N-3 PUFA and Rheumatoid Arthritis in Korea: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for N-3 PUFA and Rheumatoid Arthritis in Korea (NCT01618019), a randomized na study. The primary outcome is Dose of NSAID.

2. Clinical Question

The clinical question focuses on NSAID dose rather than a direct measure of rheumatoid arthritis activity. The registry describes the purpose as assessing whether n-3 PUFA supplementation could be beneficial for patients with rheumatoid arthritis, but its primary outcome is the daily amount of NSAID required at the stated assessment time. That endpoint can be read as a measure of medication requirement in the study population; its interpretation depends on how dose was managed and recorded, details that are not reported in the registry record.

The comparison is between the supplement regimen and a capsule placebo, not between supplementation and no capsules. Both groups are described as taking 5 capsules/day. The posted primary result is based on a per-protocol analysis, with the record noting exclusions at the 16-week measurement. The precise eligibility criteria, background treatments, and procedures for adjusting NSAID use are not reported in the registry record, so the question should be kept to the groups and outcome as recorded rather than extended to other populations or treatment settings.

3. Trial Design

This was a randomized, triple-masked, parallel-group study sponsored by Hanyang University. The registry lists its phase as NA and its status as completed. The record gives a start date of 2010-11 and a primary completion date of 2011-12. Enrollment was 109.

Participants were assigned to N-3 PUFA or placebo. The active regimen was 5 capsules/day containing 2.09 g eicosapentaenoic acid and 1.165 g docosahexaenoic acid. The placebo regimen was 5 capsules/day containing sunflower with oleic acid. The registry identifies DSM Nutritional products, Switzerland, in the placebo description. The parallel design means the two groups were compared as separate arms over the trial period; the record does not describe a crossover.

Triple masking indicates that the registry classifies the study as masked at three levels, but it does not identify which roles were masked or describe how masking was maintained. The allocation is listed as randomized; the method used to generate the random sequence and the method for concealing allocation are not reported in the registry record. The planned study size, original sample-size rationale, and the detailed statistical analysis plan are also not reported in the registry record.

The primary assessment was at 16 weeks. Its description says daily NSAID requirements were assessed in a per-protocol population, except for drop-out patients, and notes that 10 participants in N-3 PUFA and 6 in placebo were excepted from the measurement. The posted primary outcome summaries contain 41 participants in N-3 PUFA and 40 in placebo. The registry does not explain in detail how the endpoint analysis population was derived from the overall enrollment or how missing measurements were handled.

Seven secondary outcomes are listed, including morning stiffness duration, physician's global assessment, patient's global assessment, pain scale, and three bone-related concentrations. Numerical results are posted for three of these secondary outcomes. The remaining listed outcomes are not reported in the registry record as numerical results.

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: Patients receiving NSAID, glucocorticoids, or DMARD were eligible if the dosage had been stable for at least 3 months prior to entering the study.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Per-protocol analysis (except for drop out patients) Measurement of NSAID requirements at 16 weeks, except for 10 in N-3 PUFA and 6 in placebo.

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 Dose of NSAID, measured over 16 week.

The primary endpoint is the daily dose of non-steroidal anti-inflammatory drug (NSAID), measured in mg/day at 16 weeks. The registry describes it as daily NSAID requirements and reports a mean and standard deviation for each group. In the posted results, the mean is 319.7 mg/day for N-3 PUFA, based on 41 participants, and 301.6 mg/day for placebo, based on 40 participants. The posted comparison estimates a mean difference of 18.14 mg/day for N-3 PUFA versus placebo.

This endpoint is used to represent the amount of NSAID required by participants at the assessment time. A group difference could describe a difference in recorded medication requirement, but the result alone does not explain why dose differed, how clinicians made dosing decisions, or whether any difference reflects changes in symptoms or other factors. Those procedures and contextual details are not reported in the registry record.

