This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Pharmacogenomic Evaluation of Antihypertensive Responses 2 (NCT01203852), a na phase 4 study. The primary outcome is Change in Blood Pressure From Baseline to Treatment.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01203852 |
| Phase | Phase 4 |
| Condition | Hypertension |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 839 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Florida |
| Results posted | Yes |
2. Clinical Question
Population
People with hypertension were enrolled. The registry record lists 839 participants and describes the primary-outcome population as patients with antihypertensive response data. That population included participants with different amounts of follow-up across the study periods: 282 completed all 3 study periods, 369 completed only period 1, and 328 completed only period 3.
Intervention
The listed drugs are metoprolol and chlorthalidone. The registry describes a combined Metoprolol + Chlorthalidone group and says participants had their current hypertension treatment withdrawn before study treatment. Its description begins with metoprolol tartrate 50 mg twice daily for two weeks, followed by possible titration to 100 mg twice daily for six additional weeks, but the description is incomplete. Full treatment details are not reported in the registry record.
Comparator
The registry classifies the study as single-group, with allocation listed as NA and masking as none. It therefore does not describe a randomized, like-for-like control group. A comparator for estimating a between-group treatment effect is not reported in the registry record.
Primary question
The primary outcome concerns change in blood pressure from baseline to treatment, measured in mmHg after 6-8 weeks of treatment. The study's broader stated aim was to investigate whether genetic factors may influence responses to a beta-blocker or a thiazide diuretic. Numerical blood-pressure results and genetic-response findings are not reported in the registry record.
The clinical question is therefore principally about measuring blood-pressure response during treatment and investigating possible genetic influences on that response. The registry's summary describes this as research toward understanding whether genetic information might eventually help guide medication selection. That stated aim is not itself evidence that a genetic marker predicts response, or that using genetic information improves blood-pressure control. Those conclusions would require relevant results, analyses, and appropriate comparisons, which are not reported in the registry record.
3. Trial Design
This is a completed phase 4 study sponsored by the University of Florida. The registry lists hypertension as the condition, enrollment of 839, and a study period beginning in 2010-08 with primary completion in 2014-04. It classifies the design as single-group, with allocation listed as NA and masking as none. These classifications indicate that the registry does not describe a randomized comparison or masking of participants or study personnel.
The listed interventions are metoprolol and chlorthalidone. The arm description names a Metoprolol + Chlorthalidone group, reports withdrawal of participants' current hypertension treatment, and begins describing a metoprolol schedule. The description ends before the treatment instructions are complete. The full treatment sequence, including complete dosing and how each drug was used across the study, is not reported in the registry record. Although the primary-outcome population refers to three study periods, their full design and timing are not reported in the registry record.
A single-group design can describe changes observed during treatment, but without a concurrent control group it cannot, by itself, separate treatment-associated change from other explanations such as natural variation or changes over time. The registry's genetic hypothesis is an investigative aim; the design details and analyses needed to evaluate genetic associations are not reported in the registry record. No further protocol details, including eligibility criteria or a complete account of treatment assignment, are reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: Healthy volunteers with mild to moderate primary hypertension between the ages of 18-70 were eligible for the study. Subjects were washed-out from their hypertension medication prior to beginning study protocol. Participants with elevated systolic blood pressure greater than 180 mmHg after wash-out were excluded from the study.
Metoprolol 8 Weeks
| Stage | Metoprolol + Chlorthalidone |
|---|---|
| STARTED | 839 |
| COMPLETED | 369 |
| NOT COMPLETED | 470 |
Reasons for not completing this period:
| Reason | Metoprolol + Chlorthalidone |
|---|---|
| Physician Decision | 470 |
Washout 2 Weeks
| Stage | Metoprolol + Chlorthalidone |
|---|---|
| STARTED | 328 |
| COMPLETED | 282 |
| NOT COMPLETED | 46 |
Reasons for not completing this period:
| Reason | Metoprolol + Chlorthalidone |
|---|---|
| Physician Decision | 46 |
Chlorthalidone 8 Weeks
| Stage | Metoprolol + Chlorthalidone |
|---|---|
| STARTED | 328 |
| Continued From Metoprolol | 282 |
| COMPLETED | 328 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: All patients with antihypertensive response data. 282 patients completed all 3 study periods. 369 patients completed only period 1. 328 patients completed only period 3.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
Population: Approximately 1000 males or females with mild to moderate primary HTN, of any race or ethnicity, between the ages of 18 and 65 will be enrolled into the PEAR2 protocol. Prospective study participants will be those with newly diagnosed HTN, untreated HTN or known HTN currently treated with antihypertensive drugs.
