Angiotensin II and Chronic Inflammation in Persistent Microvascular Dysfunction Following Preeclampsia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Angiotensin II and Chronic Inflammation in Persistent Microvascular Dysfunction Following Preeclampsia (NCT03482440), a randomized early/phase 1 study. The primary outcome is Microvascular Endothelial Function (Cutaneous Conductance, %Maximum).

2. Clinical Question

The broader research aim was to investigate mechanisms that may contribute to lasting vascular changes and chronic inflammation following preeclampsia, and to examine physiological and pharmacological factors that might mitigate those effects. The registry’s description frames the study as mechanistic research intended to inform understanding of cardiovascular risk; it does not establish that the trial evaluated later cardiovascular disease outcomes. The posted primary outcome is a short-term physiological measure taken after a brief treatment period, rather than a clinical event or long-term health outcome.

3. Trial Design

The registry describes a randomized, triple-masked, crossover study of oral salsalate and oral placebo. Its listed phase is EARLY PHASE1, its status is COMPLETED, and its enrollment is 24. The start date is 2018-08-26 and the primary completion date is 2019-07-11. The sponsor is the University of Iowa.

A crossover design means that treatment comparisons are made within a study structured around more than one treatment condition. That general feature can be useful when outcomes vary between people, because each participant may contribute information under multiple conditions. The registry does not report the treatment sequence, the duration of each period, whether a washout period was used, or how the analysis handled period or sequence effects. Those details matter when interpreting a crossover comparison and cannot be inferred from the design label alone.

The primary outcome summaries list 23 observations for oral salsalate and 23 for oral placebo. These are arm-level outcome counts, not a reason to infer how many unique participants contributed or why the counts differ from the enrollment figure. The reason for the reported outcome counts is not reported in the registry record. The record also does not describe exclusions, withdrawals, or missing outcome values.

The primary endpoint was assessed immediately following the 4 days of oral treatment. The secondary outcome, peripheral blood mononuclear cell inflammatory response to Ang II, was assessed at the completion of 4 days of oral treatment. The registry identifies two outcome measures, including the primary endpoint and one secondary endpoint, but does not post a list of reported analyses. Detailed eligibility criteria, dose, treatment adherence, and the original statistical analysis plan are not 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: this is a crossover study design - all participants (23 total) completed each arm of the study in a randomized placebo controlled study design

Overall Study

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 Microvascular Endothelial Function (Cutaneous Conductance, %Maximum), measured over immediately following the 4 days or oral treatment (salsalate or placebo).

The primary endpoint is microvascular endothelial function, expressed as cutaneous conductance as a percentage of maximal cutaneous conductance. The registry describes the measure as an endothelium-dependent vasodilation response to exogenous acetylcholine delivered through intradermal microdialysis. Cutaneous conductance is defined in the record as local red blood cell flux divided by mean arterial pressure. Reporting the response as a percentage of the maximum places the measured response on a scale relative to maximal cutaneous conductance.

This endpoint is used as a physiological measure of microvascular endothelial function. In general, an acetylcholine-evoked vascular response can be used to assess endothelial-dependent vasodilation; this is a mechanistic measure, not a direct measurement of cardiovascular disease or a long-term clinical outcome. The registry’s stated rationale links preeclampsia with possible persistent blood-vessel damage and inflammation, making a vascular function measure relevant to the study’s research question.

The assessment took place immediately following 4 days of oral salsalate or placebo. The posted mean was 95.0 for oral salsalate and 77.0 for oral placebo, with standard deviations of 6.0 and 8.0, respectively. The reported unit is % of maximal cutaneous conductance. The registry does not report a threshold for clinical importance or a minimum difference considered meaningful, so the magnitude should be interpreted as a difference on this physiological scale rather than as evidence of a particular clinical benefit.

7. Results Posted in the Registry

• Oral Salsalate: mean 95.00 versus 77.00 on control; difference 18.00 (95% CI 13.91 to 22.09), standardized effect d = 2.55; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Peripheral Blood Mononuclear Cell Inflammatory Response to Ang II

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Oral Salsalate: mean 2.37 versus 2.77 on control; difference -0.40 (95% CI -1.07 to 0.27), standardized effect d = -0.35; z-test p = 0.239.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Oral Salsalate and the control. The interval gives the range of effects that remain compatible with the data.

