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Biomedical subjects

M Haggard

Publications and source records attributed to M Haggard.

At least 19 recordsLinked to original sources
PubMed2001

Generalisability of clinical trials in otitis media with effusion.

OBJECTIVE: The impact of a randomised controlled trial (RCT) upon practice depends on its external validity (generalisability). This paper summarises and illustrates a framework for judging and augmenting external validity, emphasising its application to treatment trials in otitis media with effusion (OME) so as to permit stronger inferences in the future. METHODS: The external validity of two surgical trials in the field of OME (TARGET, UK and KNOOP-3, the Netherlands) has been examined within a framework emphasising effect modification, in four specific ways: (1) comparison of the demographic characteristics of the trial population with the domain population; (2) studying the distributions on possible effect modifiers (i.e. variables conditioning the benefit from intervention); (3) studying whether effect modification occurs in the analyses; and (4) comparing outcome measures between the randomised and the eligible but non-randomised children. RESULTS: For neither KNOOP-3 and TARGET were large discrepancies found between randomised and non-randomised children for any of the demographic variables. Differences in distributions along possible effect modifiers were found, but the overlaps were large enough for it still to be possible to study whether these factors indeed modified the outcome. Results for the randomised and non-randomised but eligible patients were similar. The results of both trials therefore appear to be generalisable to their domain populations. CONCLUSIONS: A superficial contrast in the results (KNOOP null, TARGET positive) does not amount to a contradiction, because of differences in the clinical question appropriate to the respective age and populations defined. Attention to quality of design and external validity of randomised controlled trials should achieve higher applicability.

Child↗
PubMed2001

Improving referrals for glue ear from primary care: are multiple interventions better than one alone?

OBJECTIVES: To evaluate the effect of a risk factor checklist and training video for general practitioners in reducing inter-practice variation and improving the appropriateness of referrals (assessed by their positive predictive value or PPV) of patients with suspected otitis media with effusion (OME or 'glue ear') to secondary care. METHODS: Fifty general practices (177 practitioners) from the NHS Trent region and the West of Scotland were cluster-randomised either to a control group (n = 12) or to one of three intervention groups (training video (n = 16), checklist (n = 11), or both (n = 11)). Data on all paediatric ear, nose and throat (ENT) referrals and diagnostic results at ENT clinics were collected for a one-year period pre- and post-intervention. Referral rates for OME and for closely related conditions were calculated for children aged 0-15 years, based on each practice's list size. PPV was defined as the proportion of referrals resulting in bilateral hearing loss > or = 20 dB at the ENT outpatient department. RESULTS: There was a significant improvement in the PPV, adjusted for patients' waiting time between general practitioner (GP) referral and being seen at the ENT department. The improvement in PPV pre- and post-intervention was 15% (95% confidence interval, CI: -12.1% to 41.7%) for the practices receiving both interventions, compared with a degradation of 20% pre- and post-intervention (95% CI: -32.9% to -6.4%) for practices receiving only one intervention and a degradation of 34% for those receiving no intervention. CONCLUSIONS: Disseminating a risk factor checklist and training video on glue ear to GPs using a multi-channel approach can improve the quality of referrals to ENT.

Adolescent↗
PubMed1998

Do GPs have the techniques for 'watchful waiting' in glue ear?

'Watchful waiting' for glue ear in children within primary care as a precursor or alternative to surgery is one of the increasing pressures on general practitioners (GPs) to limit outpatient referrals. An equipment survey questions whether primary care is properly equipped to 'watch', given the limited access to audiological equipment that might objectively underpin a decision on when 'waiting' should end.

Audiometry↗
PubMed1993

Candidature for hearing aids: justification for the concept and a two-part audiometric criterion.

A definition of hearing aid candidature is required for planning and other purposes. The number of candidates in the population actually receiving an adequate fitting would provide the major index of whether audiology services achieve their major public health goal. Many diverse factors determine the benefit that an individual receives from a hearing aid, and hence could in principle be included in some composite criterion for appropriate candidature reflecting the cost-effectiveness of patterns of provision. However, the complexity of universal capture, on those fitted with hearing aids, of data giving full auditory and demographic characteristics is beyond current routine NHS information systems. The most powerful known determinant established to date both of auditory disability and benefit is average hearing threshold level (HTL). Hearing threshold levels are hence both a necessary part of the fitting process and, given the data from the National Study of Hearing, a sufficient basis for computing population prevalences of hearing characteristics and service uptake in the major demographic strata. We report epidemiological data on consultation about problems with ears or hearing and uptake of hearing aids, which lead us to recommend a two-part candidature criterion on hearing threshold levels (0.5-4.0 kHz average): EITHER (a) better ear HTL > or = 35 dB OR (b) (15 dB < or = better ear HTL < 35 dB) WHEN worse ear HTL > or = 45 dB. The asymmetric component (b) may appear contentious, but is directly supported both by the epidemiological data and by further clinical data on benefit measured as performance on speech-in-noise tests. The proposed criterion is not over-liberal in clinical or related technological terms, but against the high prevalence of impairments in the population, the current provision and uptake of hearing aids in the UK still appear modest (about 3.3% in the population, and just under one-third of those qualifying by our criterion). Whatever the means of providing hearing aids, authorities charged with meeting the needs of their populations require such statistical indicators to know whether service delivery is appropriately geared. They should not use such an indicator as a basis of entitlement, as there are certainly individuals outside the criterion who receive benefit from their hearing aids. Equally, technological progress could expand the boundaries of candidature.

