A Study of HyQvia and Gammagard Liquid (Kiovig) in Adults With Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study of HyQvia and Gammagard Liquid (Kiovig) in Adults With Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) (NCT02549170), a randomized phase 3 study. The primary outcome is Epoch 1: Relapse Rate.

2. Clinical Question

The central comparison is between the percentage experiencing the defined event in the two randomized Epoch 1 groups. In the posted results, the observed percentages were 9.7% for HyQvia and 31.4% for placebo. Those figures describe the trial participants’ outcomes over the specified Epoch 1 assessment period; they are not guarantees about an individual participant’s experience or estimates for every population with CIDP.

The study also had a second part for participants who relapsed during Part 1. Those participants received intravenous immunoglobulin: Gammagard Liquid/Kiovig, or Gamunex-C for US participants, according to the registry description. That later treatment is distinct from the primary randomized comparison, which concerns subcutaneous HyQvia versus placebo in Epoch 1. The registry does not report a primary head-to-head comparison of the Epoch 2 intravenous treatments.

3. Trial Design

This was a randomized, triple-masked, parallel-group Phase III study of adults with CIDP. The registry lists planned enrollment as 138 and status as completed. Its stated study aim was to learn more about subcutaneous self-infusion with HyQvia and intravenous infusion with Gammagard Liquid/Kiovig. The registered primary outcome, however, concerns the Epoch 1 comparison of HyQvia with placebo.

In Epoch 1, participants received either HyQvia or placebo with recombinant human hyaluronidase. The registry describes the active treatment as recombinant human hyaluronidase followed by subcutaneous immune globulin, with dosing matched to each participant’s pre-randomization immunoglobulin regimen on a monthly-equivalent basis. The placebo group received recombinant human hyaluronidase followed by a matching-volume subcutaneous placebo infusion. Treatment continued for the specified Epoch 1 period or until relapse, as described for the respective groups.

Epoch 2 applied only to participants who experienced a CIDP relapse during Epoch 1. The registry describes intravenous immunoglobulin treatment for these participants, with Gammagard Liquid/Kiovig used in the listed groups and Gamunex-C used for US participants in one group. The available arm descriptions for Epoch 2 are truncated, so further details of those regimens are not reported in the registry record.

The primary outcome timeframe is Week 32 at the end of Epoch 1 treatment, or an unscheduled relapse visit or early termination assessment. The listed study dates are a start date of 2015-12-15 and a primary completion date of 2022-02-23. The sponsor is listed as Baxalta now part of Shire. The original sample-size justification, the full randomization procedure, and details of the masking implementation 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: Participants received one of the two treatments either HYQVIA/HyQvia or the 0.25% albumin placebo solution with rHuPH20 (Recombinant Human Hyaluronidase) for 6 months or until relapse in Epoch 1. Participants who relapsed during Epoch 1 received GGL/KIOVIG (participants at non-US sites) or GAMUNEX-C (participants at US sites only) in Epoch 2. A total of 138 participants were enrolled out of which 132 participants received atleast one dose of study drug.

Epoch 1: Day 1 to Approximately 32 Weeks

Reasons for not completing this period:

Epoch 2: Up to Approximately Week 61

Analysis population for the primary outcome, as defined in the registry: MITT analysis set included all randomized participants who received any double-blind study medication.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

Population: Epoch 1 safety analysis set included all participants who received any study treatment.

6. Primary Endpoint

The registry lists the primary outcome as Epoch 1: Relapse Rate, measured over Week 32 End of Epoch 1 Treatment (EOET1)/Unscheduled relapse visit assessment (UV)/Early Termination (ET).

The primary endpoint is the percentage of participants experiencing a relapse during Epoch 1. Relapse is operationalized as worsening functional disability: an increase of at least 1 point relative to the pre-subcutaneous-treatment baseline on the adjusted Inflammatory Neuropathy Cause and Treatment (INCAT) disability score in 2 consecutive assessments. The score ranges from 0 to 10, with lower values representing less disability and higher values representing more severe disability, as described in the registry.

This endpoint turns a clinical change into a prespecified event that can be counted for each participant. That makes it possible to compare the proportion meeting the relapse definition in the randomized groups. Requiring a change at repeated consecutive assessments, rather than relying on a single score, is part of the registry’s stated definition and specifies how worsening is identified for this outcome.

