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Biomedical subjects

G C Alexander

Publications and source records attributed to G C Alexander.

At least 19 recordsLinked to original sources
PubMed2001

Why hemodialysis patients fail to complete the transplantation process.

The cadaveric renal transplantation process involves steps related to medical suitability, interest in transplantation, pretransplantation workup, and movement up a waiting list. Failure to complete specific steps may be caused by remaining stationary at that step, moving backward to a previous step, or dying. Knowing the relative importance of these types of movement may enable the development of strategies that improve the efficiency and equity of the transplantation process. We examined 4,597 new dialysis patients to determine the likelihood of remaining stationary, moving backward, or dying at each of the following steps: (A) being medically suitable and possibly interested in transplantation, (B) being definitely interested, (C) completing the pretransplantation workup, and (D) moving up a waiting list and receiving a transplant. Failure to complete a step was generally caused by remaining stationary rather than moving backward or dying. The likelihood of remaining stationary ranged from 78% at step A to 90% at step D. The likelihood of backward movement ranged from 3% to 7%, whereas the likelihood of death ranged from 7% to 22%. Compared with whites, blacks were more likely to remain stationary at steps A (odds ratio [OR], 1.96) and B (OR, 1.52), more likely to move backward at step B (OR, 1.79), and less likely to die at steps A through C (ORs, 0.45 to 0.60). In conclusion, failure to move through the transplantation process is usually caused by remaining stationary at specific steps rather than moving backward or dying. The relative importance of these types of movement differs among blacks and whites.

Adolescent↗
PubMed2001

Validation of the SADL questionnaire.

OBJECTIVE: To cross-validate the psychometric characteristics of the Satisfaction with Amplification in Daily Life (SADL) questionnaire (Cox & Alexander, 1999), and to explore the SADL's construct validity. DESIGN: Thirteen private practice Audiology clinics each distributed SADL questionnaires, by mail, to 20 adults who had recently obtained hearing aids. The completed questionnaires were returned to a central site and subject anonymity was assured. There were 196 usable responses. RESULTS: Psychometric characteristics of the items were found to be very similar to those reported previously. Thus, the internal validity of the instrument was strongly supported. The assumption that the SADL quantifies satisfaction by assessing its components was evaluated by examining the relationship between SADL scores and scores on a traditional single-item satisfaction measure. A logical and statistically significant relationship was seen between the two measures, thereby supporting the construct validity of both types of data. For private-pay clients, satisfaction scores were very similar to the interim norms published by Cox and Alexander (1999). However, clients whose hearing aids were partly or fully purchased by insurance or benefits programs tended to be more satisfied than interim norms for third-party pay clients derived 5 yr ago. For most types of clients, there was a tendency toward more satisfaction in the Negative Features subscale than observed in our previous research. CONCLUSIONS: Both construct and internal validity of the SADL questionnaire were supported by this research. The previously published interim norms appear to be mostly appropriate for private-pay clients, but might require adjustment in the Negative Features subscale. Further research is needed to explore the relationship between satisfaction and device purchase issues (third-party versus private pay).

Adult↗
PubMed2001

Evaluation of a Revised Speech in Noise (RSIN) test.

A revised version of the Speech in Noise (SIN) test was developed by reallocating the recorded test material on the compact disc into different lists (blocks). The goal was to increase the equivalence and reliability of the test blocks to enhance their usefulness in research settings. The Revised Speech in Noise test has four blocks of sentences. Each block comprises twice as many sentences as in the original SIN test. There are also practice sentences for each condition. Forty-two elderly subjects with normal hearing for their age and gender provided data on the equivalence of the new test blocks. The remaining inequalities in mean scores were mostly eliminated using score weighting. Critical differences were developed to promote interpretation of scores from the same individual under different conditions. The revisions substantially improved the equivalence of test blocks and their sensitivity to performance changes. Increased test time is the associated drawback.

Aged↗
PubMed1999

Measuring Satisfaction with Amplification in Daily Life: the SADL scale.

