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Biomedical subjects

M M Brown

Publications and source records attributed to M M Brown.

At least 37 records · Page 2Linked to original sources
PubMed2001

Improvement in quality of life from photodynamic therapy: a Canadian perspective.

BACKGROUND: The Treatment of Age-Related Macular Degeneration with Photodynamic Therapy (TAP) Study showed that at 1 year, photodynamic therapy significantly reduced the chances of severe visual loss (15 letters or greater) compared with placebo treatment in patients with "predominantly classic" subfoveal choroidal neovascularization (CNV). We performed a study to determine the expected gain in quality of life associated with photodynamic therapy for the treatment of subfoveal CNV in a Canadian cohort of patients with age-related macular degeneration. METHODS: We created a decision analysis model to determine the incremental gain in quality-adjusted life years (QALYs) associated with photodynamic therapy over placebo over a 2-year period. The analysis was conducted using efficacy data derived from the TAP Study and patient-based utilities collected by means of the time trade-off technique. We conducted one-way and two-way sensitivity analyses to determine the robustness of our model. A Monte Carlo simulation was used to determine whether the observed gain in QALYs with photodynamic therapy was significant. RESULTS: Photodynamic therapy was associated with a relative increase in QALYs of 11.3% compared with placebo. In one-way and two-way sensitivity analyses, the relative increase in quality of life associated with photodynamic therapy ranged from 4.2% to 25.7%. The Monte Carlo simulation showed that the gain in QALYs conferred from photodynamic therapy was statistically significant (p < 0.001). INTERPRETATION: Photodynamic therapy improves the quality of life of Canadians with predominantly classic subfoveal CNV secondary to age-related macular degeneration.

Canada↗
PubMed2001

Quality of life associated with unilateral and bilateral good vision.

OBJECTIVE: To ascertain with patient preference-based methodology whether individuals with good visual acuity (20/20-20/25) in one eye have the same quality of life as individuals with good vision in both eyes. DESIGN: Cross-sectional comparative study. PARTICIPANTS: Consecutive patients seen in comprehensive ophthalmic and vitreoretinal practices with known ocular disease and good visual acuity (20/20 or 20/25) in one or both eyes. METHODS: Standardized patient interview. MAIN OUTCOME MEASURES: Time tradeoff and utility analysis values. RESULTS: The mean time tradeoff utility value in 81 patients with good visual acuity in one eye was 0.89 (standard deviation, 0.17; 95% confidence interval, 0.85-0.93), whereas the mean value in 66 patients with good vision in both eyes was 0.97 (standard deviation, 0.05; 95% confidence interval, 0.97-0.99). The difference between the means of the utility values in these two groups was significant using multiple linear regression (P = 0.001). CONCLUSIONS: From the patient preference-based point of view, individuals with ocular disease and good visual acuity in both eyes appear to have a higher time tradeoff utility value, and thus a better associated quality of life, than those with good visual acuity in only one eye.

Adult↗
PubMed2001

The cost-effectiveness of photodynamic therapy for fellow eyes with subfoveal choroidal neovascularization secondary to age-related macular degeneration.

