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Results for “Multivariate response regression”

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PubMed1997

Physical workload and ergonomic factors associated with prevalence of back and neck pain in urban transit operators.

STUDY DESIGN: Back and neck pain was studied cross-sectionally in 1,449 urban transit drivers by linking medical data, self-reported ergonomic factors, and company records on job history. OBJECTIVES: The goal was to examine the relation between physical workload, ergonomic factors, and the prevalence of back and neck pain. SUMMARY OF BACKGROUND DATA: Researchers, to date, have not found an independent effect of ergonomic factors on back and neck pain while accounting for the effects of past and current physical workload. METHODS: Self-reported ergonomic factors, vehicle type, physical workload (measured as duration of driving), height, weight, age, and gender were analyzed in relation to back and neck pain, using multivariable logistic regression models. RESULTS: Physical workload showed a positive dose-response relation with back and neck pain after controlling for vehicle type, height, weight, age, and gender. The odds ratio for 10 years of driving was 3.43. Additional adjustment for ergonomic factors decreased this odds ratio to 2.55. Six out of seven ergonomic factors were significantly related to the prevalence of back and neck pain after adjustment for age, gender, height, weight, and physical workload. Problems with adjusting the seat had the largest effect (odds ratio = 3.52). Women had back and neck pain twice as frequently as men. CONCLUSION: The results support the hypothesis of a causal role of physical workload for the development of back and neck pain. Ergonomic factors partially mediated the risk of back and neck pain associated with driving, suggesting a potential for prevention of back and neck pain by ergonomic redesign of transit vehicles. Elevated risks for back and neck pain for female drivers were not explained by anthropometric and ergonomic factors.

Adult↗

PubMed1994

[Interferon treatment of chronic hepatitis C--assessment of predictive factors to the effect of interferon treatment using multivariate analysis with the logistic regression model].

We treated 156 chronic hepatitis C patients with alpha-interferon (IFN) and assessed the response rate and the predictive factors to the effect of IFN treatment. Complete response (CR) rate was 39.1%, and CR with serum HCV-RNA disappearance rate was 29%. CR to IFN treatment was dependent on HCV serotype and serum HCV-RNA. Patients of serotype II and low serum HCV-RNA were effective to IFN treatment.

Adult↗

PubMed1992

Dose related acute irritant symptom responses to occupational exposure to sodium borate dusts.

A repeated measurement design was employed in the study of acute symptoms of eye and respiratory tract irritation resulting from occupational exposure to sodium borate dusts. The symptom assessment of the 79 exposed and 27 unexposed subjects comprised interviews before the shift began and then at regular hourly intervals for the next six hours of the shift, four days in a row. Exposures were monitored concurrently with a personal real time aerosol monitor. Two different exposure profiles, a daily average and short term (15 minute) average, were used in the analysis. Exposure-response relations were evaluated by linking incidence rates for each symptom with categories of exposure. Acute incidence rates for nasal, eye, and throat irritation, and coughing and breathlessness were found to be associated with increased exposure levels of both exposure indices. Steeper exposure-response slopes were seen when short term exposure concentrations were used. Results from multivariate logistic regression analysis suggest that current smokers tended to be less sensitive to the exposure to airborne sodium borate dust. There was no indication that anhydrous sodium borate was more potent than the other sodium borates in this work environment.

Adult↗

PubMed1997

Statistical modeling of dose-response relationships in clinical trials--a case study.

This paper presents a model-based assessment of the relationship between the dose of a test treatment and response. The data set used in the analysis describes the results of two clinical trials that were designed to assess the dose-response relationship of a test treatment. The models described in the paper are fit using weighted regression as implemented by the SAS procedure CATMOD. Relationships between weighted regression and other similar procedures are discussed.

Anticholesteremic Agents↗

PubMed1988

HLA-DR2, a marker for class I antigen sensitization.

After analysis of 423 hemodialysis patients in a transfusion program and 461 cadaver-donor renal transplants, we found that HLA-DR2 frequency was significantly higher in the responder (36%) than in the nonresponder patient group (19%), according to the percentage of PRA (panel reactive antibodies). Among DR2+ patients, the percentage of hypersensitized patients was twice that of DR2- patients. Graft survival curves in cadaver-donor renal transplants indicated a significantly lower survival when recipients were DR2+, even in recipient-donor pairs identical for class II antigens but mismatched for class I antigens. The prognostic probability of low response to transfusions by a stepwise logistic regression analysis showed the influence of sex and DR2 phenotype. By multivariant discriminant analysis, we found that the DR2 phenotype was one of the most influential transfusion sensitization risk factors. Our preliminary conclusion is that DR2 can be related to immune responsiveness to class I antigens.

