The Renin-Angiotensin-Aldosterone System and Parathyroid Hormone Control: The RAAS-PARC Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Renin-Angiotensin-Aldosterone System and Parathyroid Hormone Control: The RAAS-PARC Study (NCT01691781), a na na study. The primary outcome is Parathyroid Hormone Following 1 Week of ACE Inhibitor Administration.

2. Clinical Question

The study’s brief description frames the question as whether ACE inhibitors can lower parathyroid hormone. The primary outcome is a continuous measurement: parathyroid hormone in pg/mL, reported as a mean with a standard deviation, at the one-week timeframe. That description establishes what the investigators intended to measure; it does not establish that a decrease occurred.

The registry also lists urinary aldosterone excretion and serum calcium following one week of ACE inhibitor administration as secondary outcomes. The record does not state the results for those measures. It lists 3 outcome measures and 6 analyses, but does not describe how those analyses relate to particular groups or hypotheses. The primary endpoint’s population and the precise contrast, if any, used for analysis are not reported in the registry record.

Because this is not a randomized comparison and no control group is described, the clinical question should be read as a measurement after treatment in a single-group study, not as a direct comparison of lisinopril against another treatment or no treatment. Any conclusion about change would require information such as a baseline value and an analysis of change; those results are not reported in the registry record.

3. Trial Design

RAAS-PARC is a completed, single-group study sponsored by Brigham and Women's Hospital. The registry lists enrollment as 41, a start date of 2012-10, and primary completion in 2016-08. The phase and allocation are recorded as NA. Masking is listed as NONE. These design entries describe a study without a reported randomized allocation or masking; they do not establish the number of participants contributing data to any particular analysis.

The intervention was lisinopril, classified as a drug. Its arm description specifies open-label administration at 2.5-40mg daily. The primary endpoint is parathyroid hormone following one week of ACE inhibitor administration. Two secondary outcomes are named: urinary aldosterone excretion measurements following one week of ACE inhibitor therapy and serum calcium following one week of ACE inhibitor administration.

A single-group design can describe measurements collected among people receiving an intervention. Without a concurrent control group, however, the design does not by itself separate changes associated with treatment from changes that might occur over time for other reasons. The registry’s skip note also identifies that the study is not a randomized comparison and that its arms are not a like-for-like control comparison. Accordingly, the record does not support interpreting any listed groups as randomized treatment and control arms.

The study’s enrollment entry and the safety records serve different purposes. Enrollment is recorded as 41, while the adverse-event summaries give at-risk counts of 12 for the Primary Hyperparathyroidism group and 15 for the Normal group. The record does not explain the relationship between those counts, total enrollment, and the primary endpoint analysis. The number included in the endpoint analysis, exclusions, and reasons for any missing observations are not reported in the registry record.

The registry marks the study completed. Its design information does not include a detailed protocol, a sample-size justification, or a statistical analysis plan. Such details are not reported in the registry record, so the listed design features should not be extended into assumptions about how the study was planned or conducted.

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: All enrolled participants had to undergo a washout of ACE inhibitors (if applicable) during which time their blood pressure had to remain within safety parameters, and they had to complete a controlled sodium diet.

Overall Study

Reasons for not completing this period:

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.

6. Primary Endpoint

The registry lists the primary outcome as Parathyroid Hormone Following 1 Week of ACE Inhibitor Administration, measured over 1 week.

The primary endpoint is parathyroid hormone (PTH) following one week of ACE inhibitor administration. It is a continuous measure, specified as a mean with a standard deviation and expressed in pg/mL. The timeframe is 1 week. The record describes the measure as PTH values one week following ACE inhibitor therapy.

PTH is the biological measure selected to address the study’s stated question about whether ACE inhibitors can lower parathyroid hormone. In general, a continuous endpoint retains the measured value across its range rather than reducing observations to categories. A mean describes the central level of the measured values, while a standard deviation describes how spread out those values are around the mean. Those summaries are useful for characterizing measurements, but do not alone establish a treatment effect or a change over time.

The registry does not report a baseline PTH mean, a post-treatment mean, a standard deviation, a confidence interval, or a statistical test result. It also does not report whether the endpoint analysis evaluated a post-treatment value alone, a change from baseline, or another contrast. Therefore, the endpoint’s name and measurement scale are known, but the magnitude and precision of the observed PTH result are not reported in the registry record.

