Impact of different antiplatelet therapy cessation modes on outcomes in patients treated with ticagrelor with or without aspirin after PCI: the twilight-antiplatelet cessation study

Background

The Ticagrelor With Aspirin or Alone in High-Risk Patients After Coronary Intervention (TWILIGHT) trial showed that a regimen consisting of a 3-month dual antiplatelet therapy (DAPT) followed by ticagrelor monotherapy reduces the rate of bleeding events without increasing ischemic complications compared with standard DAPT [1]. Previous studies, such as Patterns of Non-Adherence to Anti-Platelet Regimens in Stented Patients (PARIS) demonstrated how deviation or cessation of the prescribed antiplatelet regimen might negatively affect clinical outcomes [2].

Purpose

The proposed analysis aims to assess the impact of different antiplatelet therapy cessation patterns on ischemic and bleeding outcomes in patients treated with ticagrelor with or without aspirin after percutaneous coronary intervention (PCI).

Methods

All 7,119 patients randomized at 3 months post-PCI in the TWILIGHT study will be included. The analyses will be conducted separately in the two treatment arms (ticagrelor plus placebo and ticagrelor plus aspirin). According to the PARIS study definitions and as prespecified in the TWILIGHT trial protocol, the occurrence of the three following antiplatelet cessation modes will be assessed: 1) discontinuation (e.g., caused by intolerable side effects or because of a safety concern); 2) interruption (temporary, <14 days, because of surgical or other invasive procedures); 3) disruption (due to non-compliance or bleeding).

The primary endpoint will be the composite of all-cause death, myocardial infarction (MI), or stroke at 12 months after randomization. The key secondary endpoint will be BARC type 2, 3 or 5 bleeding. Other secondary endpoints will include the components of the primary endpoint, cardiovascular death, definite or probable stent thrombosis and BARC types 3 or 5 bleeding. The number of events will be estimated according to the antiplatelet cessation status before the clinical event. Hazard ratios and 95% confidence intervals will be generated using Cox proportional hazards models including antiplatelet therapy cessation as a time-updated variable. If more than one cessation event occurred during follow-up, the antiplatelet therapy cessation category will change only if the more recent mode is worse than the previous: disruption will have priority over interruption, which in turn will have priority over discontinuation. Patients without cessation events will represent the reference group. All adverse events and episodes of antiplatelet cessation were independently adjudicated.

Results

The results of this analysis will be presented for the first time at ESC 2022.

Conclusion

This prespecified analysis of the TWILIGHT study will show for the first time the impact on clinical outcomes of different antiplatelet therapy cessation modes when a regimen of Ticagrelor with our without aspirin is prescribed after PCI.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Astra Zeneca, United Kingdom

Safety and efficacy of biodegradable polymer biolimus-eluting stents in patients with non-ST-elevation acute coronary syndrome: a pooled analysis of GLASSY and TWILIGHT

Background

Biodegradable polymer (BP) drug-eluting stents (DES) have shown similar safety and efficacy compared with second-generation durable polymer (DP)-DES in several randomized trials and meta-analyses. However, study participants were generally maintained on a standard dual antiplatelet therapy (DAPT) for at least 6 months after percutaneous coronary intervention (PCI). Therefore, the differences in thrombogenicity between these two stent technologies may have been unappreciated, especially among patients with acute coronary syndrome (ACS).

Purpose

We aimed to compare the safety and efficacy of BP Biolimus-Eluting Stent (BP-BES) versus 2nd generation DP-DES among ACS patients undergoing PCI and receiving ticagrelor alone or in combination with aspirin.

Methods

We pooled individual patient-level data from two randomized controlled trials, the Ticagrelor With Aspirin or Alone in High-Risk Patients After Coronary Intervention (TWILIGHT, n=9,006) (1) and the GLOBAL LEADERS Adjudication Sub-Study (GLASSY, n=7,585) (2). In order to reduce biases related to trial design differences, only NST-ACS patients not fulfilling any exclusion criterion of both studies were included and 2 separate analysis for short (0 to 3 months after PCI) and long-term (3 to 12 months after PCI) outcomes were performed. Patients were stratified according to the stent used at index PCI (BP-BES vs 2nd generation DP-DES). In both analysis, the primary outcome was major adverse cardiovascular events (MACE, a composite of cardiovascular death, myocardial infarction and definite or probable stent thrombosis); the key secondary outcomes were target-vessel failure (TVF) and BARC 2, 3 or 5 bleeding. Events rate and risk were assessed separately for the two study periods and subsequently 12-months risk estimates were derived by pooling the results of the two analysis.

Results

Out of 7,729 and 6,572 NST-ACS patients included in the two analysis, 2,321 (30%) and 2,211 (33.6%) received a BP-BES, respectively. Among patients treated with BP-BES versus DP-DES, the occurrence of MACE was similar at 3 months after PCI (1.1% vs 1.4%, adjusted HR 0.81, 95% CI 0.51–1.29), while it was significantly lower in the former group between 3 and 12 months (1.7% vs 3.1%, adj. HR 0.46, 95% CI 0.32–0.67) and in the overall period (pooled adjusted HR estimate 0.58, 95% CI 0.43–0.77).

Similarly, significant differences were observed for TVF and BARC 2, 3, or 5 bleeding, whose risk at 12 months was lower among BP-BES than DP-DES patients (pooled adj. HR estimate 0.49, 95% CI 0.38–0.63 and 0.79, 95% CI 0.79, 95% CI 0.65–0.97, respectively).

Conclusion

As compared to 2nd generation DP-DES, BP-BES was associated with a lower risk of MACE, TVF and bleeding among NST-ACS patients undergoing PCI and treated with ticagrelor with or without aspirin. The findings of this analysis are exploratory and need further confirmation.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Biosensors (Singapore)

Socioeconomic deprivation: an important largely unrecognized risk factor in primary prevention of cardiovascular disease

Background

Socioeconomic deprivation is associated with higher cardiovascular morbidity and mortality. Whether deprivation status should be incorporated in more cardiovascular risk estimation scores remains unclear.

Purpose

This study evaluates how socioeconomic deprivation status affects the performance of three primary prevention cardiovascular risk scores.

Methods

The Generation Scotland Scottish Family Health Study was used to evaluate the performance of three cardiovascular risk scores with (ASSIGN) and without (SCORE2, PCE) socioeconomic deprivation as a covariate in the risk prediction model. Deprivation was defined by Scottish Index of Multiple Deprivation score. The predicted 10-year risk was evaluated against the observed event rate for the cardiovascular outcome of each risk score. The comparison was made across three groups defined by the deprivation index score consisting of group 1 defined as most deprived, group 3 defined as least deprived and group 2 which consisted of individuals in the middle deprivation categories.

Results

The study population consisted of 15,506 individuals (60.0% female, median age of 51). Across the population 1,808 (12%) individuals were assigned to group 1 (most deprived), 8,119 (55%) to group 2, and 4,708 (32%) to group 3 (least deprived). Risk scores based on models that did not include deprivation status significantly under predicted risk in the most deprived (6.4% observed versus 4.6% predicted for SCORE2 and 6.7% observed versus 4.7% predicted for PCE, p<0.001 for both). Both risk scores also significantly overpredicted the risk in the least deprived group (4.0% observed versus 4.7% predicted for SCORE2, p=0.007 and 4.2% observed versus 4.9% predicted for PCE, p=0.028). In contrast, no significant difference was demonstrated in the observed versus predicted risk when using the ASSIGN risk score, which included socioeconomic deprivation status in the risk model.

Conclusions

Socioeconomic status is a largely unrecognized risk factor in primary prevention of cardiovascular disease. Risk scores that exclude socioeconomic deprivation as a covariate under- and overestimate the risk in the most and least deprived individuals, respectively. This study highlights the importance of incorporating socioeconomic deprivation status in risk estimation systems to ultimately reduce inequalities in health care provision for cardiovascular disease.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The British Heart Foundation.Health Data Research UK which receives its funding from HDR UK Ltd (HDR-5012) funded by the UK Medical Research Council, Engineering and Physical Sciences Research Council, Economic and Social Research Council, Department of Health and Social Care (England), Chief Scientist Office of the Scottish Government Health and Social Care Directorates, Health and Social Care Research and Development Division (Welsh Government), Public Health Agency (Northern Ireland), British Heart Foundation and the Wellcome Trust.

Association of heart rate with heart failure outcomes and the effects of empagliflozin in patients with preserved ejection fraction – EMPEROR-Preserved trial

Background and objective

High resting heart rate (HR) associates with cardiovascular death (CVD) and heart failure hospitalisation (HFH) in patients with reduced ejection fraction (HFrEF), but data are sparse in patients with preserved (HFpEF) or mildly reduced (HFmrEF) ejection fraction. Empagliflozin reduced the risk of CVD and HFH in HFpEF in the EMPEROR-Preserved trial. This study analyses the influence of HR on outcomes in patients with left ventricular ejection fraction (LVEF) >40% in EMPEROR-Preserved and evaluates the effects of empagliflozin across HR categories.

