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PubMed1989

Age of onset, age at examination, and other covariates in the analysis of family data.

Information on age of onset can easily be incorporated into regressive logistic models by assuming that age of onset follows a logistic distribution. This is analogous to previously proposed models based on the normal distribution. The two distributions, and hence the two types of models, are very similar. In each case the generalized modules power transformation can be used as a basis for more flexibly modeling the age of onset distribution.

Affective Disorders, Psychotic↗

PubMedDate not supplied

Theoretical assessment of late cardiac complication from endovascular brachytherapy for restenosis prevention.

PURPOSE: In this study, a theoretical assessment of late cardiac complication from endovascular brachytherapy is performed using the integrated logistic model. MATERIALS AND METHODS: Calculation were performed for various lengths of Ir-192 sources using alpha/beta = 3.2 for the endpoint of chronic ischemia, TD50/5 = 7,000 cGy, and TD5/5 = 5,000 cGy. The dose distribution over a standard heart was divided into volume elements with uniform dose (dose-volume histogram). Using linear-quadratic equation, the dose in each of the volume elements was converted into dose equivalent to standard fractionation external beam irradiation. The normal tissue complication probability (NTCP) for each volume element was calculated and combined together to arrive at the cumulative risk of late cardiac complication. The NTCP was plotted against the dose prescribed at 2-mm radial distance for four treatment lengths. RESULTS: (1) The overall risk of late cardiac toxicity (chronic ischemia within 5 years) was estimated to be less than 1% for current clinical trials using Ir-192. (2) There is a volume effect with higher risk for larger irradiated volume, which can come from longer treatment time, the same dose prescribed at a greater radial distance, and a longer source train. (3) The NTCP vs. dose demonstrates a sigmoidal relationship. There is a threshold dose (about 500 cGy), below which the risk is minimal; the gradient of the curve is greater for longer treatment length. CONCLUSION: If the prediction from this model is validated with clinical data, it will contribute to guidelines for dose prescription, dose escalation, evaluation of new source design, and multivessel treatment.

Angioplasty, Balloon, Coronary↗

PubMed1998

Statistical analysis of lacZ mutant frequency data from MutaMouse mutagenicity assays.

Transgenic mouse assays have provided an unprecedented opportunity to study mutagenesis in diverse rodent tissues. In this article data from MutaMouse mutagenicity assays based on the Escherichia coli gene lacZ were analyzed systematically using liver and bone marrow as potential target tissues. Sources of variation, including plates (within packaging reactions), packaging reactions (within animals) and animals, were evaluated for extra-binomial variation. Although hardly any evidence of overdispersion was detected at the plate level, limited evidence of extra-binomial variation was observed at the packaging reaction level. There was, however, much stronger evidence of overdispersion at the animal level. Statistical tests for increasing trend in mutant frequency with increasing dose were also performed at the animal level. A significant increasing trend following exposure to N-nitrosodibenzylamine was detected in liver but not in bone marrow. A logistical model was used to further describe the dose-response relationship observed in N-nitrosodibenzylamine-treated liver tissue.

Administration, Oral↗

PubMed2000

Gay men in Australia who do not have HIV test results.

Whereas most gay men in Australia know their HIV test result, a consistent minority do not. From Gay Community Periodic Surveys (n=6831) conducted during 1998 in the 5 largest cities, those who did not have HIV test results (13.3% overall) comprised 10.0% in Sydney, 15.7% in Melbourne, 13.6% in Brisbane, 15.2% in Perth and 14.0% in Adelaide, representing a significant difference between cities (P < 0.001). Gay men who did not have HIV test results differed from those who did in several ways. They were on average younger (31 vs 35 years, P<0.001) and less likely to be in professional occupations (P<0.001). They were less likely to identify themselves as 'gay' (P<0.001), spent less time with other gay men (P<0.001) and had fewer gay friends (P<0.001). They had sex with fewer different men 'in the previous 6 months' (P<0.001) and were more likely to be in a monogamous relationship or without sexual partners at the time of the survey (P<0.001). With respect to both regular and casual partners, they were more likely (P<0.001) to have 'no such partner'/'no anal intercourse' rather than 'anal intercourse' (either always protected or sometimes unprotected). These differences between gay men who did and did not have HIV test results were confirmed in a logistic regression (apart from 'amount of free time spent with gay men' and 'relationship status' which were accounted for by closely correlated variables in the reduced logistic model). Social and sexual environment appears to exert an influence on HIV testing rather than sexual risk per se.

