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Biomedical subjects

Sati Mazumdar

Publications and source records attributed to Sati Mazumdar.

13 recordsLinked to original sources

Model validation software for classification models using repeated partitioning: MVREP.

The process of assessing the prediction ability of a computational model is called model validation. For models predicting a categorical response, the prediction ability is usually quantified by prediction measures such as sensitivity, specificity, and accuracy. This paper presents a software Model Validation using Repeated Partitioning (MVREP) that implements a computer-intensive, nonparametric approach to model validation, which we call the re-partitioning method. MVREP, developed using the SAS Macro language, repeats the process of randomly partitioning a dataset and subsequently performing standard model validation procedures, such as cross-validation, a large number of times and generates the empirical sampling distributions of prediction measures. The means of the sampling distributions serve as the point estimates of prediction measures of the model. The variances of the sampling distributions provide a direct assessment of variability for the point estimates of prediction measures. An example is presented using a mouse developmental toxicity chemical dataset to illustrate how the software can be used for the assessment of structure-activity relationships models.

Animals↗

An intent-to-treat method for enhancing analysis of clinical trials with rescue medication: a mixed-model approach.

An intent-to-treat (IT) analysis includes all observed data, even those obtained after the primary treatment assignment is changed or rescue treatment is substituted. The so-called "pragmatic" approach accounts for this type of treatment change or rescue treatment. The advantage of the pragmatic approach to IT analysis is that the timing and duration of the rescue treatment can be included in the analysis with mixed-effect modeling, which estimates the difference between the randomized treatment arms while adjusting for the use (timing and duration) of the subsequent treatment. We illustrate the inclusion of information on rescue treatment timing and duration in the analysis of a two-arm randomized clinical trial comparing antidepressant medications in an elderly depressed population. In this study, the randomized treatments are found to be similar. This enhanced analysis, where information about rescue treatment is implicitly added in the model, corroborates our previous two-piece spline analysis, where information about rescue treatment was not included. In addition, a significant drug by rescue interaction indicates a differential effect of the timing of rescue treatment between the two treatments. This analytic approach illustrates the importance of collecting and incorporating data after rescue, including the timing of rescue.

Data Interpretation, Statistical↗

Evidence of increased serotonin-1A receptor binding in type 2 diabetes: a positron emission tomography study.

Animal studies have shown diabetes-induced changes in the state and function of the serotonin neuroreceptor system. Diabetes also has induced structural and functional alterations in hippocampus and been associated with altered hypothalamopituitary adrenal axis regulation. In this study, serotonin-1A (5-HT(1A)) receptor binding was measured in humans with type 2 diabetes (n=6) and healthy controls (n=6), using positron emission tomography (PET) and [carbonyl-11C]WAY 100635. Significantly greater 5-HT(1A) receptor binding was detected in mesial temporal cortex, including hippocampus (P<0.05) for type 2 subjects (relative to controls). Within the type 2 group, glycosylated hemoglobin and stressed plasma cortisol levels were positively correlated (P<0.02). These findings support previous studies that suggest serotonergic underpinnings to the neurobiology of diabetes and have shown diabetes-induced neurological changes in hippocampus.

Adult↗

Course and rate of antidepressant response in the very old.

OBJECTIVE: The authors examined elderly patients with major depression to determine the relationship of current age to treatment response course and success rate. METHODS: Three studies of elderly depressed patients provided data on antidepressant treatment response in 323 subjects, treated in protocols using either nortriptyline or paroxetine. We grouped the subjects by current age: 'young-old' (59-69, N=163), 'middle-old' (70-75, N=80), and 'older-old' (76-99, N=80). We employed mixed-effect random regression analyses to examine Hamilton Rating Scale for Depression scores over 12 weeks of acute treatment. RESULTS: Older-old patients responded as quickly and successfully as the young- and middle-old. CONCLUSIONS: Major depression in the very old can be treated as successfully as in early old age.

