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PubMed2006

Population distributions of minimum inhibitory concentration--increasing accuracy and utility.

AIMS: To generate continuous minimum inhibitory concentration (MIC) data that describes the discrete nature of experimentally derived population MIC data. METHODS AND RESULTS: A logistic model was fitted to experimentally derived MIC population cumulative distributions from clinical isolates of Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae and Staphylococcus aureus (European Committee on Antimicrobial Susceptibility Testing, BSAC and MYSTIC population susceptibility databases). From the model continuous distributions of population susceptibility were generated. The experimentally observed population distributions based on discrete MIC could be reproduced from this underlying continuous distribution. Monte Carlo (MC) simulation was used to confirm findings. Where the discrete experimental data contained few or no isolates with MIC greater or less than the antimicrobial concentration range tested, the true mean MIC was a factor of 0.707 times that normally reported and may be of little clinical significance. Where data contained isolates beyond the range of concentration used, the true MIC was dependent on the SD and the number of isolates and could be clinically significant. Subpopulations of differing susceptibilities could be modelled successfully using a modified logistic equation: this allows a more accurate examination of the data from these databases. CONCLUSIONS: The mean MIC and SD of population data currently reported are incorrect as the method of obtaining such parameters relies on normally distributed data which current MIC population data are not. SIGNIFICANCE AND IMPACT OF THE STUDY: Obtaining the distribution parameters from the underlying continuous distribution of MIC can be carried out using a simple logistic equation. MC simulation using these values allows easy visualization of the discrete data. The analyses of subpopulations within the data should increase the usefulness of horizontal studies.

Dose-Response Relationship, Drug↗

PubMed2003

Analysis of short-term multivariate competing risks data following thoracic and thoracoabdominal aortic repair.

OBJECTIVE: Estimating the overall successfulness of a treatment can be difficult when success is defined by freedom from multiple endpoints that are each subject to competing risks. We describe a method for modeling short-term competing outcomes. METHODS: We used polytomous categorical variable modeling to describe the 30-day onset of renal failure, neurologic deficit, stroke or death (events) following repair of 841 thoracoabdominal aortic aneurysms. This was to determine whether common risk factors had a multivariate association with these outcomes, and whether predictor variables might be positively associated with some outcomes and negatively associated with others. The goal was to determine whether a single aggregate-endpoint logistic model could accurately predict the probability of good outcome 30 days following surgery. RESULTS: When more than one event occurred in a single patient, the first (or most severe simultaneous) event was used for censoring. Five hundred and ninety-three out of 841 (70.5%) patients had no postoperative events. The most common event was renal failure. We detected five predictors that were significant for at least one of the four outcomes. These were age, poor preoperative renal function (RENAL), acute dissection, extent II aneurysm, and use of cerebrospinal fluid drainage and distal aortic perfusion (ADJUNCT). Only RENAL was significant for all outcomes. ADJUNCT was highly significant only for neurologic deficit in the polytomous analysis and dropped out of the aggregate-endpoint multiple logistic model. CONCLUSION: Polytomous-outcome multivariate categorical modeling can detect effects missed by aggregate models, and is a valuable and statistically powerful method for evaluating risk factor effects on multiple competing endpoints.

Adolescent↗

PubMed1998

Logistic regression model for analyzing extended haplotype data.

Recently, there has been increased interest in evaluating extended haplotypes in p53 as risk factors for cancer. An allele-specific polymerase chain reaction (PCR) method, confirmed by restriction analysis, has been used to determine absolute extended haplotypes in diploid genomes. We describe statistical analyses for comparing cases and controls, or comparing different ethnic groups with respect to haplotypes composed of several biallelic loci, especially in the presence of other covariates. Tests based on cross-tabulating all possible genotypes by disease state can have limited power due to the large number of possible genotypes. Tests based simply on cross-tabulating all possible haplotypes by disease state cannot be extended to account for other variables measured on the individual. We propose imposing an assumption of additivity upon the haplotype-based analysis. This yields a logistic regression in which the outcome is case or control, and the predictor variables include the number of copies (0, 1, or 2) of each haplotype, as well as other explanatory variables. In a case-control study, the model can be constructed so that each coefficient gives the log odds ratio for disease for an individual with a single copy of the suspect haplotype and another copy of the most common haplotype, relative to an individual with two copies of the most common haplotype. We illustrate the method with published data on p53 and breast cancer. The method can also be applied to any polymorphic system, whether multiple alleles at a single locus or multiple haplotypes over several loci.