Methods

Patients (n=5988) with HFpEF (LVEF >40%) were categorised to HR <70 beats per minute (bpm), 70–75 bpm and >75 bpm. The composite of CVD or HFH (primary outcome), first HFH, CVD, recurrent HFH and all-cause mortality were studied in the HR groups and in patients separated by sinus rhythm (SR) or atrial fibrillation (AF) and true HFpEF (EF ≥50%) or HFmrEF (EF 40–49%).

Results

Empagliflozin did not influence HR over time. At HR >75 bpm, the primary outcome (hazard ratio: 1.31, 1.13–1.52, p=0.0003), time to first HFH (hazard ratio: 1.25, 1.04–1.49, p=0.02), recurrent HFH (hazard ratio: 1.29, 1.05–1.60, p=0.02), CVD (hazard ratio: 1.49, 1.21–1.84, p=0.0001) and all-cause mortality (hazard ratio: 1.49, 1.28–1.73, p<0.0001) were increased compared to HR of <70 bpm with HR 70–75 bpm showing intermediate results. The influence of HR on the primary outcome was only observed in SR (p trend=0.005), but not in AF (p trend=0.55). Patients with true HFpEF (≥50%) or HFmrEF (40–49%) showed similar effects. The treatment effects of empagliflozin to reduce the primary outcome, time to first HFH and recurrent HFH were not modified by HR.

Conclusions

HR in SR, but not in AF, predicts heart failure outcomes in HFpEF and HFmrEF, but the effects of empagliflozin were not modified by HR.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Boehringer Ingelheim & Eli Lilly and Company Diabetes Alliance

P1932Predictors of DAPT use in patients beyond 1 year post myocardial infarction: Insights from the TIGRIS observational study

Background

International guidelines vary in their recommendations for dual antiplatelet therapy (DAPT) use beyond 1 year post-myocardial infarction (MI).

Purpose

To identify predictors of DAPT use in patients ≥1 year post-MI prior to the publication of the DAPT score and the 2017 European Society of Cardiology (ESC) guidelines for DAPT in coronary artery disease.

Methods

TIGRIS (NCT01866904) was a prospective, multi-center (369 centers in 25 countries), observational study of patients 1 to 3 years post-MI between June 2013 and November 2014. We performed a multivariable logistic regression analysis to identify independent predictors of DAPT use at 396 days post-MI (365 + 31 days overrun period to allow intended DAPT discontinuation at 1 year). Patients on oral anticoagulation were excluded.

Results

Of 8464 patients enrolled (mean age 66 years, women 24%, ST-elevation MI 53%), 40% were on DAPT at 396 days post-MI (Figure). In the subset of patients on DAPT at 396 days post-MI, aspirin was combined with clopidogrel in 84%, prasugrel in 12%, and other antiplatelet agents in 4%. DAPT use at 396 days post-MI was independently associated with geographic region, age, PCI for the index MI, and a history of multivessel disease or angina (Table). Several variables included in the DAPT score and ESC guideline recommendations (diabetes, second prior MI, hypertension, peripheral artery disease, heart failure, smoking, and renal insufficiency) were not independent predictors of DAPT use at 396 days.

Independent predictors of DAPT @396 days Variable at enrolment Patients Odds ratio (95% CI) P-value Region: Europe 3813 Reference group 0.01 North America 923 1.65 (0.56, 4.86) Latin America 1084 2.55 (1.19, 5.47) Asia and Australia 2644 3.01 (1.42, 6.36) Age <65 years 3274 1.15 (1.04, 1.28) 0.005 PCI for index MI 6925 2.08 (1.82, 2.38) <0.0001 Multi-vessel disease 5598 1.37 (1.24, 1.52) <0.0001 History of angina 829 1.46 (1.24, 1.71) <0.0001

DAPT use at 396 days post-MI by region

Conclusion

During the study period, DAPT use ≥1 year post-MI was prevalent and appeared to be influenced by regional practices. Further research is needed to determine whether the DAPT score and the 2017 ESC guidelines for dual antiplatelet therapy have changed long-term DAPT use practices.

Acknowledgement/Funding

AstraZeneca AB, Södertälje, Sweden

Effects of oral salbutamol and pirbuterol on FEV1, heart rate and blood pressure in asthmatics

In a double-blind trial the effects on ventilatory function (FEV1), heart rate and blood pressure of oral pirbuterol and oral salbutamol in various single doses were studied in ten patients with chronic asthma. Pirbuterol (15 mg) and salbutamol (4 mg) produced equal peak levels of bronchodilatation. There was no significant difference in the mean rise in heart rates caused by the two drugs, and no other significant side-effects were noted.

Rosiglitazone RECORD study: glucose control outcomes at 18 months

AIMS

To compare glucose control over 18 months between rosiglitazone oral combination therapy and combination metformin and sulphonylurea in people with Type 2 diabetes.

METHODS

RECORD, a multicentre, parallel-group study of cardiovascular outcomes, enrolled people with an HbA(1c) of 7.1-9.0% on maximum doses of metformin or sulphonylurea. If on metformin they were randomized to add-on rosiglitazone or sulphonylurea (open label) and if on sulphonylurea to rosiglitazone or metformin. HbA(1c) was managed to < or = 7.0% by dose titration. A prospectively defined analysis of glycaemic control on the first 1122 participants is reported here, with a primary outcome assessed against a non-inferiority margin for HbA(1c) of 0.4%.

RESULTS

At 18 months, HbA(1c) reduction on background metformin was similar with rosiglitazone and sulphonylurea [difference 0.07 (95% CI -0.09, 0.23)%], as was the change when rosiglitazone or metformin was added to sulphonylurea [0.06 (-0.09, 0.20)%]. At 6 months, the effect on HbA(1c) was greater with add-on sulphonylurea, but was similar whether sulphonylurea was added to rosiglitazone or metformin. Differences in fasting plasma glucose were not statistically significant at 18 months [rosiglitazone vs. sulphonylurea -0.36 (-0.74, 0.02) mmol/l, rosiglitazone vs. metformin -0.34 (-0.73, 0.05) mmol/l]. Increased homeostasis model assessment insulin sensitivity and reduced C-reactive protein were greater with rosiglitazone than metformin or sulphonylurea (all P < or = 0.001). Body weight was significantly increased with rosiglitazone compared with sulphonylurea [difference 1.2 (0.4, 2.0) kg, P = 0.003] and metformin [difference 4.3 (3.6, 5.1) kg, P < 0.001].

CONCLUSIONS

In people with diabetes, rosiglitazone in combination with metformin or sulphonylurea was demonstrated to be non-inferior to the standard combination of metformin + sulphonylurea in lowering HbA(1c) over 18 months, and produces greater improvements in C-reactive protein and basal insulin sensitivity but is also associated with greater weight gain.

Prevalence and prognostic implications of electrocardiographic left ventricular hypertrophy in heart failure: evidence from the CHARM programme

BACKGROUND

Electrocardiographic left ventricular hypertrophy (ECG LVH) is a powerful independent predictor of cardiovascular morbidity and mortality in hypertension.

OBJECTIVE

To determine the contemporary prevalence and prognostic implications of ECG LVH in a broad spectrum of patients with heart failure with and without reduced left ventricular ejection fraction (LVEF). METHODS AND OUTCOME: The Candesartan in Heart failure: Assessment of Reduction in Mortality and morbidity (CHARM) programme randomised 7599 patients with symptomatic heart failure to receive candesartan or placebo. The primary outcome comprised cardiovascular death or hospital admission for worsening heart failure. The relative risk (RR) conveyed by ECG LVH compared with a normal ECG was examined in a Cox model, adjusting for as many as 31 covariates of prognostic importance.

RESULTS

The prevalence of ECG LVH was similar in all three CHARM trials (Alternative, 15.4%; Added, 17.1%; Preserved, 14.7%; Overall, 15.7%) despite a more frequent history of hypertension in CHARM-Preserved. ECG LVH was an independent predictor of worse prognosis in CHARM-Overall. RR for the primary outcome was 1.27 (95% confidence interval (CI) 1.04 to 1.55, p = 0.018). The risk of secondary end points was also increased: cardiovascular death, 1.50 (95% CI 1.13 to 1.99, p = 0.005); hospitalisation due to heart failure, 1.19 (95% CI 0.94 to 1.50, p = 0.148); and composite major cardiovascular events, 1.35 (95% CI 1.12 to 1.62, p = 0.002).

CONCLUSION

ECG LVH is similarly prevalent in patients with symptomatic heart failure regardless of LVEF. The simple clinical finding of ECG LVH was an independent predictor of a worse clinical outcome in a broad spectrum of patients with heart failure receiving extensive contemporary treatment. Candesartan had similar benefits in patients with and without ECG LVH.