PURPOSE: Photodynamic therapy (PDT) has recently been demonstrated to be beneficial for the treatment of subfoveal choroidal neovascularization secondary to age-related macular degeneration (AMD). Herein, we determine the cost-effectiveness of PDT for the treatment of subfoveal choroidal neovascularization (CNV) in patients with disciform degeneration in one eye and whose second and better-seeing eye develops visual loss secondary to predominantly classic subfoveal CNV. The analysis was performed from the perspective of a for-profit third-party insurer. DESIGN: Cost-utility Markov models were created to determine the cost-effectiveness of PDT under two different scenarios, by using efficacy data derived from the Treatment of Age-Related Macular Degeneration with Photodynamic Therapy (TAP) Study and patient-based utilities. METHODS: Decision analyses were performed by incorporating data from the TAP Study, expected longevity data, and patient-based utilities. Cost-effective models were then created by incorporating incremental medical costs. Various sensitivity analyses were carried out to determine the robustness of our models. A Monte Carlo simulation was also used to determine whether there was a significant difference in quality-of-life adjusted years (QALYs) gained between PDT therapy and the placebo. RESULTS: For the hypothetical patient whose second and better-seeing eye becomes affected and who has 20/40 vision at baseline in this affected eye (base case 1), PDT was associated with a 10.7% relative increase in their quality-of-life (treatment conferred an additional undiscounted 0.1342 QALYs over a 2-year period). For the hypothetical patient whose second and better-seeing eye becomes affected and who has 20/200 vision at baseline in this affected eye (base case 2), PDT was associated with a 7.8% relative increase in their quality-of-life (treatment conferred an additional undiscounted 0.0669 QALYs over a 2-year period). Sensitivity analysis showed our models were robust and that PDT was usually the dominant treatment choice. Our cost-effective model demonstrated that the cost for a QALY was $86,721 (US dollars discounted at 3%) for base case 1, assuming 5.5 treatments; and $173,984 (USD discounted at 3%) for base case 2. CONCLUSIONS: PDT will cost a third-party insurer $86,721 for an AMD patient with 20/40 vision in the better-seeing eye to obtain one QALY and $173,984 for an AMD patient with 20/200 vision in the better-seeing eye to obtain one QALY. PDT can be considered to be a treatment that is of only minimal cost-effectiveness for AMD patients who have subfoveal CNV in their second and better-seeing eyes and who have good presenting visual acuity at baseline. It is a cost-ineffective treatment for AMD patients who have poor visual acuities in their affected better-seeing eyes.

Aged↗
PubMed2001

A utility analysis correlation with visual acuity: methodologies and vision in the better and poorer eyes.

OBJECTIVE: To ascertain the correlation between visual acuity levels and ophthalmic utility values obtained using time tradeoff and standard gamble utility analysis methodologies. METHODS: Three hundred twenty-five consecutive patients with visual loss to 20/40 or less in at least one eye with predominantly vitreoretinal pathology were evaluated in a cross-sectional fashion using a standardized testing methodology to obtain ophthalmic time tradeoff and standard gamble utility values. Spearman correlation coefficients were employed to correlate the utility values with visual acuity in better seeing and poorer seeing eyes. RESULTS: The Spearman correlation coefficient for time tradeoff utility values and vision in the better seeing eye was 0.455 (p < 0.001), while that for time tradeoff utility values and visual acuity in the poorer seeing eye was 0.268 (p < 0.001). The coefficient for standard gamble utility values and the better seeing eye was 0.371 (p < 0.001), while that for standard gamble utility values and vision in the poorer seeing eye was 0.250 (p < 0.001). CONCLUSIONS: There is a greater correlation between ophthalmic utility values and vision in the better seeing eye, as versus vision in the poorer seeing eye. Time tradeoff ophthalmic utility values demonstrate a greater correlation with vision in the better seeing eye than do standard gamble utility values.

Aged↗
PubMed2001

Managing medication errors by design.

It is estimated that over 7,000 U.S. citizens perish each year from medication errors. The critically ill are among the patient group at highest risk for a medication error. Knowledge is the key to error prevention. Applying information such as risk factors for error commission, new regulatory standards, and approaches to error management will maximize your patients' and your own safety.

Humans↗
PubMed2001

The cost-effectiveness of early vitrectomy for the treatment of vitreous hemorrhage in diabetic retinopathy.

Diabetic vitrectomy has been found to be efficacious for the treatment of vitreous hemorrhage secondary to diabetic retinopathy. The purpose of this study is to determine the cost-effectiveness of early vitrectomy for the management of vitreous hemorrhage secondary to diabetic retinopathy. The analysis was performed from the perspective of a third-party insurer. A cost-utility Markov model was used to determine the cost per quality-adjusted life year (QALY) gained from early versus deferral of vitrectomy. The model used 2-, 3-, and 4-year results from the Diabetic Retinopathy Vitrectomy Study, patient-based utilities, life expectancy data, and incremental medical costs. Early vitrectomy was the dominant strategy and was associated with a gain of 0.41 QALYs over the 57-year expected life span for a hypothetical patient. The cost per additional QALY gained from early vitrectomy treatment was $1910 (US$ discounted at 3%). When sensitivity analyses were performed by varying efficacy probabilities and utilities across their 95% confidence intervals, early treatment was always the dominant strategy. Additionally, even at the extreme sensitivity values, the cost per QALY of early vitrectomy treatment remained under $10,000. Overall, early vitrectomy for the treatment of vitreous hemorrhage secondary to diabetic retinopathy is highly cost-effective.

