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C S Davis

Publications and source records attributed to C S Davis.

At least 37 records · Page 2Linked to original sources
PubMed1996

Non-parametric methods for comparing multiple treatment groups to a control group, based on incomplete non-decreasing repeated measurements.

In the comparison of two or more treatment groups to a control group, consider a study with non-decreasing repeated measurements of the same characteristic taken over a common set of time points for each subject. Based on the vector of possibly incomplete responses from each subject, this paper considers asymptotically distribution-free tests of the equality of the groups. I propose consistent point estimators of the overall treatment differences and I derive non-parametric simultaneous confidence regions for the treatment effects. An example using data from a bladder cancer study illustrates the proposed methods.

Chi-Square Distribution↗
PubMed1996

Tumor perfusion studies using fast magnetic resonance imaging technique in advanced cervical cancer: a new noninvasive predictive assay.

PURPOSE: This study investigated sequential changes in tumor blood supply using magnetic resonance (MR) perfusion imaging and assessed their significance in the prediction of outcome of patients with advanced cervical cancer. The purpose of this project was to devise a simple, noninvasive method to predict early signs of treatment failure in advanced cervical cancer treated with conventional radiation therapy. METHODS AND MATERIALS: Sixty-eight MR perfusion studies were performed prospectively in 17 patients with squamous carcinomas (14) and adenocarcinomas (3) of the cervix, Stages bulky IB (1), IIB (5), IIIA (1), IIIB (8), and IVA (1), and recurrent (1). Four sequential studies were obtained in each patient: immediately before radiation therapy (pretherapy), after a dose of 20-22 Gy/ approximately 2 weeks (early therapy), after a dose of 40-45 Gy/ approximately 4-5 weeks (midtherapy), and 4-6 weeks after completion of therapy (follow-up). Perfusion imaging of the tumor was obtained at 3-s intervals in the sagittal plane. A bolus of 0.1 mmol/kg of MR contrast material (gadoteridol) was injected intravenously 30 s after beginning image acquisition at a rate of 9 ml/s using a power injector. Time/signal-intensity curves to reflect the onset, slope, and relative signal intensity (rSI) of contrast enhancement in the tumor region were generated. Median follow-up was 8 months (range 3-18 months). RESULTS: Tumors with a higher tissue perfusion (rSI > or = 2.8) in the pretherapy and early therapy (20-22 Gy) studies had a lower incidence of local recurrence than those with a rSI of < 2.8, but this was not statistically significant (13% vs. 67%; p = 0.05). An increase in tumor perfusion early during therapy (20-22 Gy), particularly to an rSI of > or = 2.8, was the strongest predictor of local recurrence (0% vs. 78%; p = 0.002). However, pelvic examination during early therapy (20-22 Gy) commonly showed no appreciable tumor regression. The slope of the time/signal-intensity curve obtained before and during radiation therapy also correlated with local recurrence. Follow-up perfusion studies did not provide information to predict recurrence. CONCLUSION: These preliminary results suggest that two simple MR perfusion studies before and early in therapy can offer important information on treatment outcome within the first 2 weeks of radiation therapy before response is evident by clinical examination. High tumor perfusion before therapy and increasing or persistent high perfusion early during the course of therapy appear to be favorable signs. High perfusion suggests a high blood and oxygen supply to the tumor. The increase in tumor perfusion seen in some patients early during radiation therapy suggests improved oxygenation of previously hypoxic cells following early cell kill. Radiation therapy is more effective in eradicating these tumors, resulting in improved local control. Our technique may be helpful in identifying early-while more aggressive therapy can still be implemented-those patients who respond poorly to conventional radiation therapy.

Adenocarcinoma↗
PubMed1996

Usefulness of tumor volumetry by magnetic resonance imaging in assessing response to radiation therapy in carcinoma of the uterine cervix.