Alleles↗

PubMed1999

Identifying adolescents at risk for hard drug use: racial/ethnic variations.

PURPOSE: To examine early risk factors for initiation of hard drug use by 10th grade in a sample of adolescents drawn from diverse high schools and communities, compares the results across different racial/ethnic groups, and to evaluate the predictive performance of a user-friendly risk scale against the more complex logistic model. METHODS: Using longitudinal data from 4347 adolescents from California and Oregon, we developed and cross-validated logistic and additive prediction models for non-Hispanic white students (the largest group) and assessed how well each model worked for black, Hispanic, and Asian adolescents. We also developed a best logistic model for each group. Predictor variables were measured at Grade 7; the hard drug use outcome was measured at Grade 10. RESULTS: Major risk factors for initiation of hard drug use included early marijuana and cigarette use, deviant behavior, poor parent-child communication, being offered drugs, and prodrug attitudes and intentions. White adolescents had the most risk factors, followed by Hispanics, Asians, and Blacks. Specific risk factors played more important roles for some groups than others. Early marijuana use provided the strongest warning signal for all groups except Blacks, while exposure to drug offers increased the risk for all but Hispanic youth. Poor communication with parents was particularly important for Hispanic and Asian adolescents, whereas doing poorly in school was a key predictor only for Asians. Social influences to use drugs and intentions to use them were the only predictors for Blacks. Although family disruption and limited parental education were associated with an increase in risk for white adolescents, the latter had the opposite effect for Hispanics and Blacks. The simple additive model worked almost as well as the most complicated logistic model in predicting hard drug use for each group except Blacks. CONCLUSIONS: These results suggest that curbing early initiation of marijuana and cigarettes and reducing prodrug influences and attitudes may dampen initiation of other substances for most youth. They also suggest that drug prevention programs need to be sensitive to differences across racial/ethnic groups and that using social background characteristics as indicators of risk can be very misleading. Carefully constructed risk scales based on simple additive models could help guide program development and provide clinicians with useful information about a troubled adolescent's likely trajectory.

Adolescent↗

PubMedDate not supplied

Effect of passive transfer status and vaccination with Escherichia coli (J5) on mortality in comingled dairy calves.

The effect of vaccination with a commercially available R-mutant coliform mastitis vaccine on the survival of comingled dairy calves on a farm with endemic salmonellosis was examined. A total of 864 calves were randomly assigned to either vaccine (n = 435) or control (n = 429) groups. Passive transfer status of each calf was determined using refractometer determination of serum total protein concentration. Logistic models were developed to determine the effects of vaccine group and passive transfer status on calf survival to 100 days of age. In a model in which serum protein concentration was treated as a categorical variable, increasing serum total protein concentrations were associated with decreased mortality until these concentrations exceeded 6.0 g/dL. Calves with serum protein concentrations > 6.0 g/dL had increased risk for mortality compared with calves with serum protein concentrations > 5.5 g/dL but < or = 6.0 g/dL. This increased risk for mortality was supported by the results of a logistic model in which serum protein concentration was treated as a continuous variable. The increased risks associated with high serum protein concentration probably reflect the effect of dehydration in calves with occult disease. Neither model demonstrated any significant association between vaccination status and survival to 100 days of age. Based on these results, the routine immunization of calves cannot be recommended as a strategy to prevent mortality on farms with endemic salmonellosis.

Animal Husbandry↗

PubMed1997

In vivo magnetic resonance evaluation of blood oxygen saturation in the superior mesenteric vein as a measure of the degree of acute flow reduction in the superior mesenteric artery: findings in a canine model.

RATIONALE AND OBJECTIVES: The authors tested the hypothesis that changes in oxygen saturation (%HbO2) in the superior mesenteric vein (SMV), as measured with in vivo magnetic resonance (MR) oximetry, correlate with the degree of acute superior mesenteric artery (SMA) flow reduction. METHODS: Ten mongrel dogs were studied. A catheter was inserted into the SMV, and a perivascular ultrasonic flow probe and an adjustable mechanical occluder were placed around the SMA. MR oximetry was carried out at the resting state and after the SMA was constricted to predetermined levels (0%-75% of initial flow). In seven dogs, SMV blood samples were obtained immediately before and after each MR measurement; %HbO2 was measured simultaneously by using an oximeter. With linear regression analysis, the SMV %HbO2 measurements obtained at MR imaging were compared with those obtained at oximetry. With a logistic model, MR imaging changes in SMV %HbO2 were compared with the degree of SMA flow reduction. RESULTS: SMV %HbO2 measurements obtained with MR imaging correlated well with those obtained with oximetry (r = .97). Changes in SMV %HbO2 measured at MR imaging also correlated well with the degree of SMA flow reduction, as determined with a logistic model (P = .01). CONCLUSION: Noninvasive in vivo MR measurements of SMV %HbO2 can be used to determine the degree of acute SMA flow reduction with a high degree of accuracy in a canine model.

