A comparison of the reproducibility and the sensitivity to change of visual analogue scales, Borg scales, and Likert scales in normal subjects during submaximal exercise

OBJECTIVE

To assess which subjective scale, the visual analogue scale (VAS), the Borg CR10 (Borg) scale, or the Likert scale (LS), if any, is decidedly more reproducible and sensitive to change in the assessment of symptoms.

DESIGN

Prospective clinical study.

SETTING

Exercise laboratory.

PARTICIPANTS

Twenty-three physically active male subjects (mean +/- SD age of 30 +/- 4 years old) were recruited.

INTERVENTION

Each subject attended the exercise laboratory on four occasions at intervals of 1 week. Three subjective scales were used: (1) the VAS (continuous scale); (2) the Borg scale (12 fixed points); and (3) the Likert scale (LS; 5 fixed points). Four identical submaximal tests were given (2 min at 60% maximum oxygen uptake [VO(2)max] and 6 min at 70% VO(2)max). Two tests were undertaken to assess the reproducibility of scores that were obtained with each subjective scale. Two other tests were undertaken to assess the sensitivity of each scale to a change in symptom perception: a double-blind treatment with propranolol, 80 mg, (ie, active therapy; to increase the sensation of breathlessness and general fatigue during exercise) or matching placebo. The subjective scale scores were measured at 1 min 30 s, 5 min 30 s, and 7 min 15 s of exercise. Reproducibility was defined as the proportion of total variance (ie, between-subject plus within-subject variance) explained by the between-subject variance given as a percentage. Sensitivity was defined as the effect of the active drug therapy over the variation within subjects.

RESULTS

Overall, the VAS performed best in terms of reproducibility for breathlessness and general fatigue, with reproducibility coefficients as high as 78%. For sensitivity, the VAS was best for breathlessness (ratio, 2.7) and the Borg scale was most sensitive for general fatigue (ratio, 3.0). The relationships between the respective psychological and physiologic variables were reasonably stable throughout the testing procedure, with overall typical correlations of 0.73 to 0.82

CONCLUSION

This study suggests that subjective scales can reproducibly measure symptoms during steady-state exercise and can detect the effect of a drug intervention. The VAS and Borg scales appear to be the best subjective scales for this purpose.

EC4 European syllabus for post-graduate training in clinical chemistry. Version 2--1999. European Communities Confederation of Clinical Chemistry, EC4 Register Commission

In modern medicine the undeniable value and indispensability of scientific investigations are now universally recognized both for diagnostic purposes and monitoring of disease and in basic epidemiology. The direct treatment of patients is an undeniable task of doctors in medicine. Progress in laboratory science is largely the result of contributions by scientists with an adequate education and specialisation in the field, i.e. by clinical chemists. Clinical laboratory science has developed on a broad front throughout the European Community, resulting in significant differences in what constitutes a national clinical chemistry service in each state. Clinical chemistry is the medical discipline devoted to obtain, explore and employ chemical knowledge and chemical methods of investigation, in order to procure knowledge about normal and abnormal chemical processes in man. These processes are studied on a general level, in order to get insight into human health and disease, and on a patient-specific level for diagnostic or monitoring purposes. The delimitation of clinical chemistry varies from country to country, since there is no sharp boundary to haematology, immunology, molecular biology and microbiology. One of the main tasks of the clinical chemist is direction and supervision of a laboratory department in a hospital or health service (public or private), where his role involves bridging the gap between rapidly developing laboratory science and technology and the growing knowledge on characteristics of disease. He must possess fundamental biochemical knowledge and have the ability to use this knowledge most appropriately as applied to clinical requirements, i.e. diagnosis of disease and planning and monitoring of therapy. Apart from providing a competent laboratory service, the clinical chemist must be able to function as a consultant to his clinical colleagues and liaise with them in the interpretation of laboratory results. His advice and professional consultation have at least three aspects, i.e. choosing the most appropriate laboratory investigation in a certain case, ensuring that the analyses are performed in the best possible way and correctly reported and, finally, providing information and (most important) interpretation on the significance and consequences of the laboratory data obtained. As the results of laboratory investigations and the consultation of the clinical chemist have a direct and important influence on the treatment of the patient, it is to the benefit of the public that the profession of the clinical chemist is duly regulated.