Interpreting a one-week value as a change requires a defined reference measurement and an analysis that relates the two observations. A value at follow-up by itself would describe the measured level at that time, not how much it changed. The record’s description of the endpoint does not supply that additional information.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary endpoint as a continuous outcome summarized by a mean and standard deviation. It does not provide the actual PTH summaries or specify the inferential method used. The explanations below describe general statistical concepts that help interpret such an endpoint; they are not claims about procedures used in RAAS-PARC.

What does a mean describe?

For a continuous measurement, the mean is the arithmetic average of the observed values. It gives a concise description of the group’s measured level. Its interpretation depends on the observations included and on the population they represent. A mean does not show whether individual values cluster closely together or vary widely; that is why the registry also specifies a standard deviation.

The standard deviation describes the spread of observations around the mean. A larger spread means measurements are more dispersed around the average, while a smaller spread means they are more closely grouped. It is not the same as the standard error, which concerns the uncertainty of an estimated mean. Neither the mean nor the standard deviation alone describes a comparison or a change from baseline.

What would a change analysis require?

In general, a change analysis uses measurements at more than one time point for the same participants, or an explicitly defined comparison of measurements across time. It estimates how the outcome differs between the relevant observations. The choice of analysis can affect the estimate and its uncertainty. The registry names a one-week PTH measure, but does not report a baseline value or say whether the primary analysis used change from baseline. Therefore, no particular change-analysis method can be attributed to this study.

A single-group follow-up mean and a within-participant change are different quantities. The follow-up mean describes the group’s level at the follow-up time. A change estimate describes the difference between follow-up and a reference point. If there is no concurrent control group, even a measured change cannot by itself separate treatment-related change from temporal trends or other influences. This is a general limitation of interpretation, not a statement that any such change occurred in this study.

What does a confidence interval add?

In general, a confidence interval communicates the uncertainty around an estimated quantity under the assumptions of the statistical method. Its width reflects both the variability in the data and the amount of information available. A narrow interval indicates greater precision than a wide interval, but precision does not by itself establish importance or causation. The registry information described for this study includes no confidence interval for PTH, so neither the uncertainty nor the range of effect sizes compatible with the data can be assessed.

A p-value, when used, addresses how compatible the observed data are with a specified null model under stated assumptions. It does not give the probability that the null hypothesis is true, measure the size of an effect, or establish clinical relevance. The registry record does not report a PTH p-value or identify the null hypothesis and test used. No conclusion about statistical significance is therefore available from the endpoint information.

Why does the design affect interpretation?

RAAS-PARC is listed as single-group, with allocation NA and masking NONE. In general, random allocation to a concurrent comparison group can help balance known and unknown influences between groups, while masking can reduce certain forms of expectation-related influence. Those features are not listed for this study. A single-group result can describe observations in the treated group, but offers no direct randomized contrast with an untreated or alternative-treatment group.

The registry also notes that this is not a randomized comparison and that arms are not a like-for-like control comparison. Thus, if separate groups appear in study records, their labels should not be taken to mean that they were randomized treatment and control groups. The safety records list Primary Hyperparathyroidism and Normal groups, but do not provide a basis for interpreting these as comparative efficacy arms.

What can the planning illustration tell readers?

The registry describes planning assumptions for an illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. Numerical planning estimates and the observed effect are not reported in the registry record for this study. More importantly, an illustrative sample size is a planning quantity, not an observed result and not observed power. It does not demonstrate that the study detected an effect or that its endpoint estimate was precise.

A sample-size justification for the actual study, including the target effect and its rationale, is not reported in the registry record. The planning illustration’s assumptions should not be mistaken for the protocol’s original design assumptions. The record does not establish that the study was planned as a two-arm randomized trial; its registered design is single-group.

What is not specified about the analysis?