Age Factors↗

Comparison of citalopram, perphenazine, and placebo for the acute treatment of psychosis and behavioral disturbances in hospitalized, demented patients.

OBJECTIVE: Until recently, conventional antipsychotics were the standard pharmacotherapy for psychosis and behavioral disturbances associated with dementia. This double-blind, placebo-controlled study compared the acute efficacy of the selective serotonin reuptake inhibitor citalopram and the neuroleptic perphenazine with placebo for the treatment of psychosis and behavioral disturbances in nondepressed patients with dementia. METHOD: Eighty-five hospitalized patients with at least one moderate to severe target symptom (aggression, agitation, hostility, suspiciousness, hallucinations, or delusions) were randomly assigned to receive either citalopram, perphenazine, or placebo under double-blind conditions for up to 17 days. RESULTS: Patients treated with citalopram or perphenazine showed statistically significant improvement on several Neurobehavioral Rating Scale factor scores. Compared to those receiving placebo, only patients treated with citalopram showed significantly greater improvement in their total Neurobehavioral Rating Scale score as well as in the scores for the agitation/aggression and lability/tension factors. Side effect scores were similar among the three treatment groups. CONCLUSIONS: Citalopram was found to be more efficacious than placebo in the short-term hospital treatment of psychotic symptoms and behavioral disturbances in nondepressed, demented patients.

Aged↗

Combined pharmacotherapy and psychotherapy as maintenance treatment for late-life depression: effects on social adjustment.

OBJECTIVE: This study examined the effects of maintenance treatment for late-life depression on social adjustment. The authors hypothesized that elderly patients recovering from depression would have better social adjustment with medication and interpersonal psychotherapy than with medication or psychotherapy alone. METHOD: Patients aged 60 and older recovering from recurrent major depression were randomly assigned to one of four treatments: nortriptyline and interpersonal psychotherapy, nortriptyline and clinic visits, placebo and psychotherapy, or placebo and clinic visits. The Social Adjustment Scale was administered every 3 months until illness recurrence. Combined treatment was compared to monotherapy on scores over 1 year among patients who remained in recovery (N=49). RESULTS: Patients receiving nortriptyline and interpersonal psychotherapy maintained social adjustment, which declined in those receiving monotherapy. CONCLUSIONS: Treatment of late-life depression with nortriptyline and psychotherapy is more likely to maintain social adjustment than treatment with either alone. Combination therapy improves not only duration but quality of wellness.

Age Factors↗

Interrater reliability in clinical trials of depressive disorders.

OBJECTIVE: The goal of this study was to review the reported methods of rater training, assessment of interrater reliability, and rater drift in clinical trials of treatments for depressive disorders. METHOD: Two psychiatrists independently identified all original reports of clinical trials relevant to depressive disorders published between 1996 and 2000 in the American Journal of Psychiatry and the Archives of General Psychiatry. Reported methods of rater training, assessment of interrater reliability, and rater drift were systematically summarized. RESULTS: Sixty-three original papers met criteria for inclusion. Only 11 (17%) of the studies reported the number of raters. Only two (9%) of the 22 multicenter and four (10%) of the 41 single-center trials documented rater training. Only nine (22%) of the single-center trials and three (14%) of the multicenter trials reported interrater reliability, despite a median number of five raters (range=2-20). Only three (5%) of the 63 articles reported rater drift. CONCLUSIONS: Few published reports of clinical trials of treatments for depressive disorders document adequately the number of raters, rater training, assessment of interrater reliability, and rater drift.

Depressive Disorder↗

Risk factors for falls during treatment of late-life depression.

