Biomedical subjects

Richard Letz

Publications and source records attributed to Richard Letz.

8 recordsLinked to original sources

PubMed2003

Further standardization of some NES3 tests.

NES3 is a computer-based neurobehavioral testing system designed for use in investigating potential cognitive impairment. Data from NES3 tests employed in a study of epilepsy self-management were analyzed to estimate test-retest reliability for NES3 tests on a large sample and to estimate the effect of some common covariates of test performance. A total of 319 participants in an epilepsy self-management study were examined on three occasions (baseline, 3-month follow-up, and 6-month follow-up) with a set of psychological questionnaires and seven neuropsychological tests from NES3. Test-retest correlations were calculated between measures obtained at baseline and at 3 months. Principal components analysis was performed on the baseline data. The potential effects of covariates (age, education, reading test scores, depression status, and examiner) were investigated in regression models. Three-month test-retest correlations were excellent for Adult Reading Test (ART) (r=0.95), strong for Digit-Symbol (r=0.82), Sequence B (r=0.79), and Sequence A (r=0.76); and modest (r's between 0.56 and 0.67) for Digit Span Forward and Backward, Visual Span Forward and Backward, and Pattern Memory. Alternate-forms correlations were strong for HVLT (r's between 0.71 and 0.82). Principal components analysis yielded four interpretable components. Age and reading score were significant covariates of virtually all of the test summary measures, while education, gender, race, and depression were not generally significant covariates. Changes to the method of calculation of some summary measures, changes to the initial instructions to the subjects, and addition of correctional feedback to subjects during the tests appeared to improve the reliability of some NES3 tests. Implementation of the HVLT and ART in computer-assisted format added breadth of coverage to the battery. NES3 tests may provide reliable, efficient data for use in epidemiologic studies of potential cognitive effects of occupational and environmental exposures.

Adolescent↗

PubMed2003

Continuing challenges for computer-based neuropsychological tests.

A number of issues critical to the development of computer-based neuropsychological testing systems that remain continuing challenges to their widespread use in occupational and environmental health are reviewed. Several computer-based neuropsychological testing systems have been developed over the last 20 years, and they have contributed substantially to the study of neurologic effects of a number of environmental exposures. However, many are no longer supported and do not run on contemporary personal computer operating systems. Issues that are continuing challenges for development of computer-based neuropsychological tests in environmental and occupational health are discussed: (1) some current technological trends that generally make test development more difficult; (2) lack of availability of usable speech recognition of the type required for computer-based testing systems; (3) implementing computer-based procedures and tasks that are improvements over, not just adaptations of, their manually-administered predecessors; (4) implementing tests of a wider range of memory functions than the limited range now available; (5) paying more attention to motivational influences that affect the reliability and validity of computer-based measurements; and (6) increasing the usability of and audience for computer-based systems. Partial solutions to some of these challenges are offered. The challenges posed by current technological trends are substantial and generally beyond the control of testing system developers. Widespread acceptance of the "tablet PC" and implementation of accurate small vocabulary, discrete, speaker-independent speech recognition would enable revolutionary improvements to computer-based testing systems, particularly for testing memory functions not covered in existing systems. Dynamic, adaptive procedures, particularly ones based on item-response theory (IRT) and computerized-adaptive testing (CAT) methods, will be implemented in new tests that will be more efficient, reliable, and valid than existing test procedures. These additional developments, along with implementation of innovative reporting formats, are necessary for more widespread acceptance of the testing systems.

Computer Systems↗

PubMed2003

A computer-based reading test for use as an index of premorbid general intellectual level in North American English-speaking adults.