Antilymphocyte Serum↗

PubMed1996

Physicians, pharmaceutical sales representatives, and the cost of prescribing.

OBJECTIVE: To evaluate the influence of primary care physicians' attitudes toward and use of information provided by pharmaceutical representatives on prescribing costs in ambulatory practice. DESIGN: A mailed questionnaire collected information about physician demographic and practice characteristics and attitudes toward and use of information provided by pharmaceutical representatives. PARTICIPANTS: Kentucky physicians practicing primary care adult medicine (family medicine, general practice, general medicine; n = 1603). MAIN OUTCOME MEASURE: Relative cost of prescribing, based on physician responses to treatment choices for ambulatory clinical scenarios in primary care. A multivariable regression model assessed predictive relationships between independent variables and prescription costs. RESULTS: Four hundred forty-six returned questionnaires were suitable for analysis. No significant differences were noted in age, gender, days worked per week, or years since graduation between responders and a sample of nonresponders. A significant positive correlation was found between physician cost of prescribing and perceived credibility, availability, applicability, and use of information provided by pharmaceutical representatives (P < .01, Pearson's Product-Moment Correlation Coefficient). Physicians in academic or hospital-based practice settings had significantly lower prescribing costs than physicians in nonacademic and nonhospital practices (P = .001, analysis of variance). Frequency of use of information provided by pharmaceutical representatives (P = .01, multiple linear regression) and the group practice setting (P = .02, multiple linear regression) remained significant, independent positive predictors of cost in the multivariable regression model. CONCLUSIONS: Frequency of use of information provided by pharmaceutical representatives and the group practice, nonacademic and nonhospital setting may be associated with increased primary care physician prescribing costs.

Attitude of Health Personnel↗

PubMed1996

Diffusion of innovative approaches to managing hypoplastic left heart syndrome.

OBJECTIVE: To study the perceptions of outcome and the diffusion into practice of innovative approaches such as palliative surgery and heart transplantation to treat hypoplastic left heart syndrome. DESIGN: A forced-choice questionnaire was sent to 108 US neonatology section heads. Responses were analyzed using Wilcoxon matched pairs, chi 2 analysis, and multivariant logistic regression. RESULTS: Ninety-three questionnaires (86%) were returned. All respondents discussed palliative surgery or transplantation or both with parents; 71 (76%) of 93 also discussed comfort care. Nineteen (24%) of 80 recommended comfort care only, 51 (64%) of 80 recommended surgery only, and 10 (12%) of 80 recommended both. Of the 61 respondents recommending one or both surgical procedures, palliative surgery was recommended by 44 and transplantation by 33. Respondents perceived that transplantation was associated with a lower 1-year mortality than palliative surgery (P < .001) and with a better quality of life (P < .001). CONCLUSIONS: Palliative surgery and transplantation are widely used to treat hypoplastic left heart syndrome. The continued availability of comfort care suggests that these surgical procedures are still in transition from experimental technology to standard of care.

Cardiac Surgical Procedures↗

PubMed1988

Acute promyelocytic leukemia. Therapy results and prognostic factors.

From December 1976 to July 1986, 34 patients with acute promyelocytic leukemia (APL) were treated with daunorubicin (DNR) alone and simultaneous supportive therapy with low-dose heparin, platelet transfusions, and fresh frozen plasma. Two consecutive maintenance therapy regimens were employed in patients who achieved complete remission (CR): (1) a classical maintenance with methotrexate and 6-mercaptopurine, with DNR plus methyl-GAG re-inductions; (2) from 1982 an intensive sequential combination therapy regimen was administered. CR was achieved in 23 patients (68%). Only one patient had leukemic resistance. Other failures were a consequence of post-chemotherapy complications. A multivariate logistic regression analysis has been performed to evaluate the prognostic importance on response to remission induction of 25 patient and disease characteristics at diagnosis. The significant variables in decreasing order of significance were: serum albumin level, fever at diagnosis, serum creatinine level, and age. The median duration of remission and survival by Kaplan-Meier analysis were projected to be 24 and 25 months, respectively. Relapses occurred in 11 of 23 CR patients. Nine patients remained in the first remission from 5+ to 37+ months. Short-term (CR) and long-term results (duration of remission and survival) in APL treated for induction with DNR alone were similar to those obtained in other subtypes of acute myeloblastic leukemia by intensive combination chemotherapy.

Adolescent↗

PubMed1997

Sex and diagnostic evaluation of possible coronary artery disease after exercise treadmill testing at one academic teaching center.