PURPOSE: Clinical evaluation of tumor size in cervical cancer is often difficult, and clinical signs of radiation therapy failure may not be present until well after completion of treatment. The purpose of this study is to investigate early indicators of treatment response using magnetic resonance (MR) imaging for quantitative assessment of tumor volume and tumor regression rate before, during, and after radiation therapy. METHODS AND MATERIALS: Thirty-four patients with cervical cancer Stages IB [5], IIB [8], IIIA [1], IIIB [14], IVA [3], IVB [1], and recurrent [2] were studied prospectively with four serial MR examinations obtained at the start of radiation therapy, at 2-2.5 weeks (20-24 Gy), at 4-5 weeks (40-50 Gy), and 1-2 months after treatment completion. Tumor volume was assessed by three-dimensional volumetric measurements using T2-weighted images of each MR examination. The volume regression rate was generated based on the four sequential MR studies. These findings were correlated with local control, metastasis rate, and disease-free survival. Median follow-up was 18 months (range: 9-43 months). RESULTS: The tumor regression rate after a dose of 40-50 Gy correlated significantly with treatment outcome. The actuarial 2-year disease-free survival was 88.4% in patients with tumors regressing to < 20% of the initial volume compared with 45.4% in those with > or = 20% residual (p = 0.007). The incidence of local recurrence was 9.5% (2 out of 21) and 76.9% (10 out of 13), respectively (p < 0.001). Analysis by initial tumor volume showed that this observation was valid in patients with initial volumes between 40 and 100 cm3. Analysis by FIGO stage confirmed this observation in all patients except those with Stage IB. CONCLUSION: Sequential tumor volumetry using MR imaging appears to be a sensitive measure of the responsiveness of cervical cancer to irradiation. Treatment response can be assessed as early as during the course of radiation therapy by measurement of initial tumor volume and regression rate at 40-50 Gy. In patients with large (> 40 cm3) and advanced (Stage > or = IIIA) tumors, this technique may be helpful in supplementing the clinical examination for response assessment. The identification of patients at high risk for treatment failure may ultimately lead to improved clinical outcome.

Adult↗
PubMed1996

The utility of preliminary surveys to detect the cause of acute metalworking fluid hazards.

This paper describes preliminary studies undertaken to optimize a later epidemiologic study, the aim of which was to identify a causative agent of adverse respiratory effects and dermatitis among production machinists. Two methods were used to rate coolant system hazards. The results of a voluntary plantwide questionnaire with an 18% participation rate showed that both dermatologic and respiratory symptoms were higher among machine operators than among maintenance or assembly workers, that symptoms were not more prevalent early in the week, and that dermatitis may be associated with smoking status; however, the questionnaire was not helpful in rating individual coolant system hazards. The hazard ratings provided by an in-plant expert panel were strongly associated with particular synthetic coolant containing an ethoxylated phenol; however, the resulting design for a later epidemiologic study could not be implemented due to changes in coolants used at the plant.

Chromatography, High Pressure Liquid↗
PubMed1996

Obesity and prognosis in endometrial cancer.

OBJECTIVE: We tested the null hypothesis that morbid obesity as measured by the Quetelet index has no influence on survival in endometrial cancer. STUDY DESIGN: A retrospective study of 492 women with endometrial carcinoma was performed. Age, height, weight, Quetelet index, stage, cell type, grade, node status, peritoneal cytologic findings, and depth of myometrial invasion were analyzed for influence on survival. RESULTS: Mean Quetelet index was 34 (range 16 to 89). Quetelet index was < 30 in 45% of patients, 30 to 40 in 33%, and > 40 in 22%. Five percent of those with a Quetelet index > 40 had positive nodes, but 64% of patients with a Quetelet index > 40 did not have lymph node sampling done. Lack of sampling of lymph nodes in the entire group had no adverse effect on survival. In a proportional hazards regression model for time from diagnosis to death from disease, grade, node status, myometrial invasion, and stage had highly significant effects. When Quetelet index was analyzed as a continuous variable, as Quetelet index increased, time to recurrence was significantly increased (p = 0.0136), and significance was approached for survival (p = 0.0645). Quetelet index was strongly related to grade (p = 0.013), depth of myometrial invasion (p = 0.031), negative cytologic findings (p = 0.004), and stage (p = 0.011) with obese patients having better differentiated, less invasive tumors of lower stage with negative washings. CONCLUSIONS: Morbid obesity positively affects survival in endometrial carcinoma. This effect is accounted for by the association of obesity with less aggressive disease. Morbid obesity is not associated with increased death from other causes. Lack of sampling of negative lymph nodes does not adversely affect survival.

