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Biomedical subjects

N Brewer

Publications and source records attributed to N Brewer.

At least 19 recordsLinked to original sources
PubMed2005

A systematic review and economic evaluation of alendronate, etidronate, risedronate, raloxifene and teriparatide for the prevention and treatment of postmenopausal osteoporosis.

OBJECTIVES: To establish the clinical effectiveness and cost-effectiveness of selective oestrogen receptor modulators, bisphosphonates and parathyroid hormone (subject to licensing) for the prevention and treatment of osteoporosis and the prevention of osteoporotic fractures in postmenopausal women. DATA SOURCES: Electronic databases. REVIEW METHODS: Studies that met the review's entry criteria were eligible for inclusion in the meta-analyses provided that they reported fracture incidence in terms of the number of patients suffering fractures. Meta-analysis was carried out using the random-effects model. A model was constructed to estimate the cost-effectiveness of osteoporosis interventions. The model calculated the number of fractures that occurred and provided the costs associated with osteoporotic fractures, and the quality-adjusted life-years (QALYs). In addition, the conditions of breast cancer and coronary heart disease (CHD) were modelled, as some interventions have been shown to affect the risk of these conditions. RESULTS: Ninety randomised controlled trials (RCTs) met the inclusion criteria. They related to the five interventions (alendronate, etidronate, risedronate, raloxifene and teriparatide) and to five comparators (calcium, calcium plus vitamin D, calcitriol, hormone replacement therapy and exercise), as well as placebo or no treatment. All five interventions have been shown to reduce the risk of vertebral fracture in women with severe osteoporosis with adequate calcium intakes. However, none of these drugs has been demonstrated, by direct comparison, to be significantly more effective than either each other or the other active interventions reviewed in this report. The intervention costs of treating all osteoporotic women, for a period of 5 years, were in the region of pound 900-1500 million for alendronate, etidronate, risedronate and raloxifene. The cost per QALY ratios fell dramatically with age. Assuming the risks of a woman with severe osteoporosis at the threshold of osteoporosis, no treatment had a cost per QALY below pound 35,000 at 50 years of age. At 60 years of age, the cost per QALY of raloxifene was pound 26,000 assuming no impact on hip fractures, and pound 31,000 assuming an adverse effect. However, these results are driven by the effect on breast cancer and the assumptions made regarding this disease state. No other intervention had a cost per QALY below pound 35,000. When analyses were conducted assuming that the fracture risk is doubled at each site, alendronate and risedronate had cost per QALY ratios below pound 30,000 at all ages. For women at the threshold of osteoporosis, without a prior fracture and aged 70 years, the cost per QALY of the three bisphosphonates ranged from pound 34,000 to pound 41,000. Raloxifene had a cost per QALY of pound 23,000, assuming no effect on hip fracture, given assumptions regarding breast cancer. At 80 years of age, the cost per QALY of alendronate and risedronate was below pound 20,000. This was true for etidronate when incorporating observational data, but the value rose to pound 69,000 when only RCT data were used. No other intervention had a cost per QALY below pound 35,000. It was assumed that doubling the risk of fracture for women without a prior fracture would give results similar to patients at the threshold of osteoporosis with a prior fracture. CONCLUSIONS: Of the five interventions, only raloxifene appeared to reduce the risk of vertebral fracture in postmenopausal women unselected for low bone mineral density (BMD). However, as the full data have not been made public, there is some uncertainty regarding this result. None of the five interventions has been shown to reduce the risk of non-vertebral fracture in women unselected for low BMD. All of the proposed interventions provided gains in QALYs compared with no treatment in women with sufficient calcium and vitamin D intakes. The size of the QALY gain for each intervention was strongly related to the age of the patient. The estimated costs varied widely for the interventions. These net costs were markedly different by age, with some interventions becoming cost-saving at higher age ranges in patients with a prior fracture. Areas for future research include: the evidence base for the efficacy of fracture prevention in the very elderly, reanalysis of raloxifene using a dedicated breast cancer and CHD model, and more trials considering the cost-effectiveness of teriparatide.

Age Factors↗
PubMed2004

Liquid-based cytology in cervical screening: an updated rapid and systematic review and economic analysis.

