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Biomedical subjects

D A Bloch

Publications and source records attributed to D A Bloch.

At least 37 records · Page 2Linked to original sources
PubMed2000

Reliability of proxy-reported and self-reported household appliance use.

Exposure assessment presents a major challenge for studies evaluating the association between household exposure to electric and magnetic fields and adverse health outcomes, especially the reliance on proxy respondents when study subjects themselves have died. We evaluated the reliability of proxy- and self-reported household appliance exposure. We recruited 92 healthy couples through either random-digit dialing or newspaper advertisements. Trained interviewers administered questionnaires to each member of a couple independently to assess the reliability of proxy-reported household appliance use. Eighty-five couples completed a second interview 2 months later to assess the reliability of self-reported appliance use. Reliability of proxy-reported appliance exposure was good when we inquired about having any exposure to each of the eight indicator appliances during the past year (range of kappa coefficients = 0.63-0.85; median = 0.76) but was lower with increased time to recall or increased detail. Reliability of self respondents reporting 2 months apart was excellent (range of kappa coefficients = 0.75-0.94; median = 0.87) for having any exposure to the eight indicator appliances during the past year, but reliability was again lower with increased detail. When we used self reports at the first interview as the standard, little systematic over- or underreporting occurred for proxy respondents or for self respondents reporting 2 months later. Because this study did not include cases of specific disease, these findings of no systematic differences in reporting do not refer to case or control status. In summary, reliability of self respondents' reports of appliance use is very good for recent time periods and good for broad aspects of exposure in distant time periods. Proxy respondents can provide information regarding broad aspects of appliance exposure in the past year, but detailed aspects of exposure or exposure in more distant time periods is not reliable.

Adult↗
PubMed2000

Prevalence of pelvic Paget's disease of bone in the United States.

The objective of this article was to estimate the prevalence of Paget's disease of bone in the United States from a statistically derived sample of the general population. Pelvic radiographs obtained in the First National Health and Nutrition Examination Survey (NHANES-I) were reviewed for the presence of Paget's disease. Age, sex, and geographic distribution of Paget's disease of the pelvic region were determined. The overall prevalence of Paget's disease in the United States was estimated. Pelvic Paget's disease is estimated to be present in 0.71 + 0.18% of the radiographs of the general population. The disease was higher in frequency in people who were in the older decades of life with the highest prevalence of 2.32 + 0.54% in the 65- to 74-year-old people. There is a slight male predominance in the 45- to 74-year age group. The regional distribution suggests the highest prevalence in the Northeast (1.48 + 0.52%) with the lowest prevalence in the South (0.26+0.25%). The prevalence was equal in white people and black people. An estimate of the overall prevalence of Paget's disease in the United States was at least 1% and perhaps as much as 2 % of the general population with near equal sex distribution and the highest prevalence in the northeastern United States.

Adult↗
PubMed1999

Catheter ablation of accessory pathways, atrioventricular nodal reentrant tachycardia, and the atrioventricular junction: final results of a prospective, multicenter clinical trial. The Atakr Multicenter Investigators Group.

BACKGROUND: The purpose of this study was to evaluate the safety and efficacy of a temperature-controlled radiofrequency catheter ablation system. METHODS AND RESULTS: The patient population included 1050 patients who had undergone ablation of atrioventricular nodal reentrant tachycardia (AVNRT), an accessory pathway (AP), or the atrioventricular junction (AVJ). Ablation was successful in 996 patients. The probability of success was highest among patients who had undergone ablation of the AVJ, lowest in patients who had undergone ablation of an AP, and in between for patients who had undergone ablation of AVNRT. A major complication occurred in 32 patients. Four variables predicted ablation success (AVJ, AVNRT, or left free wall AP ablation and an experienced center). Four factors predicted arrhythmia recurrence (right free wall, posteroseptal, septal, and multiple APs). Two variables predicted development of a complication (structural heart disease and the presence of multiple targets), and 3 variables predicted an increased risk of death (heart disease, lower ejection fraction, and AVJ ablation). CONCLUSIONS: These findings may serve as a guide to clinicians considering therapeutic options in patients who are candidates for ablation.