The analysis population deserves attention when reading this measure. The registry labels the primary result per-protocol and says the 16-week assessment excepted 10 participants in N-3 PUFA and 6 in placebo. It also gives endpoint sample counts of 41 and 40. The record does not provide a fuller account of participant flow or missing endpoint data. The reported means therefore describe the analyzed endpoint groups, not necessarily every person enrolled or randomized.

7. Results Posted in the Registry

• N-3 PUFA: mean 319.72 versus 301.58 on control; difference 18.14 (95% CI -144.48 to 180.76), standardized effect d = 0.05; z-test p = 0.827.

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.

Duration of Morning Stiffness

• 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:
  • N-3 PUFA: mean 40.10 versus 17.55 on control; difference 22.55 (95% CI -3.35 to 48.45), standardized effect d = 0.38; z-test p = 0.088.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between N-3 PUFA and the control. The interval gives the range of effects that remain compatible with the data.

Physician's Global Assessment

• 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:
  • N-3 PUFA: mean 1.88 versus 1.60 on control; difference 0.28 (95% CI -0.50 to 1.06), standardized effect d = 0.16; z-test p = 0.482.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between N-3 PUFA and the control. The interval gives the range of effects that remain compatible with the data.

Patient's Global Assessment

• 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:
  • N-3 PUFA: mean 4.00 versus 4.01 on control; difference -0.01 (95% CI -1.06 to 1.04), standardized effect d = -0.00; z-test p = 0.985.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between N-3 PUFA and the control. The interval gives the range of effects that remain compatible with the data.

Numerical results are posted for three secondary outcomes: duration of morning stiffness, physician's global assessment, and patient's global assessment. The registry also lists pain scale and three bone-related concentration outcomes, but numerical results for those four outcomes are not reported in the registry record. The available secondary estimates do not form a single, consistent pattern across the different measures. Their directions and uncertainty vary, so they do not provide a simple, uniformly aligned account alongside the primary endpoint.

Secondary outcomes can add context because they measure other aspects of participants' status, but they are not substitutes for the primary outcome. NSAID dose, morning stiffness, global assessments, pain, and bone-related concentrations represent distinct measures. Agreement across measures could be informative, but differences between them are not necessarily contradictory: each reflects a different outcome and may have different variability, measurement properties, and clinical interpretation. The registry does not provide enough methodological detail to determine how these measures were prioritized or how their results were intended to inform the primary question.

The numerical secondary comparisons are unadjusted. When multiple outcomes are assessed, the chance of observing at least one apparently notable result can increase even if no outcome has a true group difference. General statistical explanation: Multiplicity procedures address the interpretation of several tests by controlling or otherwise accounting for the broader set of comparisons. The registry record does not report a multiplicity adjustment or a prespecified hierarchy for these secondary outcomes. Therefore, isolated secondary findings deserve less weight than a result supported by a clearly specified analysis plan and a coherent pattern across outcomes.

There are seven secondary outcomes listed, but only three have numerical results posted. Without results for the remainder, the full secondary-outcome pattern cannot be assessed. The record also does not report analyses for these outcomes beyond the posted arm summaries and unadjusted comparisons. These limitations argue for a restrained reading: the secondary results provide partial descriptive context, not independent confirmation of a primary conclusion.

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

• Duration of Morning Stiffness
• Physician's Global Assessment
• Patient's Global Assessment
• Pain Scale
• Osteocalcin Concentration
• BSAP Concentration
• CTX Concentration

9. Statistical Interpretation

10. Statistical Methods Explained

The primary result is a comparison of group means for a continuous outcome. A continuous measure can take a range of numerical values; here, the measure is NSAID dose in mg/day. The registry reports the mean and standard deviation in each arm. The mean describes the arithmetic center of the observed doses in that arm, while the standard deviation describes how dispersed individual values are around that mean. A large standard deviation relative to the mean difference indicates that participant values vary substantially within the groups, which can make a group contrast less precise.