Measuring physician job satisfaction in a changing workplace and a challenging environment. SGIM Career Satisfaction Study Group. Society of General Internal Medicine

BACKGROUND

Changes in the demographic, specialty, and employment sector composition of medicine have altered physicians' jobs, limiting autonomy and reducing morale. Because physician job satisfaction has been linked to clinical variables, better measurement might help to ameliorate conditions linked to medical disaffection, possibly improving health care.

OBJECTIVE

To document conceptual development, item construction, and use of content experts in designing multidimensional measures of physician job satisfaction and global satisfaction scales for assessing physicians' job perceptions across settings and specialties.

DESIGN

Using previous research, physician focus groups, secondary analysis of survey data, interviews with physician informants, and a multispecialty physician expert panel, distinct job facets and statements representing those facets were developed.

RESULTS

Facets from previously validated instruments included autonomy, relationships with colleagues, relationships with patients, relationships with staff, pay, resources, and status. New facets included intrinsic satisfaction, free time away from work, administrative support, and community involvement. Physician status items were reconfigured into relationships with peers, patients, staff, and community, yielding 10 hypothetical facets. Global scales and items were developed representing satisfaction with job, career, and specialty.

CONCLUSIONS

A comprehensive approach to assessing physician job satisfaction yielded 10 facets, some of which had not been previously identified, and generated a matching pool of items for subsequent use in field tests.

Refining the measurement of physician job satisfaction: results from the Physician Worklife Survey. SGIM Career Satisfaction Study Group. Society of General Internal Medicine

BACKGROUND

Physician job satisfaction has been linked to various patient care and health system outcomes. A survey instrument that concisely measures physicians' satisfaction with various job facets can help diverse stake-holders to better understand and manage these outcomes.

OBJECTIVE

To document the development and validation of a multidimensional physician job satisfaction measure and separate global satisfaction measures.

DESIGN

Self-administered questionnaire: Physician Worklife Survey (PWS).

SUBJECTS

A pilot study employed a national American Medical Association Masterfile sample of US primary care physicians and random samples from four states. Responses (n = 835; 55% return rate) were randomly assigned to developmental (n = 560) or cross-validation (n = 275) samples. A national sample (n = 2,325; 52% response rate) of physicians was used in a subsequent validation study.

RESULTS

A 38-item, 10-facet satisfaction measure resulting from factor and reliability analyses of 70 pilot items was further reduced to 36 items. Reliabilities of the 10 facets ranged from .65 to .77. Three scales measuring global job, career, and specialty satisfaction were also constructed with reliabilities from .84 to .88. Results supported face, content, convergent, and discriminant validity of the measures.

CONCLUSIONS

Physician job satisfaction is a complex phenomenon that can be measured using the PWS.

Increasing the impact of cardiological treatments. How best to reduce deaths

AIMS

To determine the extent to which increases in the uptake of effective treatments could further reduce coronary heart disease mortality in Scotland.

METHODS AND RESULTS

A cohort-based mortality model combining effectiveness data from published meta-analyses with available information on uptake of all coronary heart disease treatments in all patient categories in Scotland (population 5.1 million). In 1994, medical and surgical coronary disease treatments prevented or postponed an estimated 2722 deaths (minimum estimate 1373, maximum estimate 5986). Increasing treatment uptake to 100% of all eligible patients was considered unrealistic. Increasing uptake to 80% would have prevented or postponed a further 4078 deaths (39% from increases in secondary prevention therapies, 29%, 13%, 10% and 9% from the treatments of heart failure, acute myocardial infarction, hypertension and angina respectively).