The registry posts one secondary endpoint: peripheral blood mononuclear cell inflammatory response to Ang II, measured at the completion of 4 days of oral treatment. Its treatment-condition means are 2.37 ng/ml after salsalate and 2.77 ng/ml after placebo. The unadjusted comparison is not conclusive because its confidence interval spans zero. This secondary pattern does not mirror the clear positive direction of the primary vascular endpoint, but the endpoints measure different biological responses and should not be expected to be interchangeable.

The primary outcome concerns acetylcholine-evoked cutaneous conductance, whereas the secondary outcome concerns an inflammatory response in peripheral blood mononuclear cells. A difference in one endpoint alongside an uncertain comparison for the other does not establish that the vascular result is independent of inflammation, or that either endpoint explains the other. The registry does not report a direct association analysis or mediation analysis between these measures.

Secondary findings generally carry less inferential weight when multiple outcomes or comparisons may have been examined without a clearly reported multiplicity plan. Testing several hypotheses increases the opportunity for chance findings if each is interpreted at the same threshold without adjustment. The registry reports one secondary outcome measure, but does not report a multiplicity adjustment, a hierarchy among outcomes, or a complete analysis plan. The secondary comparison should therefore be treated as supportive or exploratory rather than as a stand-alone confirmatory conclusion.

The absence of a conclusive secondary comparison is not proof that the inflammatory response is unchanged. The result is uncertain, and the registry does not report a prespecified equivalence margin or another analysis designed to rule out a meaningful range of differences. Nor does the presence of a primary result make the secondary result statistically significant by association. Each outcome needs interpretation based on its own scale, uncertainty, measurement timing, and analysis assumptions.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Peripheral Blood Mononuclear Cell Inflammatory Response to Ang II

9. Statistical Interpretation

10. Statistical Methods Explained

The outcome is continuous: each observation is a measured value on a numerical scale. The registry reports means and standard deviations for both treatment conditions. A mean describes the average observed response, while a standard deviation describes how spread out individual values are around that average. These summaries help show both the central response and the variability among observations, but they do not display the distribution of individual measurements.

What does the mean difference represent?

The mean difference expresses the salsalate mean relative to the placebo mean, in the original outcome units. For the primary outcome, the reported difference is 18.0 percentage points of maximal cutaneous conductance. A positive value indicates a higher reported mean in the salsalate condition than in the placebo condition. For the secondary outcome, the reported difference is -0.4 ng/ml, indicating a lower reported mean in the salsalate condition. These are unadjusted comparisons based on the posted summary statistics; they are not adjusted estimates from a reported regression or crossover model.

In general, an unadjusted comparison does not account for other variables unless that adjustment is explicitly part of the analysis. The registry does not report covariate-adjusted analyses. It also does not report participant-level data or the calculations used in a sponsor analysis, so the posted summary statistics do not permit independent assessment of all modeling choices.

What does a confidence interval describe?

In general, a confidence interval represents a range of estimates compatible with the data and the method’s assumptions. It communicates uncertainty about the estimated mean difference, rather than the range in which most individual observations fall. A narrower interval indicates greater precision for the estimated difference; a wider interval indicates more uncertainty. An interval containing zero is compatible with no mean difference under the stated method, while an interval entirely on one side of zero supports a difference in that direction within that method. These interpretations depend on the analysis assumptions being appropriate.

The primary comparison’s interval is entirely above zero. The secondary comparison’s interval spans zero. The corresponding unadjusted p-values are p < 0.001 for the primary endpoint and 0.239 for the secondary endpoint. A p-value measures how unusual the observed data, or more extreme data, would be under a specified null model and its assumptions. It is not the probability that the null hypothesis is true, and it does not measure clinical importance.

Why does the crossover design matter?

General statistical guidance is that crossover data often call for methods that account for measurements made under more than one condition in the same participant. Pairing can change the uncertainty of a treatment contrast because within-person responses may be related. The registry labels the design crossover, but does not report the pairing information, treatment sequence, period effects, washout details, or a crossover-specific analysis. The posted comparison includes arm-level counts and summary statistics, but the record does not explain how dependence between conditions was handled. It is therefore important not to assume that the reported unadjusted calculation captures every design feature.

