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PubMed2000

Utilization of multiple imperfect assessments of the dependent variable in a logistic regression analysis.

Often, in biomedical research, there are multiple sources of imperfect information regarding a dichotomous variable of interest. For example, in a study we are conducting on the relationship between cocaine use and stroke risk, information on the cocaine use of each study patient is available from three fallible sources: patient interviews; urine toxicology testing, and medical record review. Regression analyses based on a rule for classifying patients from this information can result in biased estimation of associations and variances due to the misclassification of some subjects and to the assumption of certainty. We describe a likelihood-based method that directly incorporates multiple sources of information regarding an outcome variable into a regression analysis and takes into account the uncertainty in the classification. The method can be applied when some sources of information are missing for some subjects. We show how the availability of multiple sources can be exploited to generate estimates of the quality (for example, sensitivity and specificity) of each source and to model the degree to which missing data are informative. A fitting algorithm and issues of identifiability are discussed. We illustrate the method using data from our study.

Adult↗

PubMed1996

A multiple stepwise logistic regression analysis of trauma history and 16 other history and dental cofactors in females with temporomandibular disorders.

The simultaneous contribution of 11 occlusal factors, dental attrition severity, orthodontic history, trauma (motor vehicle accident [MVA] and non-MVA), and age in defining two independent large populations of females diagnosed with five mutually exclusive temporomandibular disorders was tested through multiple stepwise logistic regression analysis. Non-MVA trauma was significant in both groups in defining disc displacement (DD) with and without reduction, and osteoarthrosis (OA) (both primary and following DD). Anterior open bite was also a significant factor in defining OA in both groups. Much smaller contributions were also made by missing teeth in one of the populations with OA following DD, and by retruded contact position-intercuspal position slide lengths and overjet in one of the primary OA populations. Motor vehicle accident trauma was significant in defining myofascial pain (MP) in both populations, and laterotrusive attrition mildly defined MP in one population. Only a minority of total variance was explained: 6% to 8% of DD with reduction; 10% to 14% of DD without reduction; 11% to 20% of OA following DD; 17% to 38% of primary OA; and 4% to 10% of MP. Non-MVA trauma was the major defining feature of the temporomandibular joint intracapsular disorders, and MVA trauma explained a very small percentage of the MP patients. Implications are discussed and recommendations are made for future research.

Adolescent↗

PubMed2006

Fluorescence-suppressed Raman technique for quantitative analysis of protein solution using a micro-Raman probe, the shifted excitation method, and partial least squares regression analysis.

A practical Raman analyzing technique with suppression of the strong fluorescent background in order to obtain quantitative information is proposed in the present study. The technique is based on the shifted excitation method and partial least squares regression (PLSR) analysis. The Raman system consists of a single Raman spectrometer, a background-free electrically tunable Ti:Sapphire laser (BF-ETL), and a micro-Raman probe (MRP). The system allows one to obtain reliable shifted excitation Raman spectra with a simple operation. The PLSR analysis successfully provides quantitative information from the obtained spectra with the suppression of random noise including photon shot noise. The present study demonstrates that the technique is effective for extracting quantitative information concealed behind a fluorescent background that is more than 200 times stronger than the Raman signal.

Animals↗

PubMed1996

Risk factors for serious nonsteroidal-induced gastrointestinal complications: regression analysis of the MUCOSA trial.

