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Biomedical subjects

M A Stone

Publications and source records attributed to M A Stone.

At least 37 records · Page 2Linked to original sources
PubMed1998

Reasons for non-compliance with screening for infection with Helicobacter pylori, in a multi-ethnic community in Leicester, UK.

In this study, we aimed to identify reasons for non-compliance with a screening programme for Helicobacter pylori (H pylori), in a multi-ethnic community and to assess the effectiveness of Asian language materials towards increasing compliance. A serological screening test for infection with H pylori was offered to 200 Asians and 200 non-Asians (mainly Europeans), aged 21-55 y, registered at a single general practice. Reasons for non-attendance for screening were identified by reply slip or interview. A second group of 200 Asians who were offered screening were sent information in Gujarati as well as English. When information was mailed in English only, 30% Asians and 22% non-Asians attended (P = 0.09, ns). Stated reasons for non-attendance in the Asian group were not generally language related; reasons were similar in the Asian and non-Asian groups and were most frequently related to other commitments. The use of materials in Gujarati did not improve compliance. Language problems should not be assumed to dominate reasons for non-compliance with screening in ethnic minority groups. In common with those of UK origin, subjects from ethnic minority groups may more generally have insufficient interest in preventive medicine for them to prioritise health screening above other commitments.

Adult↗
PubMed1998

Lack of correlation between self-reported symptoms of dyspepsia and infection with Helicobacter pylori, in a general population sample.

OBJECTIVE: To investigate any correlation between infection with Helicobacter pylori (H. pylori) and overall symptoms of dyspepsia, in a general population sample. DESIGN: Analysis of test results and questionnaire replies from a population screening study involving subjects registered at a single general practice in Market Harborough, UK. METHODS: H. pylori status was established using a commercial enzyme-linked immunosorbent assay (ELISA), and frequent dyspepsia was assessed using a previously validated self-completion symptom questionnaire. RESULTS: Complete results for dyspepsia and H. pylori status were obtained and analysed for 1524 men and women aged 21-55 years at the start of the study. In those who attended for screening, the prevalence of dyspepsia was 39%, with a 15% prevalence of infection with H. pylori. No significant correlation was found between H. pylori status and frequent dyspepsia, upper abdominal pain or reflux-like symptoms. Adjustment for age, gender, smoking and alcohol consumption did not alter these findings. CONCLUSION: The analysis suggested that H. pylori infection does not play an important role in overall symptoms of non-ulcer dyspepsia in the community, nor is it important in protecting against acid reflux in patients without duodenal ulcer.

Adult↗
PubMed1998

Results of Helicobacter pylori screening and eradication in a multi-ethnic community in central England.

OBJECTIVES: To determine the prevalence of Helicobacter pylori and risks for infection in a multi-ethnic inner city population, and to assess the effectiveness with which the infection can be eradicated in a relatively asymptomatic population of this type. DESIGN: Analysis of results from a small research-based community programme of screening and eradication. Tests were offered to matched groups of Asians and non-Asians from the general population. METHODS: Those who attended for screening had a serological screening test for infection with H. pylori. Data concerning possible risk factors for infection were collected by means of questionnaires. Subjects testing positive were offered a prescription for eradication therapy (ranitidine bismuth citrate and clarithromycin) through their general practitioner, and success of eradication therapy was assessed by urea breath test. RESULTS: The overall prevalence of infection in 155 subjects was found to be 51%. The difference between positive test rates in Asians (53%) and non-Asians (47%) was not significant (P=0.611). In Asians, age and social class were risk factors for infection, but not gender or birth outside the UK. Results were similar in those born in India and East Africa. Of the 79 people who tested positive, 64 (81%) elected to take eradication therapy. Compliance with medication was estimated to be 95% and successful eradication was achieved in 92% of cases. CONCLUSION: Social class is more important than Asian ethnic origin as a predictor of H. pylori status. Good rates of H. pylori eradication can be achieved in subjects from the general population living in inner city communities.

Breath Tests↗
PubMed1998

General population screening for infection with Helicobacter pylori: a realistic option?