Adult↗

PubMed2002

Relationship of clinical depression to periodontal treatment outcome.

BACKGROUND: Depression has been associated with periodontal disease; however, its relationship to periodontal treatment outcome (PTO) has not been investigated. METHODS: Data were obtained by chart abstraction and computer databases on 1,299 health maintenance organization (HMO) patients aged 30 to 64 who had concurrent medical, dental, and pharmacy benefits, and who had an initial periodontal examination during 1996, 1997, or 1998. Depression (yes/no) was the main independent variable and was determined by presence of any diagnosis code for depression on the patient record. PTO was determined by the difference in percent of sites with probing depth (PD) > or = 5 mm between the initial and 1-year post-treatment periodontal exams. Sub-median periodontal treatment outcome (SMPTO) was defined as a reduction in fewer than the median percent of sites (7.33%) with PD > or = 5 mm. Information on sociodemographics, periodontal therapy, calculus and plaque, number of remaining teeth, smoking, antidepressant medications, and diabetes were collected. RESULTS: A total of 697 patients had a periodontal exam at both baseline and follow-up. Of these, 12.2% had depression. In a multivariable logistic model, depression (odds ratio [OR] 2.16, 95% confidence interval [Cl] 1.12 to 4.16) and 4-month recall treatment (OR 2.34, Cl 1.46 to 3.75) were associated with SMPTO, while percent of sites at baseline with PD > or = 5 mm (OR 0.93, Cl 0.91 to 0.94), number of remaining teeth at baseline (OR 0.94, Cl 0.89 to 0.99), and number of teeth lost during the study period (OR 0.75, Cl 0.58 to 0.96) were negatively associated. Periodontal surgery, age, gender, smoking, plaque, calculus, diabetes, and antidepressant medication were not significant in the model. CONCLUSION: Clinical depression may have a negative effect on periodontal treatment outcome in this group model HMO population.

Adult↗

PubMed2000

Complex segregation analysis of deafness in Dalmatians.

OBJECTIVE: To use pedigree analysis to evaluate the feasibility of a major locus model for deafness in Dalmatians. ANIMALS: 605 purebred Dalmatians from 42 families. PROCEDURE: Hearing loss was evaluated through the brainstem auditory-evoked response. Dogs were classified into mutually exclusive categories: normal hearing, unilaterally deaf, or bilaterally deaf. Information was collected on sex, coat color, presence or absence of a color patch at birth, and eye color. Statistical analyses were performed by use of regressive logistic models designed for complex segregation analysis. Genetic correlations among eye color, deafness, and color patch were estimated. RESULTS: Prevalence of hearing loss was 11% for dogs classified as unilaterally deaf and 5% for dogs that were bilaterally deaf. Complex segregation analysis detected statistical evidence of a single allele with an expected frequency of 0.21 that had an effect on the prevalence of deafness. Results of analyses suggested that this locus cannot completely explain the inheritance and incidence of deafness in Dalmatians. Genetic correlation estimates among deafness, eye color, and color patch revealed strong interrelationships among these characteristics. CONCLUSIONS AND CLINICAL RELEVANCE: To reduce the incidence of hearing loss in Dalmatians, unilaterally deaf, blue-eyed dogs should not be considered as potential parents.

Alleles↗

PubMed2005

Bayesian neural networks for bivariate binary data: an application to prostate cancer study.