OBJECTIVES: To update an earlier published report reviewing the effectiveness and cost-effectiveness of liquid-based cytology (LBC). DATA SOURCES: Electronic bibliographic databases, relevant articles, sponsor submissions and various health services research-related resources. REVIEW METHODS: The selected data were reviewed and assessed with respect to the quality of the evidence. Pooled estimates of the parameters of interest were derived from the original and the updated studies. Meta-analyses were undertaken where appropriate. The mathematical model developed for the original rapid review of LBC was adapted to synthesise the updated data to estimate costs, survival and quality-adjusted survival of patients tested using LBC and using Papanicolaou (Pap) smear testing. Cost data from published sources were incorporated into the above model to allow economic, as well as clinical, implications of treatment to be assessed. The primary incremental cost-effectiveness ratio is the cost per life year gained (LYG), although estimates of the cost per quality-adjusted life-year (QALY) gained are also presented. A sensitivity analysis was undertaken to identify the key parameters that determine the cost-effectiveness of the treatments, with the objective of identifying how robust the results of the economic analysis are, given the current level of evidence. RESULTS: From the evidence available, it is likely that the LBC technique will reduce the number of false-negative test results. Modelling analyses undertaken as part of this study indicate that this would reduce the incidence of invasive cancer. There is now more evidence to support improvements emanating from the use of LBC screening in terms of a reduced number of unsatisfactory specimens and a decrease in the time needed to obtain the smear samples. The estimated annual gross cost of consumables and operating equipment, and other one-off conversion costs associated with introducing the new technique, will be between 17 British pounds and 38 British pounds million in England and Wales, depending on the LBC system and the configuration of the service. Analyses based on models of disease natural history, conducted in this study, showed that conventional Pap smear screening was extendedly dominated by LBC (LBC was always more cost-effective than conventional Pap smear testing over the same screening interval). Comparing LBC across alternative screening intervals gave a cost-effectiveness of under 10,000 British pounds per LYG when screening was undertaken every 3 years. The cost-effectiveness results were relatively stable under most conditions, although if screening outcomes such as borderline results and colposcopy are assumed to induce even small amounts of disutility then LBC screening at 5-yearly intervals may be the most cost-effective option. CONCLUSIONS: This updated analysis provides more certainty with regard to the potential cost-effectiveness of LBC compared with conventional Pap smear testing. However, there is uncertainty regarding the relative effectiveness (and cost-effectiveness) of the two main LBC techniques. Further research in the area of utility assessment may be worthwhile and possibly a full cost-effectiveness study of LBC based on a trial of its introduction in a low-prevalence population, although the results of the modelling analysis provide a robust argument that LBC is a cost-effective alternative to conventional cervical cancer screening. A randomised comparison of the two main techniques may also be useful.

Cost-Benefit Analysis↗
PubMed2004

Rituximab (MabThera) for aggressive non-Hodgkin's lymphoma: systematic review and economic evaluation.

