thigh muscles. Forty-three adult male (mean age +/- SD = 25 +/- 5 yr) volunteers underwent magnetic resonance imaging (MRI) to determine the CSA of the thigh muscles at the midfemur level as well as midthigh circumference and anterior thigh skinfold assessment. Multiple regression analyses were used to derive equations for predicting quadriceps, hamstrings, and total thigh muscle CSA of the dominant limb from the anthropometric dimensions on a random sample of 30 of the subjects. Cross-validation (CV) analyses were performed for each equation on: (a) the nondominant thigh of the derivation group (N = 30); (b) the dominant thigh of the CV group (N = 13); and (c) the nondominant thigh of the CV group (N = 13). The CV total error values for the quadriceps, hamstrings, and total thigh muscle CSA ranged from 5.4 to 14.4, 3.3 to 5.5, and 10.0 to 25.4 cm2, respectively. The anthropometric equations are recommended for one-time estimates of muscle CSA values in healthy, well-nourished young adult males when more sophisticated procedures are not available.

Adult↗

PubMed1995

Evaluation of near infra-red interactance for assessment of subcutaneous and total body fat.

OBJECTIVE: Near infra-red interactance (NIRI) has been used for assessment of total body fatness, but its relationship with composition at the measurement site is not clear. This study examines the relationship of interactance with subcutaneous adipose tissue and muscle thickness as well as total body fat content. DESIGN: (i) Validation of NIRI by comparison with subcutaneous tissue thicknesses from ultrasound. (ii) Cross-validation of techniques for estimation of body fat content. SETTING: Laboratory. SUBJECTS: (i) 54 young adults (27 male and 27 female) and (ii) 63 middle-aged men. INTERVENTIONS: Measurements of subcutaneous adipose tissue thickness and muscle thickness using ultrasound, near infra-red interactance (Futrex 5000) and skinfold thicknesses were made at five sites in young adults. In middle-aged men total body fat was assessed by densitometry, NIRI and skinfold thickness. Measurements were made in duplicate by a single trained observer. RESULTS: Interactance measurements were related to subcutaneous adipose tissue thickness, although the relationship varied according to measurement site r = 0.09 at anterior thigh to 0.78 at biceps; P = 0.31 to < 0.0001). Muscle thickness explained additional variance in interactance only at biceps in women. Subcutaneous adipose tissue thickness correlated better with skinfold thickness (r = 0.56 to 0.92; P = 0.002 to < 0.0001) than with interactance. Mean difference in fat mass from densitometry +/- 95% limits of agreement was -1.61 +/- 7.68 kg for NIRI and -2.84 +/- 6.56 kg for skinfold thickness in middle-aged men. NIRI tended to underestimate higher (and overestimate lower) levels of fatness. CONCLUSIONS: NIRI performed no better than skinfolds in assessment of either subcutaneous or total body fat.

Adipose Tissue↗

PubMed1995

[Body density assessment utilizing skinfold thickness and age in Japanese women].

A study was conducted to investigate the validity of skinfold-based prediction equations for body density (g/ml) by Nagamine and Suzuki (1964), and to formulate more convenient and more useful equations for predicting body density from skinfold and age in women. Subjects of the study were 512 healthy women aged 18-66 years in or near Nagasaki City. The dependent variable in the multiple regression equation, body density, was determined by hydrostatic weighing. Independent variables included eight skinfolds, the sum of two skinfolds (triceps, subscapular), the sum of three skinfolds (triceps, subscapular, and abdominal), age, and body surface area. Skinfolds were measured with an Eiken-model skinfold caliper. Age (mean 30.1, range 18-66 yrs.), weight (mean 52.6, range 38.0-83.3 kg), height (mean 157.0, range 142.0-172.0 cm), and body density, (mean 1.04125, range 0.98806-1.08650 g/ml) were also recorded. Percent body fat was calculated using the formula by Brozek et al. and ranged from 6.4% to 48.3%. Multiple correlation coefficients (MR) and standard error (SE) of 10 regression equations (A-J) for predicting body density in women were compared. The best-fitting and the most convenient prediction equation for body density was equation-E. The regression equation developed for predicting body density was: body density = 1.07931-0.00059 x sum of three skinfolds(mm)-0.00015 x age (MR = 0.77 and SE = 0.0089). The equation was cross-validated on a different sample of 46 women. The correlation coefficient between predicted and hydrostatically determined body density was 0.813 (p < 0.001). Equation-E (Tahara's equation) appears to be useful in body density analysis particularly when the subjects are Japanese women, aged 18-50 yrs, with percent body fat 17 to 34%.