Prostate cancer is one of the most common cancers in American men. The cancer could either be locally confined, or it could spread outside the organ. When locally confined, there are several options for treating and curing this disease. Otherwise, surgery is the only option, and in extreme cases of outside spread, it could very easily recur within a short time even after surgery and subsequent radiation therapy. Hence, it is important to know, based on pre-surgery biopsy results how likely the cancer is organ-confined or not. The paper considers a hierarchical Bayesian neural network approach for posterior prediction probabilities of certain features indicative of non-organ confined prostate cancer. In particular, we find such probabilities for margin positivity (MP) and seminal vesicle (SV) positivity jointly. The available training set consists of bivariate binary outcomes indicating the presence or absence of the two. In addition, we have certain covariates such as prostate specific antigen (PSA), gleason score and the indicator for the cancer to be unilateral or bilateral (i.e. spread on one or both sides) in one data set and gene expression microarrays in another data set. We take a hierarchical Bayesian neural network approach to find the posterior prediction probabilities for a test and validation set, and compare these with the actual outcomes for the first data set. In case of the microarray data we use leave one out cross-validation to access the accuracy of our method. We also demonstrate the superiority of our method to the other competing methods through a simulation study. The Bayesian procedure is implemented by an application of the Markov chain Monte Carlo numerical integration technique. For the problem at hand, our Bayesian bivariate neural network procedure is shown to be superior to the classical neural network, Radford Neal's Bayesian neural network as well as bivariate logistic models to predict jointly the MP and SV in a patient in both the data sets as well as in the simulation study.

Bayes Theorem↗

PubMed2003

Can EuroSCORE predict direct costs of cardiac surgery?

OBJECTIVE: The aim of this study is to determine if a preoperative risk stratification model can identify different surgical costs. METHODS: Four hundred and eighty-eight patients undergoing open heart surgery between March 2000 and March 2001 were classified with the EuroSCORE model. Direct variable costs were prospectively collected, surgical team costs excluded. The multivariate analysis was used to find variables independently associated with costs. RESULTS: Of the 488 patients enrolled 342 (70%) were males, mean age 65+/-10 years, 57 (12%) had myocardial infarction, 20 (4%) had ejection fraction <30%, 56 (11%) were operated in emergency, 26 (5%) had a re-operation. 113 (23.2%) were operated for valvular disease, 30 (6.1%) were operated for thoracic aortic surgery, one (0.2%) was operated for interatrial septal defect, 79 (16.2%) were operated for other intervention in addition to coronary bypass and 265 (54.3%) for isolated coronary bypass. The mean intensive care unit length of stay (ICU-LOS) was 2.3+/-4.1 days and the postoperative LOS was 8.2+/-5.3 days. According to EuroSCORE, 117 patients (24%) were at low, 187 (38%) at medium, and 184 (38%) at high risk. Costs were significantly and directly correlated with preoperative risk model with a correlation coefficient of 0.47 and an increase of costs of 3.5% (95% CI 2.3-4.7, P<0.0001) for each single rise of risk score. The relationship EuroSCORE vs. direct costs is, respectively: EuroSCORE 0-2 ==> 6863+/-861 Euro; 3-4 ==> 8292+/-3714 Euro; 5-6 ==> 8908+/-3480 Euro; 7-8 ==> 10,462+/-6123 Euro; 9-10 ==> 13,711+/-12,634 Euro; >10 ==> 21,353+/-18,507 Euro. Excluding EuroSCORE from the preoperative logistic model, age, preoperative creatinine, critical condition, ejection fraction, re-operation and sex were independently correlated with costs. CONCLUSIONS: From our data the EuroSCORE model developed to predict (30-day postoperative) hospital mortality could be used to predict direct operative costs and identify patients with different levels of resource consumption.

Age Factors↗

PubMed1996

Perceived social norms as crucial determinants of mother's injury-preventive behaviour.