OBJECTIVES: To consider the effectiveness of a community programme of Helicobacter pylori (H pylori) screening and eradication run in collaboration with general practitioners. Specifically, to assess numbers successfully eradicating H pylori and consequently reducing the prevalence of infection, and to identify and consider areas of poor compliance. SETTING: A large general practice in Market Harborough, Leicestershire, UK. METHODS: A general population sample of 4015 subjects aged 21-55 was offered a serological screening test for H pylori through their general practitioners. Those testing positive were offered a prescription for eradication treatment and an information pack designed to encourage good compliance. Successful eradication was assessed by a urea breath test. RESULTS: The screening test was accepted by 1566 (39%) of those invited, with men and younger people least likely to attend. Of the 235 (15%) subjects who tested positive, 186 (79%) were treated and eradication was confirmed in 170 (95%) of the 179 subjects who had a urea breath test. Overall, eradication was confirmed in 4% (170/4015) of those offered screening. Assuming a 15% overall prevalence of H pylori infection, it is estimated that H pylori was eradicated in 29% of those infected in the target group. CONCLUSIONS: When an intervention was used to encourage good compliance, the eradication rate was high. Effectiveness was limited most strongly by the acceptance rate for the screening test, but also by the rate of uptake of eradication treatment. If benefits of population screening can be shown, appropriate interventions to improve compliance in these areas would need consideration.

Adult↗
PubMed1997

Near patient testing for Helicobacter pylori: a detailed evaluation of the Cortecs Helisal Rapid Blood test.

OBJECTIVE: To evaluate the Cortecs Helisal Rapid Blood test for accuracy overall and in specific subgroups by age and ethnic origin. Additionally, to assess readability of results, including inter-observer error, with consideration also given to usability and acceptability. DESIGN: A prospective evaluation using four reference tests. SETTING: A hospital endoscopy unit. METHODS: Two hundred patients attending for endoscopy were recruited for H. pylori testing with the Helisal test, plus antral biopsies for CLO test, culture and histology and serology using a commercial enzyme-linked immunosorbent assay (ELISA). The Helisal test was carried out and results read strictly according to the manufacturer's instructions. Two or more reference tests positive were taken as a gold standard positive; all results negative as negative and any remaining cases were regarded as equivocal. Performance figures were calculated twice, treating patients with equivocal status as either positive or negative. Results were in most cases double-read, blinded, by two observers and readings subsequently compared. RESULTS: The test was considered convenient, easy to use and acceptable to symptomatic patients, but a notable proportion (10%) of results were very difficult to read. Sensitivity was acceptable (91-92% overall, 95% confidence interval (CI) 82-97%), but specificity was poor overall (56-62%, 95% CI 45-72%), and particularly in patients aged 45 years or over (44-51%) and those of South Asian origin (42-50%). CONCLUSION: The test could be appropriate for testing younger symptomatic patients. Its usefulness was, however, found to be limited by poor readability of some results and poor specificity. Reading of some results as equivocal would be appropriate.

Adult↗
PubMed1997

Effects of fast-acting high-frequency compression on the intelligibility of speech in steady and fluctuating background sounds.

This study examines whether speech intelligibility in background sounds can be improved for persons with loudness recruitment by the use of fast-acting compression applied at high frequencies, when the overall level of the sounds is held constant by means of a slow-acting automatic gain control (AGC) system and when appropriate frequency-response shaping is applied. Two types of fast-acting compression were used in the high-frequency channel of a two-channel system: a compression limiter with a 10:1 compression ratio and with a compression threshold about 9 dB below the peak level of the signal in the high-frequency channel; and a wide dynamic range compressor with a 2:1 compression ratio and with the compression threshold about 24 dB below the peak level of the signal in the high-frequency channel. A condition with linear processing in the high-frequency channel was also used. Speech reception thresholds (SRTs) were measured for two background sounds: a steady speech-shaped noise and a single male talker. All subjects had moderate-to-severe sensorineural hearing loss. Three different types of speech material were used: the adaptive sentence lists (ASL), the Bamford-Kowal-Bench (BKB) sentence lists and the Boothroyd word lists. For the steady background noise, the compression generally led to poorer performance than for the linear condition, although the deleterious effect was only significant for the 10:1 compression ratio. For the background of a single talker, the compression had no significant effect except for the ASL sentences, where the 10:1 compression gave significantly better performance than the linear condition. Overall, the results did not show any clear benefits of the fast-acting compression, possibly because the slow-acting AGC allowed the use of gains in the linear condition that were markedly higher than would normally be used with linear hearing aids.