Adolescent↗
PubMed1999

Tissue oxygen distribution in head and neck cancer patients.

BACKGROUND: The importance of hypoxia in limiting the sensitivity of tumor cells to ionizing radiation has long been known. METHODS: We evaluated the tissue oxygenation status with a polarographic needle electrode system in 37 patients with malignancies of the head and neck and correlated the pO2 of 25 patients with treatment outcome. RESULTS: Sixteen tumors contained areas of severe hypoxia, defined by pO2 values below 2.5 mm Hg. Tumor oxygenation parameters were not correlated with hemoglobin, age, and history of tobacco use. There were no subcutaneous PO2 values below 10 mm Hg (ie, no areas of moderate or severe hypoxia), whereas this degree of hypoxia was commonly found in the tumors. Though not statistically significant, hypoxic tumors showed trends for poorer treatment outcome. CONCLUSION: Our data demonstrate a great interindividual variability in the oxygenation of head and neck cancers and appears unassociated with clinical parameters. The method is capable of identifying patients with poorly oxygenated tumors, thereby providing important information for selecting patients who might need customized therapy designed to kill hypoxic tumor cells. Hypoxic tumors show a consistent trend for poor treatment outcome.

Adult↗
PubMed1999

Patient preferences in coronary revascularization.

BACKGROUND: This study was performed to assess patient preferences for consequences of 3 coronary revascularization procedures: angioplasty, conventional coronary bypass surgery, and minimally invasive coronary bypass surgery. METHOD: A nationwide sample of 3 types of respondents was recruited: respondents with no heart disease (n = 89), respondents with heart disease who had not undergone cardiac surgery (n = 97), and respondents with heart disease who had undergone cardiac surgery (n = 118). RESULTS: Sixty-two percent ranked the risk of repeat revascularization as the most important concern, followed by postprocedure pain (22%), time to recovery of physical functioning (8%), time in hospital (4%), and body appearance (4%). Respondents preferred angioplasty to conventional and minimally invasive cardiac surgery if the 3-year risk of repeat revascularization with angioplasty were to decline to less than 28% and 21%, respectively. CONCLUSION: These data suggest that patient preference should influence individual and policy recommendations when choosing among coronary revascularization procedures.

Data Collection↗
PubMed1999

DNA damage measured by the comet assay in head and neck cancer patients treated with tirapazamine.

Tirapazamine (TPZ) [3-amino-1,2,4-benzotriazine 1,4-dioxide, SR4233, WIN 59075, and Tirazone] is a novel anticancer drug that is selectively activated by the low oxygen environment in solid tumors. By killing the radioresistant hypoxic cells, TPZ potentiates the antitumor efficacy of fractionated irradiation of transplanted tumors in mice. As this cell kill is closely correlated with TPZ-induced DNA damage, we investigated whether human head and neck cancers would show DNA damage similar to that seen in mouse tumors following TPZ administration. TPZ-induced DNA damage in both transplanted tumors in mice and in neck nodes of 13 patients with head and neck cancer was assessed using the alkaline comet assay on cells obtained from fine-needle aspirates. The oxygen levels of the patients' tumors were also measured using a polarographic oxygen electrode. Cells from the patients' tumors showed DNA damage immediately following TPZ administration that was comparable to, or greater than, that seen with transplanted mouse tumors. The heterogeneity of DNA damage in the patients' tumors was greater than that of individual mouse tumors and correlated with tumor hypoxia. The similarity of TPZ-induced DNA damage in human and rodent tumors suggests that tirapazamine should be effective when added to radiotherapy or to cisplatin-based chemotherapy in head and neck cancers.

Animals↗
PubMed1999

An intervention to increase patients' trust in their physicians. Stanford Trust Study Physician Group.

