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L L Kupper

Publications and source records attributed to L L Kupper.

At least 73 records · Page 4Linked to original sources
PubMed1981

Matching in epidemiologic studies: validity and efficiency considerations.

Validity and efficiency issues are considered with regard to the use of matching and random sampling as alternative methods of subject selection in follow-up and case-control studies. We discuss the simple situation involving dichotomous disease and exposure variables and a single dichotomous matching factor, and we consider the influence on efficiency of a possible loss of subjects due to matching constraints. The decision to match or not should be motivated by efficiency considerations. An efficiency criterion based on a comparison of confidence intervals under matching and random sampling for the effect measure of interest (the risk ratio and risk difference in follow-up studies, and the odds ratio in case-control studies) leads to the following conclusions when the sampling method does not influence the size of the comparison group. In follow-up studies, matching on a confounder is expected to lead to a gain in efficiency over random sampling, while matching on a nonconfounder is not expected to result in a loss of efficiency. In case-control studies, the same conclusions hold, except that matching is not as advantageous as in follow-up studies and can lead to a loss of efficiency in some situations (usually of little practical importance). When matching reduces the size of the comparison group, there is likely to be a meaningful gain in efficiency due to random sampling only when the matched comparison group is at most 40-50% the size of the randomly-sampled comparison group is a follow-up study, and at most 50-65% the size in a case-control study.

Follow-Up Studies↗
PubMed1981

Comparisons of confidence intervals for attributable risk.

Confidence intervals for the attributable risk in various epidemiologic study designs are obtained, via a transformation, from the confidence interval for the natural logarithm of the product of the probability of being exposed to the risk factor, and the risk ratio minus one. When the estimated attributable risk is between .21 and .79, the width of the logarithmic transformation (LT)-based interval is less than that for a maximum likelihood (ML)-based interval. This simple sufficient condition applies to all three well-known epidemiologic study designs. Computer simulation results further demonstrate the superiority of the LT-based interval to the ML-based one when the sufficient condition is satisfied.

Epidemiologic Methods↗
PubMed1980

Department of Epidemiology and Public Health, School of Medicine, Yale University, New Haven, CT.

This paper distinguishes between 2 concepts for measuring the incidence of disease: risk and rate. Alternative procedures for estimating these measures from epidemiologic data are reviewed and illustrated. An attempt is made to integrate statistical principles with epidemiologic methods while minimizing the use of higher mathematics. Several theoretical and practical criteria are discussed for choosing the appropriate incidence measure in the planning of a study and for selecting the best method of estimation in the analysis.

Epidemiologic Methods↗
PubMed1979

Analysis of dichotomous response data from certain toxicological experiments.

In certain toxicological experiments with laboratory animals, littermate data are frequently encountered. It is generally recognized that one characteristic of this type of data is the "litter effect", i.e., the tendency for animals from the same litter to respond more alike than animals from different litters. In this paper attention is restricted to dichotomous response variables that frequently arise in toxicological studies, such as the occurrence of fetal death or a particular malformation. Various techniques for estimating the underlying probability of response are discussed. A number of generalized models that have recently been proposed to take the litter effect into account are breifly reviewed and compared to the simpler binomial and Poisson models. Various procedures for assessing the significance of treatment-control differences are presented and their relative merits discussed. Finally, future research needs in this area are outlined.

Animals↗
PubMed1978

The use of a correlated binomial model for the analysis of certain toxicological experiments.

In certain toxicological experiments with laboratory animals, the outcome of interest is the occurrence of dead or malformed fetuses in a litter. Previous investigations have shown that the simple one-parameter binomial and Poisson models generally provide poor fits to this type of binary data. In this paper, a type of correlated binomial model is proposed for use in this situation. First, the model is described in detail and is compared to a beta-binomial model proposed by Williams (1975). These two-parameter models are then contrasted for goodness of fit to some real-life data. Finally, numerical examples are given in which likelihood ratio tests based on these models are employed to assess the significance of treatment-control differences.

Abnormalities, Drug-Induced↗
PubMed1978

Alternatives to Rothman's approach for assessing synergism (or antagonism) in cohort studies.

K.J. Rothman has explored in some detail the issue of assessing the potential presence of synergism (or antagonism) in data generated from either a cohort or a case-control study. Arguing that the "natural" scale for quantifying the joint effects of two or more factors acting in combination is the probability scale, he has proposed a procedure based on a ratio-type index for evaluating two-factor interaction in the presence of non-zero background effects. In this paper, the authors review the rationale underlying Rothman's approach for a cohort study. They then present what they maintain is a simpler and more appropriate test procedure (utilizing a linear contrast of the observed risks) for the additive approximation to his basic probabilistic model of "no interaction." A likelihood ratio test based on his original model is also proposed, as well as a closed form approximation to it. Finally, the assessment of interaction in cohort studies involving exposure factors measured at more than two levels is addressed.