CONCLUSIONS

Many eligible patients are currently not receiving treatment that is effective in reducing coronary heart disease mortality. Increasing treatment uptake could prevent or postpone a further 4080 deaths each year in Scotland, approximately, more than doubling the present benefit from treatment. By implication, about 30 000 additional deaths could be prevented, annually, in the U.K. Comparable symptom and morbidity benefits might also be expected. Future clinical audit activities should focus particularly on secondary prevention and heart failure treatments.

The health economics of the treatment of hyperlipidemia and hypertension

In the current economic climate it is important to demonstrate that healthcare resources are being used efficiently. As a consequence, pharmacoeconomic analyses are invaluable for assessing the cost-effectiveness of new therapeutic strategies. A condition with recurrent morbid events that are costly to treat provides the greatest potential for cost savings. In contrast, there is less opportunity to redeem original treatment costs when a condition is associated with infrequent and inexpensive morbidity. Consequently, treatment strategies that have a rapid onset and substantial impact on disease progression are likely to be the most highly cost-effective forms of therapy. Elevated blood pressure in the elderly and established coronary heart disease (CHD) are both associated with high rates of costly cardiovascular events (eg, stroke, myocardial infarction, and heart failure). Clinical trials have shown that administration of blood-pressure-lowering agents to elderly hypertensives and the treatment of hypercholesterolemia with statins in the secondary prevention of CHD are highly effective strategies for reducing this morbidity. Pharmacoeconomic analyses of the data from these clinical trials now provide an additional assessment of their cost-effectiveness. The results of these analyses suggest that blood-pressure-lowering therapy for the elderly and the use of statins to control hypercholesterolemia in patients at high risk of CHD are extremely cost-effective, compared with many other routine medical interventions.

Candesartan in heart failure--assessment of reduction in mortality and morbidity (CHARM): rationale and design. Charm-Programme Investigators

BACKGROUND

Chronic heart failure (CHF) is an increasing burden to health care. Pharmacological treatment with angiotensin-converting enzyme (ACE) inhibitors and beta blockers improve survival and reduce hospitalizations in patients with low left ventricular ejection fraction (LVEF). Despite these therapies, morbidity and mortality remains problematic. Furthermore, 30% to 50% of patients with CHF have a preserved LVEF. It is not known if treatments are of benefit in this group.

DESIGN

Candesartan in Heart Failure-Assessment of Reduction in Mortality and Morbidity (CHARM) is a program designed to investigate the clinical usefulness of the long-acting angiotensin II type 1 receptor blocker, candesartan cilexetil, in a broad spectrum of patients with symptomatic heart failure. Patients with systolic dysfunction, tolerant or intolerant to an ACE-inhibitor, and patients with preserved systolic function are included. Specifically, the CHARM program consists of 3 independent, parallel, placebo-controlled studies in patients with (1) LVEF less than or equal to 40%, ACE-inhibitor treated (n = 2,300); (2) LVEF less than or equal to 40%, ACE-inhibitor intolerant (n = 1,700); (3) LVEF greater than 40%, not treated with ACE inhibitors (n = 2,500). The 3 studies will be combined to evaluate the effect of candesartan cilexetil on all-cause mortality in the broad spectrum of symptomatic heart failure. The primary objective in each trial is to evaluate the effects on the combined endpoint of cardiovascular mortality or CHF hospitalization. Other endpoints include the effects on myocardial infarction, all-cause hospitalization, and resource utilization. CHARM is intended to randomize 6,500 patients with symptomatic heart failure from 26 countries in Europe, the United States, Canada, South Africa, and Australia. The CHARM program started to enroll patients in March 1999. The follow-up period is a minimum of 2 years. The study is expected to end in the third quarter of 2002.