Adult↗
PubMed1996

A computer program for regression analysis of ordered categorical repeated measurements.

RMORD is an easy-to-use FORTRAN program for the analysis of clustered ordinal data using the method of Stram, Wei, and Ware. This method constitutes an extension of the proportional-odds model to the situation in which groups of responses are correlated. At each measurement occasion, a proportional-odds regression model is fit to the data by maximizing the occasion-specific likelihood function. The joint asymptotic distribution of the occasion-specific regression parameter estimators is obtained along with a consistent estimator of their asymptotic covariance matrix. RMORD may be used when ordinal measurements are obtained at a common set of observation times for multiple subjects or clusters. Both missing data and covariates which vary within clusters can be accommodated. The program can be run on microcomputers, workstations, and mainframe computers. Two examples illustrating the usage and features of RMORD are provided.

Age Distribution↗
PubMed1996

Risk factors for occupational injuries among older workers: an analysis of the health and retirement study.

OBJECTIVES: This study examined risk factors for occupational injury among older workers. METHODS: We analyzed data on 6854 employed nonfarmers from the Health and Retirement Study (HRS), a population-based sample of Americans 51 through 61 years old. RESULTS: Occupational injuries were associated with the following: the occupations of mechanics and repairers (odds ratio [OR] = 2.27), service personnel (OR = 1.68), and laborers (OR = 2.18); jobs requiring heavy lifting (OR = 2.75); workers' impaired hearing (OR = 1.60) and impaired vision (OR = 1.53); and jobs requiring good vision (OR = 1.43). Self-employment was associated with fewer injuries (OR = 0.47). CONCLUSIONS: These results emphasize the importance of a good match between job demands and worker capabilities.

Accidents, Occupational↗
PubMed1995

The natural history of the systemic inflammatory response syndrome (SIRS). A prospective study.

OBJECTIVE: Define the epidemiology of the four recently classified syndromes describing the biologic response to infection: systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis, and septic shock. DESIGN: Prospective cohort study with a follow-up of 28 days or until discharge if earlier. SETTING: Three intensive care units and three general wards in a tertiary health care institution. METHODS: Patients were included if they met at least two of the criteria for SIRS: fever or hypothermia, tachycardia, tachypnea, or abnormal white blood cell count. MAIN OUTCOMES MEASURES: Development of any stage of the biologic response to infection: sepsis, severe sepsis, septic shock, end-organ dysfunction, and death. RESULTS: During the study period 3708 patients were admitted to the survey units, and 2527 (68%) met the criteria for SIRS. The incidence density rates for SIRS in the surgical, medical, and cardiovascular intensive care units were 857, 804, and 542 episodes per 1000 patient-days, respectively, and 671, 495, and 320 per 1000 patient-days for the medical, cardiothoracic, and general surgery wards, respectively. Among patients with SIRS, 649 (26%) developed sepsis, 467 (18%) developed severe sepsis, and 110 (4%) developed septic shock. The median interval from SIRS to sepsis was inversely correlated with the number of SIRS criteria (two, three, or all four) that the patients met. As the population of patients progressed from SIRS to septic shock, increasing proportions had adult respiratory distress syndrome, disseminated intravascular coagulation, acute renal failure, and shock. Positive blood cultures were found in 17% of patients with sepsis, in 25% with severe sepsis, and in 69% with septic shock. There were also stepwise increases in mortality rates in the hierarchy from SIRS, sepsis, severe sepsis, and septic shock: 7%, 16%, 20%, and 46%, respectively. Of interest, we also observed equal numbers of patients who appeared to have sepsis, severe sepsis, and septic shock but who had negative cultures. They had been prescribed empirical antibiotics for a median of 3 days. The cause of the systemic inflammatory response in these culture-negative populations is unknown, but they had similar morbidity and mortality rates as the respective culture-positive populations. CONCLUSIONS: This prospective epidemiologic study of SIRS and related conditions provides, to our knowledge, the first evidence of a clinical progression from SIRS to sepsis to severe sepsis and septic shock.