Interventional versus conservative treatment in acute non-ST elevation coronary syndrome: time course of patient management and disease events over one year in the RITA 3 trial

OBJECTIVE

To determine whether, in acute non-ST elevation coronary syndrome, the benefit from early invasive coronary intervention compared with a conservative strategy of later symptom-guided intervention varies over time.

METHODS

In RITA 3 (Randomised Intervention Trial of unstable Angina 3) patients were randomly assigned to coronary angiography (median 2 days after randomisation) and appropriate intervention (n = 895) or to a symptom-guided conservative strategy (n = 915).

RESULTS

In the first week patients in both groups were at highest risk of death, myocardial infarction (MI) or refractory angina (incidence rate 40 times higher than in months 5-12 of follow up). There were 22 MIs and 6 deaths in the intervention group (largely due to procedure-related events, 14 MIs and 3 deaths) versus 17 MIs and 3 deaths in the conservative group. In the rest of the year there were an additional 12 versus 27 MIs, respectively (treatment-time interaction p = 0.021). Over one year in the intervention group there was a 43% reduction in refractory angina; 22% of patients underwent coronary artery bypass surgery and 35% underwent percutaneous coronary intervention only, which reduced refractory angina but provoked some early MIs; and 43% were still treated medically, mostly because of a favourable initial angiogram.

CONCLUSION

Any intervention policy needs to recognise the high risk of events in the first week and the substantial minority of patients not needing intervention. Intervention may be best targeted at higher risk patients, as the early hazards of the procedure are then offset by reduced subsequent events.

5-year outcome of an interventional strategy in non-ST-elevation acute coronary syndrome: the British Heart Foundation RITA 3 randomised trial

BACKGROUND

The long-term outcome of an interventional strategy in patients with non-ST-elevation acute coronary syndrome is unknown. We tested whether an interventional strategy (routine angiography followed by revascularisation) was better than a conservative strategy (ischaemia-driven or symptom-driven angiography) over 5 years' follow-up.

METHODS

In a multicentre randomised trial, 1810 patients (from 45 hospitals in England and Scotland, UK) with non-ST-elevation acute coronary syndrome were randomly assigned to receive an early intervention (n=895) or a conservative strategy (n=915) within 48 h of the index episode of cardiac pain. In each group, the aim was to provide the best medical treatment, and also to undertake coronary arteriography within 72 h in the interventional strategy with subsequent management guided by the angiographic findings. Analysis was by intention to treat and the primary outcome (composite of death or non-fatal myocardial infarction) had masked independent adjudication. RITA 3 has been assigned the International Standard Randomised Control Trial Number ISRCTN07752711.

FINDINGS

At 1-year follow-up, rates of death or non-fatal myocardial infarction were similar. However, at a median of 5 years' follow-up (IQR 4.6-5.0), 142 (16.6%) patients with intervention treatment and 178 (20.0%) with conservative treatment died or had non-fatal myocardial infarction (odds ratio 0.78, 95% CI 0.61-0.99, p=0.044), with a similar benefit for cardiovascular death or myocardial infarction (0.74, 0.56-0.97, p=0.030). 234 (102 [12%] intervention, 132 [15%] conservative) patients died during follow-up (0.76, 0.58-1.00, p=0.054). The benefits of an intervention strategy were mainly seen in patients at high risk of death or myocardial infarction (p=0.004), and for the highest risk group, the odds ratio of death or non-fatal myocardial infarction was 0.44 (0.25-0.76).

INTERPRETATION

In patients with non-ST-elevation acute coronary syndrome, a routine invasive strategy leads to long-term reduction in risk of death or non-fatal myocardial infarction, and this benefit is mainly in high-risk patients. The findings provide support for national and international guidelines in the need for more robust risk stratification in acute coronary syndrome.

Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycaemia in Diabetes (RECORD): study design and protocol

AIMS/HYPOTHESIS

Studies suggest that in addition to blood glucose concentrations, thiazolidinediones such as rosiglitazone improve some cardiovascular (CV) risk factors and surrogate markers, that are abnormal in type 2 diabetes. However, fluid retention might lead to cardiac failure in a minority of people. The aim of the Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycaemia in Diabetes (RECORD) study is to evaluate the long-term impact of these effects on CV outcomes, as well as on long-term glycaemic control, in people with type 2 diabetes.

MATERIALS AND METHODS

RECORD is a 6-year, randomised, open-label study in type 2 diabetic patients with inadequate blood glucose control (HbA1c 7.1-9.0%) on metformin or sulphonylurea alone. The study is being performed in 327 centres in Europe and Australasia. After a 4-week run-in, participants were randomised by current treatment stratum to add-on rosiglitazone, metformin or sulphonylurea, with dose titration to a target HbA1c of < or = 7.0%. If confirmed HbA1c rises to > or = 8.5%, either a third glucose-lowering drug is added (rosiglitazone-treated group) or insulin is started (non-rosiglitazone group). The same criterion for failure of triple oral drug therapy in the rosiglitazone-treated group is used for starting insulin in this group. The primary endpoint is the time to first CV hospitalisation or death, blindly adjudicated by a central endpoints committee. The study aim is to evaluate non-inferiority of the rosiglitazone group vs the non-rosiglitazone group with respect to CV outcomes. Safety, tolerability and study conduct are monitored by an independent board. All CV endpoint and safety data are held and analysed by a clinical trials organisation, and are not available to the study investigators while data collection is open.

RESULTS

Over a 2-year period a total of 7,428 people were screened in 25 countries. Of these, 4,458 were randomised; 2,228 on background metformin, 2,230 on background sulphonylurea. Approximately half of the participants are male (52%) and almost all are Caucasian (99%).

CONCLUSIONS/INTERPRETATION

The RECORD study should provide robust data on the extent to which rosiglitazone, in combination with metformin or sulphonylurea therapy, affects CV outcomes and progression of diabetes in the long term.

Issues in data monitoring and interim analysis of trials

OBJECTIVES

To address issues about data monitoring committees (DMCs) for randomised controlled trials (RCTs).

DATA SOURCES

Electronic databases. Handsearching of selected books. Personal contacts with experts in the field.

REVIEW METHODS

Systematic literature reviews of DMCs and small group processes in decision-making; sample surveys of: reports of RCTs, recently completed and ongoing RCTs and policies of major organisations involved in RCTs; case studies of four DMCs; and interviews with experienced DMC members. All focused on 23 prestated questions.

RESULTS

Although still a minority, RCTs increasingly have DMCs. There is wide agreement that nearly all trials need some form of data monitoring. Central to the role of the DMC is monitoring accumulating evidence related to benefit and toxicity; variation in emphasis has been reflected in the plethora of names. DMCs for trials performed for regulatory purposes should be aware of any special requirements and regulatory consequences. Advantages were identified for both larger and smaller DMCs. There is general agreement that a DMC should be independent and multidisciplinary. Consumer and ethicist membership is controversial. The chair is recognised as being particularly influential, and likely to be most effective if he or she is experienced, understands both statistical and clinical issues, and is facilitating in style and impartial. There is no evidence available to judge suggested approaches to training. The review suggested that costs should be covered, but other rewards must be so minimal as to not affect decision-making. It is usual to have a minimum frequency of DMC meetings, with evidence that face-to-face meetings are preferable. It is common to have open sessions and a closed session. A report to a DMC should cover benefits and risks in a balanced way, summarised in an accessible style, avoiding excessive detail, and be as current as possible. Disadvantages of blinded analyses seem to outweigh advantages. Information about comparable studies should be included, although interaction with the DMCs of similar ongoing trials is controversial. A range of formal statistical approaches can be used, although this is only one of a number of considerations. DMCs usually reach decisions by consensus, but other approaches are sometimes used. The general, but not unanimous, view is that DMCs should be advisory rather than executive on the basis that it is the trial organisers who are ultimately responsible for the conduct of the trial.