A review of quality-of-life evaluations in patients with congestive heart failure

The factors that may lead to an impaired quality of life in congestive heart failure (CHF) are physical symptoms, psychological problems, treatment adverse effects and social limitation. There are now several general and disease-specific quality-of-life (QOL) questionnaires which have been used to measure treatment effects in clinical trials in CHF. We review the design and validation of both generic and disease-specific QOL questionnaires which have been used in clinical trials in CHF. We then evaluate the performance of these QOL questionnaires in recent clinical trials in CHF in relation to other outcome measures. We conclude that there are important differences between these QOL questionnaires. The choice of a QOL questionnaire is relevant to both patient compliance and clinical outcomes in CHF trials. The 36-Item Short Form (SF-36) Health Survey, a generic QOL questionnaire, and the Minnesota Living with Heart Failure questionnaire, a disease-specific QOL questionnaire, have returned informative data in most trials in which they have been used. QOL questionnaires require further development if this important outcome is to be reliably measured in future clinical trials in CHF.

Contemporary management of patients with left ventricular systolic dysfunction. Results from the Study of Patients Intolerant of Converting Enzyme Inhibitors (SPICE) Registry

AIMS

The reported prevalence of angiotensin-converting enzyme (ACE) inhibitor use in patients with heart failure varies considerably. Recent reports suggest that many patients who could benefit from such therapy are not receiving ACE inhibitors. The Study of Patients Intolerant of Converting Enzyme Inhibitors (SPICE) Registry was established to understand better the demographics, characteristics, and contemporary use of ACE inhibitors in an international registry.

METHODS AND RESULTS

Between August 1996 and April 1997, each of 105 study centres from eight countries in North America and Europe was invited to review retrospectively the medical records of 100 consecutive patients with left ventricular ejection fractions </=35%. The median age of the 9580 Registry patients was 66 years, 26% were women, the median ejection fraction was 27%, and the primary aetiology of left ventricular dysfunction was ischaemic (63%). Eighty percent of patients were receiving ACE inhibitors. The most common reason for non-use of ACE inhibitors was intolerance (9%).

CONCLUSION

The SPICE Registry provides a contemporary description of the demographics and management of patients with documented left ventricular systolic dysfunction. The contemporary use of ACE inhibitors (80%) appears to be higher than previously reported and the main reason for non-use is perceived intolerance (9%).

The reproducibility of symptoms during a submaximal exercise test in chronic heart failure

AIMS

The aim of this study was to evaluate the use of a submaximal test with a symptom limited endpoint and to measure the reproducibility of symptoms in patients with CHF.

METHODS

Ten patients with chronic heart failure were studied. Based on two maximal treadmill tests an individual protocol using a constant work rate at a submaximal intensity was derived. The projected maximum treadmill time for the constant workrate was between 8 and 17 min. Tests were carried out 1, 2, 4 and 6 weeks after the maximum tests. Every 2.5 min during the submaximal test patients recorded their symptoms of breathlessness and fatigue using computer automated visual analogue (VAS) and Borg CR10 scales. The measure of reproducibility used was the proportion of total variability explained by the between subject variability.

RESULTS

Using the VAS scale, general fatigue was reasonably reproducible ranging from 77-86%. For VAS breathlessness reproducibility ranged from 66% to 83%. Reproducibility for breathlessness and fatigue for the Borg CR10 scale was much lower than the VAS scale. Reproducibility for the treadmill times was 51% but increased to 76% if one test of one subject was excluded.

CONCLUSIONS

The use of the VAS during submaximal exercise offers a useful means of evaluating symptoms in CHF and potentially their response to treatment. These findings show that individual submaximal protocols can be easily prescribed for CHF patients. Using such an approach, clinically desirable tests lasting around 12 min can be developed. These tests are reasonably reproducible and may provide a useful means of assessing patient disability and the impact of treatment.

