This page separates information reported in the ClinicalTrials.gov record from statistical interpretation. The ClinicalTrials.gov record contains the trial design, primary endpoint definition, enrollment, timing, and serious-adverse-event counts, but no formal statistical-analysis estimates, confidence intervals, or p-values.
1. Trial at a Glance
CATIS was a randomized, double-blind, parallel-group clinical trial evaluating active antihypertensive treatment in acute ischemic stroke. The registry reports an enrollment of 4071 participants and a primary composite endpoint assessed over a 2-week time frame.
| Feature | CATIS |
|---|---|
| Trial name | China Antihypertensive Trial in Acute Ischemic Stroke |
| NCT identifier | NCT01840072 |
| Therapeutic area | Neurology |
| Condition | Ischemic Stroke |
| Phase | NA |
| Status | COMPLETED |
| Allocation | RANDOMIZED |
| Design model | PARALLEL |
| Masking | DOUBLE |
| Primary purpose | TREATMENT |
| Enrollment | 4071.0 |
| Lead sponsor | Tulane University |
| Sponsor type | OTHER |
2. Clinical Question
The central statistical question was whether an active antihypertensive treatment strategy could change the risk of the registered composite clinical outcome compared with usual care in patients with ischemic stroke.
Population
Patients enrolled in CATIS with the registry-listed condition of ischemic stroke.
Intervention
Active antihypertensive treatment, described in the registry as an active antihypertensive treatment intervention.
Comparator
Usual care.
Primary question
Does active antihypertensive treatment alter the registered combination of death within 14 days after randomization and major disability at 14 days or at hospital discharge if earlier than 14 days?
3. Trial Design
Active antihypertensive treatment
- Active antihypertensive treatment
- Randomized parallel-group assignment
- Double-blind trial design
- Serious adverse events: 0/2038
Usual care
- Usual care comparator
- Randomized parallel-group assignment
- Double-blind trial design
- Serious adverse events: 0/2033
The arm-specific serious-adverse-event denominators sum to the reported enrollment: 2038 participants in the active antihypertensive treatment arm and 2033 in the usual-care arm, for 4071 participants overall.
4. Trial Timeline
Trial start
The registry lists August 2009 as the trial start.
Primary completion
The registry lists May 2013 as the primary completion date.
Registry status
The ClinicalTrials.gov record identifies CATIS as completed.
5. Primary Endpoint
| Endpoint | Registered definition | Time frame |
|---|---|---|
| A Combination of Death Within 14 Days After Randomization and Major Disability at 14 Days or at Hospital Discharge if Earlier Than 14 Days. | Major disability was defined as a score of 3 to 5 on the modified Rankin Scale at 14 days after randomization. Scores on the modified Rankin Scale range from 0 to 6, with a score of 0 indicating no symptoms; a score of 5 indicating severe disability (ie, bedridden, incontinent, or requiring constant nursing care and attention); and a score of 6 indicating death. | 2 weeks |
This endpoint combines two clinically important outcomes: death within 14 days and major disability at the specified assessment point. The composite therefore does not represent a single continuous measurement. It represents whether a participant experiences the registered composite outcome during the defined early post-randomization period.
The registry definition makes the distinction between disability and death explicit. In particular, the primary endpoint combines death with scores of 3 to 5 rather than treating every modified Rankin Scale score as equivalent.
6. Understanding the Composite Endpoint
A composite endpoint is constructed by combining multiple clinically relevant events into a single primary outcome. Here, the registry defines the composite as death within 14 days after randomization together with major disability at 14 days or at hospital discharge if earlier than 14 days.
Why use a composite?
A composite can capture more than one clinically important unfavorable outcome within a single prespecified endpoint.
What is counted?
The registered definition counts death and major disability according to the stated modified Rankin Scale criteria and timing.
Why timing matters
The outcome is explicitly tied to the first 14 days after randomization, with hospital discharge used if earlier than 14 days for the disability assessment.
Why interpretation requires care
A treatment effect on the composite does not automatically establish that every component changes to the same degree.
7. Statistical Methodology
The ClinicalTrials.gov record identifies the trial as randomized, double-blind, and parallel-group, and identify the composite endpoint and its 2-week time frame. They do not provide a formal statistical-analysis result for the primary endpoint: no formal statistical analyses were posted.