The posted comparison is an unadjusted mean difference. It compares the N-3 PUFA mean with the placebo mean without a reported covariate adjustment. The estimated mean difference is 18.14 mg/day. Its confidence interval is -144.5 to 180.8 mg/day, and the unadjusted p-value is 0.827. The calculation uses the posted means, standard deviations, and arm sample sizes. The registry does not report a separate analysis from the study investigators for this endpoint. No discrepancy is identified between the posted summaries and the recalculation.

What does a confidence interval express?

General statistical explanation: A confidence interval gives a range of values compatible with the observed data under a specified statistical procedure and its assumptions. It communicates uncertainty about an estimated quantity. It is not a guarantee that the true value lies inside the interval, and it is not a range of individual outcomes. Wider intervals represent less precision than narrower intervals. For a difference between two means, an interval that includes zero does not establish that the group means differ; it also does not establish that they are exactly the same.

For this trial's primary comparison, the interval includes zero and extends in both directions. That feature means the data do not tightly determine the direction or size of the underlying mean difference. The interval should be considered alongside the point estimate and the analysis population, rather than using only the estimate or p-value.

What does the p-value say?

General statistical explanation: A p-value measures how compatible the observed test statistic is with a null model, under the test's assumptions. It is not the probability that the null hypothesis is true, the probability that the result occurred by chance, or a measure of clinical importance. The primary p-value is explicitly unadjusted. The registry does not state the full testing procedure, any covariate adjustment, or a hierarchy of hypotheses. As a result, the unadjusted p-value should be understood as a simple summary of the posted comparison, not as evidence that all design and analysis issues have been addressed.

Why can variability affect precision?

General statistical explanation: When individual measurements vary widely within each group, the group means are estimated less precisely for a given number of observations. A mean difference can be small relative to the spread of participant values, and that combination can yield a broad confidence interval. The primary endpoint has substantial variability in both arms, as indicated by the posted standard deviations of 407.1 mg/day and 337.2 mg/day. The resulting interval is broad. This is a description of statistical precision, not a statement about whether the observed variation is clinically important.

What does the per-protocol label imply?

The registry calls the primary result a per-protocol analysis and notes that 10 participants in N-3 PUFA and 6 in placebo were excepted from the 16-week measurement. The posted endpoint summaries contain 41 and 40 participants. The record does not give a detailed definition of protocol adherence, a full participant-flow account, or a complete explanation of how the analyzed groups relate to randomized participants. A per-protocol result generally describes participants meeting specified analysis criteria, but the exact criteria for this trial are not reported in the registry record. The result should not be assumed to have the same interpretation as an analysis retaining all randomized participants in their assigned groups.

The registry lists eight outcome measures and identifies seven secondary outcomes, while numerical results are posted for three secondary outcomes. It does not report the statistical analysis plan, adjustments for multiple testing, interim analyses, or detailed handling of missing observations. Those omissions limit how specifically the posted estimates can be connected to a prespecified testing strategy. They also make it difficult to assess whether the displayed outcomes represent all planned analyses.

The trial is randomized, triple masked, and parallel, according to its registry classification. Those design labels describe important features, but the record does not give the random-sequence method, allocation concealment, masking roles, or a detailed account of implementation. Statistical interpretation can recognize the stated design without assuming methods that are not described. Likewise, the registered sample-size assumptions for an original design are not reported in the registry record. The planning calculations associated with the observed effects are a separate illustration and do not reconstruct the trial's initial design rationale.

Overall, the numerical summary supports a descriptive comparison of the reported endpoint groups. The precision of that comparison, the analysis population, the unadjusted nature of the calculation, and the incomplete description of analysis procedures should all remain visible when interpreting the result. General statistical concepts explain what these quantities mean; they do not fill in unreported trial procedures.

11. Confidence Intervals and Precision

The primary estimated mean difference is 18.14 mg/day for N-3 PUFA versus placebo. Its 95% confidence interval runs from -144.5 to 180.8 mg/day. Because the interval extends below and above zero, the posted results do not settle the direction of the difference. Its width also indicates that the estimate is imprecise: the compatible values span a substantial range around the point estimate.

