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 The Effect of n-3 Polyunsaturated Fatty Acids in Patients With Psoriatic Arthritis (NCT01818804), a randomized na study. The primary outcome is Change in Heart Rate Variability (HRV) Measure.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01818804 |
| Phase | NA |
| Condition | Psoriatic Arthritis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 145 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Aalborg University Hospital |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns adults with psoriatic arthritis. The brief description specifies men and women aged > 18 years classified using the CASPAR criteria. It also lists exclusions, including cardiac arrhythmias, conduction disturbances, and treatment with biological drugs or oral corticosteroids. The registry’s enrollment field records 145, while the brief description says 156 participants will be included; the difference between these entries is not explained in the registry record.
Intervention
The intervention is n-3 polyunsaturated fatty acids from fish oil. The brief description states an intended daily supplement dose of 3 g. The primary endpoint is assessed at 24 weeks. The registry record does not provide further details about adherence, dose changes, or the timing of the primary endpoint measurement within that timeframe.
Comparator
The comparator arm received olive oil. The brief description calls the study placebo-controlled, while the intervention listing identifies olive oil as the comparator; the registry record does not explain whether or how olive oil served as a placebo. The posted results report an arm-specific mean change for each group, but no direct comparison estimate between the groups.
Primary question
The primary question is whether the mean change in heart rate variability differs between the n-3 polyunsaturated fatty acid and olive oil groups at 24 weeks. Heart rate variability is described as a non-invasive measure of autonomic regulation of the heart and as a cardiovascular disease risk marker. The registry record posts a mean and a 95% confidence interval for each arm. It does not report a between-group estimate, confidence interval, or test for this endpoint, so the arm-specific results alone do not quantify the treatment contrast.
3. Trial Design
The registry describes a randomized, parallel-group dietary supplement trial involving people with psoriatic arthritis. The listed arms are n-3 polyunsaturated fatty acids from fish oil and olive oil. The trial is marked completed, and its phase is listed as NA. Aalborg University Hospital is named as sponsor. The registry dates the start to 2013-03 and primary completion to 2015-12.
The brief description characterizes the study as double-blind, placebo-controlled, and multicenter. A separate structured entry lists quadruple masking. Those descriptions differ, and the registry record does not explain the masking terminology or the role of olive oil as a placebo. The described sites are departments of rheumatology, nephrology, and cardiology at Aalborg University Hospital and Vendsyssel Hospital in Region Northern Denmark.
The brief description says participants were adults classified by CASPAR criteria and lists cardiac arrhythmias, conduction disturbances, biological drug treatment, and oral corticosteroid treatment among the exclusions. It describes an intended inclusion period from spring 2013 to spring 2015. The enrollment field records 145, whereas the brief description gives a planned inclusion of 156; the registry record does not reconcile these entries. The posted arm results list 68.0 participants for n-3PUFA and 60.0 for olive oil. The reason the arm counts differ from the enrollment entry is not reported in the registry record.
The primary endpoint is change in heart rate variability at 24 weeks. Change in PWV is listed as a secondary outcome, and the registry identifies three outcome measures overall. Additional details about allocation procedures, concealment, adherence monitoring, and the protocol’s 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.
Overall Study
| Stage | n-3PUFA | Olive Oil |
|---|---|---|
| STARTED | 73 | 72 |
| COMPLETED | 68 | 65 |
| NOT COMPLETED | 5 | 7 |
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.