Diagnosis-Related Groups↗
PubMed1995

Effect of recall period on the reporting of occupational injuries among older workers in the Health and Retirement Study.

Studies of injury morbidity often rely on self-reported survey data. In designing these surveys, researchers must chose between a shorter recall period to minimize recall bias and a longer period to maximize the precision of rate estimates. Using data from the Health and Retirement Study, which employed a recall period of 1 year, we examined the effect of the recall period on rates of occupational injuries among older workers as well as upon rate ratios of these injuries for nine risk factors. We fit a stochastic model to the occupational injury rates as a function of time before the interview and used this model to estimate what the injury rates would have been had we used a 4-week recall period. The adjusted occupational injury rate of 5.9 injuries per 100 workers per year was 36% higher than the rate based on a 1-year recall period. Adjustment for recall period had much less effect on rate ratios, which typically varied by < 10%. Our work suggests that self-reported surveys with longer recall periods may be used to estimate occupational injury rates and also may be useful in studying the associations between occupational injuries and a variety of risk factors.

Accidents, Occupational↗
PubMed1995

Postoperative radiation therapy in clinical stage I endometrial cancer: corpus, cervical, and lower uterine segment involvement--patterns of failure.

PURPOSE: To evaluate involvement of the lower uterine segment (LUS) in adenocarcinoma of the endometrium and to identify patterns of treatment failure. MATERIALS AND METHODS: Two hundred four patients, aged 29-92 years, with endometrial carcinoma underwent surgery. Postoperative radiation therapy was administered for adverse histologic criteria, including deep myometrial invasion, high grade, or LUS involvement. RESULTS: The incidence of tumor involvement of the LUS was 19%; of the cervix, 14%; and of the corpus, 67%. Distant metastasis occurred in 3% of patients with LUS involvement and in 17% of patients with cervical involvement. The local recurrence rate was 50% among patients with LUS involvement with no other risk factors and no postoperative radiation therapy and was 3% among those who underwent radiation therapy (P = .023). CONCLUSION: Early local-regional spread may be the primary mechanism of treatment failure in tumor invasion of the LUS. Aggressive local management, including postoperative radiation therapy, may be necessary.

Adenocarcinoma↗
PubMed1995

Low-dose methotrexate may cause air trapping in patients with rheumatoid arthritis.

Both rheumatoid arthritis (RA) and methotrexate (MTX) are reported to be associated with the development of pulmonary disease. To determine whether MTX enhanced the risk of developing abnormalities in pulmonary function in patients with RA, we prospectively studied 31 subjects (12 male, 19 female) with the diagnosis of classic RA for an average period of 4.4 yr (range, 1 to 5 yr). Each subject was placed on low-dose weekly MTX (mean 17 mg, range 2.5 to 40) for control of RA symptoms. Other medications included non-steroidal anti-inflammatory agents and prednisone if required for control of arthritis symptoms. No other immunosuppressive therapy was used. Each subject was evaluated by pulmonary function tests (PFT) and chest X-ray initially, and at 1, 2, 3.5, and 5 yr. Chest X-rays obtained initially and at the end of the study period were found to be normal. The percent predicted values for initial PFTs in the study group were within the normal range. From the beginning to the end of the observation period, the following mean changes in lung function were observed: 1.9% increase in TLC, 5.1% increase in residual volume (RV), 1.8% increase in FVC, 0.71% decrease in FEV1, 14.7% improvement in alveolar-arterial oxygen (A-aO2) difference, and a 12.7% increase in single-breath diffusing capacity (DLCO). To determine whether MTX (average dose, weekly dose, or cumulative dose) was significantly related to changes in pulmonary function, we used multivariate techniques to control for the initial measure of lung function while assessing the relationship between MTX and the subsequent measures of lung function.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Randomization model methods for evaluating treatment efficacy in multicenter clinical trials.