General statistical explanation: A confidence interval represents uncertainty about an estimated group contrast under the calculation's assumptions. A narrow interval gives a more precise estimate than a wide one; an interval that includes zero does not demonstrate equality. The interval is not a prediction interval for individual NSAID doses, and it does not mean that all plausible effects are equally likely.

The unadjusted p-value of 0.827 is consistent with the broad uncertainty in the estimate, but it should not be used alone to judge the result. A p-value does not indicate the size or practical importance of a difference. The estimate and interval communicate the direction, scale, and uncertainty more directly. The registry does not report an adjusted estimate or an investigator-reported primary comparison that could be used to assess whether another prespecified analysis leads to a different conclusion.

The endpoint summaries include 41 participants in the N-3 PUFA arm and 40 in placebo. Total enrollment was 109, and the record notes participants excepted from the 16-week measurement. The relationship between the randomized population, those exceptions, and the analyzed endpoint population is not fully reported. This limits assessment of how missing endpoint information could affect precision or the comparison itself.

The posted interval is based on a simple unadjusted comparison using summary statistics. It does not capture uncertainty from unreported modeling choices, missing-data assumptions, multiplicity, or deviations from the stated analysis population. The interval is useful, but it is not a complete account of every source of uncertainty in the trial.

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 sample-size planning estimates are expressed as participants per arm because the primary endpoint is continuous; they are not total event counts. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is specified as a fraction of the observed effect. The estimates illustrate the sample sizes associated with those assumptions, not the trial's original design. The trial's own original sample-size assumptions and justification are not reported in the registry record.

The 80% power column indicates the number of participants per arm estimated to give an 80% chance of detecting the specified effect under the planning assumptions, if that effect and the calculation assumptions hold. The 90% power column applies the same idea at a higher target chance of detection. Power is a property of a planned study under specified assumptions; it is not a measure of whether a result is true or important.

The rows use the full observed effect and smaller fractions of that effect. The smaller the effect a future study aims to detect, the more participants it generally needs, all else held constant. This is a general feature of sample-size planning: a subtler group difference is harder to distinguish from random variation than a larger one. The estimates can therefore be read as planning illustrations across different target effect sizes, not as claims about the number of participants required for every possible study.

These calculations are not observed power. They use the effect estimated from the posted trial results for planning, and the observed effect itself is uncertain. The very large estimates associated with small fractions of an observed effect illustrate how estimates can change sharply when planning targets are reduced, especially when the original estimated contrast is small. They should not be treated as a retrospective judgment about whether this completed trial was adequately designed.

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 = 18.140; pooled standard deviation σ = 374.219.
2. n = 2 × (1.96 + 0.842)² × 374.219² / 18.140² = 6,680.6, rounded up to 6,681 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 <- 18.14                      # observed difference in means
sigma <- 374.218851279789                     # 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(1618019)
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 = 6,681 (80% power), 8,944 (90% power)
 75% of observed effect: n per arm = 11,877 (80% power), 15,900 (90% power)
 50% of observed effect: n per arm = 26,723 (80% power), 35,774 (90% power)
power.t.test: 6681.5 
Simulated power at n = 6,681 per arm: 0.805 (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 lists one primary outcome and seven secondary outcomes. Numerical secondary results are posted for three of the seven listed measures. A multiplicity strategy, such as an adjustment for multiple comparisons or an order in which hypotheses were to be tested, is not reported in the registry record. The posted secondary p-values are unadjusted. When several outcomes are examined, unadjusted tests do not account for the fact that many opportunities exist to observe a result that appears unusual. This makes secondary findings less conclusive unless a prespecified testing strategy and the full set of results are available.