Animals↗

PubMed1992

Predictors of postoperative myocardial ischemia in patients undergoing noncardiac surgery. The Study of Perioperative Ischemia Research Group.

OBJECTIVE: To identify predictors of postoperative myocardial ischemia in patients scheduled to undergo major noncardiac surgery. DESIGN: Historical, clinical, laboratory, and physiological data were obtained prospectively before and during surgery to identify potential univariate predictors of postoperative myocardial ischemia, which then were entered into multivariate logistic models. Continuous two-lead electrocardiograms before, during, and after surgery were used to identify episodes of myocardial ischemia. SETTING: Department of Veterans Affairs tertiary care hospital. PATIENTS: A consecutive sample of 474 men at high risk for or with coronary artery disease who were scheduled to undergo major noncardiac surgery (95% compliance rate). MAIN OUTCOME MEASURE: Significant variables identified by multivariate logistic models that are associated with postoperative myocardial ischemia. RESULTS: Five major preoperative predictors of postoperative myocardial ischemia were identified: (1) left ventricular hypertrophy by electrocardiogram; (2) history of hypertension; (3) diabetes mellitus; (4) definite coronary artery disease; and (5) use of digoxin. The risk of postoperative myocardial ischemia increased progressively with the number of predictors present: in 22% of patients with no predictors, in 31% with one predictor, in 46% with two predictors, in 70% with three predictors, and in 77% with four predictors. CONCLUSION: Patients subgroups who are at high risk for developing postoperative myocardial ischemia and who might benefit the most from intensive Holter monitoring in the postoperative period now can be identified preoperatively.

Aged↗

PubMed2001

Clinical predictors of spontaneous acute urinary retention in men with LUTS and clinical BPH: a comprehensive analysis of the pooled placebo groups of several large clinical trials.

OBJECTIVES: To comprehensively evaluate clinical predictors of spontaneous acute urinary retention (AUR) across pooled data of placebo-treated patients from clinical trials conducted in men with lower urinary tract symptoms and clinically diagnosed benign prostatic hyperplasia. METHODS: Data from the placebo-treatment groups of several prospective, randomized clinical trials conducted in the United States (n = 3040), Scandinavia, Canada, and worldwide (n = 2295) were combined in the analyses. More than 110 variables were considered individually and in combination as predictors of AUR using logistic regression analysis and classification and regression tree methods with a split-sample approach to cross-validation. RESULTS: The different methods of analysis identified consistent potential predictors of episodes of AUR. When prostate volume was included in the analyses, it was selected as the initial variable discriminating men with and without subsequent AUR. Omitting prostate volume because of its availability in only a subset of men, a logistic model including serum prostate-specific antigen (PSA), urinating more than every 2 hours, symptom problem index, maximum urinary flow rate, and hesitancy of urination had good predictive properties (area under the receiver-operating characteristic curve [AUC] = 0.742 +/- 0.047), as did a model with PSA (AUC = 0.716 +/- 0.045). A classification and regression decision tree with the same variables predicted AUR (AUC = 0.74, sensitivity = 72%, specificity = 67%) as well as did a tree with PSA alone (AUC = 0.70, sensitivity = 75%, specificity = 64%). CONCLUSIONS: Prostate volume and serum PSA are strong predictors of AUR in placebo-treated men with lower urinary tract symptoms and clinically diagnosed benign prostatic hyperplasia who were screened for prostate cancer. From more than 110 variables, logistic models and decision trees with PSA alone were comparable to expanded models that included PSA, urinary frequency and hesitancy, flow rate parameters, and symptom problem index, and to a scoring algorithm.

Algorithms↗

PubMed2006

The measurement of change in functional ability: dealing with attrition and the floor/ceiling effect.