The West of Scotland coronary prevention study: economic benefit analysis of primary prevention with pravastatin

OBJECTIVE

To estimate the economic efficiency of using pravastatin to prevent the transition from health to cardiovascular disease in men with hypercholesterolaemia.

DESIGN

Economic benefit analysis based on data from the West of Scotland coronary prevention study. Treatment specific hazards of developing cardiovascular disease according to various definitions were estimated. Scottish record linkage data provided disease specific survival. Cost estimates were based on extracontractual tariffs and event specific average lengths of stay calculated from the West of Scotland coronary prevention study.

SUBJECTS

Men with hypercholesterolaemia similar to the subjects in the West of Scotland coronary prevention study.

MAIN OUTCOME

Cost consequences, the number of transitions from health to cardiovascular disease prevented, the number needed to start treatment, and cost per life year gained.

RESULTS

If 10,000 of these men started taking pravastatin, 318 of them would not make the transition from health to cardiovascular disease (number needed to treat, 31.4), at a net discounted cost of 20m Pounds over 5 years. These benefits imply an undiscounted gain of 2,460 years of life, and thus 8121 Pounds per life year gained, or 20,375 Pounds per life year gained if benefits are discounted. Restriction to the 40% of men at highest risk reduces the number needed to treat to 22.5 (5601 Pounds per life year gained (undiscounted) and 13,995 Pounds per life year gained (discounted)).

CONCLUSIONS

In subjects without evidence of prior myocardial infarction but who have hypercholesterolaemia, the use of pravastatin yields substantial health benefits at a cost that is not prohibitive overall and can be quite efficient in selected high risk subgroups.

Antigenic and immunogenic properties of synthetic peptide-based T-cell determinant polymers

Presentation of T-cell determinants to the immune system in multimeric form has clear advantages and the production of synthetic peptide-based polymers using the solubilisable KS resin described by Goddard et al. [1] provides a method of assembling such polymers and also offers the means for making heteropolymers. The present study investigates the potential of polymeric synthetic peptide constructs in eliciting proliferative T-cell responses to determinants of the influenza virus hemagglutinin. The induction of vigorous CD4+ T-cell immunity was achieved with a polymeric construct containing two different T-cell determinants. The data presented here also highlight the fact that distancing the determinant from the support backbone with appropriate amino acid residues is an important consideration for the success of these polymeric immunogens. This approach may be readily applied in other systems where induction of helper T-cell responses are required.

An economic analysis of the Survival and Ventricular Enlargement (SAVE) Study. Application to the United Kingdom

Recent studies have shown that ACE inhibitors reduce morbidity and mortality after myocardial infarction (MI). While these trials have obvious clinical implications, the widespread introduction of a new treatment for a condition as common as MI also has clear cost implications. The results of the post-MI studies with ACE inhibitors suggest that restricted use of treatment-in high-risk patients-is likely to be most cost effective, whereas treatment of all MI survivors, many of whom are at low risk, will be least cost effective. An approach somewhere in between may maximise clinical benefit at an acceptable cost. Economic analysis may help in deciding how these drugs might be best used after MI. We have conducted a cost-effectiveness and cost-utility analysis of the Survival and Ventricular Enlargement (SAVE) study, which reported the benefit of ACE inhibitors in intermediate-risk patients. Assuming all MI survivors require measurement of left ventricular function before selection for treatment (the approach used in the SAVE study), the incremental cost per life-year gained (LYG), over 4 years, using prophylactic captopril is approximately 10000 pounds sterling (Pounds) [1994 to 1995 values]. The cost per quality-adjusted life-year (QALY) is similar. These incremental cost per LYG and cost per QALY ratios compare favourably with other commonly used symptomatic and prophylactic treatments, and argue for extending post-MI use of ACE inhibitors to intermediate-as well as high-risk patients.