Epidemiology↗
PubMed1976

Physician management in primary care.

Minimal explicit consensus criteria in the management of patients with four indicator conditions were established by an ad hoc committee of primary care physicians practicing in different locations. These criteria were then applied to the practices of primary care physicians located in a single community by abstracting medical records and obtaining questionnaire data about patients with the indicator conditions. A standardized management score for each physician was used as the dependent variable in stepwise regression analysis with physician/practice and patient/disease characteristics as the candidate independent variables. For all physicians combined, the mean management scores were high, ranging from .78 to .93 for the four conditions. For two of the conditions, care of the normal infant and pregnant woman, the management scores were better for pediatricians and obstetricians respectively than for family physicians. For the other two conditions, adult onset diabetes and congestive heart failure, there were no differences between the management scores of family physicians and internists. Patient/disease characteristics did not contribute significantly to explaining the variation in the standardized management scores.

Adult↗
PubMed1976

Communication, compliance, and concordance between physicians and patients with prescribed medications.

Forty-six practicing physicians and 357 patients with diabetes mellitus or congestive heart failure were the subjects for this study, which focuses on the impact of medication regimen and doctor-patient communication in affecting patient medication-taking behavior and physician awareness of these behaviors. Four types of medication errors were defined: omissions, commissions, scheduling misconceptions and scheduling non-compliance. The average error rates were 19 per cent, 19 per cent, 17 per cent and 3 per cent, respectively. The combined average error was 58 per cent; scheduline non-compliance on the part of the patient was a minor component. Specific aspects of the medication regimen were associated with increased errors: (1) the more drugs involved between the doctor-patient pair, the greater the errors of omission and commission; and (2) the greater the complexity of the scheduling, the greater the errors of commission and scheduling misconceptions. If the patient did not know the function of all his drugs, errors of commission and scheduling misconception increased. Neither characteristics of patients nor the severity of disease were influential in determining the extent of medication errors. For patients with congestive heart failure, good communication of instructions and information from physician to patient was associated with low levels of all types of errors.

Aged↗
PubMed1975

Doctor-patient communication and outcomes among diabetic patients.

This study reports on 242 diabetic patients from the practices of 42 physicians. Communication from physician to patient was studied to determine the effect of communication on subsequent patient outcomes. Patients and physicians were questioned on instructions provided for diabetic management and self-care. The average level of effective communication for all patients in the study was 67 percent. Insulin-dependent diabetics had the best communication scores, those controlled on diet alone the poorest, while oral medication patients were intermediate. Although overall communication scores showed no significant correlation with diabetic control status, patient satisfaction, compliance in taking prescribed medication, or frequency of hospitalization, specific communication items were highly correlated with corresponding behavioral outcomes.

Administration, Oral↗
PubMed1975

Correlates of satisfaction and dissatisfaction with medical care: a community perspective.

The attitude of the public toward physicians and medical services is an issue of current concern and debate. To address this problem, an instrument was developed using Thurstone scaling methods in conjunction with a Likert format and a modified scoring technique. Following pretesting of the instrument among both patient and population samples, a survey was conducted among the residents of a probability sample of households in a city of 200,000 people. The attitude questionnaire was completed by 1,713 adults in 1,112 households. Overall, attitudes were favorable toward the professional competency and the personal qualities of physicians. Accessibility, including costs and convenience, were less highly regarded. Men were less satisfied than women and blacks less satisfied than whites. Particularly negative attitudes were expressed toward the personal qualities of physicians by young blacks, whereas among blacks over 60 the negative effect was toward cost and convenience. Having a regular physician and long attendance with that physician were correlated with positive attitudes. The most negative sentiment was expressed by women without regular source of care. Medical services are being sought and obtained by a large segment of society, but problems of costs and acceptability for the elderly, low social class persons, members of large families, and for blacks still remain.

Community Health Services↗
PubMed1975

Practice characteristics and quality of primary medical care: the doctor-patient relationship.

Physician and practice characterisitics were reviewed in relation to the quality of the doctor-patient relationship in primary medical care. This relationship was defined in terms of communication between physicians and patients, patient satisfaction with care, and physician awareness of patient concerns. The study subjects were mothers of infants and pregnant women, identified from the offices of a random sample of primary care physicians is a single community. The patients of 49 physicians, 363 pregnant women and the mothers of 523 infants were the subjects of the study. When controlled for patient characteristics, communication was better for pediatricians with mothers of infants and for obstetricians with pregnant women as compared with other physicians. Mothers of infants were more highly satisfied with care provided by residency-trained physicians; pregnant women were more satisfied with non-Board certified physicians. Physician awareness of patient concerns presented a mixed pattern of associations with several physicians and practice characteristics. These findings suggest that physician credentials are not consistently associated with the three identified dimensions of the doctor-patient relationship.

Adult↗