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Biomedical subjects

T Colton

Publications and source records attributed to T Colton.

At least 55 records · Page 3Linked to original sources
PubMed1988

A prospective randomized trial of outpatient versus inpatient cardiac catheterization.

To evaluate the safety and cost of outpatient cardiac catheterization, we conducted a randomized trial at three hospitals of outpatient (n = 192) as compared with inpatient (n = 189) cardiac catheterization in low-risk patients. Outpatients had the following complication rates as compared with inpatients: hematoma, 12 versus 8.5 percent; numbness or weakness of extremity, 0.5 versus 1.6 percent; cold or blue extremity, 1.6 versus 1.1 percent; and acute myocardial infarction, 1.6 versus 0.5 percent. None of these differences were statistically significant. No deaths or strokes occurred in either group. Twenty-three patients (12 percent) assigned to the outpatient group required hospitalization because of complications of catheterization. In the outpatient group, the relative risk for hematoma was 1.42 (95 percent confidence interval, 0.77 to 2.29), and the relative risk for myocardial infarction within one week was 2.95 (95 percent confidence interval, 0.3 to 28.1). There were no significant differences between the two groups in whether they resumed normal activities or in the rates of rehospitalization within one week of the procedure. Total catheterization-related charges per patient were $679 lower for outpatients, with a savings in total hospital charges (including charges for subsequent therapeutic procedures) of $885 per patient. We conclude that elective cardiac catheterization as an outpatient procedure for selected patients is feasible and safe. Given the small size of our sample, however, we urge caution in interpreting these findings, since they do not exclude a small increase in complication rates with outpatient cardiac catheterization.

Ambulatory Care↗
PubMed1988

Forced vital capacity and the risk of hypertension. The Normative Aging Study.

This report describes the development of hypertension among 1,270 males (aged 23-80 years at the time of entry into the study) observed prospectively for 10 years who had a baseline blood pressure of less than 140/90 mmHg and who underwent baseline spirometry. Subjects were participants in the Normative Aging Study, a longitudinal study on aging initiated in 1961 at the Veterans Administration Outpatient Clinic in Boston, Massachusetts. Blood pressures were taken at five- and 10-year follow-up examinations. The age-adjusted incidence of hypertension during the follow-up period was found to be inversely related to forced vital capacity. Multiple logistic regression was employed to assess the relation of forced vital capacity to the subsequent development of hypertension after controlling for baseline levels of age, weight, cigarettes smoked per day, and systolic and diastolic blood pressures. Forced vital capacity was a statistically significant and negative predictor, indicating that lower values of forced vital capacity were associated with the subsequent development of hypertension. This was consistently found in several logistic regression analyses with a standardized odds ratio associated with forced vital capacity of approximately 0.7. Although the physiologic mechanism for this association is unknown, these findings may have importance in identifying subjects at risk and may also provide insight into disease pathogenesis.

Adult↗
PubMed1987

Health problems reported by residents of a neighborhood contaminated by a hazardous waste facility.

A symptom prevalence survey was conducted of a neighborhood exposed to airborne hazardous wastes. Residents' responses were compared to those of a nearby control population. The results revealed that the exposed group had more self-reported complaints referable to the respiratory system (wheezing, shortness of breath, chest discomfort, persistent colds, coughs), constitutional complaints (always fatigued, bowel dysfunction), and irregular heart beat. When the effect of a documented irritant source in a small portion of the control population was removed, the exposed group also complained more often of irritation of the eyes and nose. There was a biological gradient for several of these effects. Efforts to eliminate the influence of confounding and recall bias are discussed. The results suggest either that the general population reacts to chemicals at levels much lower than the available occupational literature would indicate or that the effects are more long lasting than previously thought.

Adolescent↗
PubMed1987

The relationship of nonspecific bronchial responsiveness to the occurrence of respiratory symptoms and decreased levels of pulmonary function. The Normative Aging Study.