Brief tests of vocabulary or reading ability are often used as an index of general intellectual level to hypothesize deficits in patients, to establish comparability of comparison groups, and as a covariate of performance on other neuropsychological tests. We evaluated a new variant of a reading test for potential use in estimating premorbid general intellectual ability and implementation as a computerized-adaptive test. A total of 319 outpatients who participated in an epilepsy self-management study were tested on three occasions, completing the Wide-Range Achievement Test-3 (WRAT-3) Reading test at baseline and the NES3 Adult Reading Test (ART) at the 3-month follow-up. At the 6-month follow-up, some participants completed the ART and some the NES2 Vocabulary test. ART and WRAT-3 Reading scores obtained 3 months apart were highly correlated (r=0.87, n=179), while ART and NES2 Vocabulary scores were somewhat less correlated (r=0.80, n=61). The ART test-retest correlation was high (r=0.95, n=79). The ART distribution was spread out more evenly at the high end than that of the WRAT-3 Reading. ART score was significantly related to education, race, income, and examiner category, but was unrelated to age category and depression status. Non-significant gender differences were observed. An item-response theory (Rasch model) analysis showed good fit of the model to the observed data and yielded an improved ranking of the ART items in order of difficulty. The NES3 ART exhibited high reliability and strong association with WRAT-3 Reading. These results suggest that the NES3-ART may be useful as an index of general intellectual ability for comparison of groups and for use as a covariate in data analyses among English-speaking, North American adults. The Rasch model analysis provides a basis for implementing the ART as a computerized-adaptive test, which should improve its time efficiency and reduce participant burden in taking the test.

Adolescent↗

PubMed2003

The association of stigma with self-management and perceptions of health care among adults with epilepsy.

OBJECTIVE: The purpose of this study was to examine the perception of stigma among adults with epilepsy including its association with epilepsy self-management and perceptions of health care. METHODS: Participants for the study were recruited from two epilepsy centers and a neurology clinic. Individuals agreeing to participate in the study were asked to complete three assessments each 3 months apart. Data were collected from 320 adult men and women with epilepsy; 314 provided responses on stigma and were included in this analysis. RESULTS: Participants ranged in age from 19 to 75 years (mean=43). Fifty percent of the sample was female, and 80% was white. The mean age of seizure onset was 22 years, and 76% of participants reported having had a seizure within the past year. Analysis suggests levels of perceived stigma are similar for men and women and across ethnic and age groups. However, participants who were not married or living with a partner, were not working for pay, and had limited income reported higher levels of stigma than did married participants, those working for pay, and those in higher income brackets. Participants reporting higher levels of stigma included those who had their first seizure before the age of 50 and a seizure in the last year. Participants whose seizures interfered more with activities, who rated their seizures as under less control, and who were not legally able to drive also reported higher levels of stigma. Tests of association between stigma and health-related variables revealed that participants reporting higher levels of perceived stigma also reported lower levels of self-efficacy to manage epilepsy; more negative outcome expectancies related to treatment and seizures; and lower levels of medication management, medication adherence, and patient satisfaction. However, they also reported greater management of information related to seizures. In regression analysis, income, age at first seizure, seizures during the past year, lower self-efficacy, negative outcome expectancies for seizures, and less patient satisfaction explained 54% of the variance in perceived stigma. CONCLUSIONS: The results of the study suggest that perceived stigma is significant for people with epilepsy and is associated with factors that are known to be important in the management of epilepsy. Understanding who is at greatest risk for feeling stigmatized could lead to the development of preventive measures.

Adolescent↗

PubMed2003

The epilepsy medication and treatment complexity index: reliability and validity testing.

Medications are the most common treatment for epilepsy. Regimens vary from once per day dosing to several pills several times per day. More complex regimens have been associated with lower adherence rates. To date, medication complexity has been measured by the number of pills and the number of times per day the pills are taken. However, complexity also includes special instructions (e.g., take at a separate time than other medications) and the specific administration actions (e.g., take 1/2 pill). This article describes the development of an instrument designed to measure the complexity associated with epilepsy treatment regimens. The medication complexity tool (MCI) was modified to create the Epilepsy Medication and Treatment Complexity Index (EMTCI). The EMTCI comprises four sections: (a) general medication information, (b) frequency of administration, (c) special instructions, and (d) administration actions. Points are given for dosing schedules, special instructions, and administration actions. A total complexity score is calculated by adding points for each section. One form is completed for each medication prescribed for each person. The initial development of the EMTCI included revising the MCI to make it applicable to epilepsy medication. Interrater and intrarater reliability assessments were conducted. The EMTCI was administered to adults with epilepsy as part of a larger study of self-management in people with epilepsy. Data from that study were used for further assessments of the EMTCI including test-retest reliability, criterion validity, and construct validity. The EMTCI shows evidence of both reliability and validity. Information from the tool can be used to describe the medication complexity of epilepsy medication regimens in much greater detail than has been done previously for this population. This information is useful in describing the treatment and adherence issues for persons with epilepsy.