The measure is used to assess whether participants experience a meaningful worsening of functional disability over the Epoch 1 treatment period. The registry identifies the INCAT disability score as an effective and responsive tool for assessing clinical response in CIDP. The endpoint is therefore a functional-disability measure, not simply a record of treatment exposure or an adverse event count.

The result depends on the stated threshold, baseline reference, and consecutive-assessment requirement. It should be interpreted as the percentage meeting that particular relapse definition by the specified assessment timeframe, not as a complete summary of every possible change in disability or every aspect of health.

7. Results Posted in the Registry

• Epoch 1: HYQVIA/HyQvia: 9.7% (6/62) versus 31.4% (22/70) on control; risk difference -21.8 percentage points (95% CI -34.9 to -8.6), risk ratio 0.31 (0.13–0.71); unadjusted two-proportion z-test p = 0.002.

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.

Epoch 1: Percentage of Participants Who Experience a Worsening of Functional Disability

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Epoch 1: HYQVIA/HyQvia: 37.5% (21/56) versus 54.4% (37/68) on control; risk difference -16.9 percentage points (95% CI -34.3 to 0.4), risk ratio 0.69 (0.46–1.03); unadjusted two-proportion z-test p = 0.060.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Epoch 1: HYQVIA/HyQvia and the control. The interval gives the range of effects that remain compatible with the data.

Epoch 1: Change From Pre-Subcutaneous (SC) Treatment Baseline in Rasch-built Overall Disability Scale (R-ODS)

• 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 errors.
• Result:
  • Epoch 1: HYQVIA/HyQvia: mean -0.90 versus -6.10 on control; difference 5.20 (95% CI 0.58 to 9.82), standardized effect d = 0.40; z-test p = 0.027.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically higher for Epoch 1: HYQVIA/HyQvia than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Epoch 1: Number of Participants Who Develop Binding and/or Neutralizing Antibodies to Recombinant Human Hyaluronidase (rHuPH20)

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Epoch 1: HYQVIA/HyQvia: 1.6% (1/62) versus 10.0% (7/70) on control; risk difference -8.4 percentage points (95% CI -16.1 to -0.7), risk ratio 0.16 (0.02–1.27); unadjusted two-proportion z-test p = 0.044.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically lower for Epoch 1: HYQVIA/HyQvia than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcomes cover related but distinct aspects of the study: functional disability, time to relapse, change in R-ODS, adverse events, infusion-associated events, and development of antibodies to recombinant human hyaluronidase. These outcomes add context to the primary relapse comparison, but they do not all measure the same construct or use the same analysis population.

Across the posted secondary findings with numerical comparisons, the functional-disability worsening and R-ODS results point in a direction consistent with the primary comparison. The functional-disability comparison is less conclusive by its reported interval and p-value, while the R-ODS analysis reports a difference in least-squares means. The antibody outcome concerns a different biological measure and is not a substitute for clinical disability outcomes. Safety outcomes describe reported adverse events rather than efficacy.

These secondary findings should be read as supportive or contextual rather than as equivalent confirmation of the primary result. The registry lists numerous secondary outcomes, and the record does not report a multiplicity adjustment. In general, when multiple hypotheses are tested, unadjusted p-values carry less weight because the chance of observing a seemingly notable result across many tests can increase. This is particularly relevant when outcomes are not clearly identified as a hierarchy of confirmatory tests.

Some secondary measures have different denominators from the primary endpoint. That may reflect outcome-specific availability or analysis populations, but the reasons are not reported in the registry record. Comparisons across endpoints therefore need to account for differences in measurement and analyzed participants rather than assuming every result represents the same set of observations.

The secondary outcomes can help describe the broader pattern of functional and safety information, but they should not be used to expand the primary conclusion beyond the registered relapse measure. Their interpretation depends on the specific endpoint, its uncertainty, the applicable analysis population, and the unreported multiplicity plan.

