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Biomedical subjects

G G Koch

Publications and source records attributed to G G Koch.

At least 19 recordsLinked to original sources
PubMed1992

Results of a randomized trial of partner notification in cases of HIV infection in North Carolina.

BACKGROUND: We sought to compare two methods of notifying sex partners of subjects infected with the human immunodeficiency virus (HIV) or persons who had shared needles with them (needle-sharing partners): "patient referral," in which the responsibility for notifying partners was left to the patient, and "provider referral," in which providers attempted to notify partners. METHODS: Names of sex partners and needle-sharing partners and information on how to locate them were obtained from consenting HIV-infected subjects identified in the HIV-testing programs at three public health departments in North Carolina. The subjects were randomly assigned to a patient-referral group (in which patients had the initial responsibility for notifying their partners) or a provider-referral group (in which the study counselor notified the partners). The success of attempts to notify partners was monitored by means of interviews with counselors conducted both in the field and at the health department. RESULTS: Of 534 HIV-positive persons identified at the health departments, 247 (46 percent) did not return for counseling after the test, 8 were counseled outside the study, and 117 (22 percent) were ineligible. Of the 162 invited to participate, 88 (54 percent) declined and 74 (46 percent) agreed. The subjects were mostly male (69 percent), black (87 percent), homosexual or bisexual (76 percent of the men), and had a median age of 30 years. Thirty-nine were assigned to the provider-referral group and 35 to the patient-referral group. In the provider-referral group 78 of 157 partners (50 percent) were successfully notified, whereas in the patient-referral group only 10 of 153 (7 percent) were notified. Of the partners notified by the counselors, 94 percent were not aware that they had been exposed to HIV. Overall, 23 percent of the partners notified and tested were HIV-positive. CONCLUSIONS: In this trial, leaving the notification of partners up to the subjects (patient referral) was quite ineffective, despite the North Carolina law requiring that partners be notified. Partner notification by public health counselors (provider referral) was significantly more effective. Although the effectiveness of notification procedures is constrained by the accuracy of the information provided by HIV-infected patients, counselors who notify the partners of an infected patient can refer them to educational, medical, and support services targeted to persons at high risk for HIV infection and may encourage the adoption of less risky behavior.

Adult↗
PubMed1992

Fluoride uptake in hard tissues of fetal guinea pigs in response to various dose regimens.

This study was designed to explore various aspects of maternal-fetal fluoride metabolism. In its first phase, 57 female guinea pigs were bred and randomly assigned to a control group (I) or one of three experimental groups: (II) 3 parts/10(6) fluoride in drinking water, (III) a single daily oral dose and (IV) 3 parts/10(6) fluoride in water and a single daily oral fluoride dose. The total mean doses received by groups II and III were similar. The total mean dose received by group IV was approximately double that for groups II and III. Samples of maternal plasma, and fetal bone and enamel were collected on the 57th day of gestation. In its second phase, 53 pregnant guinea pigs were given drinking water containing 0, 2, 4, 6 or 8 parts/10(6) fluoride during gestation. On the 57th day of gestation samples of maternal and fetal enamel were collected. All samples in both phases of the study were assayed for fluoride using the microdiffusion, ion-selective electrode method. In the first part of the study, mean fetal enamel fluoride by group was: I, 21.6 parts/10(6); II, 38.6 parts/10(6); III, 33.5 parts/10(6); IV, 54.9 parts/10(6). In the second phase, maternal enamel was linearly related to the fluoride dose. The same was true for fetal enamel except at the 8 parts/10(6) fluoride level in the water where there was no increase over the 6 parts/10(6) group. At all dose levels, fetal enamel fluoride uptake was approximately an order of magnitude less than maternal enamel fluoride uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1992

Ureaplasma urealyticum and large colony mycoplasma colonization in female children and its relationship to sexual contact, age, and race.

In order to determine if Ureaplasma urealyticum (Uu) or large colony mycoplasma (LCM) colonization was related to a history of sexual abuse, the type of sexual contact, an enlarged vaginal introitus transverse diameter (greater than 4 mm), age or race, 452 female children, ages 1-12 years, were evaluated by the Child Sexual Abuse Team at Wake Medical Center in Raleigh, NC. Thirty-six girls were deleted because of inadequate cultures. When controlled for race and age, Uu throat (T), vaginal (V), and rectal (R) colonization and LCM vaginal and rectal colonization were not related to any of the other variables listed above. The enlarged vaginal introital diameter was related to a history of sexual abuse (p less than .001). Uu and LCM vaginal colonization rates were increased in black girls as compared to white girls (p less than .05). Uu V, Uu R, LCM V, and LCM R colonization increased with age. In our study population, Uu and LCM colonization was not a useful marker of sexual contact.

