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L W Pickle

Publications and source records attributed to L W Pickle.

At least 19 recordsLinked to original sources
PubMed1992

The logistic modeling of interobserver agreement.

An approach to the logistic modeling of interobserver agreement is described that allows for the estimation of a commonly employed measure of agreement. The dependent variable is defined to be 1 if the two raters agree, and 0 otherwise. Covariates may be included in the regression equation in order to obtain adjusted or subgroup-specific estimates of percent agreement. As an empirical example, logistic models were fitted to data from a validation study of the agreement between interview information and physician records on the history of post-menopausal estrogen use, from a case-control study of breast cancer conducted on Oahu, Hawaii. Variables found to be related to agreement in previous univariate analyses were examined as covariates in the logistic model. The directly calculated estimates of percent agreement agreed well with the modeled estimates derived from the regression coefficients. Thus, the logistic model may provide a useful alternative to existing methods for the description of interobserver agreement.

Breast Neoplasms↗
PubMed1992

The logistic modeling of sensitivity, specificity, and predictive value of a diagnostic test.

A method is described for modeling the sensitivity, specificity, and positive and negative predictive values of a diagnostic test. To model sensitivity and specificity, the dependent variable (Y) is defined to be the dichotomous results of the screening test, and the presence or absence of disease, as defined by the "gold standard", is included as a binary explanatory variable (X1), along with variables used to define the subgroups of interest. The sensitivity of the screening test may then be estimated using logistic regression procedures. Modeled estimates of the specificity and predictive values of the screening test may be similarly derived. Using data from a population-based study of peripheral arterial disease, the authors demonstrated empirically that this method may be useful for obtaining smoothed estimates of sensitivity, specificity, and predictive values. As an extension of this method, an approach to the modeling of the relative sensitivity of two screening tests is described, using data from a study of screening procedures for colorectal disease as an example.

Arterial Occlusive Diseases↗
PubMed1992

Sensitivity and specificity-like measures of the validity of a diagnostic test that are corrected for chance agreement.

Chance agreement may account for a sizeable proportion of the specificity of a screening test when the disease prevalence is low. Conversely, the observed sensitivity may be largely accounted for by chance agreement when the prevalence of disease is high. We derive descriptive statistics that are analogous to sensitivity and specificity and corrected for the agreement expected by chance. These coefficients of validity are shown to be dependent on the true prevalence of disease, as well as sensitivity and specificity.

Humans↗
PubMed1991

Regression methods for estimating attributable risk in population-based case-control studies: a comparison of additive and multiplicative models.

A regression method that utilizes an additive model is proposed for the estimation of attributable risk in case-control studies carried out in defined populations. In contrast to previous multivariate procedures for the estimation of attributable risk, which have utilized logistic regression techniques to adjust for confounding factors, the model assumes an additive relation between the covariates included in the regression equation. As an empirical example, additive and logistic models were fitted to matched case-control data from a population-based study of childhood astrocytoma brain tumors. Although both models fitted the data well, the additive model provided a more satisfactory estimate of the risk attributable to multiple exposures, in the absence of significant additive interaction. In contrast to the results from the logistic model, the adjusted estimates of the risk attributable to each factor included in the additive model summed to the overall estimate for all of the factors considered jointly. Thus, the additive approach provides a useful alternative to existing procedures for the multivariate estimation of attributable risk when the additive model is determined to be appropriate on the basis of goodness-of-fit.

Astrocytoma↗
PubMed1991

Lung cancer risk associated with cancer in relatives.

Family history data from an incident case-control study of lung cancer conducted in the Texas Gulf Coast region between 1976 and 1980 were analyzed to evaluate the contribution of cancer in first-degree relatives to lung cancer risk. Odds ratios (OR) increased slightly as the number of relatives with any cancer increased (reaching 1.5 with 4 or more relatives with cancer). Risks were higher for tobacco-related cancers (OR = 1.5 for 2 or more relatives with these tumors) and greatest for first-degree relatives with lung cancer (OR = 2.8 for lung cancer in 2 or more relatives). For cases of squamous cell carcinoma and adenocarcinoma of the lung, risks with 3 or more relatives with any cancer were increased 2-fold (OR = 1.8 and 1.9 respectively), and a significantly elevated risk was found for having a first-degree relative with lung cancer for each histologic type (ORs from 1.7-2.1). Having a spouse with lung cancer increased lung cancer risk (OR = 2.5), and cases with lung cancer reported in a first-degree relative were diagnosed at an earlier age, as were case siblings with lung cancer.