Adolescent↗

PubMed1995

The use of APACHE III to evaluate ICU length of stay, resource use, and mortality after coronary artery by-pass surgery.

OBJECTIVE: To identify patient characteristics that are associated with increased ICU length of stay, resource use, and hospital mortality after coronary artery bypass surgery. DESIGN: Prospective, multicenter study. SETTING: Six tertiary care hospitals. PARTICIPANTS: A consecutive sample of 2,435 unselected ICU admissions following coronary artery by-pass surgery. MATERIALS AND METHODS: Demographic, operative characteristics and APACHE III score were collected during the first postoperative day; and APACHE III scores and therapeutic interventions during the first three postoperative days. Hospital survival and ICU length of stay were also recorded. Multivariate equations were derived and cross-validated to predict hospital mortality, ICU length of stay, and ICU resource use. RESULTS: Unadjusted hospital mortality rate was 3.9% (range 1.0% to 6.0%), mean ICU length of stay was 3.7 days (range 3.2 to 4.7 days), and first 3-day ICU resource use (TISS points) was 99 (range 68 to 116). The range of actual to predicted ICU length of stay varied from 0.86 to 1.26; and resource use from 0.71 to 1.16. CONCLUSIONS: A limited number of operative characteristics, the post-operative acute physiology score (APS) of APACHE III and patient demographic data can predict hospital death rate, ICU length of stay, and resource use immediately following coronary by-pass surgery. These estimates may compliment assessments based on pre-operative risk factors in order to more precisely evaluate and improve the efficacy and efficiency of cardiovascular surgery.

APACHE↗

PubMed1995

New 5H-[1,3]thiazolo[3,2-a]pyrido[3,2-e]pyrimidin-5-one derivatives as diuretics.

A series of new 5H-[1,3]thiazolo[3,2-a]pyrido[3,2-e] pyrimidin-5-ones 3-substituted and/or 8,9-hydrogenated was prepared and tested for their diuretic, natriuretic and kaliuretic activities on male Wistar rats at a dosage of 25 mg/kg or less. Diuretic and saliuretic activities were strongly influenced by substituents in 3-position. Quantitative structure-activity relationships show that electron withdrawn substituents in 3-position enhance both diuretic and saliuretic activities at 25 mg/kg. Global analysis of the variations introduced on pyridine, pyrimidine and thiazole rings of this tricyclic system showed an increases of diuretic and natriuretic activities when the formal charge on N9a and C9b increases. Potassium ion excretion also increases, although not as drastically a in the earlier cases. Regression equations were calculated by partial least squares method (PLS) and validated by the cross-validation (leave-one-out) technique.

Animals↗

PubMed1995

Enhancing refusal skills: identifying contexts that place adolescents at risk for unwanted sexual activity.

Refusal skills training is one approach to reducing school-age pregnancy and sexually transmitted disease. The generalization of these skills is dependent, in part, on the relevance to participants of the training scenarios. We identified and cross-validated relevant contexts for inclusion in scenarios for refusal skills training. Fifty-six sexually active female adolescents identified 59 contexts associated with unwanted sexual activity. Fifty-one additional subjects rated these on 9-point Likert scales according to how common and difficult each was for them. Unsupervised activity where alcohol is present or feeling an obligation to engage in sexual activity emerged as high risk contexts. The most common and difficult contexts provide points of departure for the development of relevant training scenarios for refusal skills training, thereby contributing to generalization of these skills and reducing the risk of unwanted sexual activity within this population.

Adolescent↗

PubMed1995

Failure of predicted VO2peak to discriminate physical fitness in epidemiological studies.