Controversy exists as to whether a sex bias exists that affects the diagnostic approach to suspected coronary artery disease: previous studies have used coronary angiography, but not other noninvasive testing, as a primary end point. This investigation examined posttest sex differences in diagnostic evaluation after exercise treadmill testing according to a broader end point than just coronary angiography alone. The design was a cohort analytic study with a 90-day follow-up. The study was done at the Cleveland Clinic Foundation, an academic group practice. Patients included consecutive adults (1023 men and 579 women) with chest pain but no documented coronary disease who were referred for symptom-limited exercise treadmill testing without adjunctive imaging; none had undergone prior invasive cardiac procedures. Main outcome measures included (1) performance of any subsequent diagnostic study (invasive or noninvasive) and (2) performance of coronary angiography as the next diagnostic study. During follow-up, 89 (8.7%) men and 48 (8.3%) women underwent a second diagnostic study (odds ratio 0.95; 95% confidence interval 0.66 to 1.37; p > 0.8), whereas 64 (6.3%) men and 21 (3.6%) women went straight to coronary angiography (odds ratio 0.56; 95% confidence interval 0.34 to 0.93; p = 0.02). In multivariable logistic regression analyses, which considered baseline clinical characteristics, the ST-segment response, and other prognostically important exercise responses, women tended to be less likely than men to be referred to any second test (adjusted odds ratio 0.70; 95% confidence interval 0.42 to 1.19; p > 0.1) but were markedly and significantly less likely to be referred straight to coronary angiography (adjusted odds ratio 0.33; 95% confidence interval 0.17 to 0.65). After exercise treadmill testing, women were only slightly less likely than men to be referred for subsequent diagnostic testing; they were, however, much less likely to be referred straight to coronary angiography as opposed to another noninvasive study.

Academic Medical Centers↗

PubMed1998

Long-term survival following neoadjuvant chemotherapy and radical surgery in locally advanced cervical cancer.

The aim of this study was to analyse the long-term survival and the relationships between prognostic factors at presentation, chemoresponsiveness and disease outcome in patients with locally advanced cervical cancer treated by neoadjuvant chemotherapy and radical surgery (RS). Two consecutive studies of neoadjuvant chemotherapy containing cisplatin, bleomycin plus/minus methotrexate followed by radical hysterectomy and systematic aortic and pelvic lymphadenectomy were carried out between January 1986 and September 1990 on 130 patients with > or = 4 cm stage IB2-III cervical cancer. Survival analysis was performed using the Kaplan and Meier test and Cox's multivariate regression analysis. 128 (98%) of the patients enrolled were evaluable for clinical response and survival, 83% (106) of the patients responded to chemotherapy, with a 15% complete response rate. Logistic regression analysis demonstrated that International Federation of Gynecology and Obstetrics (FIGO) stage, cervical tumour size, parametrial involvement and histotype are highly predictive of response. Responding patients underwent laparotomy, but 8% were not amenable for radical surgery. The 10-year survival estimates were 91%, 80% and 34.5% for stage IB2-IIA bulky, IIB and III, respectively (P < 0.001). After Cox's regression analysis, the parameters significantly associated with survival were the same factors predicting response to neoadjuvant chemotherapy. No stage IB2-IIA bulky patient has so far relapsed, while 12% stage IIB and 56% stage III patients recurred. The 10-year disease-free survival estimates are 91% and 44% for stage IB2-IIB and III, respectively (P < 0.001). Metastatic nodes and persistent tumour in the parametria were the only two independent factors for disease-free survival after multiple regression analysis. After a long-term follow-up (median follow-up 98 months (20-129+)), our results give new evidence of the prognostic value of response to neoadjuvant chemotherapy and of a possible therapeutic benefit of the sequential treatment adopted which, however, must be verified in a randomised setting.

Adult↗

PubMed1985

Prognostic value of B-cell mitogen-induced and spontaneous thymidine uptake in vitro in chronic B-lymphocytic leukaemia cells.

Blood lymphocytes from 50 patients with chronic B-lymphocytic leukaemia (B-CLL) were cultured in vitro with and without the polyclonal B-cell activators (PBA) dextran sulphate (DxS), lipopolysaccharide from E. coli (LPS), and Epstein Barr virus (EBV). Patients with blood lymphocytes that showed a high spontaneous or PBA-induced 3H-thymidine uptake in 4 d cultures had a significantly shorter therapy-free survival than patients whose lymphocytes showed a low thymidine uptake. The DxS-induced cellular thymidine uptake was the most powerful predictor of prognosis. Eighteen patients with leukaemic cells responding to DxS stimulation had a median therapy-free survival of 17 months and a probability of 5 year therapy-free survival of less than 0.1, whereas for 30 patients with DxS unresponsive cells the corresponding figures were greater than 120 months and greater than 0.7, respectively (log rank, P less than 0.0001). A multivariate Cox's regression analysis revealed that the DxS-induced leukaemic cell response was of greater prognostic importance than clinical features such as blood counts and staging according to Rai and Binet. Therefore PBA-induced leukaemic cell thymidine uptake seems valuable in the prediction of prognosis in B-CLL.