OBJECTIVES: To determine the clinical and cost-effectiveness of adding rituximab to the CHOP (cyclophosphamide, doxorubicin, vincristine, prednisolone) chemotherapy regime for adult patients with diffuse large B-cell lymphoma (DLBCL). DATA SOURCES: Electronic bibliographic database. REVIEW METHODS: Comparative studies were selected for review if they addressed the clinical or cost-effectiveness of adding rituximab to CHOP in people aged at least 18 years with DLBCL. The internal validity of the study was assessed through the use of the validated Jadad scoring system. Data were abstracted into standardised data extraction forms. Costs were estimated through resource use data taken from the published trial and the unpublished sponsor submission. Unit costs were taken from published sources, where available. An economic evaluation was undertaken to evaluate the cost-effectiveness of R-CHOP compared with CHOP alone for patients with DLBCL using data sources and methodology similar to the manufacturer's submission. RESULTS: In the systematic review of effectiveness, one randomised controlled trial was identified. The study was, in most respects, methodologically rigorous and well conducted and the statistical evidence favoured the addition of rituximab to CHOP. The total cost of rituximab with CHOP (R-CHOP) and CHOP alone estimated from the model developed by ScHARR was 14,456 pounds and 5773 pounds, respectively, for patients aged 60 years and over, and 15,181 pounds and 7311 pounds for patients aged less than 60 years over a 15-year time horizon. The ScHARR model estimated that the addition of rituximab to CHOP generated an additional 0.82 QALY at an extra cost of 8683 pounds compared with CHOP alone therapy over a 15-year time horizon, a cost/quality-adjusted life-year (QALY) ratio of 10,596 pounds for patients aged 60 years or more. For patients aged under 60 years, 1.05 QALY were generated at an additional cost of 7870 pounds, a cost/QALY ratio of 7533 pounds. Assuming that the societal value of a QALY was 30,000 pounds then R-CHOP is cost-effective compared with CHOP in the treatment of DLBCL. CONCLUSIONS: In the short term, the addition of rituximab to the CHOP regimen increased the likelihood of a complete-response by 20% without a significant rise in the risk of a serious adverse event in people aged 60 years or older. Over a 2-year follow-up period, the intervention reduced the risk of death, progression or relapse by 45% and reduced the risk of death by 47% in this population. There is no direct evidence for the clinical effectiveness of adding rituximab to CHOP in the treatment of DLBCL in those aged 18-59 years, although data from phase I and II trials confirm its safety and efficacy in a preclinical setting. The cost-effectiveness modelling presented here has shown that rituximab in combination with CHOP chemotherapy regimen is likely to be considered a cost-effective treatment for DLBCL when compared with the current standard treatment, CHOP chemotherapy only. Analysis of quality of life (QoL) in the area of NHL is limited and only one cost-utility analysis for the treatment of CHOP in NHL was identified. Both the SCHARR and the manufacturer's models utilised QoL utility scores from an unpublished data source. Further research within this area would help to improve the robustness of QoL utility analysis within DLBCL and also NHL as a whole. Further clinical trials might also establish whether R-CHOP may replace peripheral blood stem cell transplant in high-risk patients and whether the doses of chemotherapy in the elderly may be reduced if rituximab is added to less intensive regimens.

Adult↗
PubMed2003

The clinical and cost-effectiveness of pulsatile machine perfusion versus cold storage of kidneys for transplantation retrieved from heart-beating and non-heart-beating donors.

OBJECTIVES: To evaluate the clinical and cost-effectiveness of machine perfusion (MP) compared to cold storage (CS), as a means of preserving kidneys prior to transplantation. Transplantation of kidneys from both heart-beating donors (HBDs) and non-heart-beating donors (NHBDs) is considered. Finally to review whether the use of MP can allow valid testing of kidney viability prior to transplantation. DATA SOURCES: Fifteen electronic bibliographic databases were searched. The reference lists of relevant articles and sponsor submissions were hand searched and various health service research-related resources were consulted via the Internet. REVIEW METHODS: A literature search was undertaken to identify relevant studies and a meta-analysis performed on the studies that had appropriate comparator groups and reported sufficient data. A structured review examined tests of viability of kidneys on MP. Economic modelling was used to determine the cost-effectiveness and cost-utility of MP. RESULTS: The meta-analysis suggested that the use of MP, as compared with CS, is associated with a relative risk of delayed graft function (DGF) of 0.804 (95% confidence limits 0.672 to 0.961). There was no evidence to suggest that this effect is different in kidneys taken from HBDs as opposed to NHBDs. Meta-analysis of 1-year graft survival data showed no significant effect, but the studies, even when aggregated, were severely underpowered with respect to the likely impact on graft survival. The size of effects demonstrated were in line with those predicted by an indirect model of graft survival based on the association of DGF with graft loss. The economic assessment indicated that it is unlikely that in the UK health setting complete cost recovery will be obtained from a reduction in the incidence of DGF. The probability that MP is cheaper and more effective than CS in the long term was estimated at around 80% for NHBD recipients and 50-60% for HBD recipients. Flow characteristics of the perfusate of kidneys undergoing MP may be an indicator of kidney viability, but data were inadequate to calculate the sensitivity and specificity of any test based on this. The concentration of alpha-glutathione-S-transferase (a marker of cell damage) in the perfusate may be the basis of a valid test. A threshold of 2800 micrograms/100 g gave a sensitivity of 93% and specificity of 33% (and hence a likelihood ratio of 1.41). CONCLUSIONS: The baseline analysis indicated that in the long-term MP would be expected to be cheaper and more effective than CS for both HBD and NHBD recipients. A definitive study of the clinical benefit of MP in order to establish its effect on DGF and longer term graft survival would be valuable, together with an economic evaluation of the benefits. While direct evidence relating to improvements in graft survival would be preferable, the small predicted improvement indicates that a very large sample size would be required. In addition to seeking direct evidence of the impact on DGF, research quantifying the impact of DGF on graft survival in this technology is required. Research is also needed to establish whether a valid test (or combination of tests) of kidney viability can be developed.