Nonspecific bronchial responsiveness was assessed by an abbreviated methacholine challenge test in 458 male participants of the Normative Aging Study, who also completed a respiratory questionnaire and spirometry. A positive response to the methacholine challenge test was defined as a greater than or equal to 20% decline in FEV1 during the test. Cigarette smoking was significantly associated with a positive methacholine response (p less than 0.001). Logistic regression analyses indicated that there was a significant association between a positive response to methacholine and both any wheeze (p = 0.002) and persistent wheeze (p less than 0.001) after taking into account smoking status and age; an association between responsiveness and chronic cough was of borderline significance (p = 0.06). Multiple linear regression analyses indicated that positive methacholine responsiveness was independently associated with lower levels of FEV1 (p less than 0.001) and FEF25-75 (p less than 0.001). Using the log of the dose-response slope rather than a dichotomous variable to characterize responder status yielded very similar results in the linear and logistic models. The findings of this cross-sectional study suggest that increased level of nonspecific responsiveness is significantly associated with wheeze and cough symptoms and decreased levels of pulmonary function in adult men. Longitudinal follow-up of these men should shed light on the importance of nonspecific responsiveness as a risk factor for the subsequent development of chronic obstructive pulmonary disease.

Adult↗
PubMed1987

Vasoactive neurochemicals identified in omentum: a preliminary report.

There has been increasing interest in biologic, immunologic, and chemical activity originating from omental tissue. Since clinical improvement has been observed in some patients very shortly after surgically transposing their omentum to the spinal cord or brain, the question arose as to whether neurochemicals might be present in omental tissue; a possible explanation for some of these neurological changes. This paper reports the presence of vasoactive neurochemicals in canine omental tissue. It remains unclear, however, whether the omentum produces or simply concentrates these and other neurochemicals.

Animals↗
PubMed1986

Qualitative overview of randomized trials of aminoglycosides.

A qualitative overview was conducted of randomized clinical trials comparing two or more of the following aminoglycoside antibiotics--amikacin. gentamicin, netilmicin, sisomicin, and tobramycin--with respect to efficacy, nephrotoxicity, or auditory toxicity. Design features considered included number of participants in each treatment arm, proportion of randomized participants available for analysis, blinding of evaluators, and report of statistically significant results. The proportion of participants eligible for analysis was less than or equal to 75 percent for 66 percent of the comparisons regarding nephrotoxicity, 43 percent regarding efficacy, and 19 percent regarding auditory toxicity. Twenty-nine percent of the trials reported that evaluators were blinded to treatment group assignments. The results of most trials showed no significant differences, although sample sizes were, in general, smaller than necessary to detect moderate differences. Quantitative overviews may be a useful means of detecting real differences in risk that are not apparent from the results of several individual small trials.

Amikacin↗
PubMed1985

A comparison of pregnancy history recall and medical records. Implications for retrospective studies.

Using data from the Diethylstilbestrol-Adenosis (DESAD) Project, a study of the effects of diethylstilbestrol (DES) exposure during fetal life, the authors compared prenatal records with obstetric history from mother's questionnaires completed 10 or more years after the birth of their daughters. Except for the history of hospitalization and trunk x-ray, no differences were observed in agreement (questionnaire compared with record) between the group of DES-exposed mothers identified through review of their prenatal records and the comparison group of mothers who were not exposed. The authors also compared data from mothers of DES-exposed daughters who initiated their own enrollment in the study (walk-ins and referrals). To obtain prenatal records for these women, physicians were contacted. They would usually supply drug exposure data but not the other obstetric history requested. Mothers of these walk-ins and referrals had slightly better agreement between questionnaire and records when compared with the two groups identified by review of prenatal records. In general, there was good to excellent agreement for all groups when mothers' recall of personal history (past miscarriage, past pregnancy, etc.) was compared with their medical records. However, for medical intervention such as drugs and x-rays, agreement was poor. Of the DES-exposed mothers identified through review of their prenatal records, 29% could not remember whether they took DES. An additional 8% said they did not take DES when it was recorded in their charts.

Clinical Trials as Topic↗
PubMed1985

An investigation of bias in a study of nuclear shipyard workers.

