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PubMed1993

The American Joint Committee on Cancer. Criteria for prognostic factors and for an enhanced prognostic system.

The American Joint Committee on Cancer proposes the following criteria for evaluating putative prognostic factors: they must be (1) significant, (2) independent, and (3) clinically important. Furthermore, we suggest the criteria for selecting a prognostic system that includes TNM and new prognostic factors. These criteria are: (1) easy for physicians to use; (2) provides predictions for all types of cancer; (3) provides the most accurate relapse and survival predictions at diagnosis and for every year lived for each patient; (4) provides group survival curves, where the grouping can be by any variable including outcome and therapy; (5) accommodates missing data and censored patients and is tolerant of noisy and biased data; (6) makes no a priori assumptions regarding the type of data, the distribution of the variables, or the relationships among the variables; (7) can test putative prognostic factors for significance, independence, and clinical importance; (8) accommodates treatment information in the evaluation of prognostic factors; (9) accommodates new putative prognostic factors without changing the model; (10) accommodates emerging diagnostic techniques; (11) provides information regarding the importance of each predictive variable; and (12) is automatic.

Humans↗

PubMed1991

Mixed model segregation analysis of LDL-C concentration with genotype-covariate interaction.

Mixed model complex segregation analyses have in the past ignored the possibility of genotype-covariate interaction. Only in the nonmixed model with polygenic heritability equal to zero have segregation analyses been performed that allowed for genotype specific regression of the phenotype on covariates. We present an extension of Hasstedt's [1982] mixed model likelihood approximation which does allow for genotype-covariate interaction in the mixed model. Following description of this approximation, we validate the likelihood calculation by a Monte Carlo procedure based on the actual pedigree and missing data structure used in a complex segregation analysis of low density plus very low density lipoprotein cholesterol (LDL-C + VLDL-C) in baboons. The observed averages of the bootstrap parameter estimates adequately recover the generating values, which included parameters specifying genotype-covariate interaction. We then applied both a traditional complex segregation analysis and an analysis with genotype-covariate interaction to test for the presence of a major locus affecting LDL-C levels in baboons. The model including genotype-covariate interaction was significantly different from the model without interactions, and strongly supported the hypothesis that there is a segregating Mendelian locus as opposed to a random environmental factor. This major locus accounts for approximately 46% of the variance in LDL-C levels, as compared to 40% explained by a locus with no genotype-covariate interaction.

Animals↗

PubMed2026

Effects of Dynamic Neck Sensorimotor Biofeedback Training in Individuals With Mechanical Neck Pain: A Pilot Randomized Controlled Trial.

Mechanical neck pain (MNP) is commonly accompanied by pain-related functional limitations, sensorimotor disturbances, and fear of movement, which together may contribute to persistent disability. This preliminary randomized controlled trial study investigated the short-term effects of dynamic neck sensorimotor-based biofeedback training in individuals with MNP. 20 MNP patients from outpatient clinics were assigned to a biofeedback training group or a control group. The training group underwent dynamic biofeedback exercises twice weekly for 2 weeks, whereas the control group performed repeated cervical movements without biofeedback. Outcomes included cervical kinematics as repositioning errors (RPE), movement units (MU), maximal range of motion (ROM), and subjective measures, including pain intensity, Neck Disability Index (NDI), and Fear-Avoidance Beliefs Questionnaire (FABQ). All participants completed post-intervention assessments; adherence in the training group was 100%, with no missing data and no adverse events reported. Within the biofeedback training group, participants receiving biofeedback training demonstrated greater improvements in cervical repositioning accuracy during flexion (51.95%, p = 0.04) and extension (46.67%, p = 0.02), along with reductions in fear-avoidance beliefs related to physical activity and work (p < 0.05); these changes were less apparent in the active control group. Exploratory regression analyses suggested associations between improvements in repositioning accuracy and pain reduction, and between increased cervical range of motion and improvements in fear-avoidance beliefs related to physical activity. These pilot findings suggest that dynamic sensorimotor biofeedback training may improve proprioceptive acuity and fear-avoidance beliefs in individuals with MNP, supporting further evaluation in an adequately powered randomized trial.