Adult↗
PubMed1994

Laparoscopic live-donor nephrectomy.

Laparoscopic nephrectomy with ablative intent has been performed clinically. The current study aimed to determine whether a physiologically and anatomically intact kidney suitable for transplantation could be harvested laparoscopically. Three weeks after an ablative laparoscopic right nephrectomy, 15 pigs were divided into two groups: the study group (n = 10) underwent a laparoscopic live-donor left nephrectomy of the solitary kidney and conventional autotransplantation; the control group (n = 5) underwent an open live-donor left nephrectomy of the solitary kidney and conventional autotransplantation. All study kidneys underwent laparoscopic in situ hypothermic perfusion. The mean length of the left renal artery and vein were similar in the study and control groups: 3.1 cm and 3.4 cm, respectively, in the study group compared with 2.5 cm and 3.8 cm, respectively, in the control group (P = 0.5). No intraoperative renal vascular injuries or postoperative ureteral complications were noted in either group. Renal histopathologic examination immediately after live-donor nephrectomy and at 1 month post-transplant showed similar findings in the two groups. The mean serum creatinine at 7 and 30 days postoperatively was not significantly different: 2.1 mg/dL and 1.6 mg/dL, respectively, in the study group and 1.7 mg/dL, and 1.4 mg/dL, respectively, in the control group (P = 0.4). We conclude that laparoscopic live-donor nephrectomy can be performed safely and reproducibly in the porcine model.

Adenosine Triphosphate↗
PubMed1994

Cardiac troponin-T immunoassay for diagnosis of acute myocardial infarction.

We evaluated the analytical and clinical performance of an immunoassay for cardiac troponin T (cTnT). Within-run and total imprecision ranged from 1.6 to 11.3%. The sensitivity and linear range was 0.015 and 13 micrograms/L, respectively. Frozen samples were stable for at least 8 weeks. No interferences were seen with lipids or bilirubin (total and conjugated). Hemoglobin caused a negative bias at concentrations > 4 g/L. Heparinized plasma showed a 6% negative bias compared with serum. The clinical utility of cTnT was compared with that of creatine kinase (CK)-MB (mass assay). The sensitivity of cTnT measurements from 63 patients with acute myocardial infarction (AMI) (cTnT cutoff 0.1 microgram/L) was 60% at 0-3 h, 59% at 3-6 h, 94% at 6-9 h, 90% at 9-12 h, 99% at 12-24 h, 92% at 24-48 h, 83% at 48-72 h, and 100% at 72-96 h. Corresponding results for CK-MB (cutoff 5.0 micrograms/L and 2.5% relative index) were 45%, 64%, 82%, 97%, 87%, 81%, 54%, and 59%. The specificity of the markers from 49 non-AMI patients was 46% and 79% for cTnT and CK-MB, respectively. We show that CK-MB is more specific for diagnosis of AMI, and propose that cTnT is more sensitive to myocardial injury.

Bilirubin↗
PubMed1994

Family physicians' evaluation of the practice management education received during residency training.

BACKGROUND: In view of the increasing complexity associated with managing the "business side" of medical practice, the relevance of various practice management topics to the careers of family physicians was examined, along with how well those topics were taught during residency, and ways to improve this training. METHODS: A total of 563 family physicians were surveyed two years after graduating from residencies and asked to rank the relevance of selected practice management topics, to assess how adequately these topics were covered during their residencies, and to evaluate which were the most effective methods for teaching practice management. RESULTS: The subjects rated practice management topics as "mostly relevant" or "extremely relevant," while 94% of those same topics were rated as having been "only slightly covered" or "not covered at all" during residency training. Frequently cited comments for improving this area included the development of a more formal, required business curriculum, greater use of community practitioners and outside speakers, more resident involvement in the management of the residency practice's business office functions, and the creation of practice management rotations in community practitioners' offices. CONCLUSIONS: The results indicated that, despite improvements in practice management training during the past decade, this area still needs greater attention to prepare physicians to succeed in private practice.

Family Practice↗
PubMed1993

Demonstrating instrument-reagent flexibility: a carbamazepine enzyme immunoassay reagent system.