OBJECTIVE: To develop a self-report inventory to quantify satisfaction with hearing aids. DESIGN: The inventory was developed in several stages. To determine the elements that are most important to satisfaction for most people, we conducted structured interviews and then designed a questionnaire. Hearing aid owners responded to the questionnaire, indicating the relative importance of 14 different elements in their hearing aid satisfaction. Analyses indicated that the elements could be placed into four importance content areas. Trial satisfaction items were designed for each content area and submitted to focus groups to identify highly salient items as well as ambiguous items. A 25-item satisfaction questionnaire then was developed and disseminated to hearing aid owners. Results were obtained from 257 individuals. These data were analyzed to generate the final questionnaire. RESULTS: Fifteen items, divided into four subscales, were selected for the final Satisfaction with Amplification in Daily Life (SADL) questionnaire. The questionnaire yields a Global satisfaction score and a profile of subscale scores, which address Positive Effects, Service and Cost, Negative Features, and Personal Image. A preliminary evaluation of retest stability was conducted with 104 subjects. Ninety percent critical differences for the various scores ranged from 0.9 to 2.0 score intervals on a 7 point scale. CONCLUSIONS: The SADL scale is both brief enough to be clinically acceptable and comprehensive enough to provide a valid assessment of an inherently multidimensional variable. Additional assessment is necessary to refine understanding of its test-retest properties, explore validity issues, and determine clinical, research, and administrative applications of the data.

Aged↗
PubMed1999

Personality and the subjective assessment of hearing aids.

Relatively little is known about the influence of patients' personality features on the responses they make to self-assessment items used to measure the outcome of a hearing aid fitting. If the personality of the hearing aid wearer has a significant influence on self-report outcome data, it would be important to explore the relevant personality variables and to be cognizant of their effects when using subjective outcome data to justify decisions about clinical services or other matters. This investigation explored the relationship between several personality attributes and responses to the Abbreviated Profile of Hearing Aid Benefit (APHAB). It found that more extroverted patients tend to report more hearing aid benefit in all speech communication situations. In addition, patients with a more external locus of control tend to have more negative reactions to loud environmental sounds, both with and without amplification. Anxiety also played a small additional role in determining APHAB responses. Although personality variables were found to explain a relatively small amount of the variance in APHAB responses (usually around 10%), these outcomes should alert practitioners and researchers to the potential effects of personality variables in all self-report data.

Aged↗
PubMed1998

Barriers to cadaveric renal transplantation among blacks, women, and the poor.

CONTEXT: Cadaveric renal transplantation rates differ greatly by race, sex, and income. Previous efforts to lessen these differences have focused on the transplant waiting list. However, the transplantation process involves a series of steps related to medical suitability, interest in transplantation, pretransplant workup, and movement up a waiting list to eventual transplantation. OBJECTIVE: To determine the relative importance of each step in explaining differences in cadaveric renal transplantation rates. DESIGN: Prospective cohort study. SETTING AND PATIENTS: A total of 7125 patients beginning long-term dialysis between January 1993 and December 1996 in Indiana, Kentucky, and Ohio. MAIN OUTCOME MEASURES: Completion of 4 separate steps during each patient-year of follow-up: (A) being medically suitable and possibly interested in transplantation; (B) being definitely interested in transplantation; (C) completing the pretransplant workup; and (D) moving up a waiting list and receiving a transplant. RESULTS: Compared with whites, blacks were less likely to complete steps B (odds ratio [OR], 0.68; 95% confidence interval [CI], 0.61-0.76), C (OR, 0.56; 95% CI, 0.48-0.65), and D (OR, 0.50; 95% CI, 0.40-0.62) after adjustment for age, sex, cause of renal failure, years receiving dialysis, and median income of patient ZIP code. Compared with men, women were less likely to complete each of the 4 steps, with ORs of 0.90, 0.89, 0.80, and 0.82, respectively. Poor individuals were less likely than wealthy individuals to complete steps A, B, and C, with ORs of 0.67, 0.78, and 0.77, respectively. CONCLUSIONS: Barriers at several steps are responsible for sociodemographic differences in access to cadaveric renal transplantation. Efforts to allocate kidneys equitably must address each step of the transplant process.

Adult↗
PubMed1998

Dialysis patient ratings of the quality of medical care.