CONCLUSIONS

Some form of data monitoring should be considered for all RCTs, with reasons given where there is no DMC or when any member is not independent. An early DMC meeting is helpful, determining roles and responsibilities; planned operations can be agreed with investigators and sponsors/funders. A template for a DMC charter is suggested. Competing interests should be declared. DMC size (commonly three to eight people) is chosen to optimise performance. Members are usually independent and drawn from appropriate backgrounds, and some, particularly the chair, are experienced. A minimum frequency of meetings is usually agreed, with flexibility for more if needed. The DMC should understand and agree the statistical approach (and guidelines) chosen, with both the DMC statistician and analysis statistician competent to apply the method. A DMC's primary purpose is to ensure that continuing a trial according to its protocol is ethical, taking account of both individual and collective ethics. A broader remit in respect of wider ethical issues is controversial; arguably, these are primarily the responsibility of research ethics committees, trial steering committees and investigators. The DMC should know the range of recommendations or decisions open to it, in advance. A record should be kept describing the key issues discussed and the rationale for decisions taken. Errors are likely to be reduced if a DMC makes a thorough review of the evidence and has a clear understanding of how it should function, there is active participation by all members, differences are resolved through discussion and there is systematic consideration of the various decision options. DMCs should be encouraged to comment on draft final trial reports. These should include information about the data monitoring process and detail the DMC membership. It is recommended that groups responsible for data monitoring be given the standard name 'Data Monitoring Committee' (DMC). Areas for further research include: widening DMC membership beyond clinicians, trialists and statisticians; initiatives to train DMC members; methods of DMC decision-making; 'open' data monitoring; DMCs covering a portfolio of trials rather than single trials; DMC size and membership, incorporating issues of group dynamics; empirical study of the workings of DMCs and their decision-making, and which trials should or should not have a DMC.

Do men benefit more than women from an interventional strategy in patients with unstable angina or non-ST-elevation myocardial infarction? The impact of gender in the RITA 3 trial

AIMS

The RITA 3 trial randomized patients with non-ST-elevation myocardial infarction or unstable angina to strategies of early intervention (angiography followed by revascularization) or conservative care (ischaemia or symptom driven angiography). The aim of this analysis was to investigate the impact of gender on the effect of these two strategies.

METHODS AND RESULTS

In total, 1810 patients (682 women and 1128 men) were randomized. The risk factor profile of women at presentation was markedly different to men. There was evidence that men benefited more from an early intervention strategy for death or non-fatal myocardial infarction at 1 year (adjusted odds ratios 0.63, 95% confidence interval 0.41-0.98 for men and 1.79, 95% confidence interval 0.95-3.35 for women; interaction p-value=0.007). Men who underwent the assigned angiogram were more likely to be put forward for coronary artery bypass surgery, even after allowing for differences in disease severity.

CONCLUSION

An early intervention strategy resulted in a beneficial effect in men which was not seen in women although caution is needed in interpretation. Further research is needed to evaluate why women do not appear to benefit from early intervention and to identify treatments that improve the prognosis of women.

Neonatal head circumference, neonatal weight, and risk of hayfever, asthma and eczema in a large cohort of adolescents from Sheffield, England

BACKGROUND

Neonatal physical characteristics, including head circumference and birth weight, have been hypothesized to be markers of in utero thymic development. Greater head circumference and lower birth weight have been linked in previous studies to subsequent development of asthma, and greater birth weight has been associated with subsequent development of eczema.

OBJECTIVE

To investigate potential associations between neonatal head circumference and weight and hayfever, asthma and eczema in a cohort of adolescents from Sheffield, England.

METHODS

Responses to a questionnaire inquiring about physician-diagnosed hayfever, asthma and eczema among adolescents in Sheffield, England, were linked to previously recorded measurements of weight at birth and at 1 month and head circumference at 1 month. Logistic regression methods were used to relate diagnoses to neonatal measurements and potential confounders.

RESULTS

The cohort consisted of 10,809 adolescents, of whom 16.5% reported hayfever, 18.0% asthma, and 16.2% eczema. After adjusting for sex, age at the time of the questionnaire, maternal age and gestational age at birth, number of older and younger siblings, time since birth of next older sibling, neonatal sickness, type of neonatal feeding, and maternal and paternal educational backgrounds, hayfever was the only disease associated with neonatal measurements. Comparing the highest with the lowest fifths of distributions, lifetime prevalence of hayfever was positively associated with neonatal head circumference (adjusted odds ratio 1.23, 95% CI 1.03 to 1.47) and with birth weight (1.17, 0.99 to 1.39). Hayfever was inversely related to the ratio of head circumference to birth weight (0.89, 0.75 to 1.05) and to gestational age. The associations with head circumference and birth weight were not substantially altered by further adjustment for gestational age.

CONCLUSION

Greater neonatal head circumference may be associated with an increased risk of hayfever, but the inverse relationship between hayfever prevalence and the ratio of head circumference to birth weight challenges the prior hypothesis that greater head circumference relative to body mass reflects abnormal thymic development in utero, increasing the likelihood of allergic sensitization.

A comparison of two methods for the estimation of precision with incomplete longitudinal data, jointly modelled with a time-to-event outcome

Several methods for the estimation and comparison of rates of change in longitudinal studies with staggered entry and informative drop-outs have been recently proposed. For multivariate normal linear models, REML estimation is used. There are various approaches to maximizing the corresponding log-likelihood; in this paper we use a restricted iterative generalized least squares method (RIGLS) combined with a nested EM algorithm. An important statistical problem in such approaches is the estimation of the standard errors adjusted for the missing data (observed data information matrix). Louis has provided a general technique for computing the observed data information in terms of completed data quantities within the EM framework. The multiple imputation (MI) method for obtaining variances can be regarded as an alternative to this. The aim of this paper is to develop, apply and compare the Louis and a modified MI method in the setting of longitudinal studies where the source of missing data is either death or disease progression (informative) or end of the study (assumed non-informative). Longitudinal data are simultaneously modelled with the missingness process. The methods are illustrated by modelling CD4 count data from an HIV-1 clinical trial and evaluated through simulation studies. Both methods, Louis and MI, are used with Monte Carlo simulations of the missing data using the appropriate conditional distributions, the former with 100 simulations, the latter with 5 and 10. It is seen that naive SEs based on the completed data likelihood can be seriously biased. This bias was largely corrected by Louis and modified MI methods, which gave broadly similar estimates. Given the relative simplicity of the modified MI method, it may be preferable.

Regression of area mortality rates on explanatory variables: what weighting is appropriate?

"One can often gain insight into the aetiology of a disease by relating mortality rates in different areas to explanatory variables. Multiple regression techniques are usually employed, but unweighted least squares may be inappropriate if the areas vary in population size. Also, a fully weighted regression, with weights inversely proportional to binomial sampling variances, is usually too extreme. This paper proposes an intermediate solution via maximum likelihood which takes account of three sources of variation in death rates: sampling error, explanatory variables and unexplained differences between areas. The method is also adapted for logit (death rates), standardized mortality ratios (SMRs) and log (SMRs). Two [United Kingdom] examples are presented."

Interventional versus conservative treatment for patients with unstable angina or non-ST-elevation myocardial infarction: the British Heart Foundation RITA 3 randomised trial. Randomized Intervention Trial of unstable Angina

BACKGROUND

Current guidelines suggest that, for patients at moderate risk of death from unstable coronary-artery disease, either an interventional strategy (angiography followed by revascularisation) or a conservative strategy (ischaemia-driven or symptom-driven angiography) is appropriate. We aimed to test the hypothesis that an interventional strategy is better than a conservative strategy in such patients.

METHODS

We did a randomised multicentre trial of 1810 patients with non-ST-elevation acute coronary syndromes (mean age 62 years, 38% women). Patients were assigned an early intervention or conservative strategy. The antithrombin agent in both groups was enoxaparin. The co-primary endpoints were a combined rate of death, non-fatal myocardial infarction, or refractory angina at 4 months; and a combined rate of death or non-fatal myocardial infarction at 1 year. Analysis was by intention to treat.

FINDINGS

At 4 months, 86 (9.6%) of 895 patients in the intervention group had died or had a myocardial infarction or refractory angina, compared with 133 (14.5%) of 915 patients in the conservative group (risk ratio 0.66, 95% CI 0.51-0.85, p=0.001). This difference was mainly due to a halving of refractory angina in the intervention group. Death or myocardial infarction was similar in both treatment groups at 1 year (68 [7.6%] vs 76 [8.3%], respectively; risk ratio 0.91, 95% CI 0.67-1.25, p=0.58). Symptoms of angina were improved and use of antianginal medications significantly reduced with the interventional strategy (p<0.0001).

INTERPRETATION

In patients presenting with unstable coronary-artery disease, an interventional strategy is preferable to a conservative strategy, mainly because of the halving of refractory or severe angina, and with no increased risk of death or myocardial infarction.

