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Biomedical subjects

M Aickin

Publications and source records attributed to M Aickin.

16 recordsLinked to original sources
PubMed1992

The effectiveness of adherence intervention in a colon cancer prevention field trial.

BACKGROUND: Adherence interventions were implemented in a 1-year community-based colon cancer prevention clinical trial (n = 110) using wheat bran fiber and calcium dietary supplements. The adherence promotion strategy was guided by a theoretical model. METHODS: The adherence intervention contains both a generalized portion given to all participants and an individualized portion given to marginal (50-74% intake) and low (under 50% intake) adherers. A regression model was employed to assess the effectiveness of the interventions both at the first intervention and at subsequent times. RESULTS: The Health Behavior in Cancer Prevention Model-based adherence promotion intervention was associated with retention of participants, both during the run-in period and after randomization (P = 0.05); and maximization of the percentage of the 13.5-g recommended fiber supplement consumed during the trial (92.5%). The positive effects of the adherence intervention were greater with first-time nonadherers and the control group than with the experimental group. The high-fiber group had notably more biological GI effects from the increased fiber intake, more preexisting comorbidities, and lower perceived cognitive and physical health status. CONCLUSIONS: Randomized participants had excellent adherence overall. Retention rates in the trial were better than would be expected without the adherence intervention, especially among those participants who may have been at higher risk for dropping out of the study. This suggests that a systematic, theoretically based adherence strategy should be further tested in clinical trial settings in which lower adherence is a problem.

Aged↗
PubMed1992

Reasons related to adherence in community-based field studies.

This study identified participants' reasons for good, marginal or poor adherence, or withdrawing from community-based clinical studies using a dietary and/or drug intervention. Adults aged 48-75 years participated in one of three studies related to decreasing colon polyp recurrence. Qualitative data from progress notes (N = 675) and end-of-study evaluations (N = 87) were coded using constant comparative analysis with 100% content validity panel agreement. Most common reasons for non-adherence were barriers such as side-effects, interference with vacation plans, unrelated illness, forgetting and competing outside stressors. Participation motivators were benefits such as altruism, medical benefits, free service and staff rapport. Findings supported the Health Behavior in Cancer Prevention model-based approach to adherence interventions and provided directions for adherence promotion in future community-based clinical studies.

Aged↗
PubMed1992

Assessment of the spatial occurrence of childhood leukaemia mortality using standardized rate ratios with a simple linear Poisson model.

Reports of a suspected cluster of childhood leukaemia cases in West Central Phoenix have led to a number of epidemiological studies in the geographical area. We report here on a death certificate-based mortality study, which indicated an elevated rate ratio of 1.95 during 1966-1986, using the remainder of the Phoenix standard metropolitan statistical area (SMSA) as a comparison region. In the process of analysing the data from this study, a methodology for dealing with denominator variability in a standardized mortality ratio was developed using a simple linear Poisson model. This new approach is seen as being of general use in the analysis of standardized rate ratios (SRR), as well as being particularly appropriate for cluster investigations.

Adolescent↗
PubMed1991

A criterion for the adequacy of a simple design when a complex model will be used for analysis.

Sample size computations for relatively complex analyses, such as multiple linear regression, are made difficult by the fact that various quantities that are required by the usual formulas will not be available until the completion of the trial. This fact makes sample size justifications in the design phase of the trial more tenuous than one would like. Here it is shown that for randomized clinical trials it usually suffices to compute sample size on the basis of a simpler model for the analysis than that which will actually be used. Therefore, standard formulas generally provide valid, although possibly inefficient, sample size determinations.

Clinical Trials as Topic↗
PubMed1991

Reduction of murine cutaneous UVB-induced tumor-infiltrating T lymphocytes by dietary canthaxanthin.

The effect of dietary canthaxanthin, retinyl palmitate, or their combination on the tumor-infiltrating T-lymphocyte response (T-TIL) in de novo murine ultraviolet type B irradiation-induced tumors was investigated to elucidate potential mechanisms of action of these compounds. We found that dietary canthaxanthin greatly reduced the number of tumor-infiltrating helper/inducer, suppressor/cytotoxic, and interleukin-2 receptor-positive T lymphocytes and also observed a concomitant statistically significant increase in tumour incidence in canthaxanthin-fed animals. The addition of retinyl palmitate to the canthaxanthin diet ameliorated this negative effect on TIL and the development of skin tumors. We conclude that dietary retinyl palmitate and canthaxanthin can modulate the host T-cell immune response within a growing tumor and may affect tumorigenicity.

Animals↗
PubMed1991

Estimation of population denominators for public health studies at the tract, gender, and age-specific level.

In epidemiologic and public health studies of disease incidence in geographic subpopulations, attention is properly directed toward the ascertainment of accurate numerators. Population or person-years denominators are generally given less consideration, under the assumption that estimates produced by sources other than the state health department are sufficiently accurate. Here, we report our experience in estimating person-years denominators in the highly urbanized, rapidly expanding population of Maricopa County, Arizona. The usual sources of population estimates were found to be of little use for public health purposes, and so we report on a method for obtaining smoothed person-years figures that can accurately reflect population acceleration which varies from one time period to another. Our method is to regress the logarithm of census enumerations on quadratic or tertic polynomials in time. We describe how differential reliability of census figures can be incorporated into our procedure, and how the problem of missing census data can be handled by an iterated regression method. Our evidence suggests that the logarithmic regression model works well, even in the face of rapid and erratic population growth or decline.