Dialysis patients receive medical care from a variety of physicians. Little is known about how dialysis patients assess the quality of this care. We sought to determine (1) who dialysis patients receive medical care from, (2) how they rate the quality of such care, and (3) how ratings differ for care provided by generalists, nephrologists, and other specialists. We performed a cross-sectional interview study of 148 patients from four chronic hemodialysis units. Using a structured questionnaire, we asked subjects about each condition for which they received care in the preceding 12 months. For each condition, subjects mentioned the type of physician who provided care and then rated their overall satisfaction with care as well as six components of quality of care (availability of doctor, technical skill, personal manner, explanations provided, amount of time spent, and how much patient was helped). We found that generalists, nephrologists, and other specialists provided care for 14%, 48%, and 38% of conditions for which patients received care. Sixty-nine percent of overall satisfaction ratings were very good or better. Of the six components of quality of care, explanations and amount of time received the lowest ratings. On multivariate analysis, increased patient age, black race, and care for acute illnesses were associated with lower ratings of quality of care. There was no difference in ratings of care provided by generalists, nephrologists, and other specialists. In conclusion, dialysis patients receive most of their medical care from nephrologists and other specialists. Although they generally rate this care highly, we recommend that providers pay special attention to explanations provided, time spent with patients, and care for acute illness.

Adult↗
PubMed1997

The contour test of loudness perception.

OBJECTIVE: This article presents the underlying rationale, normative data, and reliability data for a test of loudness perception (the Contour Test) that was devised for use in clinical hearing aid fitting. The Contour Test yields data describing the sound level required for each of seven categories of loudness ranging from very soft to uncomfortably loud. DESIGN: Two experiments are described. Experiment 1 yielded norms for the test. The subjects were 23 male and 22 female normal-hearing listeners. Test stimuli included warble tones at six frequencies and broad band speech. Experiment 2 assessed the reliability of the test results. Ten hearing-impaired listeners responded to the test at two frequencies on two occasions separated by several days. Both experiments also evaluated the effect of using different stimulus increment sizes on the measured levels of loudness categories. RESULTS: Based on the data from experiment 1, norms for each category of each stimulus are reported in terms of mean level and typical between-subject variation in responses. Data are provided in HA-12 cm3 coupler levels as well as in hearing levels (dB HL). The shape of the loudness growth function for warble tones was somewhat different from that for speech. When data were expressed in HL, there were no differences in mean loudness category levels across warble tone test frequencies. Thus, test frequencies were combined and equations were generated to describe the upper and lower limits of typical normal performance for warble tone stimuli. These equations can be used to construct a template for clinical comparison of normative values to patient loudness growth curves. Experiment 2 provided information about the test-retest variability of data yielded by the Contour Test. Reliability appears to be similar to that of the few other category scaling tests described in the literature. Most test-retest differences were 6 dB or less. Although a moderate variation in test increment size did not significantly affect the loudness category levels for young normal-hearing listeners, levels corresponding to loudness categories were significantly higher when larger increments were used with elderly hearing-impaired listeners. CONCLUSIONS: Evidence from this and other research indicates that standardized measurement of loudness perception is an achievable goal for clinical practice. The Contour Test appears to offer a viable approach to clinical measurement of loudness perception: It has good patient acceptance and combines fairly rapid administration with acceptable reliability. Details of test procedures and scoring sheets for manual administration can be downloaded from the Internet at www.ausp.memphis.edu/harl. However, it is important to keep in mind that the application of loudness perception data for narrowband stimuli (such as warble tones) to hearing aid prescription is complicated by the need to account for the effects of loudness summation across bandwidth. There is a need for additional research to establish an empirical link between clinically measured loudness perception and optimal amplification characteristics.

Adolescent↗
PubMed1996

Benefit acclimatization in elderly hearing aid users.