PURPOSE: To investigate the effect of a one-day workshop in which physicians were taught trust-building behaviors on their patients' levels of trust and on outcomes of care. METHOD: In 1994, the study recruited 20 community-based family physicians and enrolled 412 consecutive adult patients from those physicians' practices. Ten of the physicians (the intervention group) were randomly assigned to receive a one-day training course in building and maintaining patients' trust. Outcomes were patients' trust in their physicians, patients' and physicians' satisfaction with the office visit, continuity in the patient-physician relationship, patients' adherence to their treatment plans, and the numbers of diagnostic tests and referrals. RESULTS: Physicians and patients in the intervention and control groups were similar in demographic and other data. There was no significant difference in any outcome. Although their overall ratings were not statistically significantly different, the patients of physicians in the intervention group reported more positive physician behaviors than did the patients of physicians in the control group. CONCLUSIONS: The trust-building workshop had no measurable effect on patients' trust or on outcomes hypothesized to be related to trust.

Adult↗
PubMed1999

Plans, designs, and analyses for clinical trials of anti-cocaine medications: where we are today. NIDA/VA/SU Working Group on Design and Analysis.

Increased interest in addiction psychopharmacology has raised unique methodologic issues in the design, conduct, and analysis of outcomes in clinical trials of therapeutic agents for drug dependence. This article summarizes issues raised at a meeting in Palo Alto, California, on November 4, 1996, that was sponsored by the Medication Development Division of the National Institute on Drug Abuse and the Department of Veterans Affairs Cooperative Studies Program to discuss the methodologic issues in clinical trials of cocaine pharmacotherapy.

Behavior Therapy↗
PubMed1999

Children's symptoms in the wake of Challenger: a field study of distant-traumatic effects and an outline of related conditions.

OBJECTIVE: The Challenger space shuttle explosion in January 1986 offered an opportunity to determine what, if any, symptoms of posttraumatic stress disorder (PTSD) and bereavement normal latency-age children and adolescents would develop after a distant, horrifying event. METHOD: With a structured interview, the authors assessed the symptoms of 153 randomly selected children from Concord, N.H., and Porterville, Calif. Responses were statistically compared between East Coast children, who saw the event on television and who generally cared more about the teacher aboard Challenger, and West Coast children, who heard about it first; between latency-age children and adolescents; and between children seen 5-7 weeks later and those same children seen 14 months later. RESULTS: More than 60% of the subjects feared at least one stimulus related to Challenger within the first 5-7 weeks of the explosion. The East Coast and latency-age groups appeared significantly more symptomatic than did the West Coast and adolescent groups. Over the 14-month study period, most symptoms dramatically faded. However, adolescents' diminished expectations for the future in general increased, and latency-age children's changed approach to space careers held relatively steady. Three East Coast latency-age children met the DSM-III-R symptom requirements for PTSD in 1986; no children met these in 1987. CONCLUSIONS: Children's symptomatic patterns after Challenger relate to the patterns for PTSD listed in diagnostic manuals and to three symptoms not in the DSM-IV list. To the authors, distant traumas appear to be one of a newly defined spectrum of trauma-related conditions that include relatively evanescent symptoms and a few longer-lasting ones. These symptoms may affect large numbers of normal children.

Adolescent↗
PubMed1999

Falls in older Mexican-American women.

OBJECTIVE: To determine the frequency of falls and identify risk factors for falls among older Mexican-American women. DESIGN: A prospective cohort study with an average follow-up of 2.7 years. SETTING: A clinical center at the Palo Alto Veterans Affairs Medical Center, California. PARTICIPANTS: 152 community-dwelling Mexican-American Caucasian women aged 59 years or older. OUTCOME MEASURES: Falls and injurious falls, as determined by monthly telephone interviews. RESULTS: The rate of falls was 508 per 1000 person-years (95% confidence interval (CI), 440-577). Injurious falls requiring medical attention occurred at a rate of 79 per 1000 person-years (95% CI, 52-107). Factors that were associated independently with an increased risk of falling were older age, a history of arthritis or rheumatism, a history of high thyroid, having fainted at least once in the year before baseline, current use of psychotropic medications, and walking fewer than 5 blocks a day. Those persons with an average time for the chair stand test had a lower risk of falling than those with the slowest times or the fastest times. CONCLUSIONS: The frequency of falls and injurious falls in this cohort of 152 relatively acculturated, healthy, older Mexican-American women was similar or slightly higher than previously reported rates for non-Hispanic Caucasian(s). Many of the factors associated with falls in this study were similar to those reported for non-Hispanic Caucasian women, suggesting that fall prevention measures tested mainly among non-Hispanic Caucasian women would also be appropriate for Mexican-American women.