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

• Epoch 1: Percentage of Participants Who Experience a Worsening of Functional Disability
• Time to Relapse
• Epoch 1: Change From Pre-Subcutaneous (SC) Treatment Baseline in Rasch-built Overall Disability Scale (R-ODS)
• Epoch 1: Number of Participants Experiencing Any Treatment-Emergent Serious and/or Non-serious Adverse Events (SAEs and/or AEs), Regardless of Causality
• Epoch 1: Number of Participants Experiencing Causally Related Serious and/or Non-Serious Adverse Events (SAEs and/or AEs)
• Epoch 1: Number of Participants With Serious and/or Non-serious Adverse Reactions (ARs) Plus Suspected ARs
• Epoch 1: Number of Treatment-emergent Serious and/or Non-serious Adverse Events (SAEs and/or AEs) Associated With Infusions Regardless of Causality
• Epoch 1: Number of Causally Related Serious and/or Non-serious Adverse Events (SAEs and/or AEs) Associated With Infusions

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary at the participant level: each participant either met the registry’s relapse definition during the assessment period or did not. A percentage is therefore used to describe the frequency of the event in each group. The group percentages are the observed event proportions among the participants included in the corresponding primary outcome analysis.

A risk difference compares those two proportions by subtraction, expressed in percentage points when the proportions are displayed as percentages. A negative risk difference for HyQvia versus placebo means the observed event proportion was lower in the HyQvia group. This measure is directly interpretable as an absolute difference in event frequency; it is not the same as a relative risk or an odds ratio.

A confidence interval describes the precision of an estimate under the statistical method used. In general, it represents a range of values compatible with the observed data and the model’s assumptions. For a risk difference, zero is the value corresponding to no difference between the groups. Whether an interval includes zero is one way to assess how compatible the results are with no group difference, but it does not measure clinical importance or establish the probability that a particular effect is true.

The registry reports a Chi-squared analysis and a Newcombe confidence interval for the primary comparison. The Chi-squared method assesses whether the observed event distributions differ between groups; the Newcombe method is used to construct an interval for the difference between proportions. The registry labels the analysis as a superiority analysis. The record does not report enough detail to reconstruct every implementation choice or any covariate adjustment for the primary endpoint.

The simple recalculation uses the posted event counts and group denominators to estimate an unadjusted difference between the two proportions. It is a descriptive check based on the posted summary statistics, not a replacement for the trial’s reported analysis. Its point estimate and interval are close to the registry result, but its p-value and interval differ. The registry analysis remains the trial’s own reported analysis. No discrepancy is flagged in the record.

The primary analysis population is described as the MITT analysis set, comprising all randomized participants who received any double-blind study medication. This definition is narrower than every randomized participant regardless of treatment receipt. The registry reports 70 participants in the placebo primary outcome group and 62 in the HyQvia group, while the planned enrollment is 138. Group sizes can vary across specific outcomes because the registry reports outcome-specific analysis denominators. The record does not explain all reasons for those variations.

The primary confidence interval is a 95% interval. In general, a confidence interval gives information about statistical precision: wider intervals indicate greater uncertainty about the estimated effect, while narrower intervals indicate more precision under the chosen method. It does not account automatically for every possible source of bias, nor does it guarantee that the underlying assumptions are correct.

For continuous outcomes such as change in R-ODS score, the registry reports least-squares means and a standard error, with an ANCOVA analysis for the comparison. In general, ANCOVA estimates group differences while accounting for specified covariates, but the covariates and full model details are not reported in the registry record. The standard error describes uncertainty in the estimated mean, not the spread of individual participant scores.

For binary secondary outcomes, the registry lists proportions and comparison statistics. The same general distinction applies: an event percentage describes how often the event occurred in each analysis group, while the risk difference describes the absolute contrast between those percentages. A confidence interval communicates uncertainty in that contrast. The endpoint-specific analysis populations and methods may differ, so findings across outcomes should not be treated as if they all came from one identical analysis.

Over-dispersion is a general issue when observed variation exceeds what a statistical model expects. It can make standard errors too small and intervals too narrow if ignored. The primary outcome is a participant-level binary endpoint, and the registry does not report an over-dispersion adjustment for it. No conclusion about whether such an adjustment was needed can be drawn from the available record.

Multiplicity arises when several outcomes or comparisons are assessed. In general, conducting many tests without adjustment increases the chance that at least one result will appear statistically notable by chance. The registry lists many secondary outcomes, but a multiplicity procedure is not reported in the registry record. Thus secondary p-values should be interpreted as unadjusted unless the record specifies otherwise; they should not be treated as definitive confirmatory tests.