The purpose was to describe four-year change in functional ability among older persons and the relationship to sex, age, and other background factors. The baseline study, performed in 1986, is based on a random sample of older persons (n=1261). Follow-up data were collected four-years later (n=912). The analyses of change in functional ability were based on the assumption that the categories reflected an underlying latent continuous dimension. The change in functional ability, DeltaFA, was calculated by a logistic model for paired observations and applied in parallel analyses with and without inclusion of the dead to deal with the attrition problem. Fifty percent had no change in functional ability, 37% had declined and 13% improved. Models including the dead showed more functional decline with increasing age but this was not the case when the dead were excluded. Functional change was not related to sex, functional ability at baseline, relative wealth, social network, self-rated health, and life-satisfaction. Inclusion of the dead in statistical models for the study of change in functional ability reduced the attrition problem. A logistic model for paired observations of functional ability at two points in time reduced the problem related to the floor/ceiling problem.

Aged↗

PubMed2002

Nocturia in relation to sleep, somatic diseases and medical treatment in the elderly.

OBJECTIVE: To assess the influence of somatic diseases, symptoms and medication on nocturnal micturition in an elderly population. SUBJECTS AND METHODS: All 10 216 members of the pensioners' association in two Swedish counties were asked to participate in a questionnaire survey. The questions concerned their general state of health, occurrence of somatic diseases and symptoms, number of voiding episodes per night, and the use of drugs. RESULTS: There were 6143 evaluable questionnaires, of which 39.5% were from men. The mean (sd) age of the men and women participating were 73.0 (6.0) and 72.6 (6.7) years, respectively. In a multivariate logistic model, significant independent correlates of having > or = 3 nocturnal voids (vs < or = 2 voids) were: being 70-79 years vs < 70 years (odds ratio, OR, 1.7, 95% confidence interval, CI, 1.3-2.2), being > or = 80 years old vs < 70 years (OR, 1.9, CI, 1.3-2.5) and poor sleep vs good sleep (OR, 2.6, CI, 2.1-3.2), sequelae after stroke (OR, 2.0, CI, 1.1-3.6), irregular heart beats (OR, 1.6, CI, 1.2-2.1) and diabetes (OR, 1.5, CI, 1.1-2.3). Sex, spasmodic chest pain and snoring were all deleted by the logistic model. CONCLUSION: Increasing age, poor sleep, irregular heart beats, diabetes and stroke are associated with an increase in nocturnal micturition in the elderly.

Age Factors↗

PubMed2001

Ovulation induction and risk of endometrial cancer: a pilot study.

OBJECTIVE: To determine whether women with endometrial carcinoma are more likely to have been exposed to fertility drugs, in particular clomiphene, than healthy population controls. STUDY DESIGN: A nationwide case-control, pilot study. About 128 living women 35-64 years old, with a histologically confirmed diagnosis of endometrial carcinoma that was first diagnosed and reported to The Israel Cancer Registry between 1 January 1989 and 31 December 1992 were enrolled. The controls were 255 women from the same dialing areas selected by random digit dialing. A variety of demographic and clinical parameters were compared between cases and controls. A multivariate logistic model, controlling for age, was used to assess the independent effects of factors found to be significantly associated with endometrial cancer on univariate analysis. RESULTS: About 7 women with endometrial carcinoma (5.5%) and 10 healthy controls (3.9%) reported that they had used any fertility drug (crude odds ratio (OR) 1.4; 95% confidence interval (CI) 0.47-4.2). Use of fertility drugs did not meet the criteria for entry into the logistic model. The following parameters were found to be independently associated with endometrial cancer controlling for age, European-American background OR=2.2, (95% CI 1.3-3.7, P=0.004); nulliparity OR=2.7 (95% CI 1.1-6.5, P=0.03); history of infertility OR=1.8 (95% CI 1.0-3.3, P=0.05); BMI> or =27 OR=2.3 (95% CI 1.4-3.9, P=0.001). The use of oral contraceptives and IUD were found to be protective, OR=0.29 and 0.37, respectively, (95% CI 0.14-0.61, P=0.001 and 0.19-0.70, P=0.003, respectively). CONCLUSIONS: We found no evidence that the use of ovulation induction agents, including clomiphene citrate, are associated with a higher risk of endometrial carcinoma. The association between infertility drugs and endometrial carcinoma should be examined in other, larger studies.

Case-Control Studies↗

PubMed2006

Cardiotrophin-1 predicts death or heart failure following acute myocardial infarction.