Age Factors↗
PubMed1992

The analysis of a multiple-dose, combination-drug clinical trial using response surface methodology.

We consider the situation where a multiple-dose, combination-drug clinical trial is conducted to identify one or more combinations that satisfy regulatory requirements. Generally, these requirements involve a compound hypothesis with multiple comparisons. The min test has been shown to be an optimal alpha-level test for testing a single combination drug. Analysis procedures in a multiple-dose, combination-drug study have typically involved classical ANOVA models or multiple regression models in a response surface methodology (RSM) framework. An inferential procedure based on an ANOVA model uses a screening test to address multiple comparison issues and multiple min tests to explicitly identify combinations satisfying regulatory requirements. An exploratory procedure based on RSM modeling is used to build a segmented linear model and a stairstep linear model to describe dose-response relationships. The two procedures are mutually supportive of one another in providing a broader assurance in the identification of effective combinations.

Analysis of Variance↗
PubMed1992

Statistical methodologies useful for the analysis of data from risk-assessment studies.

In dentistry, the vast majority of studies attempting to predict who is at high risk for getting a disease or condition, or attempting to identify risk factors for a specific disease or condition, have focused either on only one risk factor at a time, or have measured multiple potential risk factors, but analyzed their effects in isolation. Since researchers tend to agree that most dental conditions have a multiple etiology, it is necessary to develop models that consider simultaneously the effect of a number of potential risk factors on the disease or condition of interest if we are to have any understanding of the relative impact of potential risk factors. Many existing statistical techniques will aid dental researchers in identifying risk factors. However, the selection of an appropriate analytic technique depends on a number of conditions. The strategy for this paper is to discuss a wide range of possible statistical techniques that may be applied to the problem of deriving a model for identification of multiple risk factors for dental diseases and conditions. We have approached this task by presenting a number of dental research problems needing an appropriate analytic technique. Next, basic issues that must be considered in choosing an appropriate analytic strategy are discussed. These issues include features of the study design, the data structure of the variables being measured, and the types of assumptions that are applicable to provide valid inferences about the target population of interest. A matrix of possible analytic techniques is presented for various combinations of study-design and data-structure features. After a discussion of each of the techniques, the appropriate statistical techniques for each of the dental examples are described. The issues and examples presented in this paper should be of use to dental researchers who wish to investigate multiple risk factors for a disease or condition of interest.

Disease Susceptibility↗
PubMed1992

Evaluation of oral bacteria as risk indicators for periodontitis in older adults.

The prevalence of people and sites with attachment loss, pocket depth, Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Porphyromonas gingivalis are described for a random sample of 366 black and 297 white community-dwelling adults, aged 65 or over, residing in five counties in North Carolina. In addition, relationships between sites harboring these microorganisms and loss of attachment (LA) and pocket depth (PD) are presented in a manner that considers the lack of independence of sites within each person. Pocket depths and recession were measured on all teeth by trained examiners during household visits. Immunofluorescent assays for A. actinomycetecomitans, P. intermedia, and P. gingivalis were conducted on subgingival plaque samples obtained from the mesiobuccal aspect of the four first molar teeth using paper points. The prevalences of A. actinomycetemcomitans, P. intermedia, and P. gingivalis were greater in blacks than in whites. The most striking difference was seen for P. gingivalis, which was found in 38.8% of blacks and 9.4% of whites. Similar relationships were found when the percent of sites with these organisms were assessed. Blacks with P. gingivalis or P. intermedia had a higher prevalence of sites with LA greater than or equal to 7 mm as compared to blacks not infected with P. gingivalis or P. intermedia. The same was true for whites. Similar relationships between P. gingivalis or P. intermedia and PD greater than or equal to 6 mm were found for both blacks and whites.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Applicability of statistical reliability methods to the validation process.

This paper discusses some statistical considerations for the reliability of validation processes. An underlying theme is assessment of sources of variability for validation data. Confidence intervals and other statistical methods can clarify the impact of such variability. Statistical strategies for strengthening the design of systems for evaluation of validation processes are outlined.

Biological Products↗
PubMed1992

Impact of HIV testing and counseling on subsequent sexual behavior.