In order to design injury-preventive programmes aimed at parents, an understanding of injury-preventive behaviour is essential. Questionnaires were obtained from 870 mothers of 3, 4 and 9-year-olds. The perceived social norm and other determinants for injury-preventive behaviour were analysed using three multivariate logistic regression models. The final logistic models classified 73.2-82.7% of respondents correctly. Perceived norms of relatives and friends were found to be the most important determinants of mothers' injury-preventive behaviour. Injury-preventive behaviour could neither be explained by mother's perception of injury risks, nor by the perceived norms of professionals within child health care and schools. This study indicates that in order to design injury-prevention programmes, an understanding of social norms is crucial.

Adult↗

PubMed1999

Prediction of delivery among women with early preterm labor by means of clinical characteristics alone.

OBJECTIVE: This study was undertaken to assess whether individual clinical factors or combinations thereof could be used to accurately predict the risk of delivery within 1 week of admission among women with preterm labor and minimal cervical dilatation. STUDY DESIGN: We performed a case-control study of patients admitted to our institution with preterm labor and minimal cervical dilatation. A case patient was a patient who sought treatment with uterine contractions between 24 and 34 weeks' gestation with cervical dilatation </=2 cm, who received tocolysis with magnesium sulfate, and who was delivered within 7 days of admission. Control subjects were those who had the same presentation with preterm labor but were not delivered within the first 7 days after admission. The medical records of case patients and control subjects were then abstracted, and information on >70 potential predictors was recorded. Statistical analysis consisted of bivariate and multivariable methods. We also generated a multivariable clinical predictive model with the purpose of detecting a proportion as high as possible of those destined to be delivered within 1 week (high sensitivity). We estimated that we would need 50 case patients and 150 control subjects to detect an odds ratio of 2.5 for risk factors with a prevalence of 20%, an alpha error of.05, a beta error of.20, and a control subject/case patient ratio of 3:1. RESULTS: Three variables were eligible for inclusion in our logistic models according to the bivariate analyses-bleeding on admission, substance abuse, and admission white blood cell count >/=14,000 cells/microL. The simplest and most favorable model included only 2 variables, bleeding and substance abuse, and yielded a sensitivity of 46% and a specificity of 76%. The full 3-variable model had similar test characteristics. For no model were we able to achieve a sensitivity >/=50%. CONCLUSION: The results of this case-control study suggest that combinations of clinical factors do not yield an adequate level of discrimination to be used alone for predicting the likelihood of delivery within 1 week among patients with minimal degrees of cervical dilatation.

Adult↗

PubMed1997

Quantitative assessments from the clinical examination. How should clinicians integrate the numerous results?

OBJECTIVE: To describe strategies for using multiple clinical examination items to estimate disease probabilities; and to evaluate the diagnostic accuracy of each strategy. DESIGN: Prospective observational study. SETTING: Medical preoperative evaluation clinic at a university-affiliated Veterans Affairs Medical Center. PATIENTS: Previously reported consecutive series of patients referred for outpatient medical preoperative risk assessment. MEASUREMENTS AND MAIN RESULTS: Pulmonary clinical examination and spirometry were the measurements. A strategy of using likelihood ratios (LRs) from seven clinical examination items was least accurate (p < .0001). Three alternative strategies were equivalent in diagnostic accuracy (p > or = .2): (1) using the single best clinical examination item and its LR, (2) using the LRs from three clinical examination items chosen by logistic regression, and (3) using the adjusted LRs chosen in strategy 2. When compared with using LRs from all seven items, the strategies of using three LRs chosen by logistic regression or using adjusted likelihood ratios better discriminated patients with airflow limitation from those without (receiver operating characteristic [ROC] areas 0.79 vs 0.69; p = .02). Using the single best clinical finding did not statistically degrade the clinical examination's discriminating ability (ROC areas 0.79 vs 0.75; p = .20). CONCLUSIONS: Describing the rational clinical examination requires evaluating conditional independence of examination components. Conditional independence assumptions were violated when seven clinical examination items were used to estimate posterior probability of airflow limitation. Focusing on clinical examination items identified through logistic models overcame violations of independence; further statistical adjustment did not improve diagnostic accuracy. Clinicians can use the single most predictive clinical examination finding to avoid inaccuracy from violating the independence assumption.