Adult↗

PubMed1995

[Interferon treatment for chronic hepatitis C--assessment of 3 regimens in patients received more than 500MU interferon treatment and their effect predictive factors for interferon treatment using multivariate analysis with the logistic regression model].

Chronic hepatitis C patients (n = 115) were treated with interferon (IFN). Total dose employed was more than 500 MU. The response rate was assessed among the three treatment groups: 2W continuous+TIW, 4W continuous+TIW, 8W continuous+TIW. The IFN treatment effect predictive factors were also assessed. Complete response (CR) rate, CR with serum HCV-RNA disappearance rate, responders' histology activity index score changes between before and after treatment, and responders' hepatocytes HCV-RNA disappearance rate did not differ among the three treatment regimens. CR to IFN treatment was dependent on serum HCV-RNA and HCV serotype. Patients of low serum HCV-RNA and serotype II were responsive to IFN treatment.

Chronic Disease↗

PubMed1995

A survey screen for prediction of apnea.

Questionnaire data from patients presenting at three sleep disorders centers were used to develop and assess a screening tool for sleep apnea based on the reporting of the frequency of various symptoms of sleep apnea and other sleep disorders plus age, body mass index (BMI) and gender. Patients were not specifically referred for suspicion of sleep apnea. Separate factor analyses of survey responses from 658, 193 and 77 respondents from the first, second and third sites, respectively, each yielded four orthogonal factors, one of which accounted for all the questions concerned with the frequency of disordered breathing during sleep. The survey was shown to be reliable in a subset of patients from one of the sites (test-retest correlation = 0.92). Survey data were then compared to a clinical measure of sleep apnea (respiratory disturbance index) obtained from polysomnography. A multivariable apnea risk index including survey responses, age, gender and BMI was estimated using multiple logistic regression in a total sample of 427 respondents from two of the sites. Predictive ability was assessed using receiver operating characteristic (ROC) curves. The area under the ROC curve was 0.79 (p < 0.0001). For BMI alone, it was 0.73, and for an index measuring the self-report of the frequency of apnea symptoms, it was 0.70. The multivariable apnea risk index has potential utility in clinical settings.

Adult↗

PubMed1999

Integrated approach to prediction of cervical intra-epithelial neoplasia status through a case-control study.

A case-control study on cervical intra-epithelial neoplasia (CIN) was carried out on 398 subjects in the state of West Bengal, India. These samples were taken from mass screening programs organized by the authors, maintaining the uniformity of sampling to the extent possible. The cervical smears were tested by the Papanicolaou (PAP) method, following the Bethesda system for reporting of CIN status. Odds ratios and correlation coefficients among different variables, assumed to produce carcinoma of the cervix, show that 6 out of 11 variables, i.e., age, education, socio-economic status, duration of marriage, age at marriage and body surface, are associated with CIN. Multivariate analysis of logistic regression was carried out using BMDP-LR with dichotomized response variables considering CIN (0 and 1) in one group and CIN (2 and 3) in the other group. The outcome of the analysis indicated that age and educational level are 2 contributing factors for CIN. The percentage of correct classification in this analysis has improved to 74.5%, with a probability of 0.90. Polychotomous regression analysis was carried out using BMDP-PR in the next step. This analysis showed that parity was a contributing factor, in addition to age and educational level. These 3 factors provide a predictive model for identifying the high-risk group in a rational way. This approach would restrict screening to approximately 10% of the population. Subsequently, the model has been validated in a confirmatory trial among 85 new cases and was found to work satisfactorily.

Adult↗

PubMedDate not supplied

Factors influencing the effectiveness of mailed health surveys.