OBJECTIVES: This analysis evaluated the clinical and demographic risk factors for a suspected, serious nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal (GI) complication in everyday clinical practice and calculated the risk reduction associated with misoprostol therapy in these "at-risk" patients. METHODS: Using logistic regression analysis, the data set from a randomized, parallel, placebo-controlled trial of misoprostol in 8,843 rheumatoid arthritis patients taking NSAIDs (the Misoprostol Ulcer Complications Outcomes Safety Assessment trial) was modeled to identify risk factors for GI adverse events. The dependent variable was defined as a "suspected serious GI complication," and the independent variables included demographic features, level of functional disability, presence of co-morbid diseases, use of certain drugs, and treatment arm. RESULTS: Two hundred forty-two suspected serious GI complications were observed; 102 occurred in the misoprostol treatment group (risk: 2.32%) and 140 in the placebo group (risk: 3.15%). Overall risk reduction due to misoprostol therapy was 26.6% (confidence interval 5.5%-42.9%, P < .05). However, in patient groups with identified risk factors, misoprostol use decreased the risk for an adverse GI event by 38.3%-87.3%. Specifically, those who benefitted significantly from therapy with misoprostol were patients with a history of peptic ulcer disease (risk reduction 52.4%), history of previous GI bleeding (risk reduction 50%), history of significant cardiovascular disease (risk reduction 38.3%), significant functional disability (risk reduction 87.2%), and patients whose symptoms required concomitant antacid use (risk reduction 48.3%). CONCLUSION: We conclude that in everyday practice, patients who require chronic NSAID therapy and who have specific clinical risk factors may benefit from misoprostol co-therapy.

Aged↗

PubMed1987

Prognosis of chronic lymphocytic leukemia: a multivariate regression analysis of 325 untreated patients.

Three hundred twenty-five previously untreated patients with chronic lymphocytic leukemia were analyzed to identify significant prognostic factors for survival. Univariate analysis identified the following characteristics associated with survival: (1) clinical characteristics: age, race, sex, performance status, lymphadenopathy, and hepatosplenomegaly; (2) hematologic parameters: WBC count, absolute lymphocyte and granulocyte counts, hemoglobin level, and platelet count; and (3) biochemical parameters: serum albumin, calcium, uric acid, lactate dehydrogenase, alkaline phosphatase, BUN, and creatinine. Multivariate regression analysis in a randomly selected training subset of 217 patients demonstrated that the combination of uric acid, alkaline phosphatase, lactate dehydrogenase, external lymphadenopathy, and age had the strongest predictive relation to survival time. The resulting model was validated in the remaining independent subset of 108 patients and led to classification of patients into low, intermediate, and high-risk groups with five-year survival rates of 75%, 59%, and 14%, respectively, and with distinctively different annual mortality rates (P less than .01). Both the regression model and Rai staging were highly effective in identifying risk groups among the entire patient population (P less than 0.001). Overall the regression model was superior to Rai staging in defining prognostic risk groups. In addition, it was able to separate patients into significantly different risk categories within each Rai stage, thus improving on the prognostic prediction of individual patients with chronic lymphocytic leukemia.

Adult↗

PubMed1993

Reduction in the risk of bronchopulmonary dysplasia from 1980-1990: results of a multivariate logistic regression analysis.

A retrospective analysis (1980-1990) of normally formed low birthweight (< 2500 g) infants surviving to at least 28 days following intermittent positive pressure ventilation (IPPV) for longer than 12 h was performed. Bronchopulmonary dysplasia (BPD) was defined as oxygen dependency at 28 days with characteristic radiographic findings. Logistic regression analysis of risk factors, before and after the initiation of IPPV was performed on 412 infants. Decreasing birth weight (BW) and gestational age (GA) were associated with an increased risk of BPD. When controlled for these variables, predictive factors prior to IPPV were gender, age at IPPV, respiratory diagnosis, and year of birth. Following IPPV, duration of peak inspiratory pressure > 25 cm H2O, duration of fraction of inspired oxygen (FiO2) > 0.60 (DO2), maximum peak inspiratory pressure (MPIP), maximum FiO2, patent ductus arteriosus, bacteraemia and either pneumothorax or pulmonary interstitial emphysema were associated with an increased risk of BPD. Adjusting for BW and GA, there was a significant reduction in BPD risk from 1980-1990 (relative odds of 0.88 for each year compared to the previous year). This trend could be largely accounted for by decreases in MPIP and DO2 during the study period. Surfactant treatment was not independently associated with a significant change in the risk of BPD. Based on this analysis, we developed a scoring system for predicting the risk of BPD in the neonatal period which we evaluated in a random sample of infants. This predicted infants at risk of BPD with a sensitivity of 65% and a specificity of 88%.(ABSTRACT TRUNCATED AT 250 WORDS)

Birth Weight↗

PubMed2004

Insulin-like growth factor (IGF)-I, IGF binding protein-3, and cancer risk: systematic review and meta-regression analysis.