Impact of missing data due to drop-outs on estimators for rates of change in longitudinal studies: a simulation study

Many cohort studies and clinical trials are designed to compare rates of change over time in one or more disease markers in several groups. One major problem in such longitudinal studies is missing data due to patient drop-out. The bias and efficiency of six different methods to estimate rates of changes in longitudinal studies with incomplete observations were compared: generalized estimating equation estimates (GEE) proposed by Liang and Zeger (1986); unweighted average of ordinary least squares (OLSE) of individual rates of change (UWLS); weighted average of OLSE (WLS); conditional linear model estimates (CLE), a covariate type estimates proposed by Wu and Bailey (1989); random effect (RE), and joint multivariate RE (JMRE) estimates. The latter method combines a linear RE model for the underlying pattern of the marker with a log-normal survival model for informative drop-out process. The performance of these methods in the presence of missing data completely at random (MCAR), at random (MAR) and non-ignorable (NIM) were compared in simulation studies. Data for the disease marker were generated under the linear random effects model with parameter values derived from realistic examples in HIV infection. Rates of drop-out, assumed to increase over time, were allowed to be independent of marker values or to depend either only on previous marker values or on both previous and current marker values. Under MACR all six methods yielded unbiased estimates of both group mean rates and between-group difference. However, the cross-sectional view of the data in the GEE method resulted in seriously biased estimates under MAR and NIM drop-out process. The bias in the estimates ranged from 30 per cent to 50 per cent. The degree of bias in the GEE estimates increases with the severity of non-randomness and with the proportion of MAR data. Under MCAR and MAR all the other five methods performed relatively well. RE and JMRE estimates were more efficient(that is, had smaller variance) than UWLS, WLS and CL estimates. Under NIM, WLS and particularly RE estimates tended to underestimate the average rate of marker change (bias approximately 10 per cent). Under NIM, UWLS, CL and JMRE performed better in terms of bias (3-5 per cent) with the JMRE giving the most efficient estimates. Given that markers are key variables related to disease progression, missing marker data are likely to be at least MAR. Thus, the GEE method may not be appropriate for analysing such longitudinal marker data. The potential biases due to incomplete data require greater recognition in reports of longitudinal studies. Sensitivity analyses to assess the effect of drop-outs on inferences about the target parameters are important.

A score for predicting risk of death from cardiovascular disease in adults with raised blood pressure, based on individual patient data from randomised controlled trials

OBJECTIVE

To create a risk score for death from cardiovascular disease that can be easily used.

DESIGN

Data from eight randomised controlled trials of antihypertensive treatment.

SETTING

Europe and North America.

PARTICIPANTS

47 088 men and women from trials that had differing age ranges and differing eligibility criteria for blood pressure. MAIN OTUCOME MEASURE: 1639 deaths from cardiovascular causes during a mean 5.2 years of follow up.

RESULTS

Baseline factors were related to risk of death from cardiovascular disease using a multivariate Cox model, adjusting for trial and treatment group (active versus control). A risk score was developed from 11 factors: age, sex, systolic blood pressure, serum total cholesterol concentration, height, serum creatinine concentration, cigarette smoking, diabetes, left ventricular hypertrophy, history of stroke, and history of myocardial infarction. The risk score is an integer, with points added for each factor according to its association with risk. Smoking contributed more in women and in younger age groups. In women total cholesterol concentration mattered less than in men, whereas diabetes had more of an effect. Antihypertensive treatment reduced the score. The five year risk of death from cardiovascular disease for scores of 10, 20, 30, 40, 50, and 60 was 0.1%, 0.3%, 0.8%, 2.3%, 6.1%, and 15.6%, respectively. Age and sex distributions of the score from the two UK trials enabled individual risk assessment to be age and sex specific. Risk prediction models are also presented for fatal coronary heart disease, fatal stroke, and all cause mortality.

CONCLUSION

The risk score is an objective aid to assessing an individual's risk of cardiovascular disease, including stroke and coronary heart disease. It is useful for physicians when determining an individual's need for antihypertensive treatment and other management strategies for cardiovascular risk.

Wheeze associated with prenatal tobacco smoke exposure: a prospective, longitudinal study. ALSPAC Study Team

AIMS

To determine whether maternal smoking during pregnancy is a risk factor for reported wheeze in early childhood that is independent of postnatal environmental tobacco smoke (ETS) exposure and other known risk factors.

METHODS

A total of 8561 mothers and infants completed questions about smoking during pregnancy, ETS exposure, and the mother's recall of wheeze during early childhood.

RESULTS

A total of 1869 (21.8%) children had reported wheeze between 18 and 30 months of age, and 3496 (40.8%) had reported wheeze in one or more of the three study periods (birth to 6 months, 6-18 months, 18-30 months). The risk of wheeze between 18 and 30 months of age was higher if the mother smoked during pregnancy. This relation did not show a dose-response effect and became less obvious after adjustment for the effects of other factors. Average daily duration of ETS exposure reported at 6 months of age showed a dose-response effect and conferred a similar risk of reported wheeze. Factors associated with early childhood wheeze had the following adjusted odds ratios: maternal history of asthma 2.03 (1.74 to 2. 37); preterm delivery 1.66 (1.30 to 2.13); male sex 1.42 (1.28 to 1. 59); rented accommodation 1.29 (1.11 to 1.51); and each additional child in household 1.13 (1.04 to 1.24).

CONCLUSIONS

Maternal smoking during pregnancy may be a risk factor for reported wheeze during early childhood that is independent of postnatal ETS exposure. For wheeze between 18 and 30 months of age, light smoking during the third trimester of pregnancy appears to confer the same risk as heavier smoking.

Subgroup analysis and other (mis)uses of baseline data in clinical trials

BACKGROUND

Baseline data collected on each patient at randomisation in controlled clinical trials can be used to describe the population of patients, to assess comparability of treatment groups, to achieve balanced randomisation, to adjust treatment comparisons for prognostic factors, and to undertake subgroup analyses. We assessed the extent and quality of such practices in major clinical trial reports.

METHODS

A sample of 50 consecutive clinical-trial reports was obtained from four major medical journals during July to September, 1997. We tabulated the detailed information on uses of baseline data by use of a standard form.

FINDINGS

Most trials presented baseline comparability in a table. These tables were often unduly large, and about half the trials inappropriately used significance tests for baseline comparison. Methods of randomisation, including possible stratification, were often poorly described. There was little consistency over whether to use covariate adjustment and the criteria for selecting baseline factors for which to adjust were often unclear. Most trials emphasised the simple unadjusted results and covariate adjustment usually made negligible difference. Two-thirds of the reports presented subgroup findings, but mostly without appropriate statistical tests for interaction. Many reports put too much emphasis on subgroup analyses that commonly lacked statistical power.

INTERPRETATION

Clinical trials need a predefined statistical analysis plan for uses of baseline data, especially covariate-adjusted analyses and subgroup analyses. Investigators and journals need to adopt improved standards of statistical reporting, and exercise caution when drawing conclusions from subgroup findings.

Quality of life after coronary angioplasty or continued medical treatment for angina: three-year follow-up in the RITA-2 trial. Randomized Intervention Treatment of Angina

OBJECTIVES

We sought to evaluate the impact of percutaneous transluminal coronary angioplasty (PTCA) and medical treatment on self-perceived quality of life among patients with angina.

BACKGROUND

The second Randomized Intervention Treatment of Angina trial (RITA-2) implemented initial policies of PTCA or continued medical treatment in patients with angina, allowing assessment of long-term health consequences.

METHODS

A total of 1,018 patients were randomly assigned (504 to PTCA and 514 to medical treatment). The short form 36 (SF-36) self-administered quality-of-life questionnaire was completed at randomization and three months, one year and three years later. To date, 98% of patients reached one year and 67% reached three years.

RESULTS

The PTCA group had significantly greater improvements in physical functioning, vitality and general health at both three months and one year, but not at three years. These quality-of-life scores were strongly related to breathlessness, angina grade and treadmill exercise time both at baseline and at one year. The treatment differences in quality of life are explained by the PTCA group's improvements in breathlessness, angina and exercise time. The attenuation of treatment difference at three years is partly attributed to 27% of medically treated patients receiving nonrandomized interventions in the interim. For both groups, there were also improvements in ratings of physical role functioning, emotional role functioning, social functioning, pain and mental health, but for these the superiority of PTCA over medical treatment was less pronounced. After one year, 33% and 22% of the PTCA and medical groups, respectively, rated their health much better.

CONCLUSIONS

Coronary angioplasty substantially improves patient-perceived quality of life, especially physical functioning and vitality, as compared with continued medical treatment. These differences are attributed to alleviation of cardiac symptoms (specifically, breathlessness and angina), but must be balanced against the small procedure-related risks of PTCA.

The agonising negative trend in monitoring of clinical trials

Randomised clinical trials are undertaken in the hope of showing positive benefits of a new treatment, but on occasion quite the opposite trend can occur, If the interim data suggest possible negative (harmful) effects of a new treatment. The handling of such emerging negative trends is among the most complicated and ethically challenging scenarios in monitoring clinical trials through repeated interim analyses. Statistical methods are helpful to detect the point of no likely beneficial effect, and the point that separates neutral results from harmful results. However, in practice the decision whether (and exactly when) to stop such a trial involves a complex of other issues that depends on the context of the disease, the treatment being assessed, and the current practice of medicine. Owing to this complexity, an Independent Data and Safety Monitoring Board (DSMB) is best suited to deal with such a situation. Prediction of whether a negative trend will emerge in any trial is not possible. Negative trends were not anticipated in the cardiovascular trials and the trials of lung-cancer prevention described here. In the light of these experiences, all trials and their DSMBs should consider ahead of time the possibility of unexpectedly harmful results, and should document appropriately the statistical guidelines and the decision-making process required to cope with such undesirable events.