Adenocarcinoma↗
PubMed1991

Salivary analysis for determination of dextromethorphan metabolic phenotype.

Debrisoquin oxidative phenotype is a determinant of pharmacologic response for many drugs. Poor and extensive metabolizers can be identified by the dextromethorphan metabolic ratio (dextromethorphan/dextrorphan). We developed and tested a method to determine debrisoquin phenotype on the basis of the metabolic ratio in saliva. Each of 62 normal volunteers was given a 50 mg capsule of dextromethorphan hydrobromide and collected urine (0 to 8 hours) and saliva (at 3 hours). Dextromethorphan and dextrorphan in saliva and urine were assayed by HPLC. The distributions of paired urinary and 3-hour salivary metabolic ratios of samples from 61 subjects were compared. The urinary and salivary metabolic ratios were distributed trimodally and bimodally, respectively. The Spearman rank correlation coefficient for logarithm of urinary metabolic ratio vs that of salivary metabolic ratio was 0.704. All the poor metabolizers identified by urinary metabolic ratio were also identified by the metabolic ratio in saliva at 3 hours (100% concordance). This study demonstrates that salivary analysis for determination of dextromethorphan metabolic phenotype is feasible.

Administration, Oral↗
PubMed1991

Some but not all benefits of intravenous immunoglobulin therapy after marrow transplantation appear to correlate with IgG trough levels.

Multiple benefits of intravenous immunoglobulin (IVIG) therapy after marrow transplantation have been reported, including decreased incidence of acute graft-versus-host disease (GVHD), infection, sepsis, cytomegalovirus (CMV) pneumonitis and platelet use. To test the hypothesis that the observed beneficial effects of IVIG are related to the serum IgG levels achieved, we followed IgG levels (pre-infusion, 1 h and 24 h post-infusion) in 45 consecutive marrow transplant recipients. IVIG 500 mg/kg was given weekly for six doses starting day -8 pre-transplant, then every other week for a total of 11 doses. Forty-one patients (22 allogeneic, 17 autologous, two syngeneic) were evaluable. Patients with acute GVHD had significantly lower serum IgG trough levels (less than 1200 mg/dl) noted at day +20 post-transplant and afterwards than patients without GVHD (greater than or equal to 1200 mg/dl). Pharmacokinetic modeling of the data indicates that IgG half-life between day -8 and day +6 may predict which recipients are at increased risk of acute GVHD. Allogeneic recipients in the group with trough levels less than 1200 mg/dl required more platelet transfusions. Although there was no significant difference in fungal infection rates or bacteremia, sepsis was noted in only two recipients (one allogeneic, one autologous), both with serum IgG trough levels less than 1200 mg/dl. In addition, three allogeneic recipients had cytomegalovirus pneumonitis, all in the group with lower IgG trough levels. Thus, while serum IgG trough levels less than 1200 mg/dl appear to be strongly associated with acute GVHD, low levels may also be associated with increased platelet utilization, with cytomegalovirus pneumonitis, and sepsis, but not with the overall incidence of infection.

Adolescent↗
PubMed1991

Conditioning-related toxicity and acute graft-versus-host disease in patients given methotrexate/cyclosporine prophylaxis.