Captopril and norepinephrine-induced hypertrophy and haemodynamics in rats

We wished to determine whether pretreatment with captopril, an angiotension-converting enzyme (ACE) inhibitor, modified the myocardial and haemodynamic consequences of chronic administration of norepinephrine (NE) in rats. Administration of NE (0.15 mg kg(-1) h(-1) by an osmotic minipump implanted subcutaneously for 28 days) resulted in left but not right ventricular hypertrophy. Captopril (250 but not 52 mu g kg(-1) h(1) administered for 28 days) significantly attenuated the development of left ventricular hypertrophy (weight of left ventricle to body weight ratio was 0.46 +/- 0.01 0.57 +/- 0.02, 0.53 +/- 0.02, and 0.51 +/- 0.01 for vehicle, NE, and NE plus low and high dose of captopril, respectively). Chronic administration of NE caused significant increases in systolic arterial blood pressure (BP: 194 +/- 11 vs. 130 +/- 6 mm Hg), systolic left ventricular pressure, heart rate (HR: 458 +/- 13 vs. 389 +/- 15 beats/min) and dP dt(-1)(max) P(-1), an index of myocardial contractility (202 +/- 29 vs. 91 +/- 3 s(-1)). Captopril (250 mu g kg(-1) h(-1) for 28 days) significantly reduced diastolic arterial BP (from 86 +/- 6 to 53 +/- 3 mm Hg). Concomitant administration of this dose of captopril together with NE prevented the NE-induced increase in systolic arterial BP but did not modify the increases in HR or dP dt(-1) max P(-1) (261 +/- 41 and 202 +/- 29 s(-1) in captopril and NE vs. NE-alone groups). Acute administration of NE (0.1-10 mu g kg(-1) intravenously, i.v.) produced less marked increases in cardiac contractility and in arterial BP in rats chronically pretreated with NE or NE plus captopril than in animals receiving vehicle or captopril alone. Chronic administration of NE and/or captopril did not significantly modify the haemodynamic effects of the acute administration of calcium chloride. We conclude that administration of captopril at 250 but not 52 mu g kg(-1) h(-1) for 28 days attenuates NE-induced cardiac hypertrophy and that this effect is associated with a decrease in systolic arterial BP. Captopril did not modify the reduced effects of acutely administered NE in rats treated with NE for a prolonged period.

The pharmacoeconomics of ACE inhibitors in chronic heart failure

Because heart failure is common and disabling, patients with this condition utilise healthcare resources to a considerable extent. In particular, patients with heart failure frequently require hospital admission, and inpatient care is often protracted. Patients with the most advanced stages of heart failure make the greatest demands on the healthcare system. Expenditure related to the consumption of healthcare resources accounts for the 1 to 2% of total healthcare spending related to heart failure. Between two-thirds and three-quarters of this is due to the costs of hospital care. ACE inhibitors reduce progression of heart failure and also reduce the need for hospitalisation by approximately 30%. In so doing, these drugs substantially or totally offset their cost and the cost of extended life. Five independent economic analyses collectively show ACE inhibitors, at worst, to be very cost effective (in comparison to other cardiovascular therapies), cost neutral or to lead to overall cost savings when used to treat heart failure.

Effects of chronic norepinephrine administration on cardiac function in rats

We assessed the changes in the contractile response of rat hearts in vivo after chronic exposure to a range of doses of norepinephrine (NE) and determined whether free radical production played a role in these changes. Osmotic minipumps were implanted subcutaneously (s.c.) in male rats and delivered either NE (0.15-0.35 mg/kg/h) or acid saline for 10-28 days. The animals were then anaesthetised and prepared for haemodynamic measurement, and dose-response curves to acutely administered NE and calcium chloride were constructed. We analysed plasma for evidence of free radical activity by measuring the levels of thiobarbituric acid-reactive substances (TBARS). All doses of NE studied produced left, but not right, ventricular hypertrophy. Treatment with 0.25 mg/kg/h NE for 28 days produced signs of distress and, by 10 days, treatment with 0.35 mg/kg/h resulted in 33% mortality. Treatment with the two lower doses, but not the highest dose, of NE resulted in increases in basal left ventricular (LV) maximum rate of pressure generation and a marked increase in systolic, but not diastolic, arterial blood pressure (SBP, DBP). All doses of NE caused reduced responses to acutely administered NE but no marked change in the response to calcium chloride. Levels of plasma free radicals were increased only with the highest dose of NE. Over the concentration range studied, chronic administration of NE to rats causes beta-adrenoceptor downregulation and free radical production was associated only with the administration of a dose of NE that resulted in high mortality.