| Characteristic | Unit | n-3PUFA | Olive Oil | Total |
|---|---|---|---|---|
| Participants analysed | 73 | 72 | 145 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 64 | 62 | 126 |
| Age, Categorical: >=65 years | Participants | 9 | 10 | 19 |
| Age, Continuous | years | 53.2 (SD 11.4) | 50.7 (SD 11.5) | 52 (SD 11.5) |
| Sex: Female, Male: Female | Participants | 40 | 43 | 83 |
| Sex: Female, Male: Male | Participants | 33 | 29 | 62 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 | 0 | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 73 | 72 | 145 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 | 0 | 0 |
| Region of Enrollment: Denmark | participants | 73 | 72 | 145 |
6. Primary Endpoint
The registry lists the primary outcome as Change in Heart Rate Variability (HRV) Measure, measured over 24 week.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | 95% Confidence Interval |
| Unit | ms |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is change in heart rate variability (HRV), measured in milliseconds, at 24 weeks. HRV describes variation in the time between heartbeats. The registry describes it as a non-invasive measure of autonomic regulation of the heart and associates the measure with cardiovascular disease risk. In general, a physiological measure such as HRV can be used as a risk marker even when it is not itself a clinical event such as a cardiovascular diagnosis.
The registry reports a mean change and a 95% confidence interval for each arm. For n-3PUFA, the mean change is 13.38 ms, with a 95% confidence interval from -5.06 to 31.83. For olive oil, the mean change is -13.48 ms, with a 95% confidence interval from -35.0 to -8.69. These are arm-specific summaries; the registry record does not post a direct estimate of the difference in mean change between groups.
Interpreting a change score requires knowing how it was defined, including the direction of subtraction and the measurement procedures. Those details are not reported in the registry record. Nor does the record specify a threshold for a clinically important HRV change. Therefore, the endpoint summaries describe the posted measurement but do not establish the clinical meaning of its magnitude.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted primary results are arm-specific mean changes in HRV. The n-3PUFA arm has a mean change of 13.38 ms, with a 95% confidence interval from -5.06 to 31.83. The olive oil arm has a mean change of -13.48 ms, with a 95% confidence interval from -35.0 to -8.69. Each interval describes uncertainty around its own arm’s reported mean under the assumptions used to calculate it. The registry record does not report those calculation details.
These summaries do not supply the central quantity needed for a randomized treatment comparison: the estimated difference in mean change between the arms, together with its uncertainty. Without that direct estimate, the precision of the contrast cannot be read from the two arm-specific intervals alone. Comparing the intervals by eye is not a substitute for a between-group analysis. The registry record also does not post a p-value or other test result for the primary endpoint.
The numerical direction of a change should not be treated as evidence of benefit or harm without information about the change-score definition, the clinical interpretation of higher or lower HRV in this population, and the prespecified analysis. The registry record does not provide a clinical-importance threshold for HRV. The reported summaries therefore describe observed changes as recorded, but do not by themselves establish whether the difference is clinically meaningful.
The record lists 145 enrolled participants, while its brief description states that 156 participants will be included. The posted primary arm results list 68.0 for n-3PUFA and 60.0 for olive oil. The registry record does not explain the discrepancy among these enrollment figures or say how many randomized participants contributed to the primary endpoint analysis. It also does not report an analysis population, missing-data approach, or reasons for missing observations.
One secondary outcome, change in PWV, is named in the record. Numerical results for that outcome are not included in the posted results. The record indicates three outcome measures but does not provide enough analysis information to assess how outcome multiplicity was handled. Consequently, the available evidence supports a descriptive reading of the arm summaries, not a complete inferential assessment of the randomized comparison.
9. Statistical Methods Explained
What does an arm-specific mean describe? A mean summarizes the values within a group by representing their arithmetic average. For this continuous endpoint, the registry reports a mean change for each treatment arm. A group mean describes the central tendency of the recorded changes; it does not show how individual participants’ values were distributed. The posted results do not include a measure of dispersion such as a standard deviation, nor do they describe the distribution of HRV change.
What does a confidence interval communicate? A confidence interval expresses uncertainty around an estimate under the statistical procedure used to construct it. The intervals posted for the two arms are 95% confidence intervals. In general, a wider interval indicates less precision than a narrower interval, all else being equal. An interval is not a range containing a fixed proportion of individual participants’ values, and it is not a direct probability statement about the true value. The registry record does not report the interval calculation method, the model, or whether any adjustment was used.