In general, over-dispersion occurs when observed variability is greater than a model assumes. For a continuous endpoint, a model that underestimates variability may produce confidence intervals that are too narrow and p-values that are too small. The registry reports standard deviations for the outcome summaries, but does not report a diagnostic assessment of distributional assumptions or an alternative model for unusual variability. No claim about over-dispersion in these data can be made from the record.

What is known about analysis reporting?

The registry lists zero reported analyses and does not include a detailed statistical analysis plan. It does post outcome summaries and unadjusted comparisons, which support the descriptive interpretation and the simple comparison calculations displayed in the results. The record does not state whether there were interim analyses, whether the primary analysis was prespecified in its final form, how missing outcomes were handled, or which population was used for an inferential analysis. Each of these details is not reported in the registry record.

The registry’s reported comparison is not marked as discrepant from the summary-based calculation. Where sponsor analyses are available, those analyses take precedence if the posted summary-based calculation conflicts with them. In this record, no reported sponsor analysis is listed. The interpretation should therefore remain anchored to the posted summaries and their unadjusted comparisons, without claiming access to a fuller analysis.

General statistical practice also distinguishes descriptive summaries from inferential conclusions. Means and standard deviations describe the observed data; confidence intervals and p-values add an inferential comparison under particular assumptions. Neither alone establishes that an effect is clinically important, generalizable beyond the study population, or durable beyond the measured treatment period. Those questions require information and outcomes not reported in this registry record.

11. Confidence Intervals and Precision

The primary mean difference is 18.0 percentage points of maximal cutaneous conductance. Its 95% confidence interval extends from 13.91 to 22.09. The interval is entirely above zero, and p < 0.001. Together, these statistics indicate that the posted unadjusted estimate is relatively precise in the sense that its interval does not include zero and is bounded on the positive side. Precision is not the same as clinical importance; the registry does not report a threshold that would identify a meaningful clinical difference.

The secondary mean difference is -0.4 ng/ml. Its confidence interval spans zero, and the unadjusted p-value is 0.239. This interval therefore leaves uncertainty about the direction of the underlying mean difference. The result does not establish equivalence or prove the absence of an effect. Establishing equivalence would require an explicit margin and a design and analysis planned for that purpose; such information is not reported in the registry record.

In general, confidence interval width depends on the observed variability, the amount of information, and the analysis method. In a crossover study, within-participant correlation can also affect the precision of a treatment contrast. The registry does not report the paired covariance or the model used to account for the crossover structure, so the precision figures should be interpreted as those of the posted unadjusted comparison rather than as a complete assessment of design-specific precision.

The endpoint counts are 23 in each condition. The enrollment figure is 24, but the reason for the difference between enrollment and outcome counts is not reported. No missing-data method or sensitivity analysis is reported, which limits assessment of whether missing outcomes could affect precision or introduce bias.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm, not total events. The registry’s planning illustration uses a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It considers effects equal to 100%, 75%, and 50% of the observed effect. The trial’s original design assumptions and sample-size justification are not reported in the registry record.

For each assumed effect size, the 80% power column gives the estimated participants per arm for a planning scenario with an 80% chance of detecting that specified effect under the illustration’s assumptions. The 90% power column gives the corresponding participants per arm for a 90% chance. These are design-planning quantities, not guarantees about what a future study will find. The entries based on 100% of the observed effect are 3 participants per arm for 80% power and 4 for 90% power. For 75% of the observed effect, the entries are 5 and 6. For 50% of the observed effect, they are 10 and 13.

Smaller effects are harder to distinguish from random variation, so the planning illustration requires more participants per arm as the effect fraction decreases. The estimates use the observed effect as their starting point; an observed effect can be an uncertain and potentially optimistic basis for planning. These figures are planning illustrations, not observed power, and they do not establish what the original trial was designed to detect.