Because no formal statistical-analysis estimate is present in the ClinicalTrials.gov record, this page does not report a treatment-effect estimate, confidence interval, or p-value. Doing so would require information not contained in the ClinicalTrials.gov record and would violate the numerical-source restriction for this page.
What analysis would normally be considered?
For a binary composite endpoint defined over a fixed follow-up window, a common primary analysis would compare the proportion of participants experiencing the composite outcome in the two randomized groups. Depending on the prespecified statistical analysis plan, this could be expressed as a risk ratio, risk difference, odds ratio, or another appropriate effect measure, with a corresponding confidence interval and hypothesis test.
The important point is that the appropriate analysis should be determined from the trial's prespecified statistical plan and endpoint structure. The ClinicalTrials.gov record does not identify such a formal statistical result, so this page describes the analytical framework without assigning an observed treatment effect.
8. Planned Analysis
Because the registry data posted on ClinicalTrials.gov for CATIS contain a registered primary endpoint but no formal statistical analyses, the primary endpoint is presented here as a planned-analysis framework rather than as a reported statistical result.
Primary endpoint analysis framework
Compare the occurrence of the registered composite endpoint between the randomized active-treatment and usual-care groups.
No treatment-effect estimate, confidence interval, or p-value is reported in the ClinicalTrials.gov record.
| Element | What the ClinicalTrials.gov record establishes | Statistical interpretation |
|---|---|---|
| Endpoint | Death within 14 days plus major disability at 14 days or hospital discharge if earlier than 14 days | A fixed-time composite clinical endpoint |
| Time frame | 2 weeks | The comparison concerns outcomes during the prespecified early follow-up period |
| Randomization | RANDOMIZED | Random allocation provides the basis for a treatment-group comparison |
| Masking | DOUBLE | Both the treatment assignment and outcome assessment process may be less susceptible to knowledge of assignment, depending on the exact operational implementation |
| Formal result | No statistical analyses reported | No numerical treatment effect should be inferred |
9. Statistical Methods Explained
Why was randomization important?
Randomization creates the fundamental comparison between active antihypertensive treatment and usual care. In a properly conducted randomized trial, treatment assignment is determined by the randomization process rather than by investigators selecting which treatment an individual receives. This helps make differences in outcomes interpretable as treatment-group differences rather than simply differences in who received each treatment.
What does double-blind mean statistically?
The registry identifies CATIS as double-blind. Blinding can reduce the influence of knowledge of treatment assignment on participant behavior, clinical management, outcome assessment, or other trial processes. The exact people covered by the registry's double-blinding designation are not specified in the ClinicalTrials.gov record, so the page does not assign a more specific definition.
Why use a composite endpoint?
The primary endpoint combines death and major disability. A composite can increase the number of participants experiencing the primary outcome compared with a single component, potentially providing a broader measure of clinically important harm. However, interpretation requires attention to each component because a composite result does not establish that every component contributed equally.
Why does the 2-week time frame matter?
The endpoint is not an unspecified long-term outcome. The registry explicitly defines a 2-week time frame, including death within 14 days and major disability at 14 days or at hospital discharge if earlier. Consequently, the statistical comparison concerns the probability of the registered early outcome rather than an unspecified lifetime or long-term risk.
How would a risk difference be interpreted?
If a risk difference were reported, it would represent the difference in the proportions of participants experiencing the composite endpoint between the two randomized groups. A negative value, depending on the direction used to define the comparison, could indicate fewer composite events with active treatment; a positive value could indicate more. The registry-reported CATIS data do not provide the observed event proportions, so no numerical risk difference can be calculated here.
How would a confidence interval add information?
A confidence interval would describe statistical uncertainty around an estimated treatment effect. A narrow interval would indicate greater precision, while a wide interval would indicate greater uncertainty. Without a reported effect estimate and its confidence interval, the strength and precision of the CATIS treatment comparison cannot be quantified from the ClinicalTrials.gov record.
10. Interpreting Statistical Significance
The ClinicalTrials.gov record contains no p-value for the CATIS primary endpoint. Therefore, this page does not characterize the primary comparison as statistically significant or nonsignificant.
A p-value addresses compatibility of the observed data with a specified null hypothesis under the chosen statistical model and testing framework. It does not measure the magnitude of a treatment effect, the clinical importance of that effect, or the probability that a treatment works.
For a two-arm clinical trial with a binary composite endpoint, an effect estimate such as a risk difference, risk ratio, or odds ratio would show the direction and magnitude of the observed between-group difference. A confidence interval would then describe its statistical precision.