Why is a treatment contrast important? Randomization is intended to support a comparison between assigned groups. For a continuous endpoint, a common contrast is the difference between group means, defined according to the analysis plan. That contrast and its confidence interval directly address the comparative question. Here the registry posts separate means and confidence intervals but no between-group estimate, confidence interval, or test for HRV. The arm summaries cannot be combined into a valid contrast without participant-level data or additional appropriate summary information. No such recalculation is posted in the registry record.
Why not infer the contrast from the arm intervals? Each interval concerns uncertainty in one arm’s mean. The uncertainty in a difference depends on the variability and sample size in both arms, and on the analysis method. In general, whether two separate confidence intervals overlap is not a formal test of the difference between means. The record does not provide the covariance structure, endpoint-level analysis counts, or a direct contrast. Therefore, the separate intervals cannot establish the uncertainty or statistical significance of the randomized comparison.
What does randomization contribute? In general, random allocation helps balance measured and unmeasured baseline characteristics across groups on average, supporting causal interpretation of a properly conducted comparison. It does not guarantee exact balance in a particular trial, prevent missing data, or correct problems in outcome measurement or analysis. The registry identifies the allocation as randomized but does not describe the sequence-generation method, allocation concealment, baseline characteristics, or analysis adjustments. Those details cannot be assessed from the posted record.
What do the planning illustrations mean? Any sample-size estimates based on the observed effect are planning illustrations rather than observed power. The registry’s stated assumptions describe a two-sided significance level of 0.05, equal allocation, and a normal approximation, with planning effects defined as fractions of the observed effect. In general, such calculations ask how many participants per arm might be needed to detect a specified effect under stated assumptions. They do not show the probability that this completed trial detected an effect, and they do not replace a prespecified design calculation. The record does not report the trial’s own sample-size justification. Numerical planning estimates are not described in the registry record.
Why can over-dispersion matter? In general, over-dispersion means that observed variation is greater than a statistical model assumes. When a model understates variability, standard errors may be too small and confidence intervals too narrow; inference can then appear more precise than warranted. This concept is especially relevant to outcomes whose variability is not well represented by a simple model. The posted primary outcome is continuous, but the record does not describe an over-dispersion assessment or a model for the endpoint. No conclusion about over-dispersion in this trial can be drawn from the posted summaries.
What can be said about recalculation? The posted information gives arm-specific means and confidence intervals, but not the standard deviations, endpoint-specific analysis counts, or a reported contrast. A simple unadjusted re-calculation of the treatment difference is therefore not available from the registry record. There is no posted recalculated estimate that can be compared with a sponsor-reported analysis. The registry record does not report an inferential analysis for this primary endpoint, so neither a sponsor estimate nor its precedence in a discrepancy can be evaluated.
Which statistical details remain uncertain? The model, covariate adjustment, handling of repeated measurements, missing-data assumptions, and analysis population are not reported in the registry record. The record also does not state whether the primary endpoint analysis followed intention-to-treat principles, whether a per-protocol analysis was performed, or whether any sensitivity analyses were conducted. These omissions limit assessment of how the posted arm summaries relate to the randomized comparison.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies three outcome measures and names one secondary outcome, change in PWV. The primary outcome is change in HRV at 24 weeks. The record does not describe a hierarchy of outcomes, a family of confirmatory tests, or a procedure for adjusting for multiple comparisons. Whether multiplicity was considered in the trial’s statistical plan is not reported in the registry record. Without that information, the results for multiple outcomes should not be treated as if each were a single isolated test.
The record does not provide numerical results for the listed secondary outcome in the information available for this analysis. It also does not specify whether all prespecified outcomes were reported, how outcomes were selected for reporting, or whether any analyses were exploratory. The number of outcome measures alone does not show how many hypotheses were tested or how they were interpreted.