| Characteristic | Unit | Metoprolol + Chlorthalidone |
|---|---|---|
| Participants analysed | 839 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 839 |
| Age, Categorical: >=65 years | Participants | 0 |
| Age, Continuous | years | 50.3 (SD 9.0) |
| Sex: Female, Male: Female | Participants | 429 |
| Sex: Female, Male: Male | Participants | 410 |
| Region of Enrollment: United States | participants | 839 |
6. Primary Endpoint
The registry lists the primary outcome as Change in Blood Pressure From Baseline to Treatment, measured over after 6-8 weeks of treatment.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | mmHg |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is titled “Change in Blood Pressure From Baseline to Treatment.” It is a continuous outcome measured in mmHg, with the registry specifying a mean and standard deviation as its summary format. The stated timeframe is after 6-8 weeks of treatment, and the description says blood pressure is assessed before and after treatment.
In general, measuring change uses each participant's baseline value as a reference for describing the value after treatment. A mean change can summarize the direction and typical size of change across the analyzed participants, while a standard deviation describes how spread out individual changes are around that mean. Those summaries answer different questions: the mean concerns the average observed change, whereas the standard deviation concerns variability among participants. Neither alone describes the precision of the mean estimate; a confidence interval would address that uncertainty.
The registry record does not report the numerical mean change, standard deviation, confidence interval, or a test result for the primary endpoint. It also does not give the full method for combining blood-pressure measurements or specify which blood-pressure component was analyzed. Consequently, the endpoint's definition and units are available, but the magnitude and precision of the observed response are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a relevant measurement—change in blood pressure from baseline to treatment—but does not report the numerical outcome estimates. The mean change, its standard deviation, a confidence interval, and a statistical test result are not reported in the registry record. Without those results, the direction, magnitude, variability, and precision of the observed blood-pressure change cannot be described. The study's completed status does not substitute for outcome estimates.
The design classification also matters when interpreting any within-group change. This is a single-group study, not a randomized comparison with a like-for-like control arm. In general, a before-and-after change can describe what happened among participants during the study, but it does not by itself establish that treatment caused the change. Blood pressure may vary over time, and other factors may change during follow-up. A suitable comparison can help distinguish treatment effects from these alternative explanations; such a comparator is not reported in the registry record.
The study's stated interest in genetic factors should be interpreted as a research aim rather than a reported finding. The registry does not report genetic associations, the genetic variables analyzed, estimates for any genetic subgroup, or tests of whether genetic information modifies treatment response. It is therefore not possible to assess whether genetic differences were related to blood-pressure changes from this record.
The population information signals uneven completion across study periods: 282 participants completed all 3 periods, 369 completed only period 1, and 328 completed only period 3. These categories describe differing participation histories, but the registry does not explain why participants did not complete all periods or how the outcome analysis handled incomplete observations. The number contributing to a particular endpoint estimate is not reported in the registry record. As a result, the relationship between the enrolled population and the analyzed population cannot be evaluated.
Overall, the record supports describing the study's objective, design classification, endpoint, and reported safety counts. It does not support conclusions about the size or precision of the primary outcome, treatment efficacy, or genetic prediction. Such conclusions require results and analysis details that are not reported in the registry record.
9. Statistical Methods Explained
The primary outcome is continuous: blood-pressure change is measured in mmHg and summarized as a mean with a standard deviation. The registry states that response is assessed by measuring blood pressure before and after treatment. The numerical summaries and inferential results are not reported in the registry record, so the methods below explain how these statistics would generally be interpreted rather than describing calculations reported for this study.