The authors examined discrepant findings between a 1978 proportional mortality study and a 1981 cohort study of workers at the Portsmouth, New Hampshire, Naval Shipyard to determine whether the healthy worker effect, selection bias, or measurement bias could explain why only the proportional mortality study found excess cancer deaths among nuclear workers. Lower mortality from noncancer causes in nuclear workers (the healthy worker effect) partly accounted for the observed elevated cancer proportional mortality. More important, however, was measurement bias which occurred in the proportional mortality study when nuclear workers who had not died of cancer were misclassified as not being nuclear workers based on information from their next of kin, thereby creating a spurious association. Although the proportional mortality study was based on a small sample of all deaths occurring in the cohort, selection bias did not contribute materially to the discrepant results for total cancer deaths. With regard to leukemia, misclassification of occupation in the proportional mortality study and disagreement about cause of death accounted for some of the reported excess deaths.

Epidemiologic Methods↗
PubMed1985

Health experiences of operating room personnel.

In an attempt to evaluate health experiences of operating room personnel using previously published reports, the authors calculated summary relative risks (RRs) for each outcome under investigation by combining data from six studies. For each summary RR, they also calculated 95% confidence limits; when the range of the confidence interval excludes 1.0, the increased risk is statistically significant at the 0.05 level. The most consistent evidence was for spontaneous abortion among pregnant physicians and nurses who work in operating rooms, where the RR was 1.3 (95% confidence limits from 1.2 to 1.4). For liver disease there were statistically significant increased RRs among both men (1.6, 1.3-1.9) and women (1.5, 1.2-1.9), but these were based on smaller numbers of studies. Although the results of pooled analyses are suggestive, most studies of this issue have relied on voluntary responses and self-reported outcomes, so that response and/or recall bias could explain these findings. In addition, these investigations generally have examined working in operating rooms rather than actual exposure to anesthetic gases. Finally, there have been considerable improvements in operating room scavenging systems during the last decade. Thus, prospective cohort studies are needed to determine whether there is a relationship between current levels of occupational exposure to anesthetic gases and adverse outcomes, particularly spontaneous abortion and liver disease.

Abortion, Spontaneous↗
PubMed1984

Breast cancer in mothers given diethylstilbestrol in pregnancy.

We compared the incidence of breast cancer in 3033 women who had taken diethylstilbestrol (DES) in pregnancy during the period from 1940 to 1960 with the incidence in a comparable group of unexposed parous women. We ascertained vital status in 95 per cent of the exposed women and in 93 per cent of the unexposed women and received completed questionnaires for 88 and 85 per cent, respectively. With over 85,000 woman-years of follow-up in each group, the incidence of breast cancer per 100,000 woman-years was 134 in the exposed group and 93 in the unexposed group, yielding a crude relative risk of 1.4 (95 per cent confidence interval, 1.1 to 1.9). The elevated incidence did not appear to be due to bias or to confounding by other risk factors measured in the study. Breast-cancer mortality was slightly higher in the exposed women (relative risk, 1.1) but not significantly so (95 per cent confidence interval, 0.7 to 2.0). We conclude that the incidence of breast cancer is moderately increased in women given DES, but we cannot exclude the possibility that some unrecognized concomitant of DES exposure accounts for this increase.

Actuarial Analysis↗
PubMed1984

Determination of carcinogenic synergism from the latent period.

We present a method for determining the presence or absence of synergism between two carcinogens A and B from the latent period of tumors. The method is applied to data consisting of the means and standard deviations of the times at which tumors become palpable and at which death from tumor occurs in animals of three groups: those given carcinogen A alone, those given B alone, and those given both A and B. Synergism was absent in the data examined.

Animals↗
PubMed1984

Evaluating a direct observation exercise in a psychiatric clerkship.

The introduction of a direct observation exercise in the psychiatric clerkship at McMaster University is presented. Preliminary investigation of the reliability, construct validity, educational effects and feasibility of the exercise is discussed. The direct observation exercise is found to measure improvement in skills, enhance the recording of student performance, be valued by the students and feasible in the clinical setting. Directions for future evaluation research with direct observation exercises are outlined.