Aged↗

PubMed1997

Childhood sexual abuse among homosexual men. Prevalence and association with unsafe sex.

Of 327 homosexual and bisexual men participating in an ongoing cohort study pertaining to risk factors for HIV infection who completed a survey regarding history of sexual abuse, 116 (35.5%) reported being sexually abused as children. Those abused were more likely to have more lifetime male partners, to report more childhood stress, to have lied in the past in order to have sex, and to have had unprotected receptive anal intercourse in the past 6 months (odds ratio 2.13; 95% confidence interval 1.15-3.95). Sexual abuse remained a significant predictor of unprotected receptive anal intercourse in a logistic model adjusting for potential confounding variables.

Adolescent↗

PubMed1999

Teacher receptivity to a system-wide change in a centralized education system: a Rasch measurement model analysis.

The Education Department of Western Australia has implemented a new system called Student Outcome Statements, by trial in 1995/1996, then an a voluntary basis from 1997, with the intention of making it mandatory after 2001. The system describes, in order, the outcomes that students are expected to achieve in eight broad learning areas. The study has three aims. One, to create a scale for teacher receptivity to the use of Student Outcome Statements, based on eight orientations to receptivity: evaluative attitudes, behavior intentions, feelings towards Student Outcome Statements compared to the previous system, the benefits of the new system, support from significant others, alleviation of concerns, collaboration with other teachers, and involvement in decision-making. Two, to analyze the psychometric properties of the scale using the Extended Logistic Model of Rasch (Andrich, 1988; Rasch, 1960/1980) with the computer program RUMM (Andrich, Sheridan & Luo, 1997). Three, to provide advice to decision-makers about how better to implement the system of Student Outcome Statements.

Achievement↗

PubMed1997

Identification of early pregnancy landmarks by transvaginal sonography: analysis by logistic regression.

OBJECTIVE: To assess the feasibility of logistic regression analysis for determining the gestational ages at which detection of early pregnancy landmarks first can be observed. DESIGN: Retrospective analysis. SETTING: University-based tertiary care clinic. PATIENT(S): Eighty-two women with viable singleton pregnancies in whom ovulation had been achieved by an injection of hCG. INTERVENTION(S): Two hundred fifteen transvaginal sonographic scans. MAIN OUTCOME MEASURE(S): Logistic regression was used to estimate the probability of detection of sonographic findings as a function of gestational age. RESULT(S): We found that the likelihood of visualization of a gestational sac or fetal heart motion could be represented accurately by logistic equations. Gestational age at which there was 95% probability of visualization was 35.5 days for the gestational sac and 44.5 days for fetal cardiac activity. The probability of detecting fetal cardiac activity was 95% when the mean gestational sac diameter was 1.6 cm and was 99% at 1.9 cm. CONCLUSION(S): The sonographic appearances of developmental landmarks in early pregnancy occurs within well-defined gestational time periods, and the probabilities for visualization can be closely approximated using a logistic model. Our results suggest that the number of sonographic examinations required to document infertility treatment success can be minimized by surveillance at standardized gestational ages.

Adult↗

PubMed2001

Investigation of heroin profiling using trace organic impurities.

The acidic and neutral impurities in heroin samples (46 Purified South-East Asian (PSEA) and 8 non-PSEA samples) were analysed using gas chromatography. Mass spectral detection allowed the construction of a comprehensive library of over 649 impurities. A variety of statistical procedures were used to select 70 viable profiling parameters. Cluster analyses were used to investigate the similarities between samples using organic parameters. A blended PSEA profile was constructed for comparison with samples of unknown origins. Resolution between samples of PSEA/non-PSEA origins was demonstrated with a selection of 25 (18 continuous and 7 dichotomised) discriminating factors. Several predictive logistic models were created using up to 18 parameters, explaining 85-100% of the variation in the experimental data.