Humans↗

PubMed1990

A Markovian model for comparing incidences of side effects.

For clinical trials that entail observations at successive visits for the occurrence of a side effect, this paper considers a likelihood-based method to compare side effect incidence rates. The method, which employs the assumption of a Markov chain of order one for the vectors of binary responses, handles missing data due to premature withdrawals. An actual numerical example and a simulated example illustrate the technique.

Clinical Trials as Topic↗

PubMed1990

The measurement of change of quality of life in clinical trials.

A model is presented for the measurement of change of quality of life in clinical trials with time under the influence of one or more treatments. Quality of life is regarded as a multidimensional latent variable, and is measured through dichotomous item responses on a number of points in time. Change of quality of life is 'explained' with a latent logistic regression model which may include parameters for the time process, the effects of clinical treatments, and interaction parameters. By assuming the absence of patient/time interaction within treatment groups, the parameters of the time process and the treatment effects can be estimated independently of the latent quality of life parameters at the start of the treatment. Consequently, differential mortality, censoring mechanisms, and other mechanisms causing missing data can be ignored.

Breast Neoplasms↗

PubMed1991

A bibliography and comments on the use of statistical models in epidemiology in the 1980s.

This paper reviews developments in statistical modelling in epidemiology in the 1980's, with emphasis on cohort and case-control studies. The central roles of the logistic and proportional hazard models are highlighted, and it is shown how these models lead to a deeper understanding of classical designs and methods of analysis as well as to efficient new designs and analytical procedures. The important area of model misspecification is discussed, including the problems of omitted latent structure, mis-modelling of available measurements, missing data and errors in measurements. Various designs motivated by the logistic model are illustrated numerically, and designs based on the proportional hazards model are discussed, as are papers on sample size determination. There are brief introductions to the literature on other topics, including attributable risk, disease clustering, family studies and genetics, analysis of disease incidence data, infectious disease, longitudinal data, screening and miscellaneous related topics in statistics. An extensive bibliography is indexed according to the outline of the paper.

Data Interpretation, Statistical↗

PubMed1993

Time-period effects in longitudinal studies measuring average rates of change.

Random time-period effects are unexplained increases or decreases in the observed value for all individuals measured at a particular time point in a longitudinal study. They can be caused by learning effects, changes in equipment, personnel and overall subject co-operation. We investigate the consequences of time-period effects in random coefficient regression models, where interest is in the average rate of change (slope) of a continuous outcome. In a study with a single group of subjects, they can lead to conditionally biased estimates of the mean slope and its variance (conditional on the time-period effects). Calculations suggest that the increase in sample size required to maintain a specified precision of the mean slope estimate over repeated studies may be substantial. In a study with a concurrent control group, however, time-period effects do not distort the expectation, estimated variance or the distribution of the difference between the mean slopes. With missing data, in addition to time-period effects, an unbiased estimate of a single mean slope remains problematic, but one can use standard maximum likelihood techniques to obtain consistent estimators of the difference in mean slopes and its variance. This suggests the importance of a concurrent control group when potential time-period effects are of concern.

Bias↗

PubMed1988

Finding motion parameters from spherical motion fields (or the advantages of having eyes in the back of your head).

A theory is developed for determining the motion of an observer given the motion field over a full 360 degree image sphere. The method is based on the fact that for an observer translating without rotation, the projected circular motion field about any equator can be divided into disjoint semicircles of clockwise and counterclockwise flow, and on the observation that the effects of rotation decouple around the three equators defining the three principal axes of rotation. Since the effect of rotation is geometrical, the three rotational parameters can be determined independently by searching, in each case, for a rotational value for which the derotated equatorial motion field can be partitioned into 180 degree arcs of clockwise and counterclockwise flow. The direction of translation is also obtained from this analysis. This search is two dimensional in the motion parameters, and can be performed relatively efficiently. Because information is correlated over large distances, the method can be considered a pattern recognition rather than a numerical algorithm. The algorithm is shown to be robust and relatively insensitive to noise and to missing data. Both theoretical and empirical studies of the error sensitivity are presented. The theoretical analysis shows that for white noise of bounded magnitude M, the expected errors is at worst linearly proportional to M. Empirical tests demonstrate negligible error for perturbations of up to 20% in the input, and errors of less than 20% for perturbations of up to 200%.

