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Biomedical subjects

K C Cain

Publications and source records attributed to K C Cain.

52 records · Page 3Linked to original sources
PubMed1986

Optimal detection of the progression of coronary artery disease: comparison of methods suitable for risk factor intervention trials.

To assess the best method of quantitating progression of coronary disease, we studied four measurements in 114 coronary segments from 35 medically treated patients from whom angiograms were obtained 5 years apart. Only stenoses of less than 70% that were visualized in nearly identical projections on both angiograms were evaluated. Vessel edges were measured by use of catheter calibration and an automated computer algorithm yielding two "absolute dimensions" (mean and minimum diameters) and two measurements (percent stenosis and atheroma area) that required a "normal reference" diameter. The coefficient of variation for repeated segment measurements was less for mean and minimum diameter than for percent stenosis and area of atheroma. The best measure of progression of coronary disease as determined by t test comparison of different methods was the change in mean diameter over time (6.7 +/- 14.1% decrease), whether calculated on a per coronary segment or per patient basis (p less than .001). Based on this measurement and its standard deviation of progression of coronary disease in this patient subset with relatively benign disease, it is estimated that 470 patients per group would be required for an interventional study to demonstrate a 33% reduction in disease progression (207 patients for 50% reduction) at a 95% confidence level and 90% power.

Cardiac Catheterization↗
PubMed1986

The significance of bone marrow involvement in non-Hodgkin's lymphoma: the Eastern Cooperative Oncology Group experience.

Data from four clinical trials conducted by the Eastern Cooperative Oncology Group (ECOG) were used to investigate the importance of bone marrow involvement as a prognostic factor in patients with non-Hodgkin's lymphoma (NHL). A total of 502 patients, 275 with nodular, poorly differentiated lymphocytic lymphoma (NLPD) and 227 with diffuse histiocytic lymphoma (DHL) or diffuse mixed-cell lymphoma (DML), were included in this analysis. Patients were separated into four categories: stage III, stage IV with bone marrow involvement (stage IV-M), stage IV without marrow involvement (stage IV-O), and stage IV with bone marrow and other organ involvement (stage IV-OM). Among the DHL and DML patients, the incidence of marrow involvement was 23%. However, stage IV-M patients had a prognosis that is similar to stage IV-O and stage IV-OM and worse than stage III patients. In contrast, the incidence of involvement with NLPD was 59% and patients with stage IV-M had a survival not different than stage III and not worse than stage IV-O and stage IV-OM. The results suggest that the current emphasis on bone marrow biopsy(s) as a routine diagnostic staging procedure for patients with NHL should be reevaluated. The necessity for this procedure in stage III patients with NLPD is not apparent from our data. One can still justify a bone marrow biopsy in stage I and II patients and can confirm the complete clinical response when all nodes have regressed in more advanced disease.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1985

The superiority of sequential over simultaneous testing.

Diagnostic tests are typically used to help the physician select among available management options. When two or more tests are available, using them sequentially is potentially more efficient than simultaneously performing multiple tests, in that the former approach may allow the physician to perform fewer tests. In particular, we demonstrate that if two common conditions are met, any simultaneous strategy involving at least as many tests as management options can be replaced by a sequential strategy with the same outcome and a smaller expected number of tests. It follows that, in many clinical situations in which the benefits of performing fewer tests outweigh the costs that may result from delaying diagnosis, simultaneous strategies cannot be optimal. This result can decrease the number of diagnostic strategies that the physician or decision analyst needs to consider.

Decision Making↗
PubMed1984

Patient-oriented performance measures of diagnostic tests. 1. Tools for prospective evaluation of test order decisions.

Prospective assessment of a test for possible use in evaluation of a patient ideally should be based on the test's ability to affect subsequent patient management beneficially, in relation to both the costs of the test itself and the costs of misclassification of disease status. This requires specification of the costs and benefits of subsequent actions and the cost of the test, estimation of the probability of disease, knowledge of the discriminatory properties of the test, and formal decision analysis. Often, however, the physician has less complete information with which to make a test order decision. A spectrum of performance measures exists for characterising a diagnostic test, ranging from measures that are largely patient-independent to measures that are highly patient-dependent. Two measures from the patient-dependent part of the spectrum, Assignment Potential and Assignment Strength, can be useful in decision making when formal decision analysis is not feasible. A third measure, the U-Factor, is the product of the other two, and is a computational tool that facilitates formal decision analysis.

Diagnosis↗
PubMed1984

Patient-oriented performance measures of diagnostic tests. 2. Assignment potential and assignment strength.

Assignment Potential (AP) is a performance measure of a diagnostic test, characterizing the chance that, as a consequence of performing the test, the probability of disease will exceed a decision threshold, thereby permitting a management action to be taken. Another performance measure, Assignment Strength (AS) characterizes the average extent to which a decision threshold will be exceeded when the post-test probability of disease does exceed the threshold. Both AP and AS are functions of prior probability of disease and decision threshold, and can be represented as two-dimensional contour maps indicating their behavior throughout the entire probability and threshold space. AP and AS can be determined for both discrete-valued tests and tests with continuous spectra of results. The contour map displays facilitate determination of the values of these measures at any prior probability and threshold, as well as visual sensitivity analysis for ranges of prior probability and/or threshold. AP and AS may be useful to the clinician in prospective evaluation of a diagnostic test in situations where formal decision analysis is not feasible.