BACKGROUND: Insulin-like growth factor (IGF)-I and its main binding protein, IGFBP-3, modulate cell growth and survival, and are thought to be important in tumour development. Circulating concentrations of IGF-I might be associated with an increased risk of cancer, whereas IGFBP-3 concentrations could be associated with a decreased cancer risk. METHODS: We did a systematic review and meta-regression analysis of case-control studies, including studies nested in cohorts, of the association between concentrations of IGF-I and IGFBP-3 and prostate, colorectal, premenopausal and postmenopausal breast, and lung cancer. Study-specific dose-response slopes were obtained by relating the natural log of odds ratios for different exposure levels to blood concentrations normalised to a percentile scale. FINDINGS: We identified 21 eligible studies (26 datasets), which included 3609 cases and 7137 controls. High concentrations of IGF-I were associated with an increased risk of prostate cancer (odds ratio comparing 75th with 25th percentile 1.49, 95% CI 1.14-1.95) and premenopausal breast cancer (1.65, 1.26-2.08) and high concentrations of IGFBP-3 were associated with increased risk of premenopausal breast cancer (1.51, 1.01-2.27). Associations were larger in assessments of plasma samples than in serum samples, and in standard case-control studies compared with nested studies. INTERPRETATION: Circulating concentrations of IGF-I and IGFBP-3 are associated with an increased risk of common cancers, but associations are modest and vary between sites. Although laboratory methods need to be standardised, these epidemiological observations could have major implications for assessment of risk and prevention of cancer.

Breast Neoplasms↗

PubMed1994

A comprehensive study of physical parameters, biomechanical properties, and statistical correlations of iliac crest bone wedges used in spinal fusion surgery. III. Multivariable regression analysis and practical formulas for strength prediction.

Iliac crest wedges are commonly used in spinal fusion procedures and must be capable of withstanding considerable mechanical stress during the healing process. Physical parameters, mechanical properties, correlations among physical parameters, and correlations of mechanical properties versus physical parameters have been presented by the authors in companion papers. In this study, mathematical formulas have been developed, using multi-variable regression analysis, which permit calculation of the axial load-bearing capacity and compressive strength of a wedge, provided donor age, cortical bone cross-sectional area, total cross-sectional area, and wedge "width" are available. The formulas proposed are simple, easy to use, and provide acceptable accuracy. For the predicted load-bearing capacity, experimentally determined data illustrated that 59% of the calculated values had either less than 10% error or their predicted values were smaller than the observed values, 75% of the calculated values had either less than 20% error or their predicted values were smaller than the observed values. Similar accuracies were estimated for calculation of compressive strengths. Charts are generated from the established formulas, which permit a visual determination of load-bearing capacity and compressive strength of a wedge.

Aging↗

PubMed1990

Improved prediction of left ventricular mass by regression analysis of body surface potential maps.