Humans↗

PubMed1989

[General insecurity, "false" and "real" security: arguments for the routine study of hospital patients for anti-HIV].

HIV infection has become an important risk for medical personal. Use of sufficient preventive measures with all patients and patient materials is time consuming, expensive and impracticable. In the present epidemiological situation anti-HIV testing of all hospital patients will give correct information on the presence or absence of HIV infection for 999 of 1000 patients. In addition to the increased safety of medical personal, testing will have several other advantages, some for the HIV infected persons: (1) In patients with HIV-related diseases time consuming delays in diagnosing the disease can be avoided. An earlier start of therapy will improve prognosis. (2) In HIV-infected persons a therapy can be chosen which exerts the least stress to the immune system. This may delay manifestation or progression of HIV-related diseases. (3) By medical surveillance of HIV-infected persons prophylaxis and immediate therapy of opportunistic infections is possible, which may prolong survival time. (4) Counselling of persons previously unaware of their HIV infection will slow down spread of HIV in the population. (5) Missing data on prevalence and incidence of HIV infection in different geographical areas will be available. Apart from the considerable cost reduction by reducing the use of extensive preventive measures to less than 10% of patients, routine screening of all patients is already economic if testing of 10,000 patients will prevent one single new infection by counselling of people with previously unknown HIV infection.

AIDS Serodiagnosis↗

PubMed1987

Oestrogen receptor activity in breast cancer detected at a prevalence screening examination.

In view of the possible introduction of screening programmes, this study compares oestrogen receptor (ER) levels in a series of women whose primary tumour was detected by screening and an age-matched consecutive series of women whose tumours were diagnosed after symptomatic presentation. Because of missing data and other statistical considerations, the comparison was made using T1 and T2 categories of tumour only. Some differences were found: the distribution of ER levels was significantly different in the two groups, with more extreme values in the symptomatic series; the screening series, however, had more moderate/rich ER levels than the symptomatic group. Tumours of special pathological type (for example, tubular, cribriform, lobular, medullary, and mucoid) were more likely to be ER-moderate or -rich, and there were more of these tumours in the screening series. The relationship of these findings to tumour growth rate is discussed. The study highlights the difficulty of obtaining sufficient tissue for conventional DCC biochemical assays from the small non-invasive tumours found by screening, and suggests that newer alternative methods employing monoclonal antibodies may be required for such types of tumour.

Aged↗

PubMedDate not supplied

[Results of physiological and psychological studies of different body types. A study of 210 patients with cardiovascular diseases and 100 students (author's transl)].

210 male patients with myocardial infarction, functional cardiovascular diseases, and angina pectoris hospitalized in the course of a cardiac rehabilitation program had been studied. Missing data in some anthropometric variables reduced the sample to 199 patients. The body of data included various anthropometric variables and indices, parameters of the circulatory and respiratory systems, biochemical measures, personality questionnaires, and information about the psychosocial background. In order to replicate the findings a sample of 100 students was studied, too. The measures and indices of body type are influenced by age, which leads to age-dependent spurious correlations between body type and other variables if this dependency is not corrected. Different statistical approaches proved the superiority of a factor-analytic typisation based on a "body-breadth" and "body-size" factor. There is a low correlation between body type and disposition for certain diseases showing that patients with "athletic" or "pycnic" body build suffer preferably from coronary infarction. Significant differences between body types exist for blood pressure, physical fitness, several psychosocial data, and the number of previous courses of treatment. Correlations of body type with personality dimensions and bodily complaints did not occur.

Age Factors↗

PubMed1988

Factors relating to age of onset in autism.