Diagnosis↗
PubMed1984

Patient-oriented performance measures of diagnostic tests. 3. U-Factor.

When a clinician is faced with the problem of deciding whether to order a specific diagnostic test, the ideal information would be the utility of the "perform test" branch of the decision tree versus the utility of the "do not perform test" branch. This difference in utility is termed the Expected Utility of the Test ( EUT ). We propose a new performance measure of a test called the U-Factor (UF) which is related to EUT by a simple formula. UF depends on the prior probability of disease and on the decision thresholds at which one would be indifferent between any two immediately subsequent management options, and can be presented as a two-dimensional nomogram. UF is useful as a computational aid in a formal decision analysis, and may be useful as an informal measure of the value of a diagnostic test when a formal analysis is not feasible.

Costs and Cost Analysis↗
PubMed1984

Charts for the early stopping of pilot studies.

Cooperative oncology groups usually run pilot studies of new agents or combinations concurrently with their major randomized clinical trials. A primary objective of these studies is to determine whether the new regimen should be tested further in a group-wide clinical trial. The accrual goals of such pilot studies are typically fixed in advance at between 30 and 40 patients, on the grounds that this number provides a reasonably tight confidence interval on the true response rate. Nevertheless early termination of pilot studies is often desirable either because the regimen appears inactive or because early results indicate extreme activity and justify immediate testing in a randomized study. Statistical charts are provided for early termination in both these situations. The charts are read by specifying the number of evaluable patients already accrued, the number of responses observed and the minimum true response rate, theta 0, at which the regimen would be considered active. The charts provide the posterior probability that the true response rate exceeds theta 0, that is, that the regimen is active. An additional chart that computes a 90% probability interval for the true response rate, based on the observed rate and sample size, is also provided. The use of the chart is illustrated with two examples from the Eastern Cooperative Oncology Group.

Antineoplastic Agents↗
PubMed1984

Approximate case influence for the proportional hazards regression model with censored data.

A method is presented for approximating the influence of individual cases upon regression coefficient estimates obtained from the Cox proportional hazards model. Observations can thus be identified which may greatly influence statistical inferences regarding the effects of prognostic factors upon survival time. An example from a cancer clinical trial is given.

Biometry↗
PubMed1983

Analysis of survival by tumor response.

The common practice of comparing the survival of responders and nonresponders when reporting the results of cancer chemotherapy treatment is investigated. The usual method of comparing responders and nonresponders is biased in favor of responders, and these results are frequently misinterpreted as providing evidence that response prolongs survival, or that the treatment under study is effective. Two valid methods for comparing responders and nonresponders are discussed and recommendations are made concerning the analysis of survival by response. A comparison of survival by response category may be useful descriptively, but such a comparison should not be used for inference concerning treatment effectiveness.

Antineoplastic Agents↗
PubMedDate not supplied

Physicians' attitudes toward tube feeding chronically ill nursing home patients.

OBJECTIVE: To determine attitudes of physicians toward the limitation of tube feeding in chronically ill nursing home patients and the influences of patient preferences and other patient and physician variables on these decisions. DESIGN: Questionnaire-based, mailed survey. Hypothetical case scenarios derived by fractional factorial design to determine the influences of patient and family preferences, age, life expectancy, physical and cognitive functioning; direct scaling to determine the influences of legal and cost considerations. PARTICIPANTS: Randomly selected national samples of American Geriatrics Society and American Medical Association members (n = 141, participation rate 41%). MAIN RESULTS: Nearly all physicians indicated they would withhold (95%) or withdraw (92%) tube feeding in at least one of the 16 scenarios studied. Physician decisions were most highly associated with patient preferences, followed by family preferences, life expectancy, and cognitive status (p less than 0.02 to less than 0.001). When patients and families agreed, physicians concurred in 87% to 95% of the decisions. However, when patients and families disagreed, physicians concurred with patients in only 48% to 55% of the decisions. Increasing physician concern regarding legal and cost considerations was significantly associated with significantly higher and lower likelihoods of tube feeding, respectively (p less than 0.05). CONCLUSIONS: These results suggest that the majority of study physicians are willing to limit tube feeding in nursing home patients under some circumstances. Patient preferences appear to be the most important factor in these decisions, but may not be honored, especially if the wishes of patients and their families are not in concurrence.

Attitude of Health Personnel↗
PubMedDate not supplied

Parents' health, health care utilization, and health behaviors following the violent deaths of their 12- to 28-year-old children: a prospective longitudinal analysis.