This paper studies randomization model methods for analyzing data from a multicenter study comparing the effectiveness of two treatments. The Mantel-Haenszel mean score statistic, which can be used for continuous or ordered categorical response variables, is shown to be a useful nonparametric alternative to standard linear model methods for testing the significance of the average treatment difference. In an extensive simulation study, the mean score test performs nearly as well as the optimal linear model methods when the normal-theory assumptions are satisfied. A related estimator of the average treatment difference is also studied. This estimator, which is a weighted average of the center-specific mean differences, is analogous to the commonly used Mantel-Haenszel estimator of the average odds ratio in stratified 2 x 2 contingency tables. The proposed estimator is equivalent to the fixed-effects analysis of variance estimator from the main effects model, and valid estimation of its variance is feasible under very general assumptions.

Aged↗
PubMed1994

A 30-week randomized controlled trial of high-dose tacrine in patients with Alzheimer's disease. The Tacrine Study Group.

OBJECTIVE: To evaluate the efficacy and safety of high-dose tacrine hydrochloride over 30 weeks in patients with probable Alzheimer's disease. DESIGN: A 30-week randomized, double-blind, placebo-controlled, parallel-group trial. SETTING: Outpatients at 33 US centers. PATIENTS: Men and women at least 50 years of age with mild to moderate Alzheimer's disease and otherwise in good health. INTERVENTIONS: Group 1 received placebo; group 2 received 40 mg/d of tacrine for 6 weeks, then 80 mg/d for 24 weeks; groups 3 and 4 received 40 mg/d of tacrine for 6 weeks, 80 mg/d for 6 weeks, and 120 mg/d for 6 weeks. Group 3 remained on a dosage of 120 mg/d for a total of 18 weeks; after 6 weeks at 120 mg/d, group 4 titrated to 160 mg/d for the last 12 weeks. PRIMARY OUTCOME MEASURES: Clinician Interview-Based Impression (CIBI), Alzheimer's Disease Assessment Scale--Cognitive subscale (ADAS-Cog), and Final Comprehensive Consensus Assessment (FCCA). RESULTS: A total of 663 patients entered the study; 653 patients were included in an intent-to-treat (ITT) analysis; 263 had evaluable data at 30 weeks. The results of the ITT analysis revealed significant (P < or = .05) dose-response trends and between-group comparisons on CIBI and ADAS-Cog. In evaluable patients, significant dose-response trends were observed for all three primary measures (P < or = .001). Significant differences in favor of 160 mg/d of tacrine vs placebo were observed on the CIBI (P < or = .002) and ADAS-Cog and FCCA (P < or = .001), as well as caregiver-global and quality-of-life assessments (P < or = .05). On the CIBI, 23% and 42% of tacrine-treated patients in the ITT and evaluable-patient populations, respectively, were rated improved compared with 17% and 18% of placebo patients, respectively. The primary reasons for withdrawal of tacrine-treated patients were asymptomatic liver transaminase elevations (28%) and gastrointestinal complaints (16%). These adverse events were reversible on discontinuation of treatment, and many patients were able to restart tacrine. CONCLUSIONS: Tacrine produced statistically significant, dose-related improvements on objective performance-based tests, clinician- and caregiver-rated global evaluations, and measures of quality of life. There was no evidence that the large number of patient withdrawals biased the overall conclusions of the study.

Aged↗
PubMed1994

A computer program for non-parametric analysis of incomplete repeated measures from two samples.

RMNP2 is an easy-to-use FORTRAN program for the analysis of repeated measures using the non-parametric two-sample tests of Wei and Lachin (J. Am. Stat. Assoc. 79 (1984) 653-661) and Wei and Johnson (Biometrika 72 (1985) 359-364). The program compares two groups of subjects or experimental units when measurements are obtained at multiple time points, or under multiple conditions, from each subject. A strength of the methodology is that subjects with missing responses at one or more time points can be included in the analysis, under the assumption that the missing value mechanism is independent of the response. In contrast to other methods that require parametric assumptions concerning the distribution of the outcome variable, RMNP2 is applicable when the response variable is continuous but not normally distributed. The program is also useful in the analysis of ordered categorical outcomes when the number of possible responses is too large to permit application of general categorical data methodology. The program can be run on microcomputers, workstations and mainframe computers. Two examples illustrating the use and features of RMNP2 are provided.