To assess sexual behavior changes after voluntary HIV testing and routine counseling, we interviewed 235 persons at 2 anonymous test sites in North Carolina. Among the 57 (24%) persons returning for follow-up 1 year later, 70% were male; 44% were black, 37% were homosexual, 10% were bisexual; and 16% were HIV positive. Overall, 28% of returnees at the initial visit and 33% on the follow-up visit admitted to having 2 or more sexual partners in the past month. At the initial interview and at follow-up, 21% of returnees reported condom use in the past month. Homosexual men were significantly less likely to use condoms during anal sex over time (58% non-use initially vs. 74% non-use at follow-up, p = 0.04). No significant net change in high-risk sexual behaviors was found at follow-up. Overall findings indicate that the standard HIV testing and counseling provided by health departments anonymously and free of charge does not result in elimination of high-risk sexual behaviors or initiation of safer sex behaviors among those at high risk for HIV infection.

AIDS Serodiagnosis↗
PubMed1992

Porcine von Willebrand disease and atherosclerosis. Influence of polymorphism in apolipoprotein B100 genotype.

The relationship of apolipoprotein-B genotype (Lpb) to diet-induced hypercholesterolemia and atherosclerosis was studied in von Willebrand disease (vWD) and normal pigs. Von Willebrand and normal pigs developed comparable levels of hypercholesterolemia (respectively, 757.9 +/- 49.4 versus 772.8 +/- 47.9 mg/dl, P = 0.95). Pigs with Lpb1/5 and Lpb5/8 genotypes, however, developed significantly higher serum cholesterol levels than those with other Lpb genotypes (866.1 +/- 64.0 mg/dl, P = 0.0343). Coronary and aortic atherosclerosis, measured by computer-assisted automated image analyzer, were not significantly different between vWD and normal pigs. Pigs with an Lpb5 allele developed significantly more atherosclerosis than those with the Lpb3/8 or Lpb8/8 genotypes or the rare Lpb1 allele (r greater than or equal to 0.434, P less than or equal to 0.05). Polymorphism in apolipoprotein B100 genotype, then, significantly influenced the severity of diet-induced hypercholesterolemia and atherosclerotic plaque formation in vWD and normal swine without regard to the vWD genotype.

Animals↗
PubMed1991

Maintenance therapy with sucralfate in duodenal ulcer: genuine prevention or accelerated healing of ulcer recurrence?

We sought to compare the efficacy of sucralfate to placebo for the prevention of duodenal ulcer recurrence and to determine that the efficacy of sucralfate was due to a true reduction in ulcer prevalence and not due to secondary effects such as analgesic activity or accelerated healing. This was a double-blind, randomized, placebo-controlled, parallel groups, multicenter clinical study with 254 patients. All patients had a past history of at least two duodenal ulcers with at least one ulcer diagnosed by endoscopic examination 3 months or less before the start of the study. Complete ulcer healing without erosions was required to enter the study. Sucralfate or placebo were dosed as a 1-g tablet twice a day for 4 months, or until ulcer recurrence. Endoscopic examinations once a month and when symptoms developed determined the presence or absence of duodenal ulcers. If a patient developed an ulcer between monthly scheduled visits, the patient was dosed with a 1-g sucralfate tablet twice a day until the next scheduled visit. Statistical analyses of the results determined the efficacy of sucralfate compared with placebo for preventing duodenal ulcer recurrence. Comparisons of therapeutic agents for preventing duodenal ulcers have usually been made by testing for statistical differences in the cumulative rates for all ulcers developed during a follow-up period, regardless of the time of detection. Statistical experts at the United States Food and Drug Administration (FDA) and on the FDA Advisory Panel expressed doubts about clinical study results based on this type of analysis. They suggested three possible mechanisms for reducing the number of observed ulcers: (a) analgesic effects, (b) accelerated healing, and (c) true ulcer prevention. Traditional ulcer analysis could miss recurring ulcers due to an analgesic effect or accelerated healing. Point-prevalence analysis could miss recurring ulcers due to accelerated healing between endoscopic examinations. Maximum ulcer analyses, a novel statistical method, eliminated analgesic effects by regularly scheduled endoscopies and accelerated healing of recurring ulcers by frequent endoscopies and an open-label phase. Maximum ulcer analysis reflects true ulcer recurrence and prevention. Sucralfate was significantly superior to placebo in reducing ulcer prevalence by all analyses. Significance (p less than 0.05) was found at months 3 and 4 for all analyses. All months were significant in the traditional analysis, months 2-4 in point-prevalence analysis, and months 3-4 in the maximal ulcer prevalence analysis. Sucralfate was shown to be effective for the prevention of duodenal ulcer recurrence by a true reduction in new ulcer development.