Cell Survival↗
PubMed2003

Clinical and cost-effectiveness of capecitabine and tegafur with uracil for the treatment of metastatic colorectal cancer: systematic review and economic evaluation.

OBJECTIVES: To evaluate the clinical and cost-effectiveness of capecitabine and tegafur with uracil (UFT/LV) as first-line treatments for patients with metastatic colorectal cancer, as compared with 5-fluorouracil/folinic acid (5-FU/FA) regimens. DATA SOURCES: Electronic databases, reference lists of relevant articles and sponsor submissions were also consulted. REVIEW METHODS: Systematic searches, selection against criteria and quality assessment were performed to obtain data from relevant studies. Costs were estimated through resource-use data taken from the published trials and the unpublished sponsor submissions. Unit costs were taken from published sources, where available. An economic evaluation was undertaken to compare the cost-effectiveness of capecitabine and UFT/LV with three intravenous 5-FU/LV regimens widely used in the UK: the Mayo, the modified de Gramont regimen and the inpatient de Gramont regimens. RESULTS: The evidence suggests that treatment with capecitabine improves overall response rates and has an improved adverse effect profile in comparison with 5-FU/LV treatment with the Mayo regimen, with the exception of hand-foot syndrome. Time to disease progression or death after treatment with UFT/LV in one study appears to be shorter than after treatment with 5-FU/LV with the Mayo regimen, although it also had an improved adverse effect profile. Neither capecitabine nor UFT/LV appeared to improve health-related quality of life. Little information on patient preference was available for UFT/LV, but there was indicated a strong preference for this over 5-FU/LV. The total cost of capecitabine and UFT/LV treatments were estimated at 2111 pounds and 3375 pounds, respectively, compared with the total treatment cost for the Mayo regimen of 3579 pounds. Cost estimates were also presented for the modified de Gramont and inpatient de Gramont regimens. These were 3684 pounds and 6155 pounds, respectively. No survival advantage was shown in the RCTs of the oral drugs against the Mayo regimen. Cost savings of capecitabine and UFT/LV over the Mayo regimen were estimated to be 1461 pounds and 209 pounds, respectively. Drug acquisition costs were higher for the oral therapies than for the Mayo regimen, but were offset by lower administration costs. Adverse event treatment costs were similar across the three regimens. It was inferred that there was no survival difference between the oral drugs and the de Gramont regimens. Cost savings of capecitabine and UFT/LV over the modified de Gramont regimen were estimated to be 1353 pounds and 101 pounds, respectively, and over the inpatient de Gramont regimen were estimated to be 4123 pounds and 2870 pounds, respectively. CONCLUSIONS: The results show that there are cost savings associated with the use of oral therapies. No survival difference has been proven between the oral drugs and the Mayo regimen. In addition, no evidence of a survival difference between the Mayo regimen and the de Gramont regimens has been identified. However, improved progression-free survival and an improved adverse event profile have been shown for the de Gramont regimen over the Mayo regimen. Further research is recommended into the following areas: quality of life data should be included in trials of colorectal cancer treatments; the place of effective oral treatments in the treatment of colorectal cancer, the safety mechanisms needed to ensure compliance and the monitoring of adverse effects; the optimum duration of treatment; the measurement of patient preference; and a phase III comparative trial of capecitabine and UFT/LV versus modified de Gramont treatment to determine whether there was any survival advantage and to collate the necessary economic data.

Antimetabolites, Antineoplastic↗
PubMed2003

Clinical and cost-effectiveness of new and emerging technologies for early localised prostate cancer: a systematic review.