The trial’s original statistical analysis plan, including any prespecified covariates, missing-data procedures, interim analyses, and sample-size justification, is not reported in the registry record. Those omissions limit independent assessment of how fully the posted analyses reflect the original plan.

11. Confidence Intervals and Precision

The primary risk-difference estimate is -21.8 percentage points in the registry’s reported analysis, with a 95% confidence interval from -34.45 to -7.94. The interval excludes zero and spans effects of different magnitudes. It indicates that the estimated difference is not exact: the data remain compatible with a range of lower event percentages for HyQvia relative to placebo under the stated analysis.

The unadjusted recalculation gives -0.217, with a 95% confidence interval from -0.349 to -0.086. Its interval also excludes zero and is close in direction and magnitude to the reported result. The slight differences between the registry analysis and the recalculation reflect that they are not identical analyses. The registry used a Chi-squared method with a Newcombe confidence interval; the recalculation uses the posted summary counts without adjustment.

In general, a confidence interval reflects sampling uncertainty under the statistical method and assumptions used. It does not capture all possible uncertainty, such as bias from missing data, limitations in endpoint measurement, or departures from the analysis plan. Nor does it show the range of individual participants’ outcomes. It concerns uncertainty about the group-level estimate.

The reported interval is compatible with a range of effect sizes, so the point estimate alone should not be read as the only plausible magnitude. The width of the interval also matters: it communicates that precision is limited even when the interval does not cross zero. Clinical importance cannot be determined from statistical precision alone, and the record does not supply a threshold for judging the smallest clinically important difference on this risk-difference scale.

Confidence intervals for the secondary outcomes differ in their precision and, in some cases, include values compatible with no group difference. Those outcomes should be considered in light of their separate populations, methods, and multiplicity context rather than treated as interchangeable evidence.

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 illustrations show the number of participants per arm for 80% power and for 90% power. These are planning calculations based on the observed effect and are not the trial’s original design assumptions. The original sample-size justification is not reported in the registry record.

The listed 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 set to a stated fraction of the observed effect: 100%, 75%, or 50%. For time-to-event outcomes, the planning figures represent the total number of events; for all other outcomes, they represent participants per arm. The primary outcome is a binary percentage outcome, so its planning figures are participants per arm.

The 80% power column describes the illustrative number of participants per arm needed for a design to have an 80% chance of detecting the assumed effect at the stated significance level, if the planning assumptions hold. The 90% power column describes the corresponding illustration for a 90% chance. These are design-planning concepts, not probabilities that the observed result is correct.

The observed effect is used as the starting point for these illustrations. Planning for 75% or 50% of the observed effect assumes a smaller effect to detect and requires more participants per arm in the listed calculations. This reflects a general statistical principle: smaller group differences are harder to distinguish from random variation, so they generally require more information. The figures do not establish what sample size would be appropriate under different event rates, analysis methods, or design assumptions.

These calculations are planning illustrations, not observed power. They do not describe the probability that the completed trial’s result is true, and they do not replace the trial’s own design rationale, which is not reported in the registry record.

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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.314; treatment proportion p₁ = 0.097; average p̄ = 0.206.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5715 = 1.1201.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5504 = 0.4632.
4. n = (1.1201 + 0.4632)² / (-0.2175)² = 53.0, rounded up to 53 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
p0 <- 0.314285714285714                          # control proportion
p1 <- 0.0967741935483871                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(2549170)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 53 (80% power), 71 (90% power)
 75% of observed effect: n per arm = 105 (80% power), 139 (90% power)
 50% of observed effect: n per arm = 255 (80% power), 340 (90% power)
power.prop.test: 53 
Simulated power at n = 53 per arm: 0.824 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-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. Analyses Reported by the Sponsor

The registry’s own primary analysis reports a risk difference of -21.8, a 95% confidence interval from -34.45 to -7.94, and p = 0.004. It identifies a Chi-squared method and a Newcombe confidence interval. The direction indicates a lower observed relapse percentage in the HyQvia group than in the placebo group under the registered endpoint definition.

The simple recalculation from the posted group counts gives a risk difference of -0.217, a 95% confidence interval from -0.349 to -0.086, and p = 0.002. That calculation is unadjusted and is not the same statistical procedure as the reported analysis. Its direction and broad magnitude align with the reported comparison, while the exact interval limits and p-value differ.