Accidental Falls↗
PubMed1998

Donor blood monocytes but not T or B cells facilitate long-term allograft survival after total lymphoid irradiation.

BACKGROUND: Previous studies showed that a combination of posttransplant total lymphoid irradiation (TLI), rabbit antithymocyte globulin (ATG), and a single donor blood transfusion induced tolerance to ACI heart allografts in Lewis rats. All three modalities were required to achieve tolerance. The objective of the current study was to determine the subset(s) of cells in the donor blood that facilitated long-term allograft survival. METHODS: Lewis hosts received TLI, ATG, and donor cell infusion after heart transplantation. Graft survival, mixed leukocyte reaction (MLR), and intragraft cytokine mRNA were studied. RESULTS: The intravenous injection of 25 x 10(6) ACI peripheral blood mononuclear cells (PBMC) significantly prolonged graft survival as compared with that of Lewis hosts given TLI and ATG alone. Injection of highly enriched blood T cells or splenic B cells adjusted for the number contained in 25 x 10(6) PBMC failed to induce significant graft prolongation. Unexpectedly, depletion of monocytes (CD11b+ cells) from PBMC resulted in the loss of graft prolongation activity. Enriched populations of monocytes obtained by plastic adherence were more efficient in prolonging graft survival than PBMC on a per cell basis. Hosts with long-term grafts (>100-day survival) showed evidence of immune deviation, because the MLR to ACI stimulator cells was vigorous, but secretion of interferon-gamma in the MLR was markedly reduced. In situ hybridization studies of long-term grafts showed markedly reduced levels of interferon-gamma mRNA as compared with rejecting grafts. CONCLUSION: Infusion of donor monocytes facilitated graft prolongation via immune deviation.

Animals↗
PubMed1998

A simple method of sample size calculation for linear and logistic regression.

A sample size calculation for logistic regression involves complicated formulae. This paper suggests use of sample size formulae for comparing means or for comparing proportions in order to calculate the required sample size for a simple logistic regression model. One can then adjust the required sample size for a multiple logistic regression model by a variance inflation factor. This method requires no assumption of low response probability in the logistic model as in a previous publication. One can similarly calculate the sample size for linear regression models. This paper also compares the accuracy of some existing sample-size software for logistic regression with computer power simulations. An example illustrates the methods.

Humans↗
PubMed1998

Functional indices for sciatic, peroneal, and posterior tibial nerve lesions in the mouse.

The sciatic functional index previously described in rats has proven to be a reliable index of functional recovery following sciatic nerve injury and repair. A similar functional assay of sciatic, peroneal, and posterior tibial nerve lesions was developed in a mouse model. Forty-eight C57/BL6 mice were randomly divided into 4 groups: sham surgery, sciatic nerve transection, peroneal nerve transection, and posterior tibial nerve transection. Preoperative and postoperative (48 hours) walking tracks were obtained. The pawprints were analyzed in a blinded fashion for measurements of print length (PL), toe spread (TS), intermediate toe spread (IT), and the orthogonal distance from the toe of one paw to the hind pad of the opposite paw (TOF). Multiple linear regression analysis was performed using these measurements to determine their significance and appropriate weighted contribution to the index formula for each nerve lesion. For the sciatic functional index, changes in the PL (P = 0.0092) and TS (P = 0.0008) were significant, resulting in an R2 value of 0.88. For the peroneal functional index, only TS (P < 0.0001) was significant with R2 = 0.83. For the posterior tibial index, only PL (P < 0.0001) was significant with R2 = 0.89. Formulas for a sciatic, peroneal, and posterior tibial functional index were created based on the coefficients derived from the multiple linear regression analysis. The indices that were developed will allow investigators to assess functional recovery following specific nerve lesions in mice.

Animals↗
PubMed1998

Hip osteoarthritis prevalence estimates by three radiographic scoring systems.