Estimation and comparison of rates of change in longitudinal studies with informative drop-outs

Many cohort studies and clinical trials have designs which involve repeated measurements of disease markers. One problem in such longitudinal studies, when the primary interest is to estimate and to compare the evolution of a disease marker, is that planned data are not collected because of missing data due to missing visits and/or withdrawal or attrition (for example, death). Several methods to analyse such data are available, provided that the data are missing at random. However, serious biases can occur when missingness is informative. In such cases, one needs to apply methods that simultaneously model the observed data and the missingness process. In this paper we consider the problem of estimation of the rate of change of a disease marker in longitudinal studies, in which some subjects drop out prematurely (informatively) due to attrition, while others experience a non-informative drop-out process (end of study, withdrawal). We propose a method which combines a linear random effects model for the underlying pattern of the marker with a log-normal survival model for the informative drop-out process. Joint estimates are obtained through the restricted iterative generalized least squares method which are equivalent to restricted maximum likelihood estimates. A nested EM algorithm is applied to deal with censored survival data. The advantages of this method are: it provides a unified approach to estimate all the model parameters; it can effectively deal with irregular data (that is, measured at irregular time points), a complicated covariance structure and a complex underlying profile of the response variable; it does not entail such complex computation as would be required to maximize the joint likelihood. The method is illustrated by modelling CD4 count data in a clinical trial in patients with advanced HIV infection while its performance is tested by simulation studies.

Assessing treatment-time interaction in clinical trials with time to event data: a meta-analysis of hypertension trials

Exploration of the variation of treatment effect over time in randomized clinical trials with low event rates is limited by lack of power. A meta-analysis on individual patient data from such trials can partly solve the problem, but brings other computational difficulties. Using an example in hypertension, we describe appropriate methods for graphical description and statistical modelling of treatment-time interactions in large data sets. Also, a method is developed for determining the total number of events required to detect treatment-period interactions of plausible magnitude. We conclude that trialists tend to overinterpret the observed data when looking for potential treatment-time interactions by visual comparisons of survival curves, failing to realize the substantial amounts of data that are needed for their detection and estimation.

A clinical trial comparing three antithrombotic-drug regimens after coronary-artery stenting. Stent Anticoagulation Restenosis Study Investigators

BACKGROUND

Antithrombotic drugs are used after coronary-artery stenting to prevent stent thrombosis. We compared the efficacy and safety of three antithrombotic-drug regimens - aspirin alone, aspirin and warfarin, and aspirin and ticlopidine - after coronary stenting.

METHODS

Of 1965 patients who underwent coronary stenting at 50 centers, 1653 (84.1 percent) met angiographic criteria for successful placement of the stent and were randomly assigned to one of three regimens: aspirin alone (557 patients), aspirin and warfarin (550 patients), or aspirin and ticlopidine (546 patients). All clinical events reflecting stent thrombosis were included in the prespecified primary end point: death, revascularization of the target lesion, angiographically evident thrombosis, or myocardial infarction within 30 days.

RESULTS

The primary end point was observed in 38 patients: 20 (3.6 percent) assigned to receive aspirin alone, 15 (2.7 percent) assigned to receive aspirin and warfarin, and 3 (0.5 percent) assigned to receive aspirin and ticlopidine (P=0.001 for the comparison of all three groups). Hemorrhagic complications occurred in 10 patients (1.8 percent) who received aspirin alone, 34 (6.2 percent) who received aspirin and warfarin, and 30 (5.5 percent) who received aspirin and ticlopidine (P<0.001 for the comparison of all three groups); the incidence of vascular surgical complications was 0.4 percent (2 patients), 2.0 percent (11 patients), and 2.0 percent (11 patients), respectively (P=0.01). There were no significant differences in the incidence of neutropenia or thrombocytopenia (overall incidence, 0.3 percent) among the three treatment groups.

CONCLUSIONS

As compared with aspirin alone and a combination of aspirin and warfarin, treatment with aspirin and ticlopidine resulted in a lower rate of stent thrombosis, although there were more hemorrhagic complications than with aspirin alone. After coronary stenting, aspirin and ticlopidine should be considered for the prevention of the serious complication of stent thrombosis.

Long-term results of RITA-1 trial: clinical and cost comparisons of coronary angioplasty and coronary-artery bypass grafting. Randomised Intervention Treatment of Angina

BACKGROUND

Percutaneous transluminal coronary angioplasty (PTCA) and coronary-artery bypass grafting (CABG) are both effective intervention strategies for patients with coronary heart disease. We report comparative long-term clinical and health-service cost findings for these interventions in the first Randomised Intervention Treatment of Angina (RITA-1) trial.

METHODS

1011 patients with coronary heart disease (45% single-vessel, 55% multivessel) were randomly assigned initial treatment strategies of PTCA or CABG. Information on clinical events, subsequent intervention, symptomatic status, exercise testing, and use of health-care resources is available for a median 6.5 years of follow-up. Analyses were by intention to treat.

FINDINGS

The predefined primary endpoint of death or nonfatal myocardial infarction occurred in 87 (17%) PTCA-group patients and 80 (16%) CABG-group patients (p=0.64). Similarly, there was no significant treatment difference in deaths alone (39 PTCA, 45 CABG), of which 46% were cardiac related. In both groups, the risk of cardiac death or myocardial infarction was more than five times higher in the first year than in subsequent years of follow-up. 26% of patients assigned PTCA subsequently also had CABG, and a further 19% required additional nonrandomised PTCA. Most of these reinterventions occurred within a year of randomisation, and from 3 years onwards the reintervention rate averaged 4% per year. In the CABG group the reintervention rate averaged 2% per year. The prevalence of angina was consistently higher in the PTCA group, with an absolute average 10% excess compared with the CABG group (p<0.001). Total health-service costs over 5 years showed no significant difference between initial strategies of PTCA and CABG (mean difference pounds sterling 426 [95% Cl -pounds sterling 383 to pounds sterling 1235]; p=0.30). The clinical and cost comparisons showed similar patterns for patients with single-vessel and multivessel disease.

INTERPRETATION

Initial strategies of PTCA and CABG led to similar long-term results in terms of survival and avoidance of myocardial infarction and to similar long-term health-care costs. Choice of approach, therefore, rests on weighing the more invasive nature of CABG against the greater risk of recurrent angina and reintervention over many years after PTCA.

Design and current status of ACTION: A Coronary disease Trial Investigating Outcome with Nifedipine GITS. Gastro-Intestinal Therapeutic System

AIMS

To present the design of ACTION (A Coronary disease Trial Investigating Outcome with Nifedipine GITS), an ongoing multicentre clinical outcome trial with nifedipine GITS (Gastro-Intestinal Therapeutic System) in patients with stable angina pectoris.

METHODS

At least 6000 patients with optimally treated stable angina without depressed left ventricular function are randomized in equal proportions to either nifedipine GITS or matching placebo (starting dose 30 mg, maintenance dose 60 mg once daily). Patients are followed for at least four years. The primary end-point, to be analyzed by assigned treatment, includes all-cause mortality, acute myocardial infarction, emergency coronary angiography for refractory angina, overt heart failure, debilitating stroke and peripheral revascularization. For this end-point, the trial has a power of 95% to detect a relative risk reduction of 18% at the 5%, level of significance, and is large enough to exclude an excess mortality caused by nifedipine GITS of 3.1 deaths per 1000 years of treatment or greater. The pre-specified early termination rule is more conservative in the case of a beneficial effect than in the case of an adverse effect of nifedipine GITS. The first patient was randomized on 29 November, 1996. By the end of April 1998, about 5200 patients had been started on study medication.

CONCLUSIONS

Results will be available in the autumn of 2003.

The hope and the hazards of using compliance data in randomized controlled trials

This paper aims to elucidate both the advantages and limitations of using compliance data in the reporting of treatment differences in clinical trials, illustrating the issues with some recent examples. While analysis by intention-to-treat should remain the principal reporting approach for most major clinical trials, arguments are put forward as to why supplementary analyses taking account of compliance can be of value. However, continued recognition of the potential biases inherent in all such selective analysis is of key importance. Some of the possible analytical approaches are presented along with suggestions on interpretation. Particular emphasis is on one case study, a large European trial in obesity incorporating repeated measures of weight loss, drug plasma level and pill count data. In working on compliance data in clinical trials, the statistician's main responsibilities may be to undertake a cohesive analysis strategy not influenced by data dredging, to achieve clarity of exposition without undue complexity or oversimplification, and to provide appropriately cautious interpretations which take account of selection biases and data limitations.