Adult↗

PubMed2003

Neuropsychological screening for cognitive impairment using computer-assisted tasks.

The aim of this study was to validate a computer-assisted screening battery for classifying patients into two groups, those with and without cognitive impairment. Participants were all patients referred to the neuropsychology clinics at four VA medical centers during a 1-year period. Patients meeting the study inclusionary criteria (N = 252) were administered the Neurobehavioral Evaluation System-3 (NES3) computer-assisted battery. A detailed neuropsychological examination was carried out by an experienced neuropsychologist, who diagnosed the patient as cognitively impaired or not impaired. The neuropsychologist's diagnosis was the gold standard. Recursive partitioning analyses yielded several classification procedures using the NES3 data to predict the gold standard These procedures produced a set of six NES3 tasks that provide good sensitivity and specificity in predicting di- agnosis. Sensitivity and specificity for the least random classification procedure were 0.87 and 0.67, respectively. The results suggest that computer-assisted screening methods are a promising means of triaging patients.

Adult↗

PubMed2003

Neurologic outcomes of toxic oil syndrome patients 18 years after the epidemic.

Toxic oil syndrome (TOS) resulted from consumption of rapeseed oil denatured with 2% aniline and affected more than 20,000 persons. Eighteen years after the epidemic, many patients continue to report neurologic symptoms that are difficult to evaluate using conventional techniques. We conducted an epidemiologic study to determine whether an exposure to toxic oil 18 years ago was associated with current adverse neurobehavioral effects. We studied a case group of 80 adults exposed to toxic oil 18 years ago and a referent group of 79 adult age- and sex-frequency-matched unexposed subjects. We interviewed subjects for demographics, health status, exposures to neurotoxicants, and responses to the Kaufman Brief Intelligence Test (K-BIT), Programa Integrado de Exploracion Neuropsicologica (PIEN), and Goldberg depression questionnaires and administered quantitative neurobehavioral and neurophysiologic tests by computer or trained nurses. The groups did not differ with respect to educational background or other critical variables. We examined associations between case and referent groups and the neurobehavioral and neurophysiologic outcomes of interest. Decreased distal strength of the dominant and nondominant hands and increased vibrotactile thresholds of the fingers and toes were significantly associated with exposure to toxic oil. Finger tapping, simple reaction time latency, sequence B latency, symbol digit latency, and auditory digit span were also significantly associated with exposure. Case subjects also had statistically significantly more neuropsychologic symptoms compared with referents. Using quantitative neurologic tests, we found significant adverse central and peripheral neurologic effects in a group of TOS patients 18 years after exposure to toxic oil when compared with a nonexposed referent group. These effects were not documented by standard clinical examination and were found more frequently in women.

Adolescent↗

PubMed2002

Association between bone lead concentration and blood pressure among young adults.

BACKGROUND: Occupational and environmental exposure to lead has been examined for its effect on blood pressure (BP) in adults with varying results. The present analyses assessed the association between bone lead concentration and BP in early adult life in persons exposed during childhood. METHODS: Study participants included young adult members of two cohorts with different past histories of lead exposure. Lead exposure was assessed using noninvasive K-X-ray fluorescence spectroscopy to quantify bone lead concentration, an index of long-term lead exposure superior to current blood lead concentration. Systolic and diastolic BP measurements were obtained using conventional clinical methods. Multiple linear regression models were constructed to allow for control of covariates of BP identified a priori. RESULTS: Analyses were performed on 508 participants. While controlling for potential confounders, systolic BP was 4.3 mm Hg greater among members of the highest of four bone lead concentration groups (> 10 microg Pb/g bone) when compared with the lowest bone lead concentration group (< 1 microg Pb/g bone; P = 0.004), and diastolic BP was 2.8 mm Hg greater among members of the highest bone lead concentration group when compared with the lowest bone lead concentration group (P = 0.03). CONCLUSIONS: These results suggest that substantial lead exposure during childhood can increase BP during young adulthood.

Adult↗