BACKGROUND: Cardiotrophin-1 (CT-1) is an important inflammatory cytokine; its presence has been documented in patients after acute myocardial infarction (AMI). However, its role as a predictor of death or heart failure is unclear. We sought to investigate this and compared it with N terminal pro-B-type natriuretic peptide (NT-proBNP), a marker of death or heart failure. METHODS AND RESULTS: We studied 291 post-AMI patients. The plasma concentration of CT-1 and NT-proBNP was determined using in-house noncompetitive immunoassays and patients followed for death or heart failure. There were 27 deaths and 19 readmissions with heart failure. CT-1 was raised in patients with death or heart failure compared with survivors (median [range] fmol/mL, 0.9 [0.1-392.2] vs. 0.67 [0-453.3], P = .019). Using a multivariate binary logistic model CT-1 (OR 1.8, 95% CI: 1.1-3.2, P = .031) and NT-proBNP (OR 2.4, 95% CI: 1.1-5.2, P = .026) predicted death or heart failure independently of age, sex, previous AMI, serum creatinine, and Killip class. The receiver-operating curve for CT-1 yielded an area under the curve (AUC) of 0.62 (95% CI: 0.53-0.70, P = .017); for NT-proBNP the AUC was 0.77 (95% CI: 0.69-0.86, P < .001); the logistic model combining the 2 markers yielded an AUC of 0.84 (95% CI: 0.78-0.91, P < .001). CONCLUSION: After an AMI, combined levels of CT-1 and NT-proBNP are more informative at predicting death or heart failure than either marker alone.

Aged↗

PubMed1996

Predicting age at menopause.

This article reviews methodologic and clinical aspects of predicting age at menopause. Lifetable methods or logistic models applied to a perimenopausal population represent the most feasible and the least biased methods for estimating the probability of menopause by age. Information is emerging about risk factors besides age which influence risk for an earlier menopause and include a variety of medical, demographic, environmental, and genetic factors. The concept of menopause as a consequence of depleted oocytes suggests that the estimated number of ovulatory cycles might also be a useful predictor. Using these variables in a logistic model yields estimated probabilities of menopause for various risk profiles. Smokers who have accumulated more than 10 pack-years, women estimated to have had more than 300 ovulatory cycles, women with a history of depression, women who have lost one ovary at an early age, and women who have a family history of early menopause have earlier menopause and the greatest shift in the cumulative probability of menopause occurs in women with multiple risk factors.

Adult↗

PubMed1991

A comparison of exact, mid-P, and score tests for matched case-control studies.

A recently developed algorithm for generating the distribution of sufficient statistics for conditional logistic models can be put to a twofold use. First, it provides an avenue for performing inference for matched case-control studies that does not rely on the assumption of a large sample size. Second, joint distributions generated by this algorithm can be used to make comparisons of various inferential procedures that are free from Monte Carlo sampling errors. In this paper, these two features of the algorithm are utilized to compare small-sample properties of the exact, mid-P value, and score tests for a conditional logistic model with two unmatched binary covariates. Both uniparametric and multiparametric tests, performed at a nominal significance level of .05, were studied. It was found that the actual significance levels of the mid-P test tend to be closer to the nominal level when compared with those of the other two tests.

Algorithms↗

PubMed1999

A randomized design for repeated binary outcomes used to evaluate continued effectiveness of a breast cancer control intervention strategy.

The literature has not discussed in detail design and evaluation strategies for the assessment of continued effectiveness of intervention strategies. In this article we present an approach to evaluating continued effectiveness with two repeated binary outcomes that are related to the use of preventive services. We present a two-stage design with independent randomization procedures for each of two successive controlled trials and discuss the implications of the randomization plan for the statistical evaluation. Intervention effectiveness for each year is determined by an adjusted odds ratio that compares the odds of procedure use for those who received the intervention to those who did not. Changes in the two adjusted odds ratios between successive years are assessed within the context of a regressive logistic model. We demonstrate these methods by applying them to the Metropolitan Detroit Project to Reduce Avoidable Mortality from Breast Cancer. In this project, computer-generated physician mammography reminders placed prominently in medical records were used to promote mammography referrals among women visiting primary care clinics during a 2-year intervention period. An assessment of the change in intervention effectiveness as well as an adjusted estimate of the overall intervention effectiveness for the 2 years were obtained from a multivariate regressive logistic model. The advantage of this approach was its potential for reducing bias and producing a balanced comparison between intervention groups during the second year of intervention. This issue was important because previous work indicated that having had a mammogram had a significant impact on subsequent mammography use. An important component in the implementation of this design was an information management system that facilitated doing two randomization procedures efficiently. As information and computer technology advance, and as more sophisticated information systems are used for data management, designs such as these become reasonable alternatives to consider.