The registry lists 3 outcome measures and 6 analyses, but does not describe the specific statistical methods, model covariates, hypothesis structure, or handling of repeated measurements. It also does not give endpoint-level analysis counts. Without those details, readers cannot determine whether estimates were adjusted, which observations were included, or how uncertainty was calculated. No test, model, or adjustment should be inferred solely from the endpoint’s use of a mean and standard deviation.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Primary Hyperparathyroidism", "Normal")
n   <- c(12, 15)
m   <- c(70.9, 32.5)
sp  <- c(19.6, 16.7)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Primary Hyperparathyroidism  12  70.900  19.600  58.447  83.353
CARM  Normal  15  32.500  16.700  23.252  41.748

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 3 outcome measures and 6 analyses. It names PTH following one week of ACE inhibitor administration as the primary outcome, and lists urinary aldosterone excretion and serum calcium after one week as secondary outcomes. However, the record does not describe how the six analyses map to those outcomes, which hypotheses were tested, or whether any adjustment for multiple comparisons was planned or applied. A multiplicity strategy is not reported in the registry record.

In general, when several outcomes or analyses are examined, the chance of at least one apparently unusual result can increase if each is assessed separately without accounting for the collection of tests. Methods for addressing multiplicity depend on the prespecified questions and analysis plan. Without a stated plan and endpoint-level results, it is not possible to determine how multiplicity should affect interpretation of this study’s findings.

The registry does not report the number of participants with observed PTH values, the number included in each analysis, or any missing-data procedure. It does not say whether participants with incomplete measurements were excluded, whether missing values were handled through a model, or whether sensitivity analyses were conducted. These details are not reported in the registry record.

The population used for the primary analysis is also not specified. The enrollment entry is 41, but that does not identify the number analyzed for PTH. The safety summaries list different at-risk counts for their two groups; these counts do not establish the endpoint-specific analysis population. An analysis population definition, such as inclusion criteria for the primary analysis, is not reported in the registry record.

These gaps matter because the interpretation of an estimate depends on which participants and measurements contributed to it, as well as on the analyses selected. In the absence of these details and the primary endpoint result, the extent of missingness, its possible influence, and the role of multiple testing cannot be assessed.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse events and other adverse events separately for two groups. In the Primary Hyperparathyroidism group, 12 participants were listed at risk for serious adverse events and 0 were listed as affected; 12 were listed at risk for other adverse events and 2 were affected. In the Normal group, 15 were listed at risk for serious adverse events and 0 were affected; 15 were listed at risk for other adverse events and 1 was affected. Deaths are listed as 0 in both groups.

These are event summaries for the groups identified in the registry, not a randomized comparison of lisinopril with a control treatment. The record does not report a causal comparison, event timing, event-level details, or an attribution of events to the intervention. It also lists no top serious adverse event terms. The absence of listed serious events in these summaries should not be treated as proof that serious harm is impossible or that no event was observed outside the reported records.

The at-risk counts are specific to the safety summaries and should not be used as the sample size for the PTH analysis. The registry does not explain how the safety group counts relate to the enrollment entry or primary endpoint population. These figures describe what the safety record reports; broader safety conclusions are not supported by these counts alone.

13. What the Result Does, and Does Not, Mean

The registry record establishes that RAAS-PARC assessed PTH following one week of open-label lisinopril therapy, with a listed dose range of 2.5-40mg daily. It also identifies a single-group design and names urinary aldosterone excretion and serum calcium as secondary outcomes. These registry entries describe the study question and structure.

The primary PTH result itself is not reported in the registry record. No numerical mean, standard deviation, estimate of change, confidence interval, or test result is available in the registry record for the study. It is therefore not possible to determine from this information whether the measured PTH level changed, how large any change was, or how precisely it was estimated. No conclusion that the intervention did or did not lower PTH follows from the endpoint description alone.

The single-group design is also important. In general, observations after an intervention can describe what happened within the observed group, but without a concurrent randomized comparator they cannot establish what would have happened under another condition. Even if a before-and-after difference were reported, attributing that difference to the intervention would require caution. The registry does not report such a difference or its analysis.

The completed status does not substitute for endpoint results. Nor does the enrollment entry establish how many people contributed to the outcome analysis. Secondary outcome names do not establish their findings, and safety counts do not answer the primary efficacy question. The record lacks enough information to assess multiplicity, missing data, or the analysis population.

The appropriately limited interpretation is that the registry documents a one-week study of lisinopril and a planned PTH measurement, but does not provide the primary endpoint findings needed to characterize the observed result. The study’s design and recorded outcomes should be distinguished from evidence about the size, precision, or cause of any outcome.