What does the mean describe?
In general, a mean is the arithmetic average of the values included in an analysis. For a change outcome, the relevant values would be each participant's change between the specified baseline and treatment measurements. The mean change summarizes the average change in the analyzed group. It does not imply that every participant changed by that amount: individual responses may differ, and some participants' values may move in a different direction from the group average.
The exact definition of the change score matters. For example, an analysis must identify the blood-pressure measurement or component used, the baseline time point, and the treatment time point. The registry record gives the general before-and-after description and the timeframe after 6-8 weeks, but the more detailed measurement and calculation rules are not reported in the registry record. It is also not reported whether the mean was adjusted for other variables.
What does the standard deviation describe?
In general, a standard deviation describes the spread of participant values around the mean. A larger standard deviation indicates more variation in the analyzed values; it is not the uncertainty interval for the mean. Variation may reflect genuine differences in response, measurement variability, or other sources. The standard deviation cannot show which source accounts for the observed spread.
A standard deviation is also not interchangeable with a standard error or confidence interval. The standard error concerns the sampling precision of an estimate, and a confidence interval expresses a range of values compatible with the data and a stated procedure. No standard deviation, standard error, confidence interval, or uncertainty estimate for the primary outcome is reported in the registry record.
What would a confidence interval add?
In general, a confidence interval communicates the precision of an estimated effect. A relatively narrow interval indicates greater precision than a wider interval, under the assumptions of the method used. It is not a guarantee that the true value lies inside the particular interval, nor does it establish clinical importance. Interpreting an interval also depends on the study design, the outcome definition, and the population analyzed. The primary-outcome confidence interval is not reported in the registry record.
How does the design shape the analysis?
The study is classified as single-group, with allocation listed as NA and masking as none. A within-group analysis of baseline and treatment values could estimate an average change, but the record does not report the specific statistical procedure used. In general, a paired analysis accounts for the fact that baseline and follow-up measurements from the same person are related. A comparison between independent groups would address a different question and would require a comparator group; a randomized, like-for-like comparator is not reported in the registry record.
Repeated study periods can require methods that account for the structure of observations within participants. The registry population description refers to three periods and reports different completion patterns, but the treatment sequence, period-specific measurements, and analysis approach are not reported in the registry record. No assumption about a crossover, carryover, or period effect can be made from the available description.
Why does variability matter?
In general, high variability can make a group mean less precise and can complicate detection of a relationship between treatment and response. A suitable analysis may need to reflect the observed distribution and dependence among measurements. Whether the blood-pressure data required a particular model, transformation, or adjustment is not reported in the registry record. The record does not report diagnostic checks or the assumptions used for the primary analysis.
The registry lists three analyses across two outcome measures, but does not give the analysis specifications or results in the registry record for this account. The method for handling more than one outcome or analysis is not reported in the registry record. It is also not reported whether any analyses were prespecified, adjusted, or exploratory. Without those details, readers cannot evaluate the risk of selective emphasis among analyses.
Sample-size calculations, when used in general, depend on assumptions about the outcome, variability, target effect, significance level, power, and allocation. The record includes assumptions for a planning illustration based on an observed effect, including a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It labels the illustration as distinct from the trial's own design. Because this study is classified as single-group and no numerical illustration outputs or trial-specific sample-size justification are reported in the registry record, those assumptions should not be read as the actual design rationale or as observed power.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies two outcome measures and three analyses, but the analysis details are not reported in the registry record. It does not state which outcomes or analyses were designated primary for statistical testing beyond naming the primary blood-pressure endpoint, nor whether testing across outcomes, analyses, time points, or genetic variables was adjusted for multiplicity.
In general, when many hypotheses are tested, the chance of at least one apparently notable result can increase. Adjustment methods can address that issue, but the method and the hypotheses covered need to be stated to interpret results appropriately. Because the relevant analysis plan and numerical test results are not reported in the registry record, multiplicity cannot be assessed. No claim about statistical significance or the strength of evidence for genetic associations can be made from the count of analyses alone.