OBJECTIVES: To evaluate the clinical and cost-effectiveness of new and emerging technologies for early, localised prostate cancer. DATA SOURCES: Electronic databases, reference lists of relevant articles and various health services research-related resources. REVIEW METHODS: A list of new and emerging technologies was identified and agreed. A systematic review was undertaken and selected studies were reviewed against a set of criteria. An economic model was developed and used to compare the specified newer treatments with the traditional approaches. RESULTS: For neoadjuvant hormonal therapy, no evidence of benefit was seen in terms of biochemical disease-free survival. For adjuvant hormonal therapy, there was no evidence of benefit in terms of survival, but some conflicting evidence that higher risk patients may benefit. The largest number of studies reported results for brachytherapy, where some evidence suggested that it may be more effective than standard treatments for lower risk patients, although less effective for intermediate- and high-risk patients, in terms of biochemical disease-free survival. Lower quality evidence reported fewer complications than for standard treatments. Higher quality evidence suggested that disease-specific quality of life (QoL) for brachytherapy patients was lower than for patients receiving standard treatments. The review of three-dimensional conformal radiotherapy (3D-CRT) considered treatment-related morbidity, where significantly fewer gastrointestinal complications occurred than with standard radiotherapy. It was suggested that higher radiation doses achieved better disease control, although patient characteristics were often reported as independent indicators of control. The review of intensity-modulated conformal radiotherapy suggested that late gastrointestinal toxicity may be reduced compared with 3D-CRT. For cryotherapy, high rates of impotence were reported. Owing to the paucity and poor quality of evidence identified for other interventions, conclusions regarding their clinical effectiveness cannot be drawn. Cost-effectiveness estimates were based on the impact of adverse events on quality-adjusted life-years and the assessment was restricted to brachytherapy, 3D-CRT and cryotherapy compared with standard treatments. Of the new treatments included, only cryotherapy appeared not to be potentially cost-effective compared with traditional treatments, owing to the associated high incidence of impotence. CONCLUSIONS: The results of the clinical effectiveness review should be viewed in the context of the quality of the available evidence. Very few randomised controlled trials (RCTs) were identified, with the majority of included studies being descriptive case series, open to patient selection bias and measuring surrogate end-points with short-term follow-up. It is difficult therefore to draw conclusions on the relative benefits or otherwise of the newer technologies owing to the lack of substantive evidence of any quality and the lack of comparisons between the newer technologies and with standard treatments. Given the lack of high-quality clinical evidence with long-term follow-up and the uncertainty surrounding the assumptions in the economic analysis, the following areas are recommended for further research: RCTs with sufficient follow-up to measure benefits in terms of overall survival to include QoL measurement to establish trade-offs between potential adverse events and benefits of treatment; the identification of prognostic risk factors among men diagnosed with early prostate cancer; QoL studies to compare the utility of health states among patients on active monitoring, patients receiving treatment and the comparable healthy population; the relationship between surrogate end-points and survival; and the adoption of standard definitions for adverse events.

Cost-Benefit Analysis↗
PubMed2001

Sequestration and phosphorylation of the prostaglandin E2 EP4 receptor: dependence on the C-terminal tail.

The prostaglandin E2 (PGE2) EP4 subtype is one of four prostanoid receptors that use PGE2 as the preferred ligand. We have investigated the agonist-mediated regulation of EP4 using a multifaceted approach. Short-term (30 min) agonist challenge of recombinant EP4 expressed in human embryonic kidney 293 cells (EP4-HEK293 cells) with PGE2 (1 microM) resulted in the desensitization of intracellular cyclic AMP (cAMP) accumulation and a reduction in cell surface [3H]PGE2 specific binding sites. These events correlated with sequestration of EP4, as visualized by immunofluorescence confocal microscopy and phosphorylation, as shown by [32P]orthophosphate labeling of the receptor. Stimulation of protein kinase A activity in EP4-HEK293 cells (10 microM forskolin or 1 mM 8-bromo-cAMP) did not induce EP4 desensitization, sequestration, or phosphorylation. In contrast, stimulation of protein kinase C activity (100 nM phorbol 12-myristate 13-acetate) attenuated PGE2-induced adenylyl cyclase activity and increased EP4 phosphorylation, but did not induce sequestration or a reduction in [3H]PGE2 specific binding sites. EP4 receptors containing a third intracellular loop deletion [EP4 (del. 215-263)] or a carboxyl-terminal tail truncation [EP4 (del. 355)] of EP4 were used to demonstrate that the C-terminal tail governs sequestration as well as phosphorylation of the receptor.

Amino Acid Sequence↗
PubMed2001

Pharmaceutical care program for patients with reactive airways disease.