We examined the distribution of ages of onset of autism and related communication handicaps and assessed factors related to age of onset. Subjects were approximately 1,800 children seen at Division TEACCH (Treatment and Education of Autistic and related Communication handicapped CHildren) since 1970. Exact numbers of subjects varied with different analyses due to missing data. Data were gathered through direct assessment, interview, and questionnaire. Seventy-six percent of autistic children were identified by parents by 24 months of age, and 94% by 36 months. Families reporting early onset tended to seek help sooner and to be seen by TEACCH sooner. Early onset was most clearly related to severity as measured by IQ and ratings on the Childhood Autism Rating Scale (Schopler, Reichler, & Renner, 1986). The findings support the treatment of age of onset of autism by DSM-III-R (American Psychiatric Association, 1987).

Age Factors↗

PubMed1994

Beta blocker use in the treatment of community hospital patients discharged after myocardial infarction.

OBJECTIVE: To explore the reasons for underutilization of beta blocker treatment after acute myocardial infarction. DESIGN: A retrospective chart review. SETTING: Two large community hospitals in Milwaukee, Wisconsin. PATIENTS/PARTICIPANTS: All subjects (n = 694) discharged alive from July 1, 1990, to June 30, 1991, who had a diagnosis of acute myocardial infarction were eligible. Of these, 250 had missing data, resulting in a final sample of 444. RESULTS: Twenty-nine percent of the 444 patients were prescribed beta blocker therapy on discharge. Characteristics of the patients and their treatment associated with receipt of beta blocker therapy were identified with a logistic regression model. The adjusted odds ratios were 0.52 for female gender, 0.34 for no health insurance, 0.21 for chronic obstructive pulmonary disease, 0.46 for congestive heart failure, 0.28 for atrioventricular block, 1.86 for hypertension, 1.93 for chest pain during acute myocardial infarction, and 4.65 for prehospital beta blocker use. Prescription of beta blocker therapy was also influenced by receipt of other treatment modalities. The adjusted odds ratios were 0.23 for receipt of beta blocker therapy associated with myocardial revascularization, 0.18 for prescription on discharge of calcium channel blockers, and 0.22 for receipt of angiotensin-converting enzyme inhibitors. CONCLUSION: A minority of patients discharged after acute myocardial infarction receive beta blocker therapy, and women are only half as likely as men to receive it, after controlling for other factors. Though there are no data relating to whether calcium channel blockers or angiotensin-converting enzyme inhibitors lessen the protective effect of beta blocker therapy post-acute myocardial infarction, it would appear that these agents are frequently being used in lieu of beta blocker therapy for post-acute myocardial infarction patients.

Adrenergic beta-Antagonists↗

PubMed1987

The clinical use of the Ohmeda Automated Anesthesia Record Keeper integrated in the Modulus II Anesthesia System. A preliminary report.

While performing his complex array of tasks, the anesthesiologist is also responsible for maintaining an anesthetic record. Up to now, this has been done by hand. The clinical use of automated anesthesia record keeping is presently evaluated. The anesthesia records generated by the Ohmeda Automated Anesthesia Record Keeper integrated in the Modulus II Anesthesia System is compared to hand written records. The differences between the two records of identical patients are quantified as erroneous or missing data. With the criteria adapted, we found significant and clinically relevant differences which stress the importance of automated record keeping.

Anesthesiology↗

PubMed1994

Improved body weight status as a result of nutrition intervention in adult, HIV-positive outpatients.