Effect of captopril, enalaprilat and mercaptopropionyl glycine (MPG) on the oxidative activity of human isolated neutrophils

1. Neutrophil NADPH oxidase produces the superoxide anion (O2-) anion radical from oxygen. The thiol containing ACE inhibitor, captopril has been reported to inhibit isolated NADPH oxidase. The above effect of captopril, if present in intact cells, could contribute to the ability of this drug to alleviate neutrophil-mediated tissue damage. We have, therefore, investigated the effect of captopril on the oxidative activity of intact human isolated neutrophils. 2. The effects of captopril on neutrophil oxidative activity were compared with those of enalaprilat (a non-thiol ACE inhibitor) and N-mercaptopropionyl glycine (MPG) (a simple thiol). 3. The oxidative response of PMA-stimulated neutrophils measured by lucigenin chemiluminescence was not affected by any of these test agents. The thiol captopril and MPG (but not enalaprilat) caused an initial delay in luminol chemiluminescence production by PMA-stimulated neutrophils. 4. Captopril and MPG (but not enalaprilat) increased, rather than decreased oxygen uptake, when added to PMA-stimulated neutrophils. Thiol oxidation was determined to be, at least partly, responsible for the excess oxygen uptake observed. 5. NADPH oxidase activity in intact neutrophils was not affected by captopril, MPG or enalaprilat. The inhibition of NADPH oxidase activity is unlikely to contribute to the therapeutic effects of captopril and other thiols.

Does luminol chemiluminescence detect free radical scavengers?

Thiol compounds have been reported to abolish hypoxanthine/xanthine oxidase induced luminol chemiluminescence and this effect has been attributed to scavenging of superoxide (O2-)/(H2O2) produced from hypoxanthine/xanthine oxidase. Yet other workers have reported that thiol compounds have shown little, if any, reactivity towards O2-/H2O2. The aim of this study was to examine the discrepancy between these two sets of findings further. Captopril (a thiol angiotensin-converting enzyme (ACE) inhibitor) and MPG (a simple thiol) were observed to abolish hypoxanthine/xanthine oxidase induced chemiluminescence. The reactivity of captopril and MPG towards O2-/H2O2 was then determined by measurement of thiol oxidation in captopril and MPG after their incubation with hypoxanthine/xanthine oxidase. Incubation (at 10 min, 37 degrees C) with 4 mM hypoxanthine/0.03 u ml-1 xanthine oxidase resulted in 7% and 20% thiol oxidation in captopril and MPG (at 1 mM) respectively. Captopril and MPG, therefore, appeared to be ineffective scavengers of oxidants produced by hypoxanthine/xanthine oxidase. Captopril and MPG also did not affect urate production or oxygen consumption by xanthine oxidase which indicated that captopril and MPG quench luminol chemiluminescence by a mechanism that excludes the inhibition of xanthine oxidase. Hypoxanthine/xanthine oxidase induced luminol chemiluminescence may, therefore, be an unsuitable method for measuring free radical scavenging activity by drugs.