Analgesia, Obstetrical↗
PubMed1994

Determinants of progression in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive form of lung disease with a median survival of less than 5 yr. To address the progressive nature of this disease process, we investigated the determinants of decrements in lung function in patients with IPF. We prospectively evaluated 39 subjects with IPF. Our study subjects were followed for an average of 2 yr (range, 49 to 1,883 days) and lung function was measured on at least two separate occasions (mean = 9.1 separate tests) during the follow-up period. Since IPF is characterized by reduced lung volume and abnormal gas exchange, our analysis focused on the determinants of total lung capacity (TLC) and diffusing capacity of carbon monoxide (DLCO) during the period of observation. Although, on average, there was a 5.3% increase in the TLC and a 9.8% increase in DLCO between the first and last measure of lung function, 25% of the study population experienced a decline in the TLC and 28% of the study population experienced a decline in the DLCO. Decrements in TLC were independently associated with severe dyspnea (p = 0.01) and treatment with cyclophosphamide (p = 0.03). Decrements in DLCO were significantly and independently associated with more pack-years of cigarette smoking (p = 0.02), moderate (p = 0.03) or severe (p = 0.02) dyspnea, and treatment with cyclophosphamide (p = 0.0002). These findings indicate that several clinical characteristics are independently associated with subsequent declines in TLC and DLCO in patients with IPF.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchoalveolar Lavage Fluid↗
PubMed1994

Longitudinal changes in lung function among asbestos-exposed workers.

To prospectively identify the determinants of persistent or accelerated loss of lung function among workers occupationally exposed to asbestos and assess the relative contribution of cigarette smoking, asbestos-induced pleural fibrosis, and specific findings from bronchoalveolar lavage and high resolution CT scans, we examined the determinants of lung function changes in 117 subjects occupationally exposed to asbestos for at least 1 yr in a high exposure setting. A minimum of 20 yr was required between the first exposure to asbestos and entry into the study. Baseline studies included an independent assessment of dyspnea, lung volumes, diffusing capacity of carbon monoxide (DLCO), a chest radiograph, a high resolution CT (HRCT) scan, and bronchoalveolar lavage (BAL). Subjects were observed for an average of 2 yr (range, 0.5 to 4.0 yr), and lung function was measured on at least two separate occasions (mean, 4.1 separate tests). During the period of observation, there was an average 1.5% decrease in the TLC and a 2.5% decrease in the DLCO. In this longitudinal data set, after controlling for age, height, pack-years of cigarette smoking, and follow-up time, persistently lower measures of TLC were independently related to moderate to severe dyspnea (p = 0.005), diffuse pleural thickening (p = 0.007), and higher concentrations of fibronectin in BAL fluid (p = 0.01). Interstitial lung disease either on the chest radiograph or HRCT scan was not independently associated with persistently lower measures of TLC during the period of observation. However, none of the clinical variables we examined were associated with an accelerated decline in TLC.(ABSTRACT TRUNCATED AT 250 WORDS)

Asbestos↗
PubMed1994

The Clinician Interview-Based Impression (CIBI): a clinician's global change rating scale in Alzheimer's disease.

Global assessments are Food and Drug Administration-required primary outcome measures in trials of putative antidementia drugs. Global ratings are intended to provide an index of clinical importance of change that cannot be obtained from quantitative assessment measures such as mental status examinations. We examined the performance of a global assessment of change instrument, the Clinician Interview-Based Impression (CIBI), in the placebo group of a 30-week, randomized, double-blind clinical trial of tacrine in patients with Alzheimer's disease. Initially there were 184 placebo patients, of whom 125 completed the 30-week study. Descriptive statistics, correlations with changes on other assessment instruments, and test-retest reliability were determined for the CIBI. At week 30, clinicians rated more than 40% of patients on the CIBI as unchanged. The CIBI ratings were weakly but significantly correlated, in the expected direction, with change scores on the quantitative cognitive assessments. The CIBI was modestly reliable on test-retest at weeks 22 and 24 but less reliable compared with other quantitative outcome measures. Modifications of the CIBI that might improve its reliability and acceptance include (1) no restrictions on the form of the bedside mental status assessment, (2) inclusion of caregiver input, and (3) better definition of ratings on the global scale. Global instruments, if properly constructed, can provide an index of clinically important change for the assessment of dementia patients.

Aged↗