A pharmaceutical care program for patients with reactive airways disease (RAD) is described. A pharmaceutical care program for patients with RAD was developed and implemented at 36 CVS pharmacies. The impact on patient outcomes, pharmacist job satisfaction, and other variables is currently being evaluated in a controlled trial with more than 1100 patient enrollees. Guiding the program are the beliefs that pharmacists must have clinically relevant, patient-specific data to provide appropriate care; that pharmacists must have adequate training to provide pharmaceutical care; that the program must be sensitive to organizational barriers, particularly time demands; and that there must be ongoing support for the program. The program has five components: (1) computer display of patient-specific data for patients enrolled in the study, (2) distribution of tailored patient education materials, (3) use of a resource guide to facilitate the implementation of pharmaceutical care, (4) strategies to reinforce and facilitate the program, and (5) pharmacist training. While developed for community pharmacies, the program is applicable to most ambulatory care pharmacy practices. A pharmaceutical care program for patients with RAD was developed for use in community pharmacies.

Community Pharmacy Services↗
PubMed1999

Evaluation of patient-related and procedure-related factors contributing to pneumothorax following thoracentesis.

OBJECTIVE: To evaluate patient-related and procedure-related risk factors for thoracentesis-related pneumothorax. DESIGN: Prospective, nonrandomized cohort study. SETTING: Pulmonary Special Procedures Unit of a university medical center. METHODS: Thoracentesis using either a 22-gauge, a Boutin, or a Cope needle (depending on availability and operator preference) was performed by the pulmonary faculty or by pulmonary physicians-in-training under faculty supervision. In order to control for effusion size and the presence of loculations, chest radiography and pleural ultrasonography were performed prior to each thoracentesis. Potential patient-related and procedure-related risk factors for pneumothorax were analyzed at the procedure level using the presence or absence of pneumothorax on the postprocedure chest radiograph as the sole outcome variable. RESULTS: Two hundred fifty-five thoracenteses were performed in 205 adult patients (113 men and 92 women; mean age, 58.8+/-18 years) over a 3(1/2)-year period. One hundred fifty procedures were performed for diagnostic purposes, 28 procedures were performed for therapeutic purposes, and 77 procedures were performed for both diagnostic and therapeutic purposes. Based on the radiographic criteria, 152 effusions (60%) were small. Loculations were present in 76 patients (30%). Pneumothoraces occurred in 14 instances (5.4%), and chest tube drainage was required in 2 instances (0.78%). Hospitalization status, critical illness, effusion size or type, presence of loculations, operator, needle type, amount of fluid withdrawn, occurrence of dry tap, and type of thoracentesis were not associated with an increased frequency of pneumothorax. The only predictor variable demonstrating statistical significance was repeated thoracentesis. CONCLUSION: The results of a bivariate analysis suggest that pneumothorax following thoracentesis is a rare event that is not easily predictable when the procedure is performed by experienced operators in a controlled setting.

Chest Tubes↗
PubMed1996

Effects of training in monitoring accuracy on processing speed in mental retardation.

Monitoring accuracy during choice RT allows subjects to maintain fast, safe RT bands and avoid overly fast, unsafe RT bands. 5 retarded adults received trial-by-trial feedback on accuracy over a number of sessions to train monitoring of accuracy and to improve RT performance. Training was introduced according to a multiple-baseline-across-subjects (with reversal) design. Training had no significant effect on subsequent RT performance, suggesting that inefficient monitoring of accuracy may be a structural characteristic of mental retardation.

Adult↗
PubMed1995

Slowness and age: speed-accuracy mechanisms.

Young and older adults' mechanisms of trial-by-trial control of accuracy and choice reaction times (RTs) were compared in 2,000 trials. With equal mean error rates, the older group's correct and error RT were longer, and their within-subject distribution was a linear function of the younger group's. Conditional accuracy functions (CAFs) were very similar in location and shape, with both groups achieving 95% accuracy at the same RT. Combining RT distributions with CAFs showed that the older group did not track their limits as often as the younger group, and they were more careful, having fewer very fast (near random) responses, more average speed responses in long error-free runs, and more slowing following an error. All participants were faster before an error and slower immediately after, but the older participants had coarser RT control. To compensate for this, the older participants produced slower responding to avoid the very fast, high-error part of the CAF.

Adolescent↗
PubMed1994

Computerized handwriting instruction with severely mentally handicapped adults.