Intensive chemoradiotherapy conditioning regimens and acute graft-versus-host disease (GVHD) are both associated with significant morbidity and mortality after bone marrow transplantation. In this study, we investigated whether the conditioning regimen affected the development of acute GVHD. Thirty-four patients, four with severe aplastic anemia and 30 with a lymphohemopoietic malignancy, were prepared for transplantation either with cyclophosphamide (CY) alone, with CY combined with total body irradiation (TBI) or CY combined with etoposide and either TBI or busulfan. GVHD prophylaxis included methotrexate (MTX 10 mg/m2) given on days 1, 3 and 6, and daily cyclosporine (CSP) on days--1 through 180. The overall incidence of acute GVHD was 36% (15% for HLA identical, 87% for HLA non-identical recipients). However, when assessed by the severity of conditioning regimen-related toxicity, the incidence of GVHD grades II-IV (HLA identical; HLA non-identical) was 0% (0%; 0%), 37% (20%; 67%) and 50% (22%; 100%) for patients with mild, moderate and severe toxicity, respectively. Compliance with GVHD prophylaxis declined with increasing intensity and toxicity of the conditioning regimen. These data suggest that a regimen of three doses of MTX and daily CSP is as effective as four doses of MTX/CSP for GVHD prophylaxis in patients given HLA identical marrow grafts. However, GVHD regimen compliance and efficacy of GVHD prevention are inversely related to the intensity of the conditioning regimen.

Acute Disease↗
PubMed1990

Lung cancer and the debrisoquine metabolic phenotype.

In a case-control study, we tested the hypothesis that the genetically determined ability to metabolize debrisoquine is related to risk of lung cancer. Overall, individuals who were extensive metabolizers of debrisoquine were at significantly greater risk of lung cancer than those who were poor or intermediate metabolizers (odds ratio = 6.1; 95% confidence interval = 2.2-17.1). In this study, case patients had lung cancer, and control subjects had either chronic obstructive pulmonary disease or cancers other than lung cancer. Results were adjusted for age, race, asbestos exposure, and smoking. Both black and white individuals who were extensive metabolizers of debrisoquine were at significantly increased risk after similar adjustment (for blacks, odds ratio = 4.5, 95% confidence interval = 1.1-18.1; for whites, odds ratio = 10.2, 95% confidence interval = 2.0-51.4). Significantly increased risk of lung cancer was also present for individuals who were extensive metabolizers when subjects with chronic obstructive pulmonary disease or other cancers were considered separately. These data confirm that the ability to metabolize debrisoquine is a major determinant of susceptibility to lung cancer. Evaluation of the marker in other case-control settings, further exploration of racial differences, and the prospective evaluation of this marker in subgroups at high risk of lung cancer are areas worthy of further study.

Adenocarcinoma↗
PubMed1990

Occupation and pancreatic cancer risk in Louisiana.

To study the relation of occupational exposures and pancreatic cancer, we evaluated data from males (198 cases and 209 controls) participating in a hospital-based case-control study conducted in a high-risk area of Louisiana between 1979 and 1983. The questionnaire obtained information on lifetime occupational history, as well as dietary, smoking, and drinking habits and demographic characteristics. After adjustment for smoking and dietary patterns, white collar occupations showed consistent elevations in risk, whereas associations for other occupations were in general unremarkable. Although not significantly elevated, risks for truck drivers (OR = 1.7) and those with long-term employment in machine repair or as mechanics were suggestive (OR = 2.5). No association was found for jobs in oil refining or oil and gas extraction (ORs were 0.5 and 0.4, respectively), although risks were slightly elevated for long-term workers in the chemical processing industry (OR = 1.2). While these associations deserve further study, our findings are consistent with results of other studies which do not suggest that occupational exposures are important determinants of pancreatic cancer.

Adenocarcinoma↗
PubMed1989

Effect of smoking and alcohol consumption on laryngeal cancer risk in coastal Texas.

Data from case-control studies of respiratory cancer conducted in the Texas Gulf Coast region between 1975 and 1980 were used to examine the effects of smoking and alcohol on laryngeal cancer risk. Analyses were limited to living white males, aged 30-79, which included 151 histologically confirmed incident laryngeal cancer cases and 235 population-based controls. A dose-dependent effect for cigarette smoking was observed, with odds ratios ranging from 4.4 for ever smoking up to one-half pack daily, to 10.4 for smoking more than two packs per day. Risks were strongest for current smokers and declined markedly following smoking cessation. Higher risks were associated with smoking nonfiltered than filtered cigarettes. No significantly elevated risks were associated with the use of other tobacco products. Odds ratios for alcohol beverages did not increase linearly with increasing use; instead risks were twofold for consumption of four or more drinks weekly. Patterns of risk associated with beer and hard liquor were not consistent and few participants drank wine. Although the data were sparse, a dose-response effect for alcohol intake was suggested for tumors of the supraglottis (n = 23), while for nonsupraglottic cases, alcohol risks were elevated but did not increase beyond those observed for four drinks per week. Predicted risks for the combined effects of cigarette and alcohol use were intermediate between an additive and multiplicative form of interaction.