Adolescent↗
PubMed1990

Lack of impact of therapy on extent of Barrett's esophagus in 67 patients.

Sixty-seven patients with Barrett's esophagus have been prospectively followed over an average of 36 months (range 6 to 76 months) with standardized endoscopic observation and biopsies of the length of columnar epithelium. The initial length of Barrett's epithelium ranged from 1 to 16 cm, mean 5.5 cm. Specialized columnar epithelium was present in 64 of the 67 patients. Patients were treated predominantly with H2-receptor blocker therapy to relieve symptoms. Eighty-two percent of patients had less than a 1-cm change in length per year. The mean rate of change of length was -0.093 cm per year. These results confirm in a relatively large, prospective study that standard antireflux therapy for Barrett's esophagus does not result in consistent reduction in the extent of Barrett's epithelium over a three-year interval.

Adult↗
PubMed1990

Cumulative reduction of primary skin tumor growth in UV-irradiated mice by the combination of retinyl palmitate and canthaxanthin.

The effects of dietary supplementation with retinyl palmitate, canthaxanthin, or the combination of both, on photocarcinogenesis was determined in pigmented C3H/HeN mice. The basal diet was the American Institute of Nutrition Diet 76A, to which was added 120 IU of retinyl palmitate per g diet, 1% canthaxanthin, or the combination of both. Administration of the diets began 18 weeks before the first UVB radiation (280-320 nm) treatment and continued throughout the study. The UV source was a bank of 6 Westinghouse FS40 lamps which delivered to the mice a total dose of 9.9 x 10(5) J/m2, delivered over 24 weeks. These diets significantly reduced the tumor burden per mouse induced by UV irradiation, however they did not influence tumor incidence. The combination of retinyl palmitate plus canthaxanthin was more effective than either agent alone at reducing autochthonous tumor growth, a result which has not been previously reported.

Animals↗
PubMed1990

Development of a contingency recruitment plan for a phase III chemoprevention trial of cervical dysplasia.

Development of contingency recruitment plans in cancer chemoprevention research is as important as formulation of the initial plan. We found that requesting recruitment information from our initial CTCD subjects provided a framework for our contingency plan. The revised recruitment plan consisted of: 1) calling and sending letters to community gynecologists in private practice or affiliated with HMO's to explain the study and ask for referrals; 2) continued personal contact by the principal investigator with referring physicians; 3) sending thank you and follow-up letters to every physician who referred patients to the study; 4) soliciting Papanicolaou smear reports from HMO's if physicians of women with abnormal Papanicolaou smears gave permission to pathologists to release this information; 5) utilizing free media such as feature articles on the CTCD in local papers, public service announcements, and television "spots;" 6) continued use of brochures and posters printed for the initial recruitment effort; and 7) continued presentations to local professional physician and nurse groups about the study. Our contingency plan to date has provided us with 100% of our projected accrual. Thus, our recruitment methods have proved to be effective in accruing subjects for this cancer chemoprevention trial.

Double-Blind Method↗
PubMed1990

Maximum likelihood estimation of agreement in the constant predictive probability model, and its relation to Cohen's kappa.

The alpha agreement parameter is defined as the proportion of a population of items that are classified identically "for cause" by two classifiers, the remaining items being classified at random. The parameters of the corresponding constant predictive probability model are shown to be estimable by the method of maximum likelihood, and a simulation study indicates applicability of the asymptotic results to finite samples. The new estimator tends to be larger than Cohen's kappa, except in the case of uniform margins. An application is made to the validity of cancer risk items included in a cancer registry.

Humans↗
PubMed1989

dNA: a simple dBASE program for medical studies.

The dNA program is an entirely self-contained package consisting of dBASE programs and files, that can be used by an analyst with some dBASE experience to integrate multiple dBASE files into a simple, coherent system. Only minimal training is required for a naive user to operate the resulting system. The source file for creating a system also serves as the system documentation. Consistency and validity checks can be built in, and system modifications are quite simple.

Database Management Systems↗
PubMed1984

Some fallacies in the computation of paternity probabilities.

Legal identification of fathers by means of a "paternity probability" has been used in European courts for decades, and has recently been introduced into American courts and accepted by some of them. The voluminous literature on this topic contains virtually no fundamental criticism of the logical basis for the probabilistic computations. Here I suggest that the "paternity probability" suffers from three basic fallacies: (1) contrary to claims, the figure is not, in fact, the probability that the alleged father is the true father, (2) the denominator of the likelihood ratio used in the computation is driven by (sometimes self-contradictory) assumptions and is not based on facts, and (3) post-inclusionary computations are based on speculation about genotypes that does not constitute scientific evidence. It is recommended that pending the resolution of these difficulties "paternity probabilities" should not be computed or introduced as positive evidence of paternity.

Bayes Theorem↗