OBJECTIVE: To estimate and compare the age- and sex-specific prevalence of radiographic hip osteoarthritis (RHOA) in a population-based study of the Pima Indians, using 3 atlas-based methods for assessing features of RHOA. METHODS: Pelvic radiographs from 755 Pima Indians age > or = 45 years enrolled in a population-based study were read using the Kellgren/Lawrence (K/L) grading scale (grade 0-4) and 2 validated individual-radiographic-features (IRF) scales (grades 0-3 for narrowing and osteophytes). RESULTS: The age- and sex-specific prevalence of RHOA among Pima Indians assessed using the K/L scale was < 10% in all age and sex groups. The prevalence of grade > or = 2 osteophytes assessed using the 2 IRF scales were similar to each other in all age and sex groups. However, differences between the 2 IRF scoring systems were found for the prevalence of grade > or = 2 joint space narrowing. CONCLUSION: Pima Indians have an age- and sex-specific prevalence of RHOA similar to that found in the US population. Our finding of different joint space narrowing prevalence by the 2 IRF grading scales supports the use of the same atlas-based case definitions for determining disease prevalence for comparative studies.

Age Distribution↗
PubMed1998

Rheumatoid arthritis in the Pima Indians: the intersection of epidemiologic, demographic, and genealogic data.

OBJECTIVE: To describe the clinical features and familial distribution of rheumatoid arthritis (RA) in the Pima Indians. METHODS: From 1965 through 1990, all cases of RA as defined by the American College of Rheumatology (formerly, the American Rheumatism Association) 1987 criteria or all cases of seropositive, erosive disease as defined by the Rome criteria were identified in individuals who were age 20 years and older and were of 50% or more Pima/Tohono-O'odham heritage. Radiographs were reviewed by 2 musculoskeletal radiologists who were blinded to case status. Kinship coefficients were used to evaluate familial aggregation. RESULTS: Eighty-eight RA cases were identified from this population-based sample. Over 66% of the cases had seropositive disease, over 60% had erosive disease, and over 40% had subcutaneous nodules. Of the 88 RA cases, 40 were members of families with more than 1 RA case. The remainder were simplex cases. CONCLUSION: In this population, clinical markers of severe RA were present in a majority of cases. The presence of familial aggregation for RA in the Pima Indians suggests underlying genetic factors in disease pathogenesis.

Adult↗
PubMed1998

Postural balance measurements for children and adolescents.

Measurements of standing balance were determined for 92 children and adolescents, 5-18 years old, while they stood on a force plate with eyes open or eyes closed. The measurements included center-of-pressure calculations for path length per second, average radial displacement, anterior-posterior and mediolateral amplitudes, area per second, mean frequency of sway, Brownian random motion measure of short-term diffusion coefficient, and long-term scaling exponent. All balance parameters improved from youngest to oldest subjects, and the parameters improved when measured with the subjects' eyes open compared with closed. The mean values for data from three trials varied by only 5% when compared with the mean values from 10 trials. Data from this study suggest that force-plate center-of-pressure data can be used to determine differences in standing balance between children and adolescents of different ages and those with movement and balance abnormalities.

Adolescent↗
PubMed1998

Recursive partitioning for the identification of disease risk subgroups: a case-control study of subarachnoid hemorrhage.

Recursive partitioning is a nonparametric technique that produces a classification tree in which subjects are assigned to mutually exclusive subsets according to a set of predictor variables. We examined the utility of recursive partitioning as a supplement to logistic regression for the multivariable analysis of data from case-control studies, demonstrating the technique using data from women enrolled in a population-based study of subarachnoid hemorrhage. The classification tree produced by recursive partitioning consisted of three main risk subgroups: (1) elderly women who had long-standing hypertension and who were not smokers, (2) middle-aged women who were cigarette smokers and frequent binge drinkers, and (3) women in whom risk variables indicate relative estrogen deficiency (i.e., postmenopausal status, no recent exposure to hormone replacement therapy, cigarette smoking). As a supplemental method, recursive partitioning not only identifies subgroups with varying risks, but also may uncover interactions between variables that may be overlooked in the traditional application of logistic regression to case-control data.

Aged↗