Clinical Clerkship↗
PubMed1984

Multiple testing of hypotheses in comparing two groups.

Researchers frequently encounter studies that compare two groups on many variables. We discourage the use of multiple tests of hypotheses on individual variables, an approach that ignores the correlation among the variables and increases the chance of a type I error. Instead of examining each variable separately, we recommend using multivariate procedures that integrate all measures on a person into a unified analysis of the differences between the two groups. We describe three multivariate procedures: Hotelling's T2, discriminant analysis, and logistic regression. We also discuss the use of Bonferroni's adjustment to preserve the overall chance of a type I error in conducting individual tests on each variable after doing the multivariate procedures. We review the underlying assumptions and relative merits and disadvantages of the three multivariate methods and recommend which method to use in various circumstances.

Analysis of Variance↗
PubMed1984

Adenocarcinoma and Barrett's esophagus. An overrated risk?

The risk of developing esophageal cancer in Barrett's esophagus has been estimated at about 10%. This estimate is based primarily on data concerning the prevalence of that association in series of hospitalized patients and autopsies--a practice that tends to exaggerate the risk. We have reviewed retrospectively our experience with 115 patients whom we treated for Barrett's esophagus between September 1962 and March 1983, and have distinguished our data on the prevalence of esophageal cancer from that on incidence. For 8 patients, we found both Barrett's esophagus and esophageal adenocarcinoma during the initial evaluations for a prevalence ratio of 7%. We followed 105 patients not found to have esophageal cancer initially for a total of 350 person-years. Only 2 patients developed adenocarcinoma during that follow-up period for an incidence of 1 case per 175 person-years. This incidence, although some 40-fold greater than that of the general population, is substantially lower than previously estimated. Routine endoscopic and histologic surveillance has been recommended for patients with Barrett's esophagus because of the alleged high incidence of esophageal cancer. Inasmuch as that incidence now appears to be low, we question the value of such surveillance for these patients.

Adenocarcinoma↗
PubMed1983

Relief of continuous chronic pain by intraspinal narcotics infusion via an implanted reservoir.

Ten patients with intractable pain (five cancer and five nonmalignant) were treated with continuous intraspinal morphine delivered by an implanted continuous infusion system. Both patient groups were evaluated and compared using an identical battery of psychometric examinations administered before and 12 weeks after therapy. The cancer-pain group reported significant reduction in pain on serial visual pain analogue scales at 12 weeks compared with no change in the nonmalignant-pain group reports despite a much lower baseline report in the cancer group. Both groups of patients reduced their oral narcotic requirement significantly during continuous intraspinal morphine infusion. While the cancer patients took more oral narcotic at baseline, at 12 weeks no difference existed in oral intake between the two groups. Both groups required significant serial increases in infused morphine, indicating that spinal opiate receptor tolerance occurs. The results of this study confirm the sustained analgesic efficacy reported earlier in cancer-related pain syndromes, thus supporting further cautious expansion of this therapy within the cancer-related pain population. In contrast, a poor response was seen in the nonmalignant-pain group, consistent with the unsatisfactory responses to many potentially analgetic approaches to chronic nonmalignant pain. We are thus discouraged from further use of this therapy in the patient with chronic nonmalignant pain.

Administration, Oral↗
PubMed1982

Measurement of cancer incidence in the United States: sources and uses of data.

Since 1937, investigations have compiled a vast amount of information on cancer incidence in the United States. Three national cancer surveys were conducted in 1937, 1947, and 1969-71; each used somewhat different methods but covered populations who overlapped greatly. Concurrently, population-based tumor registries were developed that were capable of measuring cancer incidence. Since 1973, the Surveillance, Epidemiology, and End Results Program, an amalgam of such registries, had generated cancer incidence data for the United States. Available data provide a rough measure of the size of the cancer problem and may help those who direct prevention programs and those who plan studies of cancer etiology. Because the completeness and validity of existing incidence data are not known with certainty, comparisons among these incidence data are not known with certainty, comparisons among these incidence rates require cautious interpretation.

Evaluation Studies as Topic↗