Missing-data methods are not reported in the registry record. The primary endpoint arm entries list 68.0 for n-3PUFA and 60.0 for olive oil, but those values do not establish the endpoint analysis population or explain the difference between the posted counts and the enrollment field. The record does not say whether participants withdrew, missed the 24-week assessment, or had unusable HRV measurements. Reasons for missing observations, if any, are not reported.
Analysis populations are also not described. The registry record does not identify an intention-to-treat, modified intention-to-treat, or per-protocol population for the primary outcome. It does not report a missing-data imputation procedure, sensitivity analysis, or method for handling protocol deviations. These gaps matter because analysis choices can affect both the estimate and its uncertainty.
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 |
|---|---|---|---|
| n-3PUFA | 1 | 73 | 1.4% |
| Olive Oil | 3 | 72 | 4.2% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| n-3PUFA | 0 of 73 |
| Olive Oil | 2 of 72 |
Most frequent serious adverse event terms
| Event term | Organ system | n-3PUFA | Olive Oil |
|---|---|---|---|
| Joint inflammation | Musculoskeletal and connective tissue disorders | 0 of 73 | 2 of 72 |
| Infection | Infections and infestations | 1 of 73 | 0 of 72 |
| vertigo | Ear and labyrinth disorders | 0 of 73 | 1 of 72 |
Most frequent non-serious adverse event terms
| Event term | Organ system | n-3PUFA | Olive Oil |
|---|---|---|---|
| nausea | Gastrointestinal disorders | 0 of 73 | 2 of 72 |
Serious events with the highest arm-level rate: joint inflammation (2.8%), vertigo (1.4%), infection (1.4%).
The safety entries distinguish serious adverse events from other adverse events and give the number at risk and the number affected in each arm. For serious adverse events, the n-3PUFA group has 1 affected participant among 73 at risk, and the olive oil group has 3 affected participants among 72 at risk. For other adverse events, the entries are 0 among 73 at risk for n-3PUFA and 2 among 72 at risk for olive oil. These are counts as recorded; they are not a statistical comparison between groups.
The registry also lists serious adverse event terms with percentages: Joint inflammation, 2.8%; vertigo, 1.4%; and Infection, 1.4%. The entries do not establish whether these terms are mutually exclusive, whether an individual could contribute more than one event, or which group each term belongs to. The registry record does not provide enough detail to infer comparative risks from these term listings.
Deaths are not reported in the registry record. The safety entries do not include a comparative estimate, confidence interval, follow-up duration for safety, or explanation of event ascertainment. Small event counts can be imprecise, and descriptive counts alone do not establish that one group had more or fewer safety events in a statistically reliable way. They should be read as registry-reported observations, not as proof of safety or harm.
12. What the Result Does, and Does Not, Mean
The posted result establishes that the registry contains arm-specific mean changes in HRV at 24 weeks: 13.38 ms for n-3PUFA and -13.48 ms for olive oil, each accompanied by a 95% confidence interval. It does not provide a direct estimate of the difference between those means. Accordingly, the posted figures do not quantify the effect of assignment to one group rather than the other, with uncertainty around that comparative effect.
The result also does not determine whether a change in HRV is clinically important. The registry record does not give a threshold for meaningful change, explain the score’s clinical direction, or describe how changes relate to cardiovascular events in these participants. HRV is identified as a cardiovascular risk marker, but a risk marker is not itself a clinical outcome such as a cardiovascular event. A change in a marker cannot by itself establish a change in clinical risk.
The randomized design is relevant to causal inference in general, but a causal interpretation depends on how the study was conducted and analyzed. Information about allocation procedures, adherence, missing data, analysis populations, and the primary comparative analysis is not reported in the registry record. The posted arm summaries alone do not resolve those uncertainties.
Nor do the available entries establish whether the findings apply beyond the study population. The brief description specifies eligibility and exclusions, and the study concerns people with psoriatic arthritis. The registry record does not provide detailed demographic or clinical characteristics of participants in the posted results. Generalization to people who would not have met the described criteria cannot be assessed from these summaries.