The statistical analysis plan is not reported in the registry record. It is therefore not possible to determine which models, covariates, tests, or analysis decisions were prespecified, or whether the posted calculations match the original plan. Interim analyses are also not reported in the registry record. Their absence from the record should not be interpreted as confirmation that none occurred.

The primary outcome description refers to a per-protocol analysis and says that 10 participants in N-3 PUFA and 6 in placebo were excepted from the 16-week measurement. The posted endpoint summaries report 41 and 40 participants. A complete flow from enrollment and randomization to the analysis set is not reported in the registry record, nor is the reason for each exclusion. The record does not describe whether missing data were imputed, whether participants with incomplete measurements were otherwise included, or whether sensitivity analyses were conducted.

These details matter because analyses limited to observed or protocol-compliant participants can differ in interpretation from analyses based on all randomized participants. Missingness can also affect both the amount of information and the comparability of groups if reasons for missing measurements are related to outcomes or treatment assignment. General statistical explanation: Missing-data methods rely on assumptions about why observations are missing; different assumptions can lead to different conclusions. No particular missing-data assumption or method can be attributed to this trial from the registry record.

The endpoint population and missing-data limitations do not invalidate the posted summaries, but they constrain what can be inferred from them. They should be considered with the wide primary confidence interval, the unadjusted secondary results, and the absence of a detailed analysis plan.

15. Safety Results

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

Other (non-serious) adverse events

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

The registry reports serious adverse events in 0 of 55 participants at risk in the N-3 PUFA group and 0 of 54 participants at risk in the placebo group. It also reports 0 other adverse events in 55 participants at risk for N-3 PUFA and 0 in 54 at risk for placebo. These are the event counts recorded in the registry for the stated at-risk groups.

Zero recorded events in these groups means that the registry lists no events of those categories during the reporting period. It does not establish that the risk is zero, or rule out events that were not observed, captured, or reported. The adverse-event denominators differ from the primary endpoint sample counts, and the record does not explain the relationship between those populations. The deaths fields are not reported in the registry record; a blank or null value should not be read as a reported zero.

The registry provides no serious adverse event terms in the listed results. Without additional information on event definitions, follow-up, and completeness of reporting, these figures should be read as a summary of the posted adverse-event record rather than a comprehensive comparison of safety.

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

The primary result is a descriptive estimate of the difference in mean NSAID dose at 16 weeks among the endpoint groups represented in the registry. The point estimate is 18.14 mg/day for N-3 PUFA compared with placebo, and the confidence interval from -144.5 to 180.8 mg/day shows that the estimate is imprecise. The registry's unadjusted p-value is 0.827. These statistics do not establish a precise direction or size for the underlying group difference.

The result does not show that the treatments are identical. A broad interval that includes zero can be compatible with no difference, but it can also be compatible with non-zero differences in either direction. Conversely, the point estimate should not be treated as proof of a difference. The information in the posted results is not precise enough to resolve those possibilities. A conclusion about equivalence or non-inferiority would require a specific design and analysis framework, neither of which is reported in the registry record.

The endpoint is NSAID requirement, not a direct measure of all aspects of rheumatoid arthritis. It cannot by itself explain changes in symptoms, disease activity, or other outcomes. The registry lists several secondary measures, but numerical results are posted for only three; the remaining listed secondary results are not reported in the registry record. The available secondary findings are unadjusted and should be read as partial context rather than a definitive assessment across all outcomes.

The primary analysis is described as per-protocol, with the record noting exceptions from the 16-week measurement. The endpoint sample counts are smaller than total enrollment, and the full participant flow and handling of missing data are not reported. This means the comparison may not represent all enrolled or randomized participants in the same way an analysis of all assigned participants would.

These findings are limited to the trial's recorded population, regimens, outcomes, and assessment time. The registry does not report enough information to extend the estimate to different doses, longer periods, other populations, or different clinical settings. The statistics describe the posted data and their uncertainty; they do not amount to medical advice or a treatment recommendation.