BACKGROUND: Prior studies have found that antidepressant medications are associated with an increased risk of falling in elderly persons. However, little is known about the prevention of falls during treatment for depression in elderly persons. This study evaluated the time course and potential risk factors for falls in a treatment protocol for late-life depression to identify specific at-risk periods and risk factors for falls in this population. METHOD: One hundred four subjects aged 69 years and over were treated in a protocolized manner using paroxetine and interpersonal psychotherapy. Those who did not respond received augmentation therapy with bupropion, nortriptyline, or lithium. Subjects were assessed at baseline and weekly during treatment; demographic and clinical characteristics of those who experienced a fall during treatment were compared with those who did not fall. Cox proportional hazards models were used to define risk factors for falls in univariate and multivariate models. RESULTS: During a mean of 21 weeks of treatment, 40 subjects (38%) fell. About half (53%) of the subjects fell during the first 6 weeks of treatment. In the multivariate model, memory impairment and orthostatic changes in blood pressure during treatment were risk factors for falling. Additionally, augmentation with bupropion appeared to be a risk factor for falls in univariate analysis, but this result is preliminary due to the small number of subjects who took bupropion. CONCLUSION: Increased monitoring for falls is warranted during the acute treatment of late-life depression. When treating such patients, clinicians should be especially watchful of those with memory impairments or those who develop orthostatic blood pressure changes; orthostatic blood pressure should be measured throughout acute treatment. Additionally, augmenting paroxetine with bupropion may also increase the risk of falls, and this medication combination should be used with caution in elderly patients.

Accidental Falls↗

Sequential H(2)(15)O PET studies in baboons: before and after amphetamine.

UNLABELLED: PET and (11)C-raclopride have been used to assess dopamine activity in vivo using a paradigm that involved d-amphetamine (AMPH)-induced endogenous dopamine release that led to reductions (relative to baseline) in the (11)C-raclopride-specific binding parameter (binding potential). A common assumption in bolus injection PET studies of this type is that cerebral blood flow (CBF) does not vary during the scan. The goal of this work was to examine the effect of AMPH administration on sequential PET measures of CBF. METHODS: Eight dynamic H(2)(15)O PET scans were acquired with arterial blood sampling in 6 baboons: 4 scans before AMPH (over 60 min) and 4 scans after AMPH (over 60 min) (0.6 mg/kg AMPH). Magnetic resonance images (coregistered to PET) were used to define regions of interest that included cortex, striatum (including subregions), and cerebellum. Data were analyzed using a 1-tissue compartment model. CBF was assessed through K(1) (mL/mL/min). RESULTS: Temporal patterns of the CBF alterations were similar across regions for each baboon. For 5 of 6 baboons, a general pattern of an initial increase in K(1) was observed after AMPH that gradually declined toward baseline, after minimizing anesthesia-induced variability in the in vivo measures. Although these alterations after AMPH were statistically significant in particular subcortical regions and cerebellum, such changes would not likely influence measures of (11)C-raclopride binding potential to a significant extent. CONCLUSION: These data support previous PET studies for which constant blood flow was assumed during the bolus PET (11)C-raclopride/AMPH experiment across striatal subregions, while underscoring the importance of considering effects of anesthesia when interpreting in vivo imaging parameters.

Anesthesia↗

Intent-to-treat analysis for clinical trials: use of data collected after termination of treatment protocol.

Following patients for a period of time after termination of treatment protocols is a common practice in clinical trials of drug treatments. After termination of the protocol treatment, patients are usually provided with medical care as deemed appropriate, e.g. different doses of the same drug, augmentation with other drugs, or different drugs. Data collected on patients when they are not in the treatment protocol are termed "off-treatment" data to be differentiated from "on-treatment" data that are collected while patients are in the treatment protocol. The purpose of the present paper is to describe some recent statistical methodological advances in the use of "off-treatment" data for intent-to-treat (IT) analysis using mixture models [Biometrics 52 (1996) 1002]. Two-piece spline models conditional on the protocol treatment dropout time are developed first. The two pieces of the spline model represent the on-treatment and off-treatment segments of data and are joined at the dropout time. The weighted average of the two-piece conditional models across realizations of the dropout times provides the mixture model for the pragmatic IT analysis. The weights are the estimates of the probabilities of the dropout times. The mixture model is amenable to an explanatory analysis which assumes that the patients remain on their assigned treatments. The model allows the parameters of the splines to depend on the dropout time. Statistical inference is based on bootstrap sampling procedures. We have illustrated this methodology using data from a drug trial comparing nortriptyline and paroxetine in the treatment of major depression in older patients.