The registry lists 839 enrolled participants, while the primary-outcome population description reports 282 participants who completed all 3 study periods, 369 who completed only period 1, and 328 who completed only period 3. The reasons for incomplete participation, the timing and extent of missing outcome measurements, and the number included in each analysis are not reported in the registry record. It is also not reported whether missing values were excluded, imputed, or handled with a model using available measurements.
In general, missing-data methods rely on assumptions about why measurements are absent. Different assumptions can affect an estimate, particularly when completion patterns vary. Without a description of the missingness pattern and the analysis method, the potential influence of incomplete follow-up cannot be judged.
The analysis population is described broadly as all patients with antihypertensive response data, but the exact inclusion rules for each outcome analysis are not reported in the registry record. Whether analyses followed an intention-to-treat principle, a completer approach, or another definition is not reported. These omissions limit assessment of how representative the analyzed participants were of all enrolled participants.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| All Study Participants | 3 | 839 | 0.4% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| All Study Participants | 114 of 839 |
Most frequent serious adverse event terms
| Event term | Organ system | All Study Participants |
|---|---|---|
| Headache | Vascular disorders | 2 of 839 |
| Heart Attack | Cardiac disorders | 1 of 839 |
Most frequent non-serious adverse event terms
| Event term | Organ system | All Study Participants |
|---|---|---|
| Other | General disorders | 41 of 839 |
| Headache | Vascular disorders | 29 of 839 |
| Fatigue | General disorders | 15 of 839 |
| Dizziness | Ear and labyrinth disorders | 10 of 839 |
| Nausea | Gastrointestinal disorders | 7 of 839 |
| Diarrhea | Gastrointestinal disorders | 4 of 839 |
| Rash | Skin and subcutaneous tissue disorders | 3 of 839 |
| Bradycardia | Cardiac disorders | 2 of 839 |
| Chest Pain | Cardiac disorders | 2 of 839 |
| Dyspnea | Nervous system disorders | 1 of 839 |
Serious events with the highest arm-level rate: headache (0.2%), heart attack (0.1%).
The registry reports safety counts for all study participants, with 839 at risk for serious adverse events and 839 at risk for other adverse events. It records 3 participants affected by serious adverse events and 114 affected by other adverse events. The death count is not reported in the registry record.
The listed serious adverse-event terms are Headache at 0.2% and Heart Attack at 0.1%. These are the terms and percentages reported by the registry; the record does not give further detail about event timing, severity beyond the serious classification, relationship to treatment, or whether participants experienced more than one event. The percentages should be read as registry-reported values, not as estimates recalculated from the counts.
In general, “at risk” identifies the group used as the denominator for an adverse-event summary, while an affected count describes participants with reported events. Such counts do not by themselves establish that treatment caused an event. A complete safety interpretation also considers event definitions, follow-up duration, exposure, comparator information, and how events were collected. A concurrent randomized comparator is not reported in the registry record, and further event-level details are not reported in the registry record.
12. What the Result Does, and Does Not, Mean
The study addresses an important statistical question: how blood pressure changes during antihypertensive treatment and whether genetic differences may be associated with variation in response. The registry specifies a continuous primary endpoint measured in mmHg and identifies a single-group design. It also reports enrollment and the number of participants completing different numbers of study periods.
Those design and population details do not establish the size of the blood-pressure change. Numerical primary-outcome estimates, measures of precision, and statistical test results are not reported in the registry record. The record also does not report genetic association findings. Accordingly, it cannot establish whether a particular drug produced a specific average change, how consistent that change was across participants, or whether genetic information predicts response.
In general, a before-and-after result describes change over time among observed participants, while a controlled comparison is needed to estimate how that change differs from what would have happened under a comparator condition. The registry does not describe a randomized control group. Even if a within-group change estimate were available, it would not by itself isolate a causal treatment effect.