17. Why This Trial Matters Statistically

This trial illustrates why a point estimate should be read together with its uncertainty. The primary comparison is reported as a single mean difference, but its confidence interval spans values in both directions and is wide. A decimal-place estimate can look specific while still being uncertain. In clinical research, the interval is essential for judging how precisely the observed data locate the group difference.

It also illustrates the distinction between enrollment and the analysis population. Enrollment was 109, whereas the primary endpoint summaries contain 41 and 40 participants. The registry notes exclusions from the 16-week measurement but does not fully describe participant flow or missing-data handling. Those details affect the scope of the estimate and the reader's ability to judge potential selection effects.

The registry contains several secondary outcomes but posts numerical results for only some of them, with no reported multiplicity strategy. This highlights why multiple outcome findings need context: an unadjusted result from a set of measures carries less evidential weight than a result interpreted within a prespecified plan and a complete account of outcomes. Here the unadjusted secondary findings do not create a clearly consistent pattern that resolves the uncertainty in the primary result.

Finally, planning calculations based on an observed effect are not the same as the trial's original design calculations or a measure of observed power. Keeping planning illustrations separate from the completed trial's evidence prevents a retrospective estimate from being mistaken for the rationale used to design the study. The record's missing original sample-size rationale makes this distinction especially important.

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 primary comparison is based on an endpoint analysis population of 41 participants in N-3 PUFA and 40 in placebo, while enrollment was 109. The registry describes the primary analysis as per-protocol and notes that 10 participants in N-3 PUFA and 6 in placebo were excepted from the 16-week assessment. A full account of randomized participants, exclusions, and endpoint availability is not reported in the registry record. Reasons for missing or excluded measurements and any missing-data methods are also not reported.

The registry does not provide the original sample-size rationale or detailed analysis plan. Randomization is recorded, but sequence generation and allocation concealment methods are not reported. Triple masking is recorded, but the roles masked and the procedures used to preserve masking are not reported. No interim analysis information is reported. These omissions limit assessment of how closely the posted results reflect the intended design and analysis.

The primary outcome is an NSAID dose measure, and the registry does not describe how prescribing or dose adjustment was managed. The record also does not give enough detail to interpret the scale properties of the global assessments or the other secondary measures. Numerical results are posted for only three of the seven listed secondary outcomes, and the multiplicity approach is not reported. The secondary findings therefore offer incomplete context and are vulnerable to selective emphasis if read without the full analysis plan.

The primary estimate is unadjusted and imprecise, with a confidence interval extending in both directions. The posted comparison is a recalculation from summary statistics rather than a reported investigator analysis. No discrepancy is identified, but the recalculated result cannot recover unreported modeling, data handling, or design details. These limitations call for a cautious interpretation of the registry summaries, not a claim that the study did or did not establish an effect.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: N-3 PUFA and Rheumatoid Arthritis in Korea — NCT01618019.
• Registry record last updated 2012-10-02; status last verified 2012-08.
• Results first posted 2012-10-02.
• 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

NCT01618019, titled N-3 PUFA and Rheumatoid Arthritis in Korea, is a completed randomized, triple-masked, parallel-group study sponsored by Hanyang University. Enrollment was 109. The study compared 5 capsules/day of n-3 PUFA with 5 capsules/day of placebo and assessed daily NSAID requirements at 16 weeks.

The primary result reports means of 319.7 mg/day for N-3 PUFA and 301.6 mg/day for placebo. The unadjusted estimated mean difference is 18.14 mg/day, with a 95% confidence interval from -144.5 to 180.8 mg/day and an unadjusted p-value of 0.827. Numerical results are also posted for three secondary outcomes; the registry lists seven secondary outcomes in total. Serious and other adverse-event counts are recorded as zero in the stated at-risk groups, while deaths are not reported in the registry record.

The primary analysis population, missing-data handling, original sample-size rationale, and detailed statistical analysis plan are not reported in the registry record. The primary estimate is therefore best read as an imprecise, unadjusted comparison of the posted endpoint groups.