Versatility of immunoassay reagents is beneficial to laboratories seeking cost-effective combinations of tests and automated instrumentation. In such cases, both immunoassay analytical performance and instrument independence must be assessed. Considering this, we determined the compatibility of a new carbamazepine EMIT 2000 reagent system with two fully automated but different kinetic rate analyzers (Hitachi 704 and Cobas MIRA), comparing results to a reagent-dedicated fluorescent polarization automated device (TDx) as reference. In order to more stringently assess reagent antibody specificity, we tested recovery of purified carbamazepine spiked into sera pooled from different hospital groups (normal, renal failure, hepatic failure, term pregnancy, cord blood). Cross-reactivity was additionally tested using patient sera containing various amounts of tricyclic antidepressants, compounds structurally but not functionally related to carbamazepine. Despite distinct operational differences between analyzers, precision (< 5.5% CV) and accuracy (> 95% recovery) compared well to the TDx method. However, when carbamazepine was spiked into sera from patients with hepatic failure or at term pregnancy, all three methods measured a negative bias in recovery of 16-20%. No significant cross-reactivity was observed at normal therapeutic concentration of certain tricyclic compounds, though measurable cross-reactivity was detected when present at toxic serum concentrations. We conclude that the EMIT carbamazepine immunoassay is adaptable to the different kinetic rate analyzers studied. Analytical specificity should, furthermore, be assessed in the context of interferences likely to be clinically encountered.

Antibody Specificity↗
PubMed1993

Effect on the speech reception threshold in noise of the recovery time of the compressor in the high-frequency channel of a two-channel aid.

This paper describes two experiments in a series evaluating and optimising a hearing aid incorporating two forms of automatic gain control (AGC). The first form is a front-end AGC which is normally slow acting and which compensates for variations in the overall level of speech from one situation to another. The second form of AGC follows the front-end AGC. The signal is split into two frequency bands, and fast-acting AGC is applied in the upper band only. The bands are then recombined. The two experiments described here were aimed at determining the optimum value of the recovery time of the AGC in the high-frequency channel. Speech reception thresholds (SRTs) were measured in the presence of speech-shaped noise as a function of the recovery time, for subjects with mild-to-moderate sensorineural loss. In the first experiment the recovery time was varied over the range 10-80 ms. SRTs tended to be lowest (best) at the shorter recovery times but the effects were small. In the second experiment, the recovery time was varied over the range 5-320 ms. In this case, there was a clear trend for SRTs to increase with increasing recovery time. A recovery time of about 20 ms appears to be optimal.

Aged↗
PubMed1992

Spectral feature enhancement for people with sensorineural hearing impairment: effects on speech intelligibility and quality.

People with sensorineural hearing loss often have difficulty understanding speech in background noise at speech-to-noise ratios (0 to +6 dB) for which normally hearing people have little difficulty. Spectral analysis of speech in noise at these ratios typically shows that the major spectral prominences in the speech (formants) are well represented, but the spectral valleys between the formants are filled with noise. Hearing impaired people have a reduced ability to pick out the spectral prominences, and are more affected by the noise filling in the valleys, partly because of their reduced frequency selectivity. This paper describes a 16-channel bandpass filter bank, implemented in analog electronics, that attempts to enhance spectral features of speech in noise to improve intelligibility for the hearing impaired. Each channel generates an 'activity function' that is proportional to the magnitude of the signal envelope in that channel, averaged over a short period of time. A positively weighted activity function from the nth channel is combined with negatively weighted functions from channels n-2, n-1, n+1, and n+2, giving a correction signal used to control the gain of the bandpass signal in the nth channel. Recombining the bandpass signals results in an enhancement of spectral features of the speech in noise. Two different experiments are described here, one using the activity function as described, and the other using a non-linear transform of the activity function. In both experiments, several different weighting patterns were used in calculating the correction signal. The intelligibility of speech in noise processed by the system was measured for subjects with moderate sensorineural hearing loss. In both experiments, no improvement in intelligibility was found. However, subjective ratings of the stimuli used in Experiment 2 indicated that some subjects judged the processed stimuli to have both higher quality and higher intelligibility than unprocessed stimuli.

Electronics↗
PubMed1992

Simplified measurement of auditory filter shapes using the notched-noise method.