Randomized trials can be analyzed according to different populations, including approaches based on randomized assignment or treatment actually received. The registry-reported CATIS data do not specify a formal primary analysis population, so this page does not attribute one to the trial.
11. Safety Results
The ClinicalTrials.gov record reports serious adverse events by randomized arm as follows:
| Safety measure | Active Antihypertensive Treatment | Usual Care |
|---|---|---|
| Serious adverse events, affected / at risk | 0/2038 | 0/2033 |
Reported serious adverse events
Active antihypertensive treatment vs usual care
The ClinicalTrials.gov record reports zero affected participants in each arm for this safety measure.
This safety result should be described exactly as reported: 0 affected participants among 2038 at risk in the active antihypertensive treatment arm and 0 among 2033 at risk in the usual-care arm. It does not establish that the treatment has no possible safety risks. It describes only the serious-adverse-event measure and denominators reported in the ClinicalTrials.gov record.
12. Safety and Efficacy Are Different Questions
The primary efficacy endpoint and the serious-adverse-event measure answer different statistical questions. The primary endpoint evaluates the registered composite of early death and major disability, whereas the safety field reports serious adverse events by arm.
Efficacy endpoint
Whether participants experienced the registered death/major-disability composite during the specified 2-week period.
Safety measure
Whether participants were reported as having a serious adverse event, with affected and at-risk counts posted on ClinicalTrials.gov for each arm.
Different denominators
The registry-reported safety denominators are 2038 and 2033 for the two treatment groups.
Different interpretation
A safety count should not be substituted for the primary efficacy outcome, and vice versa.
13. What Can and Cannot Be Concluded From the Supplied Results
| Question | Supported by the ClinicalTrials.gov record? | Reason |
|---|---|---|
| Was CATIS randomized? | Yes | The allocation is listed as RANDOMIZED. |
| Was CATIS double-blind? | Yes | The masking is listed as DOUBLE. |
| Was the design parallel-group? | Yes | The design model is listed as PARALLEL. |
| Was the primary endpoint assessed over 2 weeks? | Yes | The registered endpoint time frame is 2 weeks. |
| How many participants were enrolled? | Yes | The registry-reported enrollment is 4071.0. |
| How many serious adverse events occurred in each reported arm? | Yes | The registry-reported affected/at-risk counts are 0/2038 and 0/2033. |
| What was the treatment-effect estimate for the primary endpoint? | No | No statistical analysis is reported. |
| What was the confidence interval? | No | No confidence interval is reported. |
| What was the p-value? | No | No p-value is reported. |
| Which treatment was statistically superior? | No | The ClinicalTrials.gov record does not contain a formal statistical comparison. |
14. Limitations
- No formal statistical-analysis estimates reported: no formal statistical analyses were posted, so treatment-effect estimates, confidence intervals, and p-values cannot be reported from the ClinicalTrials.gov record.
- Primary endpoint is composite: the endpoint combines death and major disability, so a composite result would require component-level interpretation as well as interpretation of the combined endpoint.
- Fixed early time frame: the primary endpoint is defined over 2 weeks. Conclusions about longer-term outcomes cannot be inferred from this endpoint alone.
- Registry endpoint wording: the registered primary endpoint is categorized as “Other / unclear” in the ClinicalTrials.gov record, so the exact statistical test specified in the protocol cannot be reconstructed from the registry summary provided here.
- Safety information is limited: the ClinicalTrials.gov record contains only serious-adverse-event affected/at-risk counts by arm. It does not provide a broader adverse-event profile.
- No subgroup results reported: the ClinicalTrials.gov record contain no subgroup estimates, confidence intervals, or interaction tests.
- No baseline table reported: baseline characteristics are not included in the ClinicalTrials.gov record and therefore are not reproduced here.
- No crossover information reported: the provided record does not establish whether crossover occurred or how it was handled analytically.
- No multiplicity information reported: the ClinicalTrials.gov record do not specify an alpha hierarchy, multiplicity adjustment, or formal type-I-error strategy.
- No interim-analysis information reported: the ClinicalTrials.gov record do not establish whether interim efficacy analyses were conducted or how alpha spending was handled.
- No missing-data strategy reported: the ClinicalTrials.gov record do not specify imputation, censoring, or other missing-outcome procedures.