Adult↗
PubMed2001

Utility values associated with blindness in an adult population.

AIM: To ascertain utility values associated with varying degrees of legal blindness. METHODS: A cross sectional study on three group of patients. There were: (1) 15 patients with complete absence of vision (no light perception) in at least one eye who were asked to assume a scenario of no light perception in the second eye as well, (2) 17 patients with light perception to counting fingers in the better seeing eye, and (3) 33 patients with 20/200-20/400 vision in the better seeing eye. Utility values were measured using the time trade-off and standard gamble methods in each of the three groups. RESULTS: The mean time trade-off utility value for the no light perception group with the theoretical scenario of bilateral absence of light perception was 0.26 (95% CI, 0.19-0.33). The mean utility value for the light perception to counting fingers group was 0.47 (95% CI, 0.33-0.61), and the mean utility value for the 20/200-20/400 group was 0.65 (95% CI, 0.58-0.72). Thus, patients with no light perception in one eye, who were presented with the same scenario in the second eye as well, were willing to trade almost 3 out of every 4 years of remaining life in return for perfect vision in each eye. Those with light perception to counting fingers would trade approximately 1 of 2 remaining years and those with 20/200-20/400 would trade approximately 1 of 3 remaining years. CONCLUSIONS: There is a wide range of utility values associated with legal blindness. The utility value decreases dramatically with perceived total loss of vision (absence of light perception in each eye), compared with counting fingers to light perception vision, indicating that the preservation of even small amounts of vision in patients with legal blindness is critically important to their wellbeing and functioning in life.

Adult↗
PubMed2001

Carotid angioplasty and stenting: are they therapeutic alternatives?

Clinical trials have shown that carotid surgery prevents stroke, but also has a significant risk of morbidity. Percutaneous transluminal angioplasty and stenting (endovascular treatment) can also be used to treat carotid stenosis and have the advantage of avoiding general anaesthesia, cranial nerve injury and the discomforts of surgery. However, there are several potential complications of endovascular treatment, including intimal dissection and plaque rupture, and the long-term consequences of restenosis. More embolic signals are detected during and immediately after carotid angioplasty than during carotid surgery, although a randomised comparison showed no difference in neuropsychological outcomes. The large published case series of carotid endovascular treatment suggest a similar major morbidity rate to surgery, but a small single centre randomised trial reported very poor results in stented patients. Trial data from the much larger Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS) has been more encouraging. Results are available from 504 patients with carotid stenosis randomised to surgery or endovascular treatment. Endovascular treatment was carried out by percutaneous transluminal angioplasty using balloon catheters with the adjunct use of stents in 22%. Audited safety analysis by intention to treat showed no difference in the outcome measure of disabling stroke or death within 30 days of treatment, but the rate of treatment related death or stroke lasting more than seven days was relatively high in both groups (endovascular treatment 10%, surgery 9.9%). Minor complications, particularly cranial nerve palsy and haematoma were significantly less frequent in the endovascular group, but restenosis was significantly more common. Both treatments appeared equally effective at preventing stroke recurrence with no difference in the rates of stroke during follow-up for up to 3 years. Techniques of carotid angioplasty and stenting improved over the course of CAVATAS, and new designs of stents, filters and protection devices are being developed. Further large, multicentre randomised trials are therefore being started which will evaluate primary stenting of carotid artery stenosis in patients with cerebrovascular disease. Until the results are available, it will remain uncertain whether angioplasty and stenting are safe and effective therapeutic alternatives to surgery.

Angioplasty, Balloon↗
PubMed2001

Physician manpower and health care expenditures in the United States: a thirty-year perspective.