A previous study from this laboratory indicated that the benefit obtained from a hearing aid in a noisy environment might increase over the first few months of hearing aid use. It was hypothesized that this acclimatization of benefit was due to a process in which the individual optimized his/her use of modified or newly available high-frequency acoustic speech cues. This investigation further explored the effect in 22 elderly individuals with mild to moderate sensorineural hearing losses, fitted unilaterally with hearing aids. None of the subjects was a current or recent hearing aid wearer. Speech intelligibility testing over a 12-week post-fitting period indicated that a significant improvement in benefit was seen for the group as a whole, probably beginning after about 6 weeks of regular hearing aid use. However, the magnitude of improvement was very small for most subjects. Only three individuals experienced a dramatic improvement in their benefit for speech in noise over this period. No evidence was found for a specific role of high-frequency cues. Seven subjects participated in a long-term follow-up in which benefit was measured after several months of use of their newly acquired personal hearing aids. Further increase in benefit was noted but was due exclusively to a decline in performance for unaided listening.

Aged↗
PubMed1995

The abbreviated profile of hearing aid benefit.

OBJECTIVE: To develop and evaluate a shortened version of the Profile of Hearing Aid Benefit, to be called the Abbreviated Profile of Hearing Aid Benefit, or APHAB. DESIGN: The Profile of Hearing Aid Benefit (PHAB) is a 66-item self-assessment, disability-based inventory that can be used to document the outcome of a hearing aid fitting, to compare several fittings, or to evaluate the same fitting over time. Data from 128 completed PHABs were used to select items for the Abbreviated PHAB. All subjects were elderly hearing-impaired who wore conventional analog hearing aids. Statistics of score distributions and psychometric properties of each of the APHAB subscales were determined. Data from 27 similar subjects were used to examine the test-retest properties of the instrument. Finally, equal-percentile profiles were generated for unaided, aided and benefit scores obtained from successful wearers of linear hearing aids. RESULTS: The APHAB uses a subset of 24 of the 66 items from the PHAB, scored in four 6-item subscales. Three of the subscales, Ease of Communication, Reverberation, and Background Noise address speech understanding in various everyday environments. The fourth subscale, Aversiveness of Sounds, quantifies negative reactions to environmental sounds. The APHAB typically requires 10 minutes or less to complete, and it produces scores for unaided and aided performance as well as hearing aid benefit. Test-retest correlation coefficients were found to be moderate to high and similar to those reported in the literature for other scales of similar content and length. Critical differences for each subscale taken individually were judged to be fairly large, however, smaller differences between two tests from the same individual can be significant if the three speech communication subscales are considered jointly. CONCLUSIONS: The APHAB is a potentially valuable clinical instrument. It can be useful for quantifying the disability associated with a hearing loss and the reduction of disability that is achieved with a hearing aid.

Adult↗
PubMed1994

Prediction of hearing aid benefit: the role of preferred listening levels.

The listening level chosen by a hearing aid wearer for receiving amplified speech in noise has a substantial impact on the benefit that the hearing aid can provide. Chosen listening levels determine (1) the extent to which audibility of speech cues is improved by amplification, (2) the in situ distortion generated by the hearing aid, and sometimes (3) the auditory resolution abilities available to the hearing-impaired listener. All of these variables have been shown to affect hearing aid benefit. Thus, to predict benefit in any particular listening environment, the listening level that the wearer would choose in that setting must be known with some precision. This paper reports two studies of chosen, or preferred, listening levels. We present evidence to show that preferred listening levels vary with changes in the listening environment, especially when the signal-to-noise ratio is favorable. We describe a method for predicting preferred listening level changes in some environments that differ in talker levels and/or signal-to-noise ratios.

Acoustic Stimulation↗
PubMed1993

Prediction of benefit from linear hearing aids in nonreverberant listening environments.

Hearing aid benefit, defined in terms of improved speech intelligibility, was measured for 16 elderly hearing-impaired subjects. Twelve conditions were tested, simulating a range of daily situations from typical home environments to moderate-sized social gatherings, and assuming a small talker-listener distance (thus maintaining essentially nonreverberant listening conditions). Each subject was fitted with the same type of programmable hearing aid. The goals were to develop a model for the prediction of benefit based on hearing loss, listening environment, and amplification variables, and to assess the potential accuracy of the model. Two models were developed using multiple linear regression analyses. The prefitting model used data that would be available before a hearing aid fitting, that is, audiogram and listening environment data. This model, although potentially useful as a counseling tool, was relatively inaccurate. Six of the 16 subjects yielded benefit data that were consistently different from the model's predictions. The postfitting model used information that could be obtained during a hearing aid fitting about audibility changes resulting from amplification. This model produced more accurate, but still imperfect predictions of benefit. Benefit obtained by three subjects deviated substantially from the predictions of the postfitting model. It was concluded that a model producing fairly accurate benefit predictions must encompass additional variables beyond those considered here. Nevertheless, these models may be useful for prediction of typical benefit for potential hearing aid wearers.