Health status, health care utilization, and health behaviors of parents bereaved by the violent deaths of their adolescent and young adult children were examined 4, 12, and 24 months later. Participants were 261 bereaved parents (171 mothers, 90 fathers). About 20% of the parents reported "poor" physical health during the early bereavement period compared with 16% of Americans the same age. Over time, mothers' health improved whereas fathers' health deteriorated. Fathers in poor health compared with fathers in good health are 15 times more likely to report emotional distress and 4.6 times more likely to report trauma symptoms. Mothers in poor health compared with mothers in good health are 11 times more likely to report emotional distress and 3 times more likely to report trauma symptoms. Mothers' reports of physician visits and medication use were higher than fathers', however, mothers' rates for both decreased significantly over time whereas fathers' rates remained constant. Over 70% of the mothers and nearly 60% of the fathers practiced 2 or more health protective behaviors over time--a finding significantly associated with fewer stress-related illnesses, days absent from work, and non-productivity at work. Implications for the findings are discussed.

Adolescent↗
PubMedDate not supplied

The relationship between psychological distress and gastrointestinal symptoms in women with irritable bowel syndrome.

BACKGROUND: Individuals with irritable bowel syndrome (IBS) are reported to experience more symptoms compatible with psychopathologic disorders, abnormal personality traits, and psychological distress. Conversely, individuals with psychiatric disorders report higher levels of gastrointestinal (GI) symptoms compatible with IBS. Thus, psychological distress may contribute to GI symptoms in individuals with IBS. OBJECTIVES: To examine psychological distress in women with IBS, women with similar GI symptoms but not diagnosed (IBS nonpatients, IBS-NP), and asymptomatic Control women. METHODS: The women (N=97) were interviewed, completed questionnaires, and maintained daily diaries for 2 months. Across-women and within-woman analyses were used to calculate the results. RESULTS: The IBS and IBS-NP groups had a higher percentage of lifetime psychopathology and recalled psychological distress. At least 40% of the women in the IBS and IBS-NP groups had positive relationships between daily psychological distress and daily GI symptoms. CONCLUSIONS: Psychological distress is an important component of the IBS symptom experience and should be considered when treatment strategies are designed.

Adult↗
PubMedDate not supplied

Bone resorption levels by age and menopausal status in 5,157 women.

OBJECTIVE: The purpose of this study was to describe bone resorption activity using a biochemical marker according to the categories of age, menopausal status, and selected drug/supplement use in middle-aged and elderly community-based women. DESIGN: This was a cross-sectional study that assessed urinary cross-linked N-telopeptide of type I collagen (NTx) and used self-report data to group women as premenopausal (Pre), perimenopausal (Peri), postmenopausal without hormone replacement therapy (Post), and postmenopausal with hormone replacement therapy (HRT). RESULTS: Mean NTx values were found to be significantly different by group and controlling for age (p = 0.001), with post hoc tests showing all pairwise group comparisons as significantly different (p = 0.001), except that the Pre and HRT groups were not significantly different. Both the Peri and the Post NTx levels were significantly higher than the Pre and the HRT groups'. NTx values in the Peri group varied with age-the youngest Peri women were similar to Pre women, and the oldest Peri women were similar to Post women. Significantly lower NTx levels were found only in the Post (p = 0.009) and HRT (p < 0.001) groups using diuretics compared with nonuse and only in the HRT group using calcium supplements compared with nonuse (p = 0.006). No differences by thyroid use were found. With a biochemical marker, the results showed that bone resorption activity differences could be demarcated in women according to age, estimated menopausal stage, and selected drug/supplement use. CONCLUSIONS: These results support the usefulness of NTx assessment for indicating bone resorption activity and therefore the potential for osteoporosis or for monitoring the efficacy of antiresorptive therapies.

Adult↗
PubMedDate not supplied

Measuring preferences for health states worse than death.

Previous research indicates that persons assigning values to ranges of health states consider some states to be worse than death. In a study of decisions regarding life-sustaining treatments, the authors adapted and assessed existing methods for their ability to identify and quantify preferences for health states near to or worse than death in a population of well adults and nursing home residents. The cognitive burdens involved in these decisions were also evaluated. Hypothetical health states based on six attributes of functional status were constructed to describe severe constant pain, dementia, and coma. The methods of rank order, category scaling, time tradeoff, and standard gamble were adapted to quantify states worse than death. Cognitive burden was assessed using completion rates, interviewer assessments, respondents' self-reporting, and investigators' evaluations. For both respondent groups, all methods showed similar degrees of cognitive burden for those able to complete the tasks and were similar in their ability to identify and quantify preferences. The majority of nursing home residents, however, were unable to complete or comprehend the measurement tasks. Most respondents evaluated their current health and severe constant pain as better than death; dementia and coma were more often considered equal to or worse than death. These results indicate that respondents can and do evaluate some health states as worse than death. The authors recommend systematic inclusion of states worse than death to describe a more complete range of preference values and routine assessment of the cognitive burdens of assessment techniques to evaluate methodologies.

Adult↗