Adult↗

PubMed1996

Two-stage designs for the logistic regression model in single-agent bioassays.

In this paper we focus on the use of a two-stage procedure for logistic regression that emphasizes predicting response through the use of the Q-optimality criterion. The use of D-optimality in the first stage is primarily to allow best possible parameter estimates as one enters the second stage. However, it is important to understand that there are many ways to formulate the two-stage procedure. It may involve any optimality criterion in either stage. In fact, theoretically, one need not stop at two stages. It was our intention in this paper to demonstrate the potential in the two-stage procedure in cases in which good initial parameter estimates are not available. Those investigators who are interested in the software for the two-stage procedure described here should contact Dr. William R. Myers.

Animals↗

PubMed2004

A risk score system for identification of patients with upper-GI bleeding suitable for outpatient management.

BACKGROUND: The aim of this study was to develop a risk score system for identification of patients with upper-GI hemorrhage who are suitable for outpatient management. METHODS: From a prospective cohort of 983 consecutive patients with upper-GI hemorrhage not associated with portal hypertension, 581 cases that did not meet pre-established criteria for admission were selected, and a logistic regression analysis was performed to identify factors associated with two adverse outcomes: recurrent bleeding and/or the need for emergency surgery. The risk score system was developed by using the beta coefficients of the logistic model, and its performance was evaluated. The results of this model were combined with pre-established criteria for admission to build a simplified scoring system for identification of patients who can be managed safely on an outpatient basis. RESULTS: Chronic alcoholism, active malignancy, prior upper digestive tract surgery, wasting syndrome, hemodynamic compromise, duodenal ulcer as the cause of upper-GI hemorrhage, and hemorrhage of unknown cause were independently associated with a greater risk of unfavorable outcomes in the group that did not meet pre-established criteria for admission. The logistic model showed a high capacity for discrimination (C statistic: 0.87) and good calibration (p value for Hosmer-Lemeshow goodness-of-fit test, 0.62), with a sensitivity of 100% and specificity of 64%. The simplified score had a sensitivity of 100% and specificity of 29% for adverse outcomes, and sensitivity of 78% and specificity of 38% for mortality. CONCLUSIONS: The score system developed in this study may be helpful in deciding between hospitalization and outpatient management for patients with upper-GI hemorrhage, but it remains to be validated in patient groups other than those used for its development.

Acute Disease↗

PubMed2001

Parotid masses: prediction of malignancy using magnetization transfer and MR imaging findings.

OBJECTIVE: We determined the most accurate criteria for predicting malignancy of masses in the parotid gland using magnetization transfer ratios. SUBJECTS AND METHODS: Lesion-to-muscle magnetization transfer ratios obtained with a spoiled gradient-recalled acquisition in a steady state sequence with a 1-kHz off-resonance pulse were measured in 72 parotid masses (52 benign lesions, 20 malignant tumors). Various MR imaging findings and lesion-to-muscle magnetization transfer ratios were simultaneously assessed using a logistic model to determine the useful factors for predicting malignancy. We also studied the clinical usage of magnetization transfer ratios. RESULTS: Of the MR imaging findings, poorly defined margins showed the highest accuracy, 81%, with 60% sensitivity and 88% specificity. Of the lesion-to-muscle magnetization transfer ratios, a ratio of greater than 0.71 was most accurate (85%), with 90% sensitivity and 83% specificity. All four recurrent tumors and 10 (91%) of 11 secondary tumors were correctly diagnosed using the magnetization transfer ratio analysis. The logistic model revealed that the margin characteristics (p = 0.084) and lesion-to-muscle magnetization transfer ratios (p < 0.001) were statistically significant predictors for malignancy. A combined criteria of poorly defined margins and a lesion-to-muscle magnetization transfer ratio of greater than 0.71 raised the accuracy to 86% and specificity to 96%, but the sensitivity decreased to 60%. CONCLUSION: A combination of MR imaging findings and lesion-to-muscle magnetization transfer ratios was the most accurate predictor of malignancy.

Female↗