The registry record does not flag a discrepancy between the posted results and the recalculation. The trial’s reported analysis should be distinguished from the recalculation because the latter is a straightforward check based on summary counts, not a substitute for the trial’s own method. The record does not provide enough detail to explain every source of numerical difference beyond the distinction in methods and the displayed rounding.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists 45 outcome measures and 4 analyses, including the primary relapse endpoint and a broad set of secondary outcomes. Assessing several outcomes creates a multiplicity issue: in general, the more statistical comparisons made, the greater the opportunity for at least one apparently notable result to occur by chance. A prespecified testing hierarchy or adjustment can address this concern, but no such procedure is reported in the registry record.

Accordingly, secondary p-values should be treated as unadjusted unless the record states otherwise. They offer evidence about their individual comparisons but should not be interpreted as if each were the sole confirmatory test. The registry identifies the primary endpoint and labels its comparison as a superiority analysis, but the full statistical analysis plan and any rules for controlling multiplicity are not reported.

The primary analysis population is the MITT set, defined as randomized participants who received any double-blind study medication. This definition is reported, but the registry does not provide a full account of how participants with unavailable endpoint assessments were handled. Missing-data methods, imputation choices, sensitivity analyses, and reasons for missing outcomes are not reported in the registry record.

Outcome-specific denominators differ across some results. The primary outcome uses 70 participants in the placebo group and 62 in the HyQvia group, while other outcomes list different denominators. Those differences should be kept in mind when comparing estimates across endpoints. The record does not give enough information to determine all reasons for changes in denominators or whether missingness differed by treatment group.

The registry also does not report interim analyses, stopping rules, the original sample-size justification, or the complete prespecified analysis plan. These omissions do not change the values posted for the primary result, but they limit independent evaluation of the full analysis strategy and the degree to which the displayed results were selected or adjusted according to prespecified procedures.

16. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: chronic inflammatory demyelinating polyradiculoneuropathy (5.7%), cerebrovascular accident (1.6%), otitis media chronic (1.6%), arrhythmia (1.4%).

For Epoch 1, the registry records serious adverse events in 5 participants in the placebo-with-rHuPH20 group and 2 participants in the HyQvia group. It records 19 participants with other, non-serious adverse events in the placebo group and 42 in the HyQvia group. No deaths are recorded for either Epoch 1 group. These are participant counts, not event rates calculated.

The serious-event figures describe what was recorded during the study; they do not by themselves establish that an event was caused by treatment. The registry also lists serious-event terms, including chronic inflammatory demyelinating polyradiculoneuropathy, cerebrovascular accident, chronic otitis media, and arrhythmia. The record’s listed percentages for those terms do not provide a complete account of event severity, timing, clinical course, or attribution.

Safety comparisons need to be interpreted with care. The groups differ in the number of participants at risk, and the posted counts do not convey the full context of exposure duration or event recurrence. The registry lists additional Epoch 2 groups, but those groups consist of participants who relapsed during Epoch 1 and then received intravenous treatment, so they are not equivalent to the randomized Epoch 1 comparison. The available record does not establish causal explanations for individual events.

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

The posted primary result shows that the observed percentage meeting the registry’s relapse definition was lower in the HyQvia group than in the placebo group during Epoch 1. The registry’s reported risk difference and its 95% confidence interval are consistent with a group difference in that direction under the stated analysis. This describes the trial outcome for the analyzed participants and the registered assessment period.

The result does not establish that every participant will have the same experience, or that the observed difference applies unchanged to people outside the trial population. It does not answer every question about CIDP, treatment choice, long-term outcomes, or other measures of health. The primary endpoint captures a particular definition of worsening functional disability; it is not a complete measure of all possible benefits and harms.

Statistical evidence and clinical importance are related but distinct. A confidence interval communicates uncertainty in the group-level estimate, while clinical interpretation also depends on how meaningful the measured difference is. The registry does not report a threshold for the smallest clinically important difference in relapse percentage, so the clinical importance of a particular magnitude cannot be established from the statistical result alone.