Adult↗
PubMed1989

Lung cancer in motor exhaust-related occupations.

The association between employment in motor exhaust-related occupations and the risk for lung cancer was examined in 2,291 male cases of lung cancer and 2,570 controls in data pooled from three U.S. case control studies carried out by the National Cancer Institute between 1976 and 1983. Most analyses were limited to subjects providing direct, in-person interviews, including 1,444 cases and 1,893 controls. For those providing direct interviews and employed 10 years or more in motor exhaust-related (MER) occupations, the age, smoking, and study area adjusted odds ratio (OR) for lung cancer was 1.5 (95% CI = 1.2-1.9). Risk was elevated for truck drivers (OR = 1.5; 95% CI = 1.1-1.9) and for other MER occupations (OR = 1.4; 95% CI = 1.1-2.0). The odds ratios associated with MER employment of 10+ years were 1.6 (95% CI = 1.2-2.1) for whites and 1.4 (95% CI = 0.9-2.1) for nonwhites; 1.2 (95% CI = 0.7-2.0) [corrected] for those with possible exposure to other recognized or reported lung carcinogens; and 1.6 (95% CI 1.2-2.1) for those without such exposure. The 50% excess risk for lung cancer associated with employment in motor exhaust-related occupations could not be explained by greater use of cigarettes or by other occupational exposures among these workers.

Aged↗
PubMed1989

The distribution of debrisoquine metabolic phenotypes and implications for the suggested association with lung cancer risk.

Debrisoquine hydroxylation exhibits wide inter-individual variation in Caucasian populations. After similar doses of the drug, extensive metabolizers excrete up to several hundred times more of the urinary metabolite 4-hydroxy-debrisoquine than do poor metabolizers. The phenotypes have traditionally been defined by the metabolic ratio (MR), or the molar ratio of debrisoquine to its chief metabolite recovered in an aliquot of an eight hour urine sample, after a test dose of the drug. Deficient metabolism is inherited as an autosomal recessive condition. We have reanalyzed previously published data from a study of lung cancer patients and controls using a computerized optimization method to more accurately estimate the parameters describing the three phenotypic distributions. Using these new distributions to categorize controls, we show that Hardy-Weinberg conditions are now fulfilled. When the newly defined phenotype parameters are employed to assign the phenotypes of cases and controls, a highly significant difference in phenotype distribution between cases and controls is still observed. This result supports the hypothesis that the debrisoquine metabolic phenotype may be associated with lung cancer susceptibility.

Chromatography, Gas↗
PubMed1989

The new United States Cancer Atlas.

Published in 1975, the Atlas of Cancer Mortality for U.S. Counties: 1950-1969 proved useful in identifying geographic patterns, especially clusters of high-rate areas, that have stimulated further epidemiologic study of specific cancer sites. These data have been updated to include population and mortality statistics through 1980. Our new atlas presents static maps of area-specific mortality rates for each decade from 1950 to 1980 among white males and females for 33 cancer sites, along with dynamic maps illustrating the trends in these rates over time. Although the geographic distribution of mortality rates has become more uniform for most cancer sites, clusters of high-rate areas have persisted for several common tumors. However, some new patterns have appeared, notably the emergence of several high-rate areas for lung cancer among women. Possible explanations for the geographic peculiarities of cancer are considered, based on the results of correlation and analytic studies prompted by the earlier maps. These successive studies indicate the value of monitoring mortality statistics on a small-area scale as a strategy for generating etiologic clues and targeting epidemiologic research, although one must be mindful of geographic fluctuations in diagnostic and reporting practices, survival rates, and migration patterns.

Chronology as Topic↗