The shape of the auditory filter at a given centre frequency can be estimated by measuring the threshold for detecting a sinusoid presented in a spectral notch in a noise masker, as a function of notch width. Laboratory studies using this method have typically been based on threshold measurements for between 13 and 19 notch widths. In this note, we describe how both the overall sharpness and asymmetry of the auditory filter in hearing-impaired subjects can be estimated with reasonable accuracy using only five notch widths. This considerably reduces the testing time needed, making it possible to apply the method in clinical testing.

Acoustic Stimulation↗
PubMed1992

Syllabic compression: effective compression ratios for signals modulated at different rates.

Compression circuits are being used increasingly in hearing aids to reduce the dynamic range of signals. Their performance is usually characterized by: (1) the threshold sound level above which the compression starts to operate; (2) the compression ratio, which is the change in input level (in dB) required to achieve a 1 dB change in output level; and (3) the attack and release times over which the signal is integrated to determine the necessary gain change. In many practical situations, the effective compression ratio obtained with dynamically varying signals such as speech is less than the compression ratio obtained using standard test signals (slow square-wave modulation with large modulation depth). This article describes the effective compression ratios achieved with sinusoidal modulation, as a function of modulation rate, level relative to the compression threshold, compression ratio and time constants. The effects of compression on a typical speech signal are also discussed.

Acoustic Stimulation↗
PubMed1992

Effects of the fitting parameters of a two-channel compression system on the intelligibility of speech in quiet and in noise.

These experiments were carried out to assess how accurately the gains and compression ratios in a two-channel compression system needed to be set. We used as a research tool a laboratory version of a two-channel full-dynamic-range compression system. The system was initially adjusted to suit each hearing-impaired subject according to the manufacturer's recommendations. Then, further adjustments were made to ensure that speech stimuli were both audible and comfortable over a wide range of sound levels. Finally, the settings of the gains and compression ratios were systematically varied from the adjusted values and the effects of this on the intelligibility of speech in quiet and in noise (12-talker babble, levels of 65 and 75 dB SPL) were measured. The results indicated that speech reception thresholds (SRTs) in quiet were significantly adversely affected by decreases in low-level gain. However, SRTs in noise were relatively unaffected by changes in low-level gain. An exception occurred at the higher noise level used, where increases in the low-level gains (with corresponding increases in compression ratios) had a significant adverse effect on the SRTs. It is concluded that, provided excessive low-level gains (associated with high compression ratios) are avoided, the main criteria for fitting such a system should be listening comfort (i.e. achieving an acceptable tonal balance, and avoiding uncomfortably loud sounds) and an appropriate value of the threshold for detecting speech in quiet (which should be a little below 50 dB SPL).

Acoustic Stimulation↗
PubMed1991

Optimization of a slow-acting automatic gain control system for use in hearing aids.

This paper describes experiments evaluating and optimizing an automatic gain control system, called dual front-end AGC (abbreviated as D), intended for use in hearing aids. This system has two purposes: (1) to compensate for variations in the overall level of speech from one situation to another by slowly changing its gain; (2) to protect the user from sudden intense transients without affecting the long-term gain. This is achieved by using two control voltages to determine the gain. One changes slowly as the input varies in level. Normally this component determines the overall gain. The other comes into operation when an intense transient occurs. It acts rapidly to reduce the gain, avoiding over-amplification of the transient, but its action ceases quickly after the end of the transient. We describe four experiments measuring speech intelligibility for subjects with cochlear hearing loss in which we determine optimum values for two of the time constants of the D system, namely the recovery time of the fast component and the attack time of the slow component. The experiments also compare the D system with linear amplification (L) and 'adaptive compression' (A). The results show: (1) for the D system, optimum values are about 80-150 ms for the recovery time of the fast component and 150-325 ms for the attack time of the slow component; (2) in situations where intense transient sounds are present, and there is either no background sound (experiment 1) or continuous speech-shaped noise as a background (experiment 2), the D system gives significantly better performance than the L or A systems. When the background noise is a single voice, reversed in time (experiment 3), the D and L systems give similar performance, and both are markedly superior to the A system; (3) when the level of speech is varied over a range of 30 dB (experiment 4), both D and A systems allow good performance over the whole range of levels. Performance for the L system worsens markedly at the lower levels.

Aged↗