The effectiveness of computerized handwriting instruction incorporating modelling of the target letter, corrective feedback and reinforcement contingent upon letter accuracy was examined with severely mentally retarded adults. Assisted by faded prompts on a sheet of paper, subjects wrote the letter 'q' while their handwriting patterns were detected by a digitized graphics tablet linked to a computer. Computerized instruction was introduced for six subjects (mean mental age = 3 years, 10 months) according to a multiple-baseline-across-subjects design. Instruction produced significant improvements in letter quality which were not simply due to the effects of practice. Subjects who had extended practice before being introduced to the computer were less responsive to the information provided by the computer and did not attain the levels of performance accuracy achieved by other subjects.

Adult↗
PubMed1990

Processing speed and mental retardation: deadline procedures indicate fixed and adjustable limitations.

Brewer and Smith (1984) showed that control mechanisms mediating speed-accuracy regulation contribute to retarded-nonretarded differences in processing speed, with poorly controlled trial-to-trial RT adjustments underlying the greater RT variability of retarded individuals. In Experiment 1, response deadlines controlled processing time, thus minimizing the influence of such control mechanisms. The obtained speed-accuracy relations showed that retarded subjects were unable to match nonretarded subjects' accuracy when responding as rapidly, thus indicating structural limitations on processing speed. The results of Experiment 2 showed, however, that significant adjustments to retarded subjects' processing speed--exceeding those produced by practice--are achievable. Extended training at a short deadline led to tighter control of RT adjustments, with substantial improvements in mean RT when subjects transferred to a self-paced RT task.

Adolescent↗
PubMed1989

Social acceptance of mentally retarded children in regular schools in relation to years mainstreamed.

This study examined whether the social status of mainstreamed retarded children among their nonretarded peers improved as a consequence of extended contact. A sociometric questionnaire was administered to the nonretarded classmates of two groups of retarded children mainstreamed for an average of 1.7 yr. and 4 yr., respectively. Social acceptance of retarded children was low relative to their nonretarded peers. However, in contrast with previous research, retarded children did not receive higher social rejection ratings. Acceptance and rejection measures did not indicate any improvement in social status of the retarded children as a result of an extended period of mainstreaming.

Child↗
PubMed1985

Age and individual differences in correct and error reaction times.

Rabbitt (1979, 1981) has argued that the slowing of choice RT performance with old age reflects less sensitive control over speed of responding. Based on the finding that old subjects' errors were as fast as young subjects', whereas their correct responses were much slower, Rabbitt suggested that old subjects often overshoot when trying to increase or reduce response speed. Data collected from a different serial, four-choice RT task in this experiment were not, however, consistent with Rabbitt's account. Error as well as correct RTs were longer in old than in young adults, with both showing similar increases with age. A post hoc examination of the aged subjects' data also indicated important individual differences within aged samples. Some subjects' RTs and error rates were no different from those of the young; other subjects' longer RTs and lower error rates were consistent with an increased emphasis on accuracy.

Adult↗
PubMed1984

How normal and retarded individuals monitor and regulate speed and accuracy of responding in serial choice tasks.

These experiments investigate whether or not differences in the way that retarded and nonretarded individuals monitor and regulate speed and accuracy of responding contribute to the slower and more variable performance of retarded subjects on choice reaction time (RT) tasks. Rabbitt (1979, 1981) suggested that efficient choice RT performance is mediated by subjects tracking increasingly faster RT bands on successive trials until, by making and recognizing errors, they discover those very fast RT levels that should be avoided and those safe bands, just above typical error levels, that should be tracked. Experiments 1A and 1B established that most retarded subjects detect their errors as efficiently as nonretarded controls, a finding that excludes the possibility that retarded subjects do not monitor accuracy efficiently but achieve comparable levels of accuracy by consistently responding within very slow RT bands that minimize likelihood of errors. Experiment 2 showed that while a qualitatively similar trial-by-trial tracking mechanism mediates the performance of both groups, retarded subjects are less efficient at constraining RTs within very fast, but safe, bands. Increasing error probabilities at longer RTs suggest that momentary fluctuations in stimulus discriminability and/or attention are factors affecting RT variability in retarded subjects. The RT patterns for various sequences of correct responses initiated and terminated by errors suggest that the effective past experience (EPEX) guiding trial-by-trial RT adjustments of retarded subjects is short and inadequate, and it was argued that this can account for much of the remaining RT variability contributing to retarded-nonretarded differences. Not only does a short EPEX increase variability by giving rise to long error-free sequences of slower than average RT but also, when combined with occasional specified random fluctuations, it suggests why retarded subjects can achieve, but not sustain, RT levels maintained by nonretarded subjects.

Adult↗