Linearly divergent treatment effects in clinical trials with repeated measures: efficient analysis using summary statistics

In many randomized clinical trials with repeated measures of a response variable one anticipates a linear divergence over time in the difference between treatments. This paper explores how to make an efficient choice of analysis based on individual patient summary statistics. With the objective of estimating the mean rate of treatment divergence the simplest choice of summary statistic is the regression coefficient of response on time for each subject (SLOPE). The gains in statistical efficiency imposed by adjusting for the observed pre-treatment levels, or even better the estimated intercepts, are clarified. In the process, we develop the optimal linear summary statistic for any repeated measures design with assumed known covariance structure and shape of true mean treatment difference over time. Statistical power considerations are explored and an example from an asthma trial is used to illustrate the main points.

Clinical trials with multiple outcomes: a statistical perspective on their design, analysis, and interpretation

This article tackles both practical and statistical issues in the handling of multiple outcomes in clinical trials, with relevance to trial design, analysis, and reporting. Specific topics illustrated by examples include: the advantage of prespecifying priorities amongst outcomes and analyses, corrections for multiple significance testing and their limited value, problems with adverse event data, the use of a single global test of significance for clinically related outcomes, the use of a combined outcome for clinical event data, and the value of exploring interrelationships amongst outcomes. The problems in handling multiple outcomes are enhanced by trials being too small, dichotomous attitudes (is the trial "positive" or not?), obsession with p-values, and the manipulative instincts of human nature. While predeclarations of priorities in analysis and reporting of multiple outcomes are important in suppressing distortive claims, it would be unfortunate if too inflexible an approach suppressed unpredictable findings from being seriously considered.

Time trends in serum cholesterol before cancer death

Following evidence of an association between low serum cholesterol and cancer from several prospective studies, this paper concentrates on individual time trends in serial measurements of serum cholesterol before a cancer-related death. The Framingham Heart Study contains repeated measurements of cholesterol at approximately 2-year intervals in 5,209 subjects, of whom 539 died from cancer during 30 years of follow-up. We quantify (1) the change in serum total cholesterol level before cancer death, and (2) the association between fall in serum total cholesterol and odds of cancer death. The mean fall in serum total cholesterol in the 4- to 6-year period before cancer death is 8.06 (95% confidence interval = 4.58-11.54) mg per dl, with some evidence of lowered cholesterol before that period. This pattern is corroborated by evidence of a substantially increased odds of cancer death if a large fall in cholesterol occurs over any 4- to 6-year period. We suggest that these time trends can plausibly be attributed to the effects of prevalent cancer on lowering serum cholesterol; our findings add weight to the argument that the low cholesterol-cancer mortality relation does not arise because of any causal contribution of low serum total cholesterol to the risk of cancer.

Long-term survival in patients with advanced immunodeficiency

OBJECTIVE

To identity prognostic factors associated with survival time in HIV-infected patients with advanced immunodeficiency.

DESIGN

Prospective cohort study.

PARTICIPANTS

A total of 1284 HIV-infected patients with serial CD4 count measurements and at least one CD4 cell count < or = 50 x 10(6)/I (CD4 < or = 50).

MAIN OUTCOME MEASURE

Survival from initial CD4 cell count < or = 50 x 10(6)/l.

RESULTS

The median survival from initial CD4 < or = 50 x 10(6)/l was 17.1 months. The risk of death increased by 2% 195% confidence interval (Cl), 1-31 for each year of age, by 10% (95% Cl, 3-16) for each 10 x 10(6)/l decrease in CD4 count, and by 14% (95% Cl, 9-18) for each 1 g/dl decrease in haemoglobin level. Compared to AIDS-free patients with CD4 < or = 50 x 10(6) cells/l, the risk of dying was 1.5-fold (95% Cl, 1.2-1.9) that of patients who had an AIDS diagnosis for fewer than 3 months prior to CD4 < or = 50, 1.8-fold for patients with an AIDS diagnosis for 4-11 months prior to CD4 < or = 50, and twice that of patients with AIDS for > or = 12 months prior to CD4 < or = 50. The risk of dying for patients whose rate of CD4 cell decline was > 40 x 10(6)/l per 6 months was 1.7-fold (95% Cl, 1.3-2.3) that of patients with an average CD4 cell loss < 40 x 10(6)/l per 6 months, after adjusting for age, haemoglobin and duration of AIDS prior to CD4 < or = 50 x 10(6) cells/l. A prognostic score was developed from the final multivariate model, based on age at CD4 < or = 50, haemoglobin at CD4 < or = 50, duration of AIDS and rate of CD4 decline prior to CD4 < or = 50.

CONCLUSIONS

Routinely available clinical and laboratory data including haemoglobin level, rate of CD4 decline and duration of AIDS can be readily translated into a prognostic score and then used to predict the survival experience of an HIV-infected patient with advanced immunodeficiency.

A comparison of aspirin and anticoagulation following thrombolysis for myocardial infarction (the AFTER study): a multicentre unblinded randomised clinical trial

OBJECTIVE

To compare aspirin with anticoagulation with regard to risk of cardiac death and reinfarction in patients who received anistreplase thrombolysis for myocardial infarction.

DESIGN

A multicentre unblinded randomised clinical trial.

SETTING

38 hospitals in six countries.

SUBJECTS

1036 patients who had been treated with anistreplase for myocardial infarction were randomly assigned to either aspirin (150 mg daily) or anticoagulation (intravenous heparin followed by warfarin or other oral anticoagulant). The trial was stopped earlier than originally intended because of the slowing rate of recruitment.

MAIN OUTCOME MEASURE

Cardiac death or recurrent myocardial infarction at 30 days.

RESULTS

After 30 days cardiac death or reinfarction, occurred in 11.0% (57/517) of the patients treated with anticoagulation and 11.2% (58/519) of the patients treated with aspirin (odds ratio 1.02, 95% confidence interval 0.69 to 1.50, P = 0.92). Corresponding findings at three months were 13.2% (68/517) and 12.1% (63/519) (0.91, 0.63 to 1.32, P = 0.67). Patients receiving anticoagulation were more likely than patients receiving aspirin to have had severe bleeding or a stroke by three months (3.9% v 1.7% (0.44, 0.20 to 0.97, P = 0.04)).

CONCLUSION

No evidence of a difference in the incidence of cardiac events was found between the two treatment groups, though the trial is too small to claim treatment equivalence confidently. A higher incidence of severe bleeding events and strokes was detected in the group receiving anticoagulation, suggesting that aspirin may be the drug of choice for most patients in this context.

Quality of life, employment status, and anginal symptoms after coronary angioplasty or bypass surgery. 3-year follow-up in the Randomized Intervention Treatment of Angina (RITA) Trial

BACKGROUND

The Randomized Intervention Treatment of Angina (RITA) trial compares initial policies of percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass graft surgery (CABG) in 1011 patients with angina. This report assesses the impact of these revascularization procedures on angina, quality of life (according to the Nottingham Health Profile), and employment over 3 years of follow-up.

METHODS AND RESULTS

Both interventions produced marked improvement in all quality-of-life dimensions (energy, pain, emotional reactions, sleep, social isolation, and mobility) and seven aspects of daily living. Patients with angina at 2 years had more quality-of-life impairment than angina-free patients, whose perceived health was similar to population norms. This reflects the close link at baseline between angina grade and quality of life. The slightly greater impairment of quality of life in PTCA compared with CABG patients is a result of their significantly higher chances of having angina, especially after 6 months. Employment status was investigated mainly for men < or = 60 years old. PTCA patients returned to work sooner (40% at 2 months compared with 10% of CABG patients), but the latter caught up by 5 months. After 2 years, 22% and 26% of CABG and PTCA patients, respectively, were not working for cardiac reasons. Patients with angina at 2 years were much more likely to be unemployed than those without.

CONCLUSIONS

The impact of angina on quality of life and unemployment is greatly alleviated by PTCA or CABG. Angina is avoided more successfully with CABG, but PTCA offers a speedier return to work. Both intervention strategies then produce similar benefits for quality of life and employment over several years.

The role of external evidence in data monitoring of a clinical trial

Data monitoring of interim results from a randomized clinical trial should take into consideration evidence from other trials. This article presents both scientific and practical issues regarding the pros and cons of formally incorporating such external evidence into the decision making process for the current trial. Guidelines on how to use other trials' data are presented, along with cautiously sceptical comments on the impracticality of using formal meta-analyses in data monitoring. The arguments are illustrated by recent examples from specific trials, and the article concludes with some general recommendations.