Double-Blind Method↗
PubMed1991

Physical and pharmacologic restraint of nursing home patients with dementia. Impact of specialized units.

This case-control study of 31 specialized dementia units and 32 traditional units in five states investigated use of physical and pharmacologic restraints among 625 patients with the diagnosis of dementia. Physical restraints were observed in use on 18.1% of dementia unit patients and on 51.6% of comparison unit patients who were out of bed during the day (adjusted odds ratio, 0.283;95% confidence interval, 0.129 to 0.619). Pharmacologic restraints were routinely given to 45.3% of dementia unit patients and 43.4% of comparison unit patients (adjusted odds ratio, 0.950; 95% confidence interval, 0.611 to 1.477). We used multivariate logistic regression to identify residence in a nonspecialized nursing home unit, nonambulatory status, transfer dependency, mental status impairment, hip fracture history, and a high nursing staff-to-patient ratio, which we found to be independent predictors of physical restraint use. Physically abusive behavior, severe mental status impairment, and frequent family visitation were found to be significant predictors of pharmacologic restraint use, while advanced patient age, large nursing home size, and patient nonambulatory status were protective against such use. These results support the conclusion that physical and pharmacologic restraint constitute separate treatment modalities with different risk factors for use, and indicate that specialized dementia units are successful in reducing the use of physical but not pharmacologic restraints.

Aged↗
PubMed1991

Correlates of cortical bone mass among premenopausal and postmenopausal Japanese women.

Few studies have examined the multifactorial risk factors of bone mass in Asian populations. This cross-sectional study was designed to explore relationships between bone mass and environmental variables, including dietary and life-style factors, in Japanese women living in Japan. A total of 178 Japanese women completed the study: 89 premenopausal, ages 35-40, and 89 postmenopausal, ages 55-60. Midradial bone mineral content (MBMC) and bone mineral content per unit area, referred to as bone density (MBMD), were measured using single-photon absorptiometry. The major results of this investigation were the following: (1) The postmenopausal women differed significantly from the premenopausal women in having lower radial bone parameters, lower mean height, later age of menarche, and higher dietary intakes of carbohydrates, vegetables, and milk with a lower intake of caffeine. (2) Current protein intake was a positive correlate of MBMC in both groups. (3) Intake of vegetables (leafy green, yellow, orange, and white) and current milk intake were positively associated with MBMC in the postmenopausal women. (4) For the premenopausal women, irregular menstrual cycles was a negative correlate of MBMC, and for the postmenopausal women, years of menopause was negatively associated with MBMC and MBMD. Longitudinal studies are needed to establish more conclusively associations among diet, life-style, and reproductive history and bone mass of Japanese women.

Adult↗
PubMed1991

An overview of statistical issues and methods of meta-analysis.

A meta-analysis is a statistical analysis of the data from some collection of studies in order to synthesize the results. In this paper we discuss issues that frequently arise in meta-analysis and give an overview of the methods used, with particular attention to the use of fixed- and random-effects approaches. The methods are then applied to two sample datasets.

Biopharmaceutics↗
PubMed1991

One-sided and two-sided tests and p values.

Several considerations for the use of one-sided and two-sided tests are discussed: the inferential posture of the design of a study, the level of stringency for supporting a conclusion, the style for reporting p values, the perspective for interpreting results in the opposite direction to the one initially expected, and the role of confidence intervals. The suggestions for addressing these issues for confirmatory biopharmaceutical studies with one-sided objectives are as follows: 1. Clear documentation of the one-sided inferential posture of a study in its protocol. 2. Sufficient sample size for at least moderate power for evaluation with two-sided stringency. 3. Use of one-sided p values to express direction of results together with distinct flags for those which are suitably extreme to support inferences for the target direction or to merit description for the opposite direction. 4. Interpretation of opposite direction results in a post hoc, exploratory, descriptive way rather than inferentially. 5. Provision of one-sided confidence intervals to clarify the nature of one-sided inferences. Alternatively, for academic studies where publication with an inferential posture is of interest for either potential direction of findings, two-sided methods are typically useful. An underlying reason for this is the adjustment provided by two-sided methods for the multiplicity in the two complementary one-sided counterparts that they encompass.