Adolescent↗
PubMed1992

Ploidy of lymphoblasts is the strongest predictor of treatment outcome in B-progenitor cell acute lymphoblastic leukemia of childhood: a Pediatric Oncology Group study.

PURPOSE: Using the technique of recursive partitioning and amalgamation analysis with verification, the Pediatric Oncology Group (POG) investigated the independent prognostic significance of previously published prognostic factors significantly associated with event-free survival (EFS) in B-progenitor cell acute lymphoblastic leukemia (ALL). PATIENTS AND METHODS: Age, leukocyte count, sex, immunophenotype (expression of cytoplasmic immunoglobulin [Ig] and of surface antigens CD10 and CD34), and DNA index (ratio of the flow cytometry-determined DNA content of leukemia cells to that of normal diploid cells) were the variables used in the evaluation of four antimetabolite-based chemotherapy regimens in 1,535 children with the newly diagnosed B-progenitor cell ALL between February 1986 and May 1990. RESULTS: There were three subgroups at widely different risks of treatment failure. A DNA index greater than 1.16 was the most prognostic feature. The final prognostic subgrouping was as follows: (1) DNA index greater than 1.16; (2) DNA index less than or equal to 1.16, age less than 11.0 years, and leukocyte count less than 50 x 10(9)/L; and (3) DNA index less than or equal to 1.16, (age greater than 11.0 years, and/or leukocyte count greater than 50 x 10(9)/L). These groups made up 20%, 53%, and 27% of the patients and had 4-year EFS rates (SE) of 90.1% (6.3%), 80.5% (5.1%), and 50.4% (7.6%), respectively. CONCLUSIONS: Use of the DNA index, leukocyte count, and age--data that are relatively inexpensive and simple to obtain--may be sufficient to stratify patients with B-progenitor cell ALL for risk-directed therapy. Patients at an extremely low risk of failing therapy (approximately 20% of cases in this study) can thus be identified and spared the toxic short-term and late effects of more intensive therapies that may be needed for children with less favorable clinical and biologic features.

Adolescent↗
PubMed1990

Magnitude of diotic summation in speech-in-noise tasks: performance region and appropriate baseline.

The diotic summation effect is one of the three types of binaural advantage for perceiving speech-in-noise. Using a within-subject design in normally-hearing subjects having no significant noise exposure, we examined its magnitude. The average advantage was +5%, at an overall performance level of 70-80% rising to +9% when an appropriate control was used to exclude order effects introduced by the within-subject design. Diotic summation is an important component of the advantage to be derived from presentation to two ears, but the size of the binaural advantage obtained depends critically on the particular monotic baseline chosen for comparison. The methodological problems of demonstrating binaural advantages (as in binaural aiding studies) are discussed.

Adult↗
PubMed1978

Changes in auditory perception in the menstrual cycle.

In a attempt to specify the critical functional components involved in the menstrual fluctuation of the upper frequency limit of the binaural beat we have obtained evidence of better performance in a variety of tasks at period and mid-cycle than at other times. These tasks include detection of physical beating, low-frequency octave matching, and lateralisation of clicks having interaural time delays in the 100 musec region. Continuous pure-tone frequency discrimination did not show a significant cyclical pattern overall but there was a tendency for low-frequency discrimination to show the described pattern. An attempt is made to reconcile some of these results with those of Wynn (1973) on absolute pitch, in terms of possible physiological and biochemical correlates. Three conclusions can be drawn: (1) The representations both of low-frequency tones and of the interaural time differences involved in some localisation tasks are particularly susceptible to alteration by the biochemical changes of the menstrual cycle: (2) The changes underlying perceptual variations are multiple, and inevitably confounded in any single task. (3) The distinction between the sensitivity and bias parameters of performance appears to be valuable in specifying menstrual effects. Several further lines of enquiry are suggested, but methodological difficulties in cycle research make it likely that more progress will come from better understanding of the physiological bases of psychoacoustic tasks using other methods, rather than from investigating natural menstrual effects.

Adult↗