14. Why This Trial Matters Statistically

This study is statistically informative as an example of why a research question, endpoint description, and result are not interchangeable. The registry states a question about whether ACE inhibitors can lower PTH, identifies a continuous PTH measure, and specifies a one-week timeframe. Those details tell readers what was to be examined, but without the endpoint estimate they do not reveal what was observed.

The single-group design also highlights the distinction between describing a follow-up measurement and estimating a comparative treatment effect. In general, a treatment effect requires a contrast that represents what happened under treatment relative to a suitable alternative. A single-group study may characterize measurements in people who received an intervention, but it lacks the randomized comparison that would directly address that contrast. The registry itself notes that the study is not a randomized comparison.

Several reporting elements are important for statistical interpretation: the PTH mean and variability, a defined estimate and its uncertainty, the analysis population, and how missing measurements were handled. None of these primary endpoint details is reported in the registry information. The registry’s entry of enrollment as 41 cannot replace an endpoint-specific count, and the safety-group counts cannot be assumed to be the efficacy-analysis counts.

The study also lists multiple outcomes and analyses without describing their relationships or any multiplicity approach. In general, clear reporting of prespecified outcomes and analytic choices helps readers distinguish the primary question from additional analyses. Here, the outcome names are available, while those analysis details are not.

These points matter because statistical interpretation depends not only on the biological question but also on the design, observed data, and analysis. The record offers a useful outline of the intended measurement and study structure, while leaving the central numerical result and key analysis details unreported.

15. 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 principal limitation for interpreting this trial record is that the primary PTH result is not reported in the registry information described. Without a mean, standard deviation, change estimate, or uncertainty interval, the endpoint’s direction, magnitude, and precision cannot be evaluated. The absence of a numerical outcome also prevents assessment of whether the findings were consistent with the study’s stated question.

The study is registered as single-group, with allocation recorded as NA and masking as NONE. No concurrent comparator is described, and the registry notes that the study is not a randomized comparison. This limits the ability of the design to support causal interpretation of any change. The record does not provide a baseline PTH result or state whether the primary analysis assessed change from baseline.

The registry lists enrollment as 41, but does not identify how many participants contributed PTH measurements or how many were included in each analysis. Missing-data handling, exclusions, and the primary analysis population are not reported in the registry record. Safety-group counts do not resolve those questions because they refer to safety summaries rather than a stated efficacy population.

The record names 3 outcome measures and 6 analyses but does not specify how those analyses were conducted or whether multiplicity was addressed. Statistical tests, model details, adjustment variables, and the study’s sample-size justification are not reported in the registry record. Although the record describes a planning illustration based on an observed effect, its numerical results and the observed effect are not present in the registry record for this study.

Finally, the registry lists a one-week endpoint and secondary measures at one week, but does not provide results for those measures or additional follow-up information. These reporting gaps restrict evaluation of both the primary question and the broader pattern of outcomes. They should be treated as limits of the registry information, not as evidence that a particular result or analysis did not occur.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: The Renin-Angiotensin-Aldosterone System and Parathyroid Hormone Control: The RAAS-PARC Study — NCT01691781.
• Registry record last updated 2017-09-21; status last verified 2017-08.
• Results first posted 2017-08-10.
• 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.

19. Record Summary

RAAS-PARC (NCT01691781) is listed as a completed, single-group study sponsored by Brigham and Women's Hospital. The registry records enrollment of 41, a start date of 2012-10, and primary completion in 2016-08. Phase and allocation are recorded as NA; masking is NONE.

The intervention was open-label lisinopril at 2.5-40mg daily. The primary endpoint was PTH following 1 week of ACE inhibitor administration, measured in pg/mL and specified as a mean with a standard deviation. Secondary outcomes were urinary aldosterone excretion and serum calcium following one week.

The registry record does not report the numerical primary endpoint result, its uncertainty, or the analysis population. It lists safety summaries for Primary Hyperparathyroidism and Normal groups, including 0 serious adverse events and 0 deaths in each group, alongside other adverse event counts. The design is not a randomized comparison, and key details about missing data, multiplicity, and statistical methods are not reported in the registry record.