Electrocardiographic left ventricular (LV) hypertrophy involving ST-T abnormalities, in addition to high QRS voltages, is associated with increased risk of cardiovascular disease mortality. Unfortunately, conventional electrocardiographic criteria have limited utility in the quantitative assessment of LV hypertrophy. Body surface potential maps, which contain diagnostic information not present in commonly used lead systems, were recorded from 117 thoracic sites and 3 limb electrodes in 72 normal subjects and 84 patients with LV hypertrophy. Multiple regression analysis was performed separately for 54 women and 102 men on 120-lead data, using as features instantaneous voltages on time-normalized P, PR, QRS and ST-T waveforms. Leads and features for optimal prediction of echocardiographically determined LV mass were selected. A total of 6 features from 3 torso sites in men, and from the same 3 sites plus 2 others in women, yielded correlations between echocardiographic and electrocardiographic estimates of LV mass of 0.89 and 0.88, respectively. The standard errors of the estimate (SEE), or average errors in predicting LV mass from the regression equations, were 31 and 22 g, respectively. The single most potent predictor in both sexes was a mid-QRS voltage measured on a lead positioned 10 cm below V1; QRS duration, late QRS and early-to-mid T-wave amplitudes recorded in the lower left flank contributed significantly to the performance of both regression models. The optimal electrode sites for electrocardiographic prediction of LV mass were outside the conventional lead locations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2003

Logistic regression analysis of potential prognostic factors for pulmonary thromboembolism.

OBJECTIVE: To identify potential prognostic factors for pulmonary thromboembolism (PTE), establishing a mathematical model to predict the risk for fatal PTE and nonfatal PTE. METHOD: The reports on 4,813 consecutive autopsies performed from 1979 to 1998 in a Brazilian tertiary referral medical school were reviewed for a retrospective study. From the medical records and autopsy reports of the 512 patients found with macroscopically and/or microscopically documented PTE, data on demographics, underlying diseases, and probable PTE site of origin were gathered and studied by multiple logistic regression. Thereafter, the "jackknife" method, a statistical cross-validation technique that uses the original study patients to validate a clinical prediction rule, was performed. RESULTS: The autopsy rate was 50.2%, and PTE prevalence was 10.6%. In 212 cases, PTE was the main cause of death (fatal PTE). The independent variables selected by the regression significance criteria that were more likely to be associated with fatal PTE were age (odds ratio [OR], 1.02; 95% confidence interval [CI], 1.00 to 1.03), trauma (OR, 8.5; 95% CI, 2.20 to 32.81), right-sided cardiac thrombi (OR, 1.96; 95% CI, 1.02 to 3.77), pelvic vein thrombi (OR, 3.46; 95% CI, 1.19 to 10.05); those most likely to be associated with nonfatal PTE were systemic arterial hypertension (OR, 0.51; 95% CI, 0.33 to 0.80), pneumonia (OR, 0.46; 95% CI, 0.30 to 0.71), and sepsis (OR, 0.16; 95% CI, 0.06 to 0.40). The results obtained from the application of the equation in the 512 cases studied using logistic regression analysis suggest the range in which logit p > 0.336 favors the occurrence of fatal PTE, logit p < - 1.142 favors nonfatal PTE, and logit P with intermediate values is not conclusive. The cross-validation prediction misclassification rate was 25.6%, meaning that the prediction equation correctly classified the majority of the cases (74.4%). CONCLUSIONS: Although the usefulness of this method in everyday medical practice needs to be confirmed by a prospective study, for the time being our results suggest that concerning prevention, diagnosis, and treatment of PTE, strict attention should be given to those patients presenting the variables that are significant in the logistic regression model.

Adolescent↗

PubMed1994

Low grade transitional cell carcinoma of the bladder. Cytologic diagnosis by key features as identified by logistic regression analysis.

BACKGROUND: Bladder cytology is being used increasingly to detect and monitor early stage bladder cancer. Because of the lack of significant cytomorphologic atypia in low grade transitional cell carcinomas (TCCs), there often is great difficulty in separating these neoplastic cells from benign urothelial cells. METHODS: In an attempt to increase diagnostic sensitivity, 82 bladder wash specimens, which included 33 low grade TCCs and 49 nonneoplastic lesions, were reviewed retrospectively. With a stepwise logistic regression analysis, three key cytomorphologic criteria useful in the separation of low grade TCC from benign urothelium were identified. RESULTS: The key cytologic criteria were increased nuclear/cytoplasmic ratios, irregular nuclear borders, and cytoplasmic homogeneity. By using contingency tables, these three criteria combined had a sensitivity of 45% and a specificity of 98% in the diagnosis of low grade transitional cell carcinoma. If any two of the criteria were present, there was a sensitivity of 85% and a specificity of 96%. CONCLUSIONS: By using these three criteria, the diagnosis of TCC can be made with a high degree of accuracy in bladder wash specimens.