The registry describes the calculation as a normal approximation and assumes equal allocation between two arms. It does not report whether the original design planning accounted for the crossover structure, paired measurements, sequence or period effects, attrition, or a different analysis method. The planning figures should therefore be read according to their stated assumptions rather than as a reconstruction of the trial’s original design.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 18.000; pooled standard deviation σ = 7.071.
2. n = 2 × (1.96 + 0.842)² × 7.071² / 18.000² = 2.4, rounded up to 3 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 18                      # observed difference in means
sigma <- 7.07106781186548                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(3482440)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 3 (80% power), 4 (90% power)
 75% of observed effect: n per arm = 5 (80% power), 6 (90% power)
 50% of observed effect: n per arm = 10 (80% power), 13 (90% power)
power.t.test: 3.7 
Simulated power at n = 3 per arm: 0.656 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

The registry identifies a primary outcome and one secondary outcome, but does not report a plan for controlling multiplicity. In general, when more than one outcome or hypothesis is tested, the chance of at least one apparently notable result by chance can increase. A prespecified hierarchy, adjustment procedure, or clear distinction between confirmatory and exploratory analyses can help readers judge the strength of evidence. The registry record does not report such details, so no adjustment should be assumed.

The record lists no reported analyses, and a detailed statistical analysis plan is not reported. It does not state whether interim analyses were conducted, how the primary analysis population was defined, or whether there were post hoc analyses. Those items are not reported in the registry record; their absence from the posted record does not establish that they did or did not occur.

Missing-data handling is also not reported. The registry gives an enrollment of 24 and outcome summaries with 23 observations in each treatment condition. It does not explain why the posted outcome counts differ from enrollment, whether the same participants contributed in both conditions, or how any missing values were handled. In a crossover study, it would be useful to know whether outcomes were available for both treatment conditions for each participant and how incomplete pairs were treated. That information is not reported.

The crossover label makes details of the analysis especially relevant. The registry does not report how the analysis addressed within-participant dependence, treatment sequence, period effects, or possible carryover. It also does not describe the masking roles or the allocation sequence. These design and analysis details cannot be posted by the summary statistics.

Because these reporting details are unavailable, the posted comparisons are best read as unadjusted summaries with their stated uncertainty, not as a complete account of the trial’s analysis. There is no basis in the registry record to infer the original sample-size justification, interim monitoring, multiplicity control, missing-data method, or the precise analysis population.

15. 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 no serious adverse events in the placebo condition and no serious adverse events in the salsalate condition. It reports no deaths in either condition. For other adverse events, the record reports zero in the placebo condition and two in the salsalate condition. The at-risk count listed for each condition is 23.

These are event counts over the reported study conditions, not estimates of comparative risk over longer follow-up. The registry does not list serious adverse event terms, and it does not provide descriptions, severity, timing, or details of the two other adverse events. The record also does not explain how events were collected or whether all events were considered related to treatment. No causal conclusion should be drawn from these counts alone.

The treatment period for the outcomes was 4 days. Safety counts from a brief study do not characterize uncommon events or longer-term safety. The absence of reported serious events in these records is not proof that serious events cannot occur; it describes what the registry reports for this study.

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

The primary result describes a higher average cutaneous conductance response after oral salsalate than after oral placebo at the endpoint assessment. The reported mean difference is 18.0 percentage points, with a confidence interval from 13.91 to 22.09 and p < 0.001. This is evidence about a measured physiological response following 4 days of treatment in this registered study.

It does not show whether the difference persists beyond the assessment, changes cardiovascular disease risk, or affects clinical outcomes. The registry does not report long-term follow-up outcomes, a clinical importance threshold for the conductance measure, or a trial comparison of cardiovascular events. The study’s stated rationale and the endpoint’s physiological relevance do not substitute for those outcome data.

The result also does not establish the mechanism behind the observed vascular difference. The secondary inflammatory-response comparison is uncertain, and the registry does not report an analysis connecting the primary and secondary measures. The two measurements address distinct aspects of vascular and inflammatory physiology; their results cannot by themselves establish a causal pathway.

The crossover design can support within-participant treatment comparisons in general, but the registry record does not report the treatment sequence, period information, washout details, or method used to account for repeated measurements. Thus, the posted summary-based comparison should be interpreted with that design reporting limitation in mind. The trial’s enrollment and outcome counts also do not reveal why the recorded numbers differ or whether missing data could influence the estimates.