Data gathered on the number of physicians and health care costs in the United States over a 30-year period from 1970 through 1999 were correlated and analyzed using bivariate linear regression. The rise in the number of practicing physicians theoretically predicts 96 percent of the variability in rise of total U.S. health expenditures, 96 percent of the variability in rise of physician service expenditures, 98 percent of the variability in rise of hospital service expenditures, and 86 percent of the variability in rise of prescription pharmaceutical expenditures. If the rate of growth in the number of physicians continues unchanged in the current fee-for-service climate, the model herein predicts that the growth in health care costs will likely continue to rise substantially faster than the rate of growth of the U.S. population and the rate of inflation. The addition of nonphysician providers with the same clinical privileges will likely exacerbate the situation of rapidly escalating medical costs. It is also possible that the excess number of physicians and other health care providers with the same clinical privileges as physicians may decrease the overall quality of health care. Reducing the rise in the number of physicians and nonphysician practitioners may help to decrease overall health care expenditures and improve overall quality of health care in the United States.

Allied Health Personnel↗
PubMed2001

The reproducibility of ophthalmic utility values.

PURPOSE: Utility values have been used in the ophthalmic literature to measure the quality of life associated with a health state. By convention, a utility value of 1.0 is associated with perfect health, and a value of 0.0 is associated with death. Construct validity of utility values has been demonstrated, particularly in regard to decreasing utility values as the vision decreases in the better seeing eye, but long-term test-retest reliability has not been demonstrated. The purpose of this study was to demonstrate the test-retest reliability of ophthalmic utility values. METHODS: One hundred fifteen patients with ophthalmic diseases and stable visual acuity underwent time trade-off utility analysis with retesting at various intervals ranging from 1 month to 2 years. The results were analyzed using the Wilcoxon signed rank test. The study was designed to have an 50% power, using a two-sided alpha of 5%, to be able to detect a 10% difference between the test and retest groups. RESULTS: The mean time from testing to retesting was 0.87 years, with a median time of 1.0 year and range of 1 month to 2 years. The mean utility value in the test group was 0.766 (SD = .21; 95% CI, 0.730-0.802), while the mean utility value in the retest group was 0.763 (SD = .22; 95% CI, 0.724-0.802). The difference between the means of the test-retest groups was not significant (P = .99). The intraclass correlation between the initial and follow-up utility scores was .5246 (P < .00005). CONCLUSIONS: Ophthalmic utility values appear to have good test-retest reliability over prolonged periods of time. This information is important because it gives researchers increased confidence in the validity of basic tools for ophthalmic cost-effective (cost-utility) analyses.

Adult↗
PubMed2000

Utility values and age-related macular degeneration.

OBJECTIVE: To ascertain the utility values associated with age-related macular degeneration and varying degrees of visual loss. DESIGN: A cross-sectional study. PARTICIPANTS: Eighty white patients with unilateral or bilateral age-related macular degeneration in 1 or both eyes, and visual loss to a minimum of the 20/40 level in at least 1 eye. MAIN OUTCOME MEASURES: Utility values were measured in 5 groups according to the visual acuity in the better-seeing eye, 1 (20/20 to 20/25), 2 (20/30 to 20/ 50), 3 (20/60 to 20/100), 4 (20/200 to 20/400), and 5 (counting fingers to light perception), using the time trade-off and the standard gamble methods. Conventionally assigned anchor utility values were 1.0 for perfect health and 0.0 for death. RESULTS: The mean utility value for the total group with age-related macular degeneration was 0.72 (95% confidence interval [CI], 0.66-0.78) using the time trade-off method and 0.81 (95% CI, 0.76-0.86) using the standard gamble method. Using the time trade-off method correlated with the visual acuity in the better-seeing eye, the results were as follow: group 1, 0.89 (95% CI, 0.82-0.96), group 2, 0.81 (95% CI, 0.73-0.89), group 3, 0.57 (95% CI, 0.47-0.67), group 4, 0.52 (95% CI, 0.38-0.66), and group 5, 0.40 (95% CI, 0.29-0.50). Thus, those patients in group 1 were willing to trade 11% of their remaining lifetime in return for perfect vision in each eye, whereas those in group 5 were willing to trade 60% of their remaining lifetime in return for perfect vision in each eye. CONCLUSION: Age-related macular degeneration causes a substantial decrease in patient utility values and is highly dependent on the degree of visual loss in the better-seeing eye.