Adult↗

PubMed1996

Effect of alcohol intake on the efficacy of interferon therapy in patients with chronic hepatitis C as evaluated by multivariate logistic regression analysis.

The effect of alcohol intake on the efficacy of interferon (IFN) therapy was evaluated retrospectively in patients with chronic hepatitis C diagnosed by liver histology and positive serum hepatitis C virus (HCV)-RNA. Patients included 119 given IFN therapy and 11 no IFN therapy. Serum HCV-RNA was measured 6 months after discontinuation of IFN therapy in 92 treated patients, 27.2% of whom showed disappearance of serum HCV-RNA. Multivariate logistic regression analysis revealed that this disappearance was affected by alcohol intake, the presence of its history (p < 0.05) or cumulative alcohol consumption (kg) (p < 0.01), and serum HCV-RNA levels (p < 0.001). The odds ratio associated with serum HCV-RNA still positive at 6 months was 7.018 (95% confidence interval: 1.444-34.062) and 1.004 (1.001-1.007) for the presence of alcohol intake history and the cumulative alcohol consumption, respectively. Other predictor variables-such as sex and age of patients, history of blood transfusion, HCV genotype, histological findings of the liver, and types of IFN-had no influence on the efficacy of the therapy. Cumulative alcohol consumption showed a negative correlation with serum HCV-RNA levels pretreatment, when the outcome variable was divided into two categories based on serum HCV-RNA levels: 10(6) copy/ml or less and 10(7) copy/ml or more. Alcohol intake was positively correlated with histological extent of alcoholic fibrosis, but affected neither grading nor staging of chronic viral hepatitis. We conclude that alcohol intake was a risk factor on the efficacy of IFN therapy in chronic hepatitis C patients. This effect was independent of serum HCV-RNA levels and histological findings specific for viral hepatitis in the liver.

Adult↗

PubMed1993

[Conditional logistic regression analysis of risk factors on congenital birth defects in Baotou].

Congenital defects are one of the common diseases in the newborns, and are important factors affecting the quality of the population. This survey was done to find risk factors related to congenital defects and to provide scientific basis for promoting birth quality. In this paper, a case-control study on 90 cases using 1:2 matching was carried out in Baotou area, and conditional logistic regression analysis showed that the following six major risk factors were associated with birth defects, i.e.: intake of certain drugs during pregnancy, exposure to radioactive rays, and contacting certain harmful chemical substances, common cold and fever during the period of pregnancy, smoking addiction of baby's father and the family history of certain defects of baby's parents.

Case-Control Studies↗

PubMed1995

Multiple linear regression analysis of hypertrophy, calcium and cadmium in hypertensive and non-hypertensive states.

Heart disease remains a major public health issue. In this study we aimed to achieve a greater mathematical and mechanistic understanding of the relationship between exposure to heavy metals and heart disease. Measurements of calcium and cadmium levels were made by flame atomic absorption spectrophotometry in tissue from hypertensive and non-hypertensive rabbits. Relationships between hypertrophy, calcium and cadmium were tested using multiple regression analysis. Multiple linear relationships occurred that showed the dependence of hypertrophy on calcium and cadmium levels, and of calcium accumulation on cadmium and hypertrophy. These data provide an insight into the mechanisms of heavy metal accumulation and the development of cardiovascular hypertrophy.

Animals↗

PubMed2004

[The COX regression analysis on the use of corticosteroids in the treatment of SARS].