The study's stated hope that genetic information might someday inform medication selection is a rationale for the research, not a demonstrated clinical application. Assessing that possibility would require reported genetic analyses and evidence that the findings are reliable and useful in the intended context. Those results are not reported in the registry record. No conclusion about treatment benefit or lack of benefit follows from the absence of numerical outcome results in this record.
13. Why This Trial Matters Statistically
This trial matters statistically because it connects a common clinical measurement—change in blood pressure—with a broader question about variability in response. The stated genetic hypothesis asks whether differences among people may help explain why responses differ. That question requires more than an average treatment response: it also requires clear outcome definitions, suitable analyses, and evidence about uncertainty and reproducibility.
The design classification is central to what can be learned. A single-group study can characterize outcomes among participants receiving study treatment, but it lacks the randomized, like-for-like control comparison needed to separate treatment-associated change from other time-related influences. That distinction is essential when interpreting before-and-after measurements. The registry record does not report a controlled comparison or numerical primary-outcome estimates.
The participant completion information also highlights a practical issue in longitudinal research. Participants contributed different amounts of follow-up across the three periods named in the record. In general, incomplete repeated measurements can affect both the analyzed population and the precision of estimates. Understanding that impact requires transparent reporting of missingness and analysis methods, neither of which is reported in the registry record.
Finally, the difference between a research aim and a result is important. Investigating genetic influences may motivate future work, but the record does not report genetic findings or an evaluation of genetic-guided treatment selection. The statistical value of such research depends on how precisely associations are estimated, how multiplicity and missing data are addressed, and whether findings can be distinguished from chance or confounding. Those details are not reported in the registry record. The record therefore identifies a question worth studying while leaving the central quantitative conclusions unresolved.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The registry record contains limited information for evaluating the primary outcome. Although it names change in blood pressure from baseline to treatment and gives the unit and timeframe, it does not report the mean change, standard deviation, confidence interval, or test result. The measurement details and full analysis method are also not reported in the registry record.
The single-group classification limits causal interpretation. Allocation is listed as NA, masking as none, and a randomized comparator is not described. The record therefore does not support a direct estimate of how outcomes would differ under a control condition. It also does not report full eligibility criteria, treatment assignment details, or a complete description of the treatment schedule. The available arm description is incomplete.
Completion varied across the three study periods described for the response population. The record does not explain why participants completed different numbers of periods, identify the number analyzed for each outcome, or specify how incomplete measurements were handled. This makes it difficult to judge the representativeness of the analysis population and the possible effect of missing data.
The genetic objective cannot be evaluated from the record because genetic variables, association estimates, uncertainty measures, and analysis details are not reported in the registry record. The relationship between the listed analyses and the study's stated genetic hypothesis is also not reported. Multiplicity handling and the distinction between planned and exploratory analyses are not reported.
Safety reporting includes participant counts and selected serious-event terms, but the record does not report the death count or further detail about event timing, treatment relationship, or event-level follow-up. These limitations describe what is absent from the registry record and do not establish that the underlying study did or did not collect the information.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Pharmacogenomic Evaluation of Antihypertensive Responses 2 — NCT01203852.
- Registry record last updated 2018-04-06; status last verified 2018-04.
- Results first posted 2015-05-19.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
Pharmacogenomic Evaluation of Antihypertensive Responses 2 is a completed phase 4 study sponsored by the University of Florida. The registry lists hypertension, enrollment of 839, a study start of 2010-08, and primary completion in 2014-04. The design is classified as single-group, with allocation listed as NA and masking as none.
The listed drugs are metoprolol and chlorthalidone. The primary endpoint is change in blood pressure from baseline to treatment, measured in mmHg after 6-8 weeks and summarized as a mean with a standard deviation. Numerical primary-outcome and genetic findings are not reported in the registry record. The response-population description reports 282 participants completing all 3 study periods, 369 completing only period 1, and 328 completing only period 3.
For safety, the registry reports 3 participants affected by serious adverse events and 114 by other adverse events among 839 at risk in each category. The death count is not reported in the registry record.