Previous investigators reported that peak oxygen uptake (VO2peak) could be accurately predicted from nonexercise test variables, and that this score would be suitable for categorizing cardiorespiratory fitness (CRF) within epidemiological studies. However, the accuracy of these models has varied considerably. The purposes of this study were: 1) assess the accuracy of predicting VO2peak with a new nonexercise model, and 2) assess the utility of the predicted VO2peak for categorizing CRF in epidemiological studies. Subjects included 2,350 men and women. Cross-validated multiple regression models revealed that age, sex, resting heart rate, body weight, percentage body fat, smoking, and physical activity were significant predictors (P < 0.001) of VO2peak. The multiple regression model for relative VO2peak (ml.kg-1.min-1) had R2 = 0.733 (SEE = 5.38), whereas the model for absolute VO2peak (l.min-1) had R2 = 0.773 (SEE = 0.425). The 95% confidence intervals for the predicted VO2peak were large (+/- 10.6 ml.kg-1.min-1 and +/- 0.833 l.min-1). These results support the notion that VO2peak can be predicted from a multiple regression model devoid of exercise test variables. However, due to the extreme variability in the predicted scores, the regression models were unable to effectively distinguish CRF categories. Therefore, despite statistical success in predicting VO2peak for the nonexercise test regression models, we conclude that such models fail to provide the accuracy needed for categorizing CRF within large epidemiological cohorts where the purpose is to assess mortality risk.

Adipose Tissue↗

PubMed1994

Semiparametric models for longitudinal data with application to CD4 cell numbers in HIV seroconverters.

The paper describes a semiparametric model for longitudinal data which is illustrated by its application to data on the time evolution of CD4 cell numbers in HIV seroconverters. The essential ingredients of the model are a parametric linear model for covariate adjustment, a nonparametric estimation of a smooth time trend, serial correlation between measurements on an individual subject, and random measurement error. A back-fitting algorithm is used in conjunction with a cross-validation prescription to fit the model. A notable feature in the application is that the onset of HIV infection is associated with a sudden drop in CD4 cells followed by a longer-term slower decay. The model is also used to estimate an individual's curve by combining his data with the population curve. Shrinkage toward the population mean trajectory is controlled in a natural way by the estimated covariance structure of the data.

Acquired Immunodeficiency Syndrome↗

PubMed1994

Validating the TMJ scale in a national sample of 10,000 patients: demographic and epidemiologic characteristics.

The accuracy and reliability of the TMJ Scale were originally determined in cross-validation studies on large, research-based patient samples. It had been assumed that the demographic characteristics and test responses of these research-based samples would be representative of the clinical population in which the TMJ Scale would ultimately find use. The present study on more than 10,000 patients that were evaluated for temporomandibular disorders in clinical practice demonstrates that the test scores, demographic variables, and the patterns of symptom severity that characterize the original TMJ Scale research sample accurately represent the general temporomandibular disorder patient population in which the TMJ Scale is now being used. The results suggest a high degree of confidence in the clinical efficacy of this assessment tool. The overall symptom severity of temporomandibular disorders was found to be normally distributed in the patient population. Women with temporomandibular disorders report a higher level of severity of all physical and psychological symptoms than men. This may explain the high female-to-male ratio in patients seeking treatment. However, a higher percentage of male temporomandibular disorder patients has clinically significant psychological and stress-related problems than do women. The severity and prevalence of symptoms associated with joint dysfunction and range of motion limitation are lower in older age groups, and the overall symptom severity of temporomandibular disorders is not higher in older age groups. However, the severity and prevalence of symptoms associated with joint dysfunction are greater in groups in which temporomandibular disorders have existed for longer durations, although pain levels do not follow this trend. There is also an association between time duration of the temporomandibular disorder and the severity of psychological problems and chronicity. Patients with chronic problems are symptomatically more impaired than those with acute problems.

Acute Disease↗

PubMed1994

Improving intensive care unit discharge decisions: supplementing physician judgment with predictions of next day risk for life support.