The secondary endpoint’s interval spans zero, so its result does not establish a difference or establish no difference. Similarly, the safety counts are limited descriptions of recorded events and do not characterize long-term or rare risks. Taken together, the posted results support a statistical difference in the primary physiological measure under the unadjusted comparison, while leaving clinical significance, persistence, mechanism, and broader safety unresolved.

17. Why This Trial Matters Statistically

This trial is statistically interesting because it combines a randomized treatment comparison with a crossover design and a continuous physiological endpoint. Continuous outcomes can convey both the direction and scale of a response, while means, standard deviations, confidence intervals, and p-values communicate different aspects of the observed data and their uncertainty.

The primary result illustrates why effect estimation and precision should be read together. The mean difference is reported in the endpoint’s own units, and its interval lies on the positive side of zero. That is a more informative description than a p-value alone, although it still does not establish clinical importance. A threshold for meaningful change is not reported in the registry.

The contrast between the primary and secondary results also demonstrates that endpoints should not be collapsed into one broad claim. A clear comparison for the vascular measure does not make the inflammatory comparison conclusive. Multiplicity planning and a prespecified interpretation hierarchy are important when studies include more than one endpoint, but these details are not reported in the record.

Finally, the crossover label makes transparent reporting of paired analysis important. Within-participant comparisons can affect precision, and period or sequence details can matter to interpretation. The registry’s arm-level summaries do not provide enough information to assess those design features. The study therefore highlights how accessible summary results can support useful reading while still leaving key analysis questions unanswered.

18. 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 does not report detailed eligibility criteria or participant characteristics, which limits assessment of how closely the study population corresponds to the broader population of women with a history of preeclampsia. It also does not report the salsalate dose, adherence, or treatment sequence, so these aspects of the intervention cannot be evaluated from the record.

Although the design is labeled crossover, the registry does not report period duration, washout details, treatment order, or the analysis method for within-participant measurements. Participant-level paired data are not available in the record. Consequently, the posted unadjusted comparison cannot establish how the crossover structure was handled or allow independent evaluation of that analysis.

The primary endpoint is a short-term physiological measure taken immediately after 4 days of treatment. The record does not provide a clinical importance threshold or long-term outcomes. It therefore cannot show whether the measured difference persists, translates into a clinical outcome, or changes later cardiovascular risk.

The registry reports enrollment of 24 and outcome counts of 23 in each condition, but does not explain the difference or describe missing-data handling. It does not report a detailed analysis plan, multiplicity control, interim analyses, or the population used for analysis. These omissions limit assessment of potential analytic choices and the robustness of the reported comparisons.

Safety reporting is brief: no serious events or deaths are listed, and two other adverse events are reported in the salsalate condition. The types and timing of those events, ascertainment methods, and treatment attribution are not reported. The record’s safety information is therefore limited and does not characterize uncommon or longer-term events.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Angiotensin II and Chronic Inflammation in Persistent Microvascular Dysfunction Following Preeclampsia — NCT03482440.
• Registry record last updated 2025-06-03; status last verified 2025-06.
• Results first posted 2025-06-03.
• 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.

22. Record Summary

NCT03482440 is a completed, randomized, triple-masked crossover study sponsored by the University of Iowa. It is listed as EARLY PHASE1 and has an enrollment of 24. The study compared oral salsalate with oral placebo in research focused on persistent microvascular dysfunction and inflammation following preeclampsia.

The primary outcome was microvascular endothelial function measured as cutaneous conductance (% of maximal cutaneous conductance) immediately following 4 days of oral treatment. The posted means were 95.0 after salsalate and 77.0 after placebo. The unadjusted mean difference was 18.0, with a 95% confidence interval from 13.91 to 22.09 and p < 0.001. One secondary inflammatory-response outcome is posted; its unadjusted comparison has a confidence interval that spans zero.

The registry does not report a detailed analysis plan, crossover-specific analysis details, missing-data methods, or multiplicity procedures. The findings describe short-term physiological measurements and do not establish long-term clinical outcomes.