Biopharmaceutics↗
PubMed1991

Magnitude and time course of extracellular potassium inhomogeneities during acute ischemia in pigs. Effect of verapamil.

Prior studies have demonstrated the presence of inhomogeneities in myocardial [K+]e after serial 10-minute occlusions of the left anterior descending coronary artery in the pig, even within restricted locations of an ischemic zone. These inhomogeneities are thought to underlie the electrophysiological abnormalities responsible for lethal ventricular arrhythmias through reentrant and nonreentrant pathways, but a clear association has not been demonstrated. As a prerequisite to establishing this association, these studies were performed to establish measurement standards for [K+]e inhomogeneity, to quantify the magnitude and time course of these inhomogeneities, to determine whether the inhomogeneities are greater in the ischemic border where lethal ventricular arrhythmias are known to originate, and to assess the effect of a known antifibrillatory drug on [K+]e inhomogeneities. [K+]e (expressed as the change in potassium equilibrium potential, dEK [mV]) was measured in 15 preparations using an average of 17 closely spaced, critically calibrated K(+)-sensitive electrodes having stable response characteristics. A series of four 10-minute occlusions each separated by a 50-minute reperfusion period were performed in each study. In half of the studies, intravenous verapamil (0.2 mg/kg bolus followed by 0.0065 mg/kg/hr) was administered before the fourth occlusion. In nine studies (five control and four verapamil), electrodes were placed in the marginal ischemic zone (from 2 mm outside to 5 mm inside the visible cyanotic border). In six other studies (three control and three verapamil), electrodes were placed in the central ischemic zone (10-20 mm within the ischemic region). We determined that the standard deviation is the best measure of inhomogeneity and that 12 equivalent measurement sites are required to estimate it with a satisfactory degree of statistical confidence. We found that after 10 minutes of ischemia, mean dEK was 1.6 times greater in the central than in the marginal ischemic zone, whereas mean standard deviation at the same time was 1.5 times greater in the marginal than in the central ischemic zone. Verapamil reduced mean dEK and mean standard deviation in both ischemic zones for most of the occlusion by delaying the rise in [K+]e and the inhomogeneity of that rise by 3-5 minutes. Comparisons of mean dEK with mean standard deviation revealed a steep linear relation in the marginal zone and a curvilinear relation in the central zone where higher mean dEK values were not accompanied by higher values for mean standard deviation. Furthermore, we determined that these relations were not altered by verapamil.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Regression-adjusted small area estimates of functional dependency in the noninstitutionalized American population age 65 and over.

Health planning efforts for the population age 65 and over have been hampered continually by the lack of reliable estimates of the noninstitutionalized long-term care population. Until recently national estimates were virtually nonexistent, and reliable small area estimates remain unavailable. However, with the recent publication of several national surveys and the 1990 Census, synthetic estimates can be made for states and counties by using multivariate methods to model functional dependency at the national level, and then applying the predicted probabilities to corresponding state and county data. Using the 1984 National Health Interview Survey's Supplement on Aging and the 1986 Area Health Resources File System, we have produced log-linear regression models that include demographic and contextual variables as predictors of functional dependency among the noninstitutionalized population age 65 and over. Age, sex, race, and the percent of the 65 and over population who reside in poverty were found to be significant predictors of functional dependency. Applying these models to 1986 Medicare Enrollment Statistics, regression-adjusted synthetic estimates of two levels of functional dependency were produced for all states and--as examples of how the rates can be used to produce additional synthetic estimates--the largest county in each state. We also produced point estimates and standard errors for the national prevalence of functional dependency among the noninstitutionalized population age 65 and over.

Activities of Daily Living↗
PubMed1991

The influence of three mass media campaigns on variables related to adolescent cigarette smoking: results of a field experiment.

BACKGROUND: This paper reports findings from a field experiment that evaluated mass media campaigns designed to prevent cigarette smoking by adolescents. METHODS: The campaigns featured radio and television messages on expected consequences of smoking and a component to stimulate personal encouragement of peers not to smoke. Six Standard Metropolitan Statistical Areas in the Southeast United States received campaigns and four served as controls. Adolescents and mothers provided pretest and posttest data in their homes. RESULTS AND CONCLUSIONS: The radio campaign had a modest influence on the expected consequences of smoking and friend approval of smoking, the more expensive campaigns involving television were not more effective than those with radio alone, the peer-involvement component was not effective, and any potential smoking effects could not be detected.

Adolescent↗