OBJECTIVE: To develop predictive equations, estimating the probability that an individual intensive care unit (ICU) patient will receive life support within the next 24 hrs. DESIGN: Prospective, multicenter, inception cohort study. SETTING: Forty-two ICUs in 40 U.S. hospitals, including 26 that were randomly selected and 14 volunteer hospitals, primarily university or large tertiary care centers. PATIENTS: A consecutive sample of 17,440 ICU admissions. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A series of multivariate equations were developed to create daily estimates of probability of life support in the next 24 hrs. These equations used demographic, physiologic, and treatment information obtained at the time of ICU admission and during the first 7 ICU days. The most important determinants of next day risk for life support were the current day's therapy and Acute Physiology Score of the Acute Physiology and Chronic Health Evaluation (APACHE) III score. Other predictor variables included diagnosis, age, chronic health status, emergency surgery, previous day Acute Physiology Score, and hospital stay and location before ICU admission. The cross-validated ICU day 1, 2, and 3 predictive equations had receiver operating characteristic areas of 0.90. Survival, ICU readmission rate, and the number and type of therapies received by patients predicted at < 10% risk for active treatment suggest that discharge of patients meeting these criteria to an intermediate care unit or hospital ward could reduce ICU bed demand without compromising patient safety. CONCLUSIONS: Accurate, objective predictions of next day risk for life support can be developed, using readily available patient information. Supplementing physician judgment with these objective risk assessments deserves evaluation for the role of these assessments in enhancing patient safety and improving ICU resource utilization.

Adolescent↗

PubMed1994

Interferon-alpha for chronic hepatitis C: an analysis of pretreatment clinical predictors of response.

To identify predictors of short-term and sustained ALT normalization after interferon treatment in adult patients with chronic hepatitis C, we performed a meta-analysis of individual patients' data, with construction and cross-validation of a prediction rule, in 361 patients from two randomized trials. In one trial, 116 subjects with transfusion-related chronic hepatitis C were treated with lymphoblastoid interferon (5 MU/m2 three times a week for 2 mo, then 3 MU/m2 three times a week for 4 or 10 mo). In the other study, 245 patients with community-acquired chronic hepatitis C received recombinant interferon-alpha 2b (10 MU three times a week for 2 mo, then 5 MU three times a week for 4 mo; then random allocation of subjects with normal aminotransferase levels to stop or continue interferon for a further 6 mo). Overall, 164 subjects (45%; 95% confidence interval, 40% to 50%) had short-term responses; 61 (18%; 95% confidence interval, 14% to 22%) maintained sustained responses. Sixty patients (17%; 95% confidence interval, 13% to 21%) withdrew from treatment because of side effects or subjective intolerance. Logistic regression analysis showed that short-term and sustained response were independently predicted by lobular structure on pretreatment liver biopsy (p < 0.0001) and by short disease duration, defined as the time elapsed since transfusion in posttransfusion cases or since the first observation of abnormal aminotransferase levels in cryptogenic disease (p < 0.01). Rules to predict short-term and sustained response to interferon were derived from these items, showing a discriminatory ability of 0.73 and 0.70.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

A neural network classifier for cerebral perfusion imaging.

UNLABELLED: Artificial neural networks have been applied to a variety of pattern recognition tasks in medical imaging and have been shown to be a powerful classification tool. The potential usefulness to discriminate normal from abnormal cerebral perfusion patterns was investigated. METHODS: Cerebral perfusion imaging with 99mTc-labeled hexamethylpropyleneimine oxime was performed on 52 normal control subjects, 29 patients with clinically diagnosed Alzheimer's disease (AD) and 25 patients with chronic cocaine polydrug abuse. Each study was registered and scaled to a common anatomic coordinate system, yielding 120 standardized cortical regions. A back-propagation neural network classifier based on regional perfusion was used to classify normal and abnormal perfusion patterns. The neural network was trained to discriminate patients with AD from age-matched normal controls and cocaine polydrug abuse patients from normal controls. The performance of the neural network in these two tasks was evaluated quantitatively by receiver operating characteristic (ROC) analysis using cross-validation. RESULTS: For patients with AD, the area under the ROC curve was 0.93 +/- 0.04. When testing with the cocaine polydrug abuser data, the area under the ROC curve was 0.89 +/- 0.04. CONCLUSION: Neural networks provide a potentially useful tool in the decision-making task to discriminate patients with AD and cocaine abuse from normal controls.

Adult↗

PubMed1993

The Social Physique Anxiety Scale: construct validity in adolescent females.

Hart, Leary, and Rejeski have developed the Social Physique Anxiety Scale (SPA), a measure of the anxiety experienced in response to having one's physique evaluated by other people. The present study cross-validated the psychometric properties of this measure in a sample (N = 236) of adolescent competitive female gymnasts. Employing structural equation modeling, the proposed unidimensional factor structure of the SPA was supported, although some questions regarding the robustness of the fit are raised. Construct validity was demonstrated by significant inverse relationships between aspects of physical efficacy (perceived physical ability and physical self-presentation confidence) and degree of social physique anxiety. These findings are discussed in terms of possible alternative factor structures and integration of social anxiety and other psychosocial constructs to better understand physical activity behavior.