Statistical reporting of clinical trials with individual changes from allocated treatment

We consider clinical trials in which information is available about subjects' treatment changes after randomization. To understand whether any difference between randomized groups in the intention-to-treat analysis can be explained by such treatment changes, we need analysis strategies which take account of treatment actually received. Selection bias is then a potentially serious problem. We relate risk in a time-dependent proportional hazards model to current treatment, with treatment combinations coded in two alternative ways. To reduce selection bias, treatment history (number of treatments dropped) and baseline covariates can be added to the model. Including current risk markers would also reduce selection bias but makes interpretation difficult. The methods are illustrated using data from the British Medical Research Council (MRC) elderly hypertension trial, with time to cardiovascular death as an outcome. Results for the comparison of diuretic and beta-blocker treatment are similar in all analyses, suggesting that selection bias is small and adding support to the hypothesis that the observed treatment differences are due to the randomized treatments themselves.

Meta-analysis of randomised trials comparing coronary angioplasty with bypass surgery

A patient with severe angina will often be eligible for either angioplasty (PTCA) or bypass surgery (CABG). Results from eight published randomised trials have been combined in a collaborative meta-analysis of 3371 patients (1661 CABG, 1710 PTCA) with a mean follow-up of 2.7 years. The total deaths in the CABG and PTCA groups were 73 and 79, respectively, with a relative risk (RR) of 1.08 (95% CI 0.79-1.50). The combined endpoint of cardiac death and non-fatal myocardial infarction occurred in 169 PTCA patients and 154 CABG patients (RR 1.10 [0.89-1.37]). Amongst patients randomised to PTCA 17.8% required additional CABG within a year, while in subsequent years the need for additional CABG was around 2% per annum. The rate of additional non-randomised interventions (PTCA and/or CABG) in the first year of follow-up was 33.7% and 3.3% in patients randomised to PTCA and CABG, respectively. The prevalence of angina after one year was considerably higher in the PTCA group (RR 1.56 [1.30-1.88]) but at 3 years this difference had attenuated (RR 1.22 [0.99-1.54]). Overall there was substantial similarity in outcome across the trials. Separate analyses for the 732 single-vessel and 2639 multivessel disease patients were largely compatible, though the rates of mortality, additional intervention, and prevalent angina were slightly lower in single vessel disease. The combined evidence comparing PTCA with CABG shows no difference in prognosis between these two initial revascularisation strategies. However, the treatments differ markedly in the subsequent requirement for additional revascularisation procedures and in the relief of angina. These results will influence the choice of revascularisation procedure in future patients with angina.

Life as an academic medical statistician and how to survive it

This article aims to review the professional life of academic medical statisticians. Topics covered include training opportunities, the shortage of medical statisticians, the relevance of PhD degrees, the varied working life (teaching, research, computing, refereeing etc.), research priorities across consultancy, collaborations and methodology, professional recognition and the variety of working environments. In conclusion, some tentative suggestions are made on how to survive happily in the world of academic medical statistics.

Environmental lead and children's intelligence: a systematic review of the epidemiological evidence

OBJECTIVE

To quantify the magnitude of the relation between full scale IQ in children aged 5 or more and their body burden of lead.

DESIGN

A systematic review of 26 epidemiological studies since 1979: prospective studies of birth cohorts, cross sectional studies of blood lead, and cross sectional studies of tooth lead.

SETTING

General populations of children > or = 5 years.

MAIN OUTCOME MEASURES

For each study, the regression coefficient of IQ on lead, after adjustment for confounders when possible, was used to derive the estimated change in IQ for a specific doubling of either blood or tooth lead.

RESULTS

The five prospective studies with over 1100 children showed no association of cord blood lead or antenatal maternal blood lead with subsequent IQ. Blood lead at around age 2 had a small and significant inverse association with IQ, somewhat greater than that for mean blood lead over the preschool years. The 14 cross sectional studies of blood lead with 3499 children showed a significant inverse association overall, but showed more variation in their results and their ability to allow for confounders. The seven cross sectional studies of tooth lead with 2095 children were more consistent in finding an inverse association, although the estimated magnitude was somewhat smaller. Overall synthesis of this evidence, including a meta-analysis, indicates that a typical doubling of body lead burden (from 10 to 20 micrograms/dl (0.48 to 0.97 mumol/l) blood lead or from 5 to 10 micrograms/g tooth lead) is associated with a mean deficit in full scale IQ of around 1-2 IQ points.

CONCLUSION

While low level lead exposure may cause a small IQ deficit, other explanations need considering: are the published studies representative; is there inadequate allowance for confounders; are there selection biases in recruiting and following children; and do children of lower IQ adopt behaviour which makes them more prone to lead uptake (reverse causality)? Even if moderate increases in body lead burden adversely affect IQ, a threshold below which there is negligible influence cannot currently be determined. Because of these uncertainties, the degree of public health priority that should be devoted to detecting and reducing moderate increases in children's blood lead, compared with other important social detriments that impede children's development, needs careful consideration.

Short-term effects of air pollution on daily mortality in Athens: a time-series analysis

BACKGROUND

Athens has a serious air pollution problem which became evident in the early 1970s. Studies for the years 1975-1982 have indicated a positive association of sulphur dioxide (SO2) with total daily mortality. Since 1983 the pollution profile in Athens has gradually changed but the levels of smoke, SO2 and carbon monoxide (CO) remain relatively high.

METHODS

The association of air pollution with daily all-cause mortality in Athens for the years 1984-1988 was investigated using daily values of SO2, smoke and CO. Autoregressive models with log-transformed daily mortality as the dependent variable, were used to adjust for temperature and relative humidity (both lagged by 1 day), year, season and day of week, as well as for serial correlations in mortality.

RESULTS

Graphic analysis revealed non-linear monotonically increasing relationships between total mortality and SO2, smoke and CO, with steeper exposure-response slopes at lower air pollution levels. Air pollution data lagged by 1 day had the strongest association with daily mortality. In three separate autoregression models for log(SO2), log(smoke) and log(CO) the regression coefficients for each were highly statistically significant (P < 0.001). Further multiple regression modelling showed that SO2 and smoke are both independent predictors of daily mortality, though to a lesser extent than temperature and relative humidity. The inclusion of CO in the model did not further improve the prediction of daily mortality. The magnitude of association is small, for instance, a 10% reduction in smoke is estimated to decrease daily mortality by 0.75% (95% confidence interval [CI]: 0.51-0.99). However, it cannot be accounted for by climatic and seasonal effects, so that a causal influence of air pollution on daily mortality seems plausible.

CONCLUSIONS

These findings suggest that current air pollution levels in Athens (and many other industrialized cities) may be responsible for substantial numbers of premature deaths, and hence remain an important public health issue.

Health service costs of coronary angioplasty and coronary artery bypass surgery: the Randomised Intervention Treatment of Angina (RITA) trial

For some patients with coronary artery disease, percutaneous transluminal coronary angioplasty (PTCA) is an alternative to coronary artery bypass grafting (CABG). We report comparative health service costs of these interventions within the Randomised Intervention Treatment of Angina (RITA) trial. Medications were costed at published UK prices; other resource use was costed with a set of unit costs estimated at two recruiting centres to the RITA trial, one in London and one outside. Over 2-year follow-up of 1011 patients, the estimated mean additional cost for those randomised to CABG compared with PTCA was 1050 pounds (95% CI 621 pounds-1479 pounds), with unit costs from the non-London centre, and 1823 pounds (1202 pounds-2444 pounds), with unit costs from the London centre. The initial average cost of treating a patient randomised to PTCA is about 52% of that of CABG, but after 2 years this increased to about 80% because of the greater need for subsequent interventions. The balance of advantage between PTCA and CABG may change after several years: funding has been obtained to continue RITA follow-up for 10 years. However, on the basis of patients' status at 2 years, the cost advantages of PTCA cannot be ignored. Further research is necessary to assess whether the advantage of PTCA in terms of cost is translated into one of cost-effectiveness.

Predictive value of repeated measurements of CD4 lymphocyte counts on progression to AIDS

OBJECTIVE

Description of the relationship between repeated measurements of CD4 lymphocyte count and development of AIDS in asymptomatic HIV-infected patients.

DESIGN

Repeated measurements of CD4 lymphocyte counts over an AIDS-free period in asymptomatic HIV-infected patients, and follow-up of the cohort to record subsequent clinical progression to AIDS.

METHODS

The cohort was studied in a double-blind randomized clinical trial. CD4 lymphocyte counts were measured on three occasions over 8 months in 851 patients.

RESULTS

Eighty subsequent clinical progressions to AIDS were recorded during a median follow-up period of 15.3 months. Each of the three measurements of CD4 lymphocyte count were separately predictive of subsequent progression to AIDS. However, when the three measurements were included simultaneously in a predictive model only the last measurement showed a significant predictive value. Change in individual CD4 count was also related to the risk of developing AIDS, but was no longer significant when the most recent measurement was included in the model.

CONCLUSION

These results indicate the closeness of the relationship between the actual state of the immune system and subsequent progression to AIDS.