The safety counts are descriptive and do not establish a comparative safety profile. The record does not provide a formal analysis of adverse events, and deaths are not reported in the registry record. Taken together, the available information permits a careful description of the posted HRV summaries and event counts, but not a definitive claim about comparative clinical benefit, harm, or cardiovascular outcomes.
13. Why This Trial Matters Statistically
This trial illustrates the distinction between reporting results within each randomized arm and reporting the randomized comparison. A mean and confidence interval for each group can describe the data, but the treatment question is addressed most directly by a between-group estimate and its uncertainty. Without that contrast, readers cannot determine from the posted results how precisely the groups differ on the primary endpoint.
It also illustrates why endpoint interpretation requires more than a numerical change. HRV is described as a cardiovascular risk marker, yet the registry record does not provide a threshold for clinically important change or connect the posted changes to cardiovascular events. Statistical summaries and clinical meaning are related but distinct questions. A precise marker estimate would still need clinical context; the available arm summaries do not supply that context.
The record contains several details that are important for evaluating the evidence: its enrollment field and brief description give different participant numbers; its structured masking entry and narrative description use different masking labels; and it identifies olive oil as the comparator while the narrative calls the trial placebo-controlled. These differences do not determine the result, but they make clear why transparent trial documentation matters.
Finally, the registry does not describe the analysis population, missing-data handling, multiplicity approach, or sample-size justification. Such information helps readers understand how planned questions were translated into analyses and how much confidence to place in reported estimates. This record therefore offers a useful case in separating descriptive information that is present from inferential and design details that are not reported.
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 principal limitation for interpreting the primary result is the absence of a reported between-group estimate. The registry gives a mean and 95% confidence interval for each arm, but no direct contrast or test for the primary endpoint. The arm summaries therefore do not provide a complete inferential answer to the randomized comparison.
Several registry entries are not reconciled. The enrollment field records 145, while the brief description states 156 participants will be included; the posted arm results give 68.0 for n-3PUFA and 60.0 for olive oil. The registry record does not explain how these figures relate to enrollment, randomization, or endpoint analysis. The structured masking field says quadruple, while the narrative says double-blind. The narrative also describes a placebo-controlled study, while olive oil is listed as the comparator. The record does not clarify these differences.
Further limitations include the lack of reported endpoint-level analysis counts, baseline characteristics, standard deviations, missing-data methods, analysis populations, model specification, and sensitivity analyses. The registry record does not explain the interval calculation or whether the analysis adjusted for baseline HRV or other variables. It also does not report a threshold for clinically important change or numerical results for the listed secondary outcome.
The safety information is limited to event counts and selected terms. Deaths are not reported in the registry record, and no formal comparative safety analysis is posted. The listed serious-event terms do not specify their arm attribution or explain whether multiple events could occur for one participant. These omissions constrain both comparative and clinical interpretation.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: The Effect of n-3 Polyunsaturated Fatty Acids in Patients With Psoriatic Arthritis — NCT01818804.
- Registry record last updated 2020-06-09; status last verified 2020-05.
- Results first posted 2020-06-09.
- 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
The registry record describes a completed randomized parallel-group trial of n-3 polyunsaturated fatty acids from fish oil compared with olive oil in people with psoriatic arthritis. The primary outcome is change in HRV at 24 weeks, measured in milliseconds. The posted arm-specific mean changes are 13.38 ms for n-3PUFA and -13.48 ms for olive oil, with their respective 95% confidence intervals.
A direct between-group estimate for the primary endpoint is not reported in the registry record. The record lists change in PWV as a secondary outcome and identifies three outcome measures overall. It also posts serious and other adverse-event counts, but no comparative safety analysis; deaths are not reported in the registry record.
Interpretation is limited by missing analysis details and unresolved differences in enrollment and masking entries. The registry record does not describe the primary analysis population, missing-data approach, multiplicity strategy, or sample-size justification.