Adolescent↗

PubMed1993

Predicting behavior of an enzyme-linked immunoassay model by using commercially available neural network software.

Setting up new immunoassays can be a laborious and expensive task. A relatively new form of multivariate analysis known as neural networks can be applied to this problem with potential savings in reagents and technician time. Neural network software programs for personal computers are now available. We applied one such software package (Brainmaker) to a model ELISA system for measuring human serum albumin. Random combinations of four variable ELISA conditions (antigen concentration, primary and secondary antibody titers, and time for chromagen development) were used to train a three-layered feed-forward network. The trained network was then used to predict measured absorbances as a function of the four input variables in separate cross-validation sets. The network adequately predicted the effect of the input variables on the absorbance produced. With use of such methods, optimal conditions for the linear dependence of absorbance on antigen concentration can be evaluated on the computer rather than in the laboratory, with subsequent savings of time and money.

Antibodies↗

PubMedDate not supplied

Schooling, occupational motivation, and personality as related to success in paramedical training.

Measures of prior school experience, motivation for working in a health care job, and personality were evaluated as potential predictors of success in Navy paramedical training. When, by multiple regression procedures, years of school completed, numbers of suspensions or expulsions from school, occupational motivation, and Comrey personality scale scores were combined with an aptitude measure that is used for guiding recruits into paramedical training, the cross-validity for predicting training completion was significantly increased (P less than 0.001) from 0.40 to 0.50. Practical means for applying these measures to the screening of candidates for paramedical training were developed. Results of the evaluation suggest that guiding people into jobs that they neither prefer nor perceive as congruent with their abilities and interests can significantly reduce the chances for occupational success.

Achievement↗

PubMed1994

Neural-network classification of normal and Alzheimer's disease subjects using high-resolution and low-resolution PET cameras.

UNLABELLED: Neural-network classification methods were applied to studies of FDG-PET images of the brain acquired from a total of 77 "probable" Alzheimer's disease and 124 normal subjects at two different centers. METHODS: Classification performances, as determined by relative-operating-characteristic (ROC) analyses of cross-validation experiments, were measured for FDG PET images obtained with either a 15-mm FWHM PETT V or a 6-mm FWHM Scanditronix PC-1024-7B camera for various methods of data representation. Neural networks were trained to distinguish between normal and abnormal subjects on the basis of regional metabolic patterns. For both databases, classification performance could be improved by increasing the "resolution" of the representation (decreasing the region size) and by normalizing the regional metabolic values to the value of a reference region (occipital region). RESULTS: The optimal classification performance for Scanditronix data (ROC area = 0.95) was higher than that for PETT V data (ROC area = 0.87). Under Bayesian theory, the classification performance with Scanditronix data corresponded to an ability to change a pre-test probability of disease of 50% to a post-test probability of either 90% for a positive classification or 10% for a negative classification. CONCLUSION: This classification can be used to either strongly confirm or rule out the presence of abnormalities.

Aged↗

PubMed1994

Prognosis of rehabilitation outcome in head injury using the Disability Rating Scale.

In this correlational study, we investigated the prediction of functional status on discharge from head injury rehabilitation in 64 adults with traumatic closed head injury. Subjects were rated on Rappaport's Disability Rating Scale during rehabilitation to obtain the Disability Rating Score on admission to rehabilitation, recovery rate during the first month of rehabilitation, and discharge Disability Rating Score. Potential prognostic variables included demographic and social characteristics, severity of injury indicators, head injury deficits present on admission to rehabilitation, and initial Disability Rating Score, and recovery rate. Multiple regression analyses were performed to determine if discharge Disability Rating Score could be predicted from subsets of the potential prognostic variables. Significant contributions were made to the regression equations by initial Disability Rating Score, recovery rate, post-traumatic amnesia and cognitive deficits. A single multiple regression containing the four significant predictors retained initial Disability Rating Score and recovery rate as significant. The findings were cross-validated on a new sample of 30 head injury patients. Initial Disability Rating Score on admission to rehabilitation emerged as a useful predictor of rehabilitation outcome.

Adolescent↗