OBJECTIVE: Malnutrition is an important consequence of infection with the human immunodeficiency virus (HIV); involuntary weight loss greater than 10% is one criterion that the Centers for Disease Control and Prevention uses for the diagnosis of acquired immunodeficiency syndrome (AIDS). This study was designed to determine whether nutrition intervention in a group of adult, HIV-positive outpatients affected weight maintenance. METHODS: We undertook a retrospective review of 175 patient charts from the AIDS Reproductive Health Clinic and the Center for Special Studies at The New York Hospital. Forty-nine charts were excluded because the patient expressed a desire to reduce weight, discontinued medical care, or died. Seven charts were eliminated because of missing data. In the remaining patients (n = 119), weights were recorded for the initial clinic contact and for a follow-up visit at least 6 months later. Nutrition intervention completed by a registered dietitian was indicated on 42 patient charts (intervention group); intervention included dietary assessment, intake analysis, appropriate counselling, follow-up, and provision of supplements as needed. The remaining 77 charts did not indicate nutrition intervention; this group was called the nonintervention group. Differences between the intervention and nonintervention groups were analyzed using the two-tailed Fisher exact test and the Mann-Whitney nonparametric test. RESULTS: Forty-two subjects (35% of the total) recieved nutrition intervention, including all of those with gastrointestinal problems (n = 10) and wasting (n = 11). Individuals in the intervention group gained a significant (P < .02) 1.2 +/- 11.4 lb (mean +/- standard deviation; median = +3 lb) compared with those in the nonintervention group who lost a mean of 3.5 +/- 12.8 lb (median = -4 lb). Twenty-six subjects (63%) in the intervention group maintained or gained weight compared with 32 subjects (42%), in the nonintervention group. CONCLUSION: The results of this study suggest that nutrition intervention in HIV-infected persons can improve nutritional status and may lead to an enhanced ability to fight infection.

Adult↗

PubMedDate not supplied

Correlates of dissociative symptomatology in patients with physical and sexual abuse histories.

Recent studies have demonstrated a high prevalence of sexual and physical abuse histories and high levels of dissociative symptoms in psychiatric inpatients. We examined whether severity, frequency, and age of onset of abuse correlated with subjects' levels of dissociative symptoms. Sixty-four women reporting a lifetime history of physical and/or sexual abuse were recruited from consecutive admissions to three wards of a psychiatric hospital. Subjects completed the Life Experiences Questionnaire (LEQ) and the Dissociative Experiences Scale (DES). Subjects' self-reports of severity, frequency, and age of onset of abuse were analyzed for correlations with DES score. More invasive sexual abuse was associated with more dissociation. Higher-frequency physical abuse was associated with more dissociation, but no conclusion could be drawn about the impact of frequent sexual abuse due to missing data. An inverse correlation was found between age of onset of abuse and degree of dissociative symptomatology. These preliminary findings are consistent with hypotheses linking more severe, more chronic, and earlier abuse to the greater development of dissociative symptoms. The findings further emphasize the importance of recognizing dissociative symptoms in the clinical setting, and of continued study into the effects of childhood trauma.

Adolescent↗

PubMedDate not supplied

A computer program for selection of variables in diagnostic and prognostic problems.

The computer program INDEP-SELECT has been developed for selection of an optimal subset from a set of possibly informative diagnostic or prognostic variables. But the program is equally useful for other discriminant analysis or pattern recognition problems involving variable selection. The approach is probabilistic; i.e., diagnostic probabilities are assigned to a patient on the basis of the values observed on the diagnostic variables. The statistical model used is largely based on the assumption of independency between the variables, but one model-parameter, the so-called 'global association factor', is added in order to take dependency into account. The stepwise forward selection strategy of adding in each selection step a new variable to the set of already selected variables, is used. The user may choose between a number of selection criteria. Such a criterion is used in order to decide in each selection step which variable should be added. All criteria are based on measures of diagnostic or prognostic performance. INDEP-SELECT is able to handle a large number of variables, also with missing data, and a large number of patients. The program is written in ANS Standard FORTRAN, and takes relatively little computation time.

Bayes Theorem↗

PubMed1994

A PC program for computing confidence bands for average and individual growth curves.

Dawson et al. (Am. J. Med. Genet. 7, 529-536, 1980) developed a procedure for constructing confidence bands for both average and individual growth curves which may be of considerable value in the study of growth and development. This paper describes their method for constructing, and provides a menu-driven GAUSS386i program for computing these confidence bands. It is demonstrated how these bands are useful for both the diagnosis and prognostication of growth patterns with known levels of confidence. It is assumed that the study is planned so that individuals will be measured at the same times, but missing data are allowed.

Confidence Intervals↗