The authors investigated sources of bias in health surveys by examining responses to their 1989 questionnaire mailed to 1,255 Massachusetts men who were eligible for dental care provided by the Department of Veterans Affairs. After a maximum of three mailings and one telephone call to nonrespondents, a total of 1,049 veterans had responded out of 1,228 finally determined to be eligible, a response rate of 85 percent. The investigators found that small differences in univariate estimates would have occurred had the field phase been terminated after the first mailing, which had a response rate of 61 percent. To evaluate multivariate distributions, they duplicated their previously published logistic regression model for sources of dental care, using only those who responded to the first and second mailings. Although model fits would have been substantively the same had the field phase been terminated after the first or the second mailings, analysis of parameter estimates and their statistical significances suggested bias that would have led to different substantive conclusions, in some instances. Another potential source of bias in surveys was found to be item omission. Fifty-eight percent of respondents answered all 46 survey questions, and 90 percent answered at least 91 percent of the questions. Fewer questions were answered by those whose responses were received last, but trends regarding missing data by age or education were not statistically significant. Although the survey using this methodology met all objectives, subject nonresponses, the ineligibility of potential respondents, item nonresponses, and skewed distributions of outcome variables combined to reduce the statistical power to detect differences among groups or to alter the analysis of the differences. These factors need to be planned for by investigators undertaking similar surveys.

Analysis of Variance↗

PubMed1989

Predicting local recurrence of carcinoma of the rectum after preoperative radiotherapy and surgery.

A prospective study of prognostic factors has been carried out in a group of 186 patients with tethered rectal carcinomas. Of these, 97 were randomized to surgery alone and 89 to receive preoperative radiotherapy (20 Gy in four fractions). DNA ploidy was determined by flow cytometry. DNA aneuploidy was detected in 60 patients (62 per cent) in the surgery only group, but in only 33 patients (37 per cent) after radiotherapy (P less than 0.01). There was a significant reduction in local recurrence in irradiated patients (P less than 0.0001). DNA diploid tumours were less likely to recur locally. This was more marked in the radiotherapy group (P = 0.01) than in the surgery only group (P = 0.06). After radiotherapy, only the surgeons' assessments of a 'curative' resection and DNA ploidy were independent predictors of local recurrence in multivariate regression analysis, whilst Dukes' classification was not. In conclusion, DNA ploidy may indicate response to radiotherapy and is an important predictor of subsequent local tumour progression.

Combined Modality Therapy↗

PubMed1994

Prior crash and violation records of pilots in commuter and air taxi crashes: a case-control study.

With a case-control design, this study examined the relationships of crash/incident history, violation history, pilot age, flight experience, and recent flight time with the likelihood of being involved in commuter aircraft and air taxi crashes. Cases (n = 725) were pilots who had been involved in commuter aircraft or air taxi crashes during 1983-88, identified from the National Transportation Safety Board aviation crash data base. From the Federal Aviation Administration (FAA) airmen information system, 1,555 pilots were randomly selected as controls. Controls were frequently-matched with cases on medical class and calendar year. Different data bases within the FAA's airmen information system were linked to ascertain information about crash/incident and violation records in the previous 3 years, age, total flight time, and flight time in the prior 6 months. Multivariate logistic regression models were fitted to estimate odds ratios and evaluate dose-response effects, non-linear relationships, and interactions. Cases had significantly higher prevalence rates of prior crash/incident and violation records. The estimated odds ratio of being involved in a commuter aircraft or an air taxi crash was 1.7 (95% confidence interval [CI], 1.3-2.4) for crash/incident history, and 1.6 (95% CI, 1.1-2.2) for violation history. A "dose-response effect" was found with both crash/incident history and violation history, with higher odds ratios for pilots with crashes versus incidents or with more serious violations. Total flight time showed a diminishing protective effect. Either very small or very large recent flight time increased the risk of being involved in a commuter aircraft or an air taxi crash.

Accidents, Aviation↗

PubMed1996

Multiple tumour marker assays in advanced cervical cancer: relationship to chemotherapy response and clinical outcome.

Serum levels of squamous cell carcinoma antigen (SCC), CA 125 and CA 15.3 were measured in 102 patients with locally advanced cervical cancer undergoing neoadjuvant chemotherapy (NACT) and radical surgery. We found a significant correlation between SCC concentration and stage, histotype, cervical tumour size and lymph node status. For CA 125 and CA 15.3, no significant difference in the distribution of marker levels according to histopathological variables was found. In a multivariate analysis, histological type, FIGO stage and SCC positivity (> 5 ng/ml) proved to be independent predictors of response to neoadjuvant chemotherapy. Moreover, logistic regression analysis showed that CA 15.3 may be a significant adjunct to SCC in the prediction of chemotherapy response. Of the three markers tested, only CA 125 was significantly related to patient survival. In the multivariate analysis, clinical response to chemotherapy and CA 125 status (> 35 U/ml) retained an independent prognostic value. Our data suggest that the tumour markers used in this study could be useful in the management of locally advanced cervical cancer. Pretreatment serum levels of SCC, together with CA 15.3 assay, may be a useful tool in the determination of response to chemotherapy, while CA 125 assay could be evaluated as a prognostic risk factor in these patients.

Adult↗