Acoustics↗
PubMed1993

Indices of frequency and temporal resolution as a function of level.

Several investigators have suggested that between-subject variations in hearing aid benefit may be related to between-subject variations in auditory resolution. Evaluation of this relationship is complicated by the need to assess resolution at several frequencies and levels in hearing-impaired listeners who may not tolerate lengthy test procedures. This paper reports data from normal-hearing listeners for abbreviated indices of frequency and temporal resolution. For a particular frequency-stimulus level combination, both indices may be derived from three pure-tone thresholds obtained with different masking stimuli. Norms are reported as a function of masker level for each index at four test frequencies. Changes in the indices as a function of masker level were consistent with expectations based on related studies by other investigators. Norms were obtained using a supra-aural earphone. Comparison of results from supra-aural and insert earphones suggested that low-frequency sound leakage substantially affected the norms for 500 Hz. Reliability of individual indices was good to excellent.

Acoustic Stimulation↗
PubMed1992

Maturation of hearing aid benefit: objective and subjective measurements.

The goals of this investigation were to determine whether hearing aid benefit improved significantly over the first 10 weeks of hearing aid use and whether time-related changes in benefit (if any) were affected by the type of benefit measurement (i.e., objective or subjective). A total of 17 hearing-impaired subjects participated, with different subjects completing different phases of the study. Benefit was measured soon after the hearing aid fitting and again after 10 weeks of adjustment to hearing aid use. Objective benefit data were determined using the Connected Speech Test. No significant changes in objective benefit were noted in noisy or reverberant listening environments when visual cues were available. However, in a low-noise setting and in a noisy setting without visual cues, improvements in objective benefit were seen over time. Subjective benefit data were derived from responses to the Profile of Hearing Aid Benefit. These data indicated significant benefit improvement over time in all five types of daily life situations assessed, although the improvement was small in reverberant and noisy environments. Significant, but modest, correlations were found between objective and subjective data for low-noise and reverberant listening environments. Comparison of experienced and novice hearing aid wearers suggested that although experienced wearers obtain more benefit than novice wearers, they evidence similar time-related changes in benefit during the first 10 weeks of new hearing aid use.

Aged↗
PubMed1991

Comparison of objective and subjective measures of speech intelligibility in elderly hearing-impaired listeners.

Three experiments were performed to evaluate the use of subjective intelligibility estimations as a method for measuring hearing aid benefit. Subjective and objective speech intelligibility scores were compared for young normal-hearing and elderly hearing-impaired listeners. Objective intelligibility scores were obtained using the Connected Speech Test (CST). This test consists of conversationally produced passages of speech that the listener repeats sentence by sentence. To provide subjective intelligibility scores, listeners estimated the percentage that they understood of each CST passage. Comparison of the two types of scores revealed that they were closely related in both groups of subjects (r = .82-.92). Although the two types of scores were essentially equal for normal-hearing subjects, the hearing-impaired listeners tended to produce subjective estimations of intelligibility that were significantly lower than their objective scores. Manipulation of visual cues and amplification, in an attempt to influence the hearing-impaired listeners' expectation of understanding speech, had no effect on the subjective-objective score differential. The difference between subjective and objective scores in the hearing-impaired group was not related to audiometric variables such as speech reception threshold, audiogram, or duration of hearing loss. It was concluded that comparative hearing aid evaluations using subjective intelligibility estimates would usually produce the same relative outcome as evaluations using the objective intelligibility measurement procedure. However, scores obtained with the objective procedure had smaller critical differences. Thus, when both types of scores are based on the same number of passages, the objective measurement procedure would be the more sensitive to differences among hearing aids.

Adolescent↗