Clinical Trials as Topic↗

Mental health training for nursing home staff using computer-based interactive video: a 6-month randomized trial.

OBJECTIVE: Mental health education for the staffs of nursing homes is difficult to provide and often inadequate. The objectives of this study were to design and assess a curriculum of staff training on depression and dementia that is accessible, educational, and relevant. DESIGN: A core curriculum of 12 computer-based interactive video training modules was created in a television news-documentary format to educate nursing home staffs. A randomized trial of the first six modules, which are dedicated to mental health and aging, was conducted at a computer site (CS), a "lecture site" (LS), and control site (CON). SETTING: Three not-for-profit nursing facilities in Western Pennsylvania. PARTICIPANTS: The certified nursing assistants, and other nursing staff participated in the study as part of their required training. INTERVENTION: Nursing staffs at the two intervention sites (CS and LS) were mandated to participate in monthly educational sessions. At the CS, the computer program scheduled staff members each month for 45 minutes of individual, self-paced training using the interactive video modules. At the LS, staff members were scheduled to attend a 45-minute monthly lecture with identical learning objectives delivered by an advanced degree nurse educator. A videotape of the lectures was shown at two additionally scheduled times during the month to accommodate all shifts. MEASUREMENTS: Compliance and satisfaction with training were monitored at both intervention sites. Knowledge was assessed at the CS, LS, and CON, before each monthly training session, and with a cumulative post-training exam, administered at the end of the 6-month study. RESULTS: Over the 6-month period, training compliance was 66% and 22% at CS and LS, respectively (P < 0.001). Satisfaction with training and the relevance of training were rated significantly higher at the CS (P < 0.0001). Before the study, assessed knowledge was similar at the CS, LS, and CON. After 6 months, the CS scored significantly higher than the LS and CON in terms of knowledge (P < 0.005). CONCLUSION: Individual, self-paced, interactive video education for nursing home staff resulted in greater compliance and satisfaction with training compared to staff receiving lectures. Knowledge of core concepts was greater for staff of the computer site compared to the staffs of either the lecture or control sites at the end of this 6-month study.

Clinical Trial↗

Verification of scale sub-domains in elderly patients with dementia: a confirmatory factor-analytic approach.

OBJECTIVE: Use of cognitive, psychiatric and behavioral domains to assess the effectiveness of a pharmacological or behavioral intervention in the treatment of neurodegenerative disorders (e.g., Alzheimer disease) aids the identification of specific types of impairment or distress in behavioral status and quality-of-life issues in this population. With confirmatory approaches to subscale development readily available, we can obtain a more precise understanding of the sub-components of a scale, potentially providing the basis for selecting behavioral and/or quality-of-life outcome measures that may be more sensitive to the effects of pharmacological or behavioral interventions. METHODS: The authors illustrate the use of a confirmatory factor-analytic approach to verify scale sub-domains of the Neurobehavioral Rating Scale (NBRS) in elderly patients with dementia. With data collected from two groups of patients being treated for significant psychiatric and behavioral symptoms, authors investigated the relationships among scale items in order to test several competing models, including a general one-factor model, a first-order multifactor model, and a second-order factor model. RESULTS: The first-order model, with seven factors, provided the best fit to the correlations among items in the NBRS, indicating the multidimensionality of problematic behaviors and symptoms exhibited by dementia patients. CONCLUSION: Authors advocate the use of a confirmatory factor-analytic approach to verify scale sub-domains in other, more widely used rating scales for patients with dementia.

Aged↗