The primary comparison should also be separated from Epoch 2, which involved participants who relapsed and received intravenous immunoglobulin. That conditional second part does not form another randomized comparison of the same kind as the Epoch 1 HyQvia-versus-placebo analysis. Nor do the secondary outcomes replace the primary endpoint; they measure related but distinct outcomes and include unadjusted analyses.

Finally, the registry record does not report important details such as full missing-data methods, multiplicity procedures, or the complete analysis plan. Those gaps do not erase the posted findings, but they limit how completely the statistical process can be assessed from the registry record alone.

18. Why This Trial Matters Statistically

This trial illustrates how a clinical question can be translated into a prespecified, measurable endpoint. Relapse was defined using a change from baseline on a functional-disability scale and a requirement for consecutive assessments. That operational definition makes the outcome more reproducible than a vague judgment of worsening, while also making clear that the result applies to that particular definition.

The randomized, triple-masked, parallel-group design supports a structured comparison of the Epoch 1 treatment groups. Reporting group percentages alongside a risk difference and confidence interval helps distinguish the observed event frequency from the uncertainty in the contrast. The sponsor-reported result and the unadjusted recalculation have the same overall direction, while their small numerical differences demonstrate why the method used for an estimate matters.

The study also shows why interpretation should not rest on a p-value alone. The estimated absolute difference, confidence interval, endpoint definition, and analysis population all contribute to understanding the evidence. The secondary outcomes add useful context, but multiplicity and differences in endpoint populations mean they should not be treated as interchangeable confirmations.

Finally, registry records can provide substantial outcome information while leaving parts of the analysis strategy unavailable. Here, details of missing-data handling, multiplicity control, and the original sample-size rationale are not reported. Recognizing both the posted findings and those gaps is an important part of statistical reading: it preserves the information in the trial without claiming more certainty than the record supports.

19. 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.
• Participant counts were reconstructed from posted percentages and arm sizes, so small rounding differences are possible.

The primary endpoint is based on a specific operational definition of relapse: a worsening of at least 1 point on the adjusted INCAT disability score relative to the pre-subcutaneous-treatment baseline in 2 consecutive assessments. Different definitions or assessment approaches could identify a different set of events. The registry does not report details that would allow independent evaluation of assessment reliability or adjudication.

The primary analysis population is the MITT set of randomized participants who received any double-blind study medication. It is not defined as every randomized participant regardless of treatment receipt. The record does not report how missing outcome measurements were handled, why analysis denominators vary across endpoints, or whether sensitivity analyses assessed the effect of missing data.

The full statistical analysis plan is not reported. In particular, the registry does not report multiplicity control for the many outcomes, the original sample-size justification, interim analyses, or all model specifications. These gaps constrain assessment of whether every analysis followed prespecified procedures.

The study has a two-part structure: Epoch 2 treatment was given to participants who relapsed during Epoch 1. Because entry to that part depended on relapse, Epoch 2 groups do not represent a direct randomized comparison of the same population as the primary Epoch 1 groups. The available Epoch 2 descriptions are also truncated.

Finally, the primary outcome focuses on relapse during the specified Epoch 1 timeframe. The posted result does not by itself address outcomes beyond that period or provide a complete account of safety, durability, or every clinically relevant aspect of CIDP.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: A Study of HyQvia and Gammagard Liquid (Kiovig) in Adults With Chronic Inflammatory Demyelinating Polyradiculoneuropathy (CIDP) — NCT02549170.
• Registry record last updated 2023-05-24; status last verified 2023-05.
• Results first posted 2023-05-24.
• 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.

23. Record Summary

NCT02549170 is a completed, randomized, triple-masked, parallel-group Phase III study in adults with CIDP. Its primary Epoch 1 comparison is subcutaneous HyQvia versus placebo with recombinant human hyaluronidase, with relapse defined as worsening functional disability on the adjusted INCAT disability score.

The registry reports relapse percentages of 31.4% for placebo and 9.7% for HyQvia. Its reported risk difference is -21.8, with a 95% confidence interval from -34.45 to -7.94 and p = 0.004. The unadjusted recalculation from posted counts is similar in direction, with differences in the exact interval and p-value.

Secondary outcomes cover disability, R-ODS, safety, and antibody development. Their interpretation is limited by unreported multiplicity and missing-data procedures. The study’s full original analysis plan and sample-size justification are not reported in the registry record.