OBJECTIVE: To explore the effectiveness of corticosteroids (GCS) and to determine how to use it in the treatment of SARS. METHODS: All reported probable cases in Beijing were reviewed. Those who fulfilled the diagnostic criteria with an integrity clinical record were recruited in the study. A database was established and all the clinical data, including patients' personal information, epidemiological history, underlying diseases, clinical manifestations, laboratory tests and therapies after hospitalization, as well as the outcome of the disease, were inputted under a quality control. Unifactor and COX multifactor regression analysis were done. The dose of GCS was all expressed in that of methylprednisolone. RESULTS: 1291 cases were in consistence with the demands mentioned above. Among them, 1084 cases (83.96%) had used GCS and 207 did not in the course of SARS. There was no significant difference of average age (t = -1.08, P = 0.2808) and the time from SARS onset to hospitalization (P = 0.2797) between the two groups. COX regression showed that the risk of fatality in the GCS group was higher than that of those who did not use GCS (RR = 1.334, 95% of CI: 0.588 - 3.026). In the patients with comorbidities, RR was 2.086 (95% of CI: 0.694 - 6.267), and RR was 0.536 (95% of CI: 0.146 - 1.970) in the patients with no comorbidity. In those without any comorbidity, the initial doses, maximal doses, average doses and cumulative doses all showed a 'J' shape change. An appropriate dose could keep RR to be the lowest whereas the doses either higher or lower than it could increase RR. The initial dose with the lowest RR was 80 - 160 mg/d, the maximum 80 - 160 mg/d, the average < 80 mg/d and the cumulative one 1000 - 3000 mg although there was no statistical significance (all P > 0.05). RR was less than 1 in non-comorbidity patients who initiated GCS therapy before the 15th day of the disease. RR was 1.415 (95% of CI: 0.195 - 10.257) in the patients who began to use GCS over this period. Counting from hospitalization, the time of GCS use also showed a 'J' type change of RR. The initiation of GCS from day 5 to 7 had the lowest RR (0.282, 95% of CI: 0.043 - 1.828) and that from day 8 to 14 was 1 (95% of CI: 0.150 - 6.654). CONCLUSION: In the treatment of SARS, GCS seems to be effective. An appropriate dose and a right time of application decrease the risk of death. The use of GCS in SARS patients with comorbidities should be with caution.

Adolescent↗

PubMed2001

Regression analysis of group testing samples.

This paper develops a general regression methodology that relates the group testing responses to individual covariate information. It can be used to study samples from a group testing procedure and to deal with a wide range of regression problems. A detailed illustration of the methodology is provided for a group testing procedure proposed by Gastwirth and Hammick. To demonstrate the utility of the method, simulation studies are performed on an HIV antibody testing data set published by Nusbacher et al.

Blood Donors↗

PubMed1979

Distribution-free regression analysis of grouped survival data.

Methods based on regression models for logarithmic hazard functions, Cox models, are given for analysis of grouped and censored survival data. By making an approximation it is possible to obtain explicitly a maximum likelihood function involving only the regression parameters. This likelihood function is a convenient analog to Cox's partial likelihood for ungrouped data. The method is applied to data from a toxicological experiment.

Animals↗

PubMed1996

[Logistic regression analysis of the influence of residential environment, residential hygiene and life style on the incidence and duration of acute respiratory disease in small children].

659 children aged between 1 and 2 years were examined in respect of the influence of the children's-facility, residential environment, residential hygiene, and way of life, as well as in respect of the influence of selected sociological factors on the number and duration of acute respiratory diseases (ARD). The evaluation of the results by using logistical regressions analysis came--among other things--to following factors, that correlated with a risen morbidity, respectively an extended duration of the illness (> 3 diseases in 6 months; > 20 days in 6 months). Apartments with wet walls, dark and too noisy apartments, children's-rooms with two outside walls, single window pane, outside-wall-gas-heaters, room-air-humidity too low, space for children in day-nurseries < 4 sqm, no carrying out of hardening-steps for the children, wind-influence to the open space of the children's-facility too strong, and shift-working by the mother.

Acute Disease↗