Asia, Southeastern↗

PubMed1992

Later development of asthma in patients with a negative methacholine inhalation challenge examined for suspected asthma.

A negative methacholine inhalation challenge (MIC) in a patient with suspected bronchial asthma is generally considered to make this diagnosis unlikely. Nevertheless, the patient may later develop asthma. To estimate the proportion that eventually becomes asthmatic, a 10 year follow-up study was carried out on 334 consecutive MIC-negative patients aged 14-80 years. The development of asthma among these patients was assessed on the basis of entitlement to preferential refund from the cost of antiasthmatic therapy granted for them under national health insurance. During the follow-up 30 patients (9%) were granted the refund. There was no significant difference between men and women in this respect. Patients who developed asthma were somewhat older than those who did not. A family history of allergy, allergic rhinitis, and positive reactions to skin prick tests were significantly more common in patients with future asthma. These patients also had a lower mean forced expiratory volume in 1 sec (FEV1) (% of predicted) and a higher mean increase in PEF after an inhaled sympathomimetic than those remaining free from asthma. In multivariate analyses with a logistic model, 3 risk indicators proved independent predictors of future asthma: age, positive family history of allergy, and FEV1 (% of predicted).

Adolescent↗

PubMedDate not supplied

Dipole density of low-frequency and spike magnetic activity: a reliable procedure in presurgical evaluation of temporal lobe epilepsy.

Conventional visual analysis and dipole density analysis of magnetoencephalographic data for both spike and low-frequency magnetic activity were compared for presurgical evaluation in temporal lobe epilepsy (TLE) in a sample of 26 drug-resistant operated TLE patients. A series of logistic regression analyses were performed. Dipole density sensitivity was superior to visual localization analysis. Three separated logistic models were calculated for interictal spikes, low-frequency magnetic activity, and the combination of both measures. A combined interictal spike/low-frequency magnetic activity model predicted correctly the operated temporal lobe in all patients. Clear-cut criteria for the probability model are proposed that are valid for 92.3% of cases in the sample. The quantitative approach proposed by this study is an evidence-based model for presurgical evaluation of temporal lobe epilepsy, which improves previous magnetoencephalographic investigations and establishes working clinical criteria for patient evaluation in TLE.

Adolescent↗

PubMed2001

Women with a pelvic mass: indicators of malignancy.

OBJECTIVE: To evaluate the efficacy of five methods: pelvic examination (PE), transvaginal ultrasonography (US), Doppler ultrasonography, serum CA125 assay and serum CA72-4 assay, alone or associated, to predict malignancy in patients presenting a pelvic mass originating in the ovary. METHODS: 92 patients underwent a standard protocol for physical examination, CA125, CA72-4, transvaginal ultrasonography and Doppler ultrasonography. RESULTS: Eighteen women were dropped from the study because they had clearly benign masses; two women were dropped from the study because they had clearly malignant lesions. Twenty-two malignant (30%) and 50 benign (70%) pelvic tumors were found. When one method was considered alone the best sensitivity (SENS) was found in physical examination (90%) and the best specificity (SPEC) was found in CA72-4: 88%. If all indicators were positive, the SPEC was 100% but the SENS was 40%. Logistic regression analysis prediction of the character of the pelvic masses was correct in 86%. CONCLUSION: Some additional information to discriminate between malignant and benign pelvic masses can be obtained from the valuation of serum tumor markers, particularly CA72-4. Also Doppler ultrasonography appeared to be useful in the differential diagnosis of pelvic tumors. The prediction of the character of the pelvic masses calculated by a logistic model in which PE, US, CA 125, and CA72-4 are included is very good.

Adult↗