15. Why This Trial Matters Statistically
CATIS is a useful statistical teaching example because its design brings together several foundational concepts in randomized clinical trials: randomization, double masking, parallel-group comparison, fixed-time outcome assessment, and a composite clinical endpoint.
| Concept | How it appears in CATIS |
|---|---|
| Randomization | The registry lists the allocation as RANDOMIZED. |
| Blinding | The registry lists masking as DOUBLE. |
| Parallel-group design | The design model is listed as PARALLEL. |
| Two-arm comparison | The registry reports 2 arms. |
| Fixed-time endpoint | The primary endpoint has a 2-week time frame. |
| Composite endpoint | The primary outcome combines death and major disability. |
| Ordinal clinical scale | Major disability is defined using modified Rankin Scale scores of 3 to 5. |
| Safety comparison | Serious adverse events are reported as affected/at-risk counts by arm. |
16. A Statistical Reading of the Primary Endpoint
The registered endpoint deserves careful attention because its structure affects the interpretation of any eventual effect estimate.
First: identify the unit of analysis
The endpoint is defined at the participant level. Each participant can either experience the registered composite outcome during the specified period or not, based on the endpoint definition.
Second: identify the event components
The composite contains death within 14 days and major disability at 14 days or at hospital discharge if earlier. Major disability is explicitly defined as a modified Rankin Scale score from 3 to 5.
Third: preserve the timing rule
The time frame is part of the endpoint definition. A result for this endpoint should therefore be interpreted as a result concerning the specified 2-week outcome, not as a generic measure of disability or survival.
Fourth: examine the effect measure
A complete statistical report would normally identify the effect measure, its confidence interval, and its hypothesis test. None of those numerical results is reported in the ClinicalTrials.gov record for CATIS.
Fifth: examine the components
If a composite endpoint shows a treatment-group difference, a complete interpretation should determine whether that difference is driven primarily by death, major disability, or both. The ClinicalTrials.gov record does not contain those component-level outcome counts.
17. Randomization as the Statistical Foundation
Randomization is the central design feature supporting causal interpretation in CATIS. The treatment assignment is not presented as a clinician-selected exposure or an observational comparison; the registry explicitly identifies the allocation as randomized.
The statistical purpose of randomization is not to guarantee identical groups. Rather, it provides a probability-based mechanism for assigning treatment that supports unbiased comparison under the assumptions of the randomized design.
The two reported safety denominators, 2038 and 2033, also show that the enrolled population was distributed between two study arms. The ClinicalTrials.gov record does not provide a formal randomization ratio, so no allocation ratio is inferred here.
18. Blinding as a Statistical Design Feature
CATIS is identified as double-blind. Blinding is important because knowledge of treatment assignment can influence behavior, reporting, clinical decisions, and outcome assessment. These influences are particularly relevant when outcomes involve clinical judgments.
Potential benefit
Blinding can reduce systematic differences in how participants or trial personnel behave after assignment.
Outcome assessment
Blinding can also reduce the opportunity for knowledge of treatment assignment to influence assessment of clinical outcomes.
What the registry establishes
The registry field establishes that the trial was double-blind.
What it does not establish here
The ClinicalTrials.gov record does not specify which individual trial roles were blinded or the operational procedures used to maintain masking.
19. Statistical Concepts in This Trial
Learn more about the methods and design concepts connected to CATIS:
20. Related Statistical Calculators
21. Sources
- ClinicalTrials.gov: NCT01840072 — CATIS.
- PubMed: PMID 27110711.
- PubMed: PMID 26910818.
- PubMed: PMID 24240777.
- PubMed: PMID 27412188.
- PubMed: PMID 42714478.
Continue with Clinical Biostats statistical methods
Explore clinical-trial design, endpoint interpretation, and statistical analysis concepts through related tutorials and calculators.
22. Record Summary
CATIS is a completed randomized, double-blind, parallel-group trial with 4071.0 enrolled participants and two treatment arms: active antihypertensive treatment and usual care. Its registered primary endpoint is a 2-week composite of death within 14 days after randomization and major disability at 14 days or at hospital discharge if earlier than 14 days, with major disability defined as a modified Rankin Scale score of 3 to 5.
The ClinicalTrials.gov record also report serious adverse events of 0/2038 in the active antihypertensive treatment arm and 0/2033 in the usual-care arm. However, no formal statistical analyses were posted. Consequently, the available data support a detailed examination of the trial's design and endpoint structure, but they do not support reporting a numerical treatment effect, confidence interval, or p-value for the primary outcome.