The effect of angiotensin-converting enzyme inhibitors on human neutrophil chemotaxis in vitro

1. Myocardial 'reperfusion injury' has been partly attributed to the production of free radicals which are cytotoxic towards cells. Neutrophils are recruited by ischaemic tissue and are one source of free radicals. Angiotensin-converting enzyme (ACE) inhibitors can reduce 'reperfusion injury' and we decided to determine if ACE inhibitors might contribute to this effect by inhibiting neutrophil chemotaxis. 2. The effects of captopril (a thiol containing ACE inhibitor) and enalaprilat (a nonthiol ACE inhibitor) and N-mercaptopropionyl glycine (MPG) (a simple thiol) on neutrophil chemotaxis were tested in an in vitro Boyden chamber assay. 3. The chemotactic response of human neutrophils to fMLP was reduced by 27.6% with MPG (n = 8; P < 0.05), by 13.2% with enalaprilat (n = 8; P = 0.075) and by 5.2% with captopril (n = 8; P = 0.66) at 5 microM (therapeutic concentration.) 4. Neutrophil chemotaxis was significantly decreased with 50 microM and 500 microM MPG and enalaprilat and 500 microM captopril. 5. Supratherapeutic concentrations of ACE inhibitors can reduce neutrophil chemotaxis at high concentrations and this effect does not appear to be -SH dependent.

The assessment of the HO. scavenging action of therapeutic agents

A new method is reported for the assessment of the HO. scavenging action of therapeutic agents. It is based on the photolysis of zinc oxide and has a detection limit of 3.3%. The scavenging order of the compounds tested was penicillamine > rentiapril > ascorbic acid > cysteine > glutathione > thiomalic acid > N-acetylcysteine > myocrysin > methionine. None were as effective as DMSO. It is argued that these compounds can have an in vivo protective effect where HO. is produced from oxidant producing cells, thus limiting radical induced damage.

Alteration of the erythrocyte glutathione redox balance by N-acetylcysteine, captopril and exogenous glutathione

The effect of the thiol containing compounds N-acetylcysteine and captopril on glutathione metabolism in human erythrocytes has been investigated non-invasively using 1H spin echo NMR. N-Acetylcysteine was found to increase the reduced form of glutathione while captopril increased the oxidized form, but no changes in the total glutathione concentration were observed. Incubation of the cells with buthionine sulphoximine to inhibit de novo glutathione synthesis did not affect the response. The results show that these compounds act by altering the redox balance of glutathione rather than by stimulating its synthesis, and that their mechanisms of action are different, and not simply due to the presence of the thiol group.

Problems solved and lives saved? Chronic heart failure

Chronic heart failure (CHF) is common, disabling and deadly. Recent studies show that ACE inhibitors reduce morbidity and mortality in all grades of CHF and may even delay or prevent the onset of overt CHF in patients with asymptomatic left ventricular dysfunction. In this review, guidelines are given for how to use these drugs both in hospital and in general practice. New evidence on the benefits of digoxin is also considered, and the management of concomitant problems such as angina and arrhythmias in patients with CHF is discussed.

Effects of ACE inhibitors on oxidation of human low density lipoprotein

Oxidation of low density lipoprotein (LDL) may be instrumental in the development of atherosclerosis. We have examined the effect of the angiotensin converting enzyme (ACE) inhibitors captopril and quinaprilat and the -SH containing compound N-acetylcysteine on LDL oxidation. Oxidation of isolated human LDL was initiated with CuCl2. Conjugated diene formation (monitored spectrophotometrically at 234 nm) gave a measure of LDL oxidation. Captopril inhibited LDL oxidation but quinaprilat did not. The lag phase to the rapid increase in absorbance at 234 nm determined was 109 (65-157) min median and range for control samples and rose to 209 (168-305) min with captopril 10 microM, a ratio of 2.1:1 for drug to control (P = 0.01). N-acetylcysteine had a similar effect to captopril (drug to control lag time ratio 2.0:1, with NAC 10 microM), i.e. suggesting resistance to oxidation was due to the -SH group of both drugs. Captopril may have a potentially anti-atherosclerotic property not shared by other ACE inhibitors.