Aged↗
PubMed2000

A gene therapy approach to enhance the targeted radiotherapy of neuroblastoma.

BACKGROUND: The aims of this study were to determine whether the introduction and expression of the noradrenaline transporter (NAT) gene into NAT-negative neuroblastoma cell lines would make them amenable to targeted radiotherapy using [(131)I]MIBG. PROCEDURE: Neuroblastoma cell lines were transfected with a eukaryotic expression vector containing the bovine noradrenaline transporter cDNA under the expression of the CMV promoter. Stable transfectants were created by selection in geneticin (G418) and were characterised for their MIBG uptake ability and susceptibility to [(131)I]MIBG therapy. RESULTS: The cell line SK-N-MC, which normally shows no ability to take up MIBG, was successfully transfected with bNAT. SK-N-MC.bNAT transfectants exhibited uptake and release kinetics similar to those of the natural NAT-expressing cell line SK-N-BE(2c). Levels of [(131)I]MIBG uptake were 33% of those of the highest naturally NAT-expressing cell line SK-N-BE(2c). Growth delay assays using multicellular spheroids indicated that this degree of [(131)I]MIBG uptake was sufficient to inhibit growth at radioactive concentrations of 4 Mbq/ml. CONCLUSIONS: These results demonstrate the feasibility of combining gene therapy with targeted radiotherapy to enhance uptake, and hence radiation dose, to neuroblastoma tumours using [(131)I]MIBG. With the appropriate delivery vehicle and tumour-specific control of expression, the introduction of noradrenaline transporter molecules may be a viable means of enhancing the response of neuroblastoma tumours to [(131)I]MIBG therapy.

Carrier Proteins↗
PubMed2000

Percutaneous transluminal angioplasty and stenting for carotid artery stenosis.

BACKGROUND: Carotid percutaneous transluminal angioplasty may be a useful non-surgical procedure for carotid stenosis, particularly for lesions not suitable for surgery. OBJECTIVES: The objective of this review was to assess the effect of carotid percutaneous transluminal angioplasty compared with carotid endarterectomy (in patients suitable for surgery) or medical therapy (in patients not suitable for surgery). SEARCH STRATEGY: We searched the Cochrane Stroke Groups trials register (to August 1997). We contacted researchers in the field and balloon catheter manufacturers. SELECTION CRITERIA: Randomised trials of carotid percutaneous transluminal angioplasty (with or without stenting) compared with carotid endarterectomy, or percutaneous transluminal angioplasty plus best medical therapy compared with best medical therapy alone, in people with carotid artery stenosis (symptomatic or asymptomatic). DATA COLLECTION AND ANALYSIS: Two reviewers independently applied the inclusion criteria. MAIN RESULTS: No completed trials were found. Two trials are underway. REVIEWER'S CONCLUSIONS: There is no evidence as yet to assess the relative effects of carotid percutaneous transluminal angioplasty in people with carotid stenosis.

Angioplasty, Balloon↗
PubMed2000

Percutaneous transluminal angioplasty and stenting for vertebral artery stenosis.

BACKGROUND: Surgery to the vertebrobasilar region is difficult and not considered in most centres. Furthermore, the basilar artery, with its penetrating branches supplying the brain stem, is likely to be extremely hazardous to dilate. OBJECTIVES: The objective of this review was to assess the effect of vertebral artery percutaneous transluminal angioplasty combined with medical care, compared to medical care alone, in people with vertebrobasilar artery disease. SEARCH STRATEGY: We searched the Cochrane Stroke Groups trials register (to August 1997). We contacted researchers in the field and balloon catheter manufacturers. SELECTION CRITERIA: Randomised trials of vertebral percutaneous transluminal angioplasty (with or without stenting) combined with best medical therapy, compared with best medical therapy alone, in people with symptomatic vertebral artery stenosis. DATA COLLECTION AND ANALYSIS: Two reviewers independently applied the inclusion criteria. MAIN RESULTS: No completed trials were found. One trial is underway, although few patients with vertebrobasilar disease have been recruited. REVIEWER'S CONCLUSIONS: There is no evidence as yet to assess the effects of percutaneous transluminal angioplasty for vertebral artery stenosis.

Angioplasty, Balloon↗