This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record.
1. Trial at a Glance
CHARM-Preserved was a randomized, double-blind, parallel phase 3 treatment trial evaluating candesartan cilexetil in congestive heart failure.
| Feature | CHARM-Preserved |
|---|---|
| Condition | Congestive Heart Failure |
| Design | Randomized, parallel, double-blind |
| Primary purpose | Treatment |
| Interventions | Candesartan (drug); Placebo (drug) |
| Lead sponsor | AstraZeneca |
| Primary completion date | 2003-05 |
2. Clinical Question
Population
Patients with congestive heart failure.
Intervention
Candesartan cilexetil.
Comparator
Placebo.
Primary question
Whether candesartan cilexetil affected cardiovascular mortality or hospitalization due to congestive heart failure.
3. Trial Design
Randomization
734 patients
Assignment
2 arms
Masking
Double
Follow-up
Registry timeframe
Endpoint
CV mortality or HF hospitalization
| Arm | Intervention |
|---|---|
| Candesartan arm | Candesartan (drug) |
| Control arm | Placebo (drug) |
4. Endpoints
| Endpoint | Registry definition | Time frame |
|---|---|---|
| Primary endpoint | Cardiovascular mortality or hospitalisation due to congestive heart failure | , 4, 6 weeks, 6 months, every 4 months thereafter until 24 months |
5. Planned Analysis
The ClinicalTrials.gov record identifies the primary endpoint as a composite cardiovascular time-to-event outcome involving cardiovascular mortality or hospitalization due to congestive heart failure. Results have not been posted on ClinicalTrials.gov.
For a composite endpoint of mortality and hospitalization, clinical trials commonly analyze the time until the first occurrence of either component using survival analysis methods. These methods account for patients who have different follow-up durations and may remain event-free at the end of observation.
6. Statistical Methodology
Composite endpoints
A composite endpoint combines multiple clinically meaningful events into one outcome. The analysis generally compares the time until the first qualifying event between randomized groups.
A composite result reflects the combined behavior of its components. Mortality events and hospitalization events may differ in clinical importance and frequency, so interpretation requires understanding which components contribute most strongly to the observed comparison.
Time-to-event analysis
Time-to-event methods are designed for outcomes where both the occurrence and timing of events matter. Patients without an observed event at the end of follow-up contribute information through their available observation period.
Randomization and masking
Random allocation helps balance known and unknown prognostic factors between treatment groups. Double masking reduces the possibility that knowledge of assigned treatment influences outcome assessment or patient management.
7. Statistical Methods Explained
Why use a composite endpoint?
Combining cardiovascular mortality and heart-failure hospitalization can increase the number of observed events compared with mortality alone, potentially improving statistical efficiency. The tradeoff is that each component must be interpreted separately when understanding clinical meaning.
How are cardiovascular death and hospitalization outcomes usually analyzed?
These outcomes are typically evaluated using time-to-event approaches because patients may have different follow-up durations and some observations may be censored.
What does randomization accomplish?
Randomization creates comparable treatment groups on average, allowing differences in outcomes to be attributed more reliably to the assigned intervention.
Why does double masking matter?
Masking helps limit bias by preventing participants and investigators from knowing treatment assignment during the study period.
Why does follow-up duration matter?
The registry specifies assessments through 24 months, meaning outcome interpretation depends on the amount of time patients are observed for cardiovascular events.
8. Limitations
- Posted results: The ClinicalTrials.gov record does not report statistical estimates, confidence intervals, or p-values.
- Endpoint composition: Composite outcomes require interpretation of their individual components.
- Registry detail: The record does not report additional analysis details such as subgroup analyses, missing-data methods, or interim analyses.
9. Why This Trial Matters Statistically
| Concept | How it appears in CHARM-Preserved |
|---|---|
| Randomized trial design | Randomized parallel comparison |
| Blinding | Double masking |
| Composite endpoint | Cardiovascular mortality or hospitalization due to congestive heart failure |
| Time-to-event analysis | Appropriate framework for outcomes occurring over follow-up |
10. Related Tutorials
Learn more about the methods used in this trial: