Immune Globulin Intravenous (IGIV) For Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Immune Globulin Intravenous (IGIV) For Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) (NCT00220740), a randomized phase 3 study. The primary outcome is Comparison of the Responder Rates Between Two Treatment Groups in the Efficacy Period.

2. Clinical Question

The clinical question is whether the proportion meeting that sustained improvement definition differed between the randomized treatment groups during the efficacy period. The endpoint combines the size of the required improvement with a requirement that it remain through the specified assessment time. It therefore does not count every temporary improvement as a response.

The registry description says that participants who deteriorated or showed no improvement between day 16 and month 6 would receive the alternate study drug for an additional 6 months. This treatment-switching description is part of the study plan, but the primary responder-rate comparison is explicitly tied to the efficacy period. The registry record does not explain in detail how switching affected endpoint handling or subsequent analyses.

3. Trial Design

This was a Phase 3, randomized, parallel-group study recorded as completed. It enrolled 117 participants and compared IGIV-C with placebo. The official title describes the study as multicenter, randomized, double-blind, and placebo-controlled. The registry masking field records quadruple masking. The record does not explain the precise roles covered by that masking designation.

The study description specifies eight courses of treatment every 3 weeks. Neurological function was measured using INCAT scores. Participants who deteriorated or showed no improvement between day 16 and month 6 were to receive the alternate study drug for an additional 6 months. The primary endpoint timeframe is six months, corresponding to the efficacy period ending at Week 24.

The primary efficacy population was the Intent-to-Treat Population, defined as all randomized subjects. The posted primary outcome counts were 59 in the IGIV-C group and 58 in the placebo group. These group sizes sum to the enrollment total, but the registry record does not provide further details about participant flow, withdrawals, adherence, or missing endpoint measurements.

The record lists three secondary outcomes: change in amplitude of the most severely affected motor nerve, change in grip strength, and time to relapse among specified IGIV-C responders or rescue successes during the randomized withdrawal period. Numerical summaries for all three secondary outcomes are not reported in the registry record. The available secondary result is for motor-nerve amplitude.

Detailed original design assumptions, including the sample-size justification, are not reported in the registry record. The record also does not report an interim-analysis plan, a complete statistical analysis plan, or the methods used to handle missing observations. Those absences limit the ability to reconstruct all design and analysis decisions from the registry entry alone.

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.

Efficacy Period

Reasons for not completing this period:

Rescue Treatment

Withdrawal Period

Analysis population for the primary outcome, as defined in the registry: The Intent-to-Treat Population was defined as all randomized subjects. This population was the primary efficacy population to be analyzed.

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 Comparison of the Responder Rates Between Two Treatment Groups in the Efficacy Period, measured over 6 months.

The primary endpoint is the percentage of participants classified as responders during the six-month efficacy period. A responder was defined as having at least 1 point improvement in the adjusted Inflammatory Neuropathy Cause and Treatment (INCAT) score, with the improvement maintained through the end of Week 24. The registry record identifies the Intent-to-Treat Population, consisting of all randomized subjects, as the primary efficacy population.

The INCAT scale measures disability in the arms and legs. The record describes separate arm and leg scores, each ranging from 0 to 5, for a total score from 0 to 10. For arm disability, the endpoints described range from no upper-limb problems to inability to use either arm for purposeful movement. For leg disability, the described range extends from walking not affected to being restricted to a wheelchair and unable to stand and walk a few steps with help.

A responder-rate endpoint turns a change in a disability score into a proportion meeting a prespecified response definition. Requiring that improvement to persist through Week 24 distinguishes the endpoint from a response observed at only one assessment. As a general statistical point, dichotomizing a score makes the result easier to express as a proportion, but it does not describe the full range or magnitude of score changes among participants. The registry record does not report additional details about the adjustment used for the INCAT score.

7. Results Posted in the Registry

• IGIV-C: 54.2% (32/59) versus 20.7% (12/58) on control; risk difference 33.5 percentage points (95% CI 17.1 to 50.0), risk ratio 2.62 (1.50–4.57); unadjusted two-proportion z-test p = <0.001.

8. Secondary Efficacy Endpoints

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

Mean Change in the Amplitude (Millivolts) in the Most Severely Affected Motor Nerve During the Efficacy Period

• 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:
  • IGIV-C: mean 0.69 versus 0.47 on control; difference 0.22 (95% CI -0.54 to 0.98), standardized effect d = 0.11; z-test p = 0.569.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between IGIV-C and the control. The interval gives the range of effects that remain compatible with the data.

The registry lists three secondary outcomes: motor-nerve amplitude, grip strength, and time to relapse during the randomized withdrawal period among specified IGIV-C responders or rescue successes. Numerical group results are available for motor-nerve amplitude; the numerical results for grip strength and time to relapse are not reported in the registry record.

The available motor-nerve amplitude result is a mean change over the six-month efficacy period. The registry reports ANCOVA with p = 0.542. A summary-based unadjusted recalculation gives a mean difference of 0.22, with a confidence interval from -0.536 to 0.976 and p = 0.569. The interval includes zero, and the registry’s test does not indicate a clear between-group difference for that outcome. This result is on a different measurement scale from the primary responder rate and should be interpreted separately.

The secondary outcomes provide additional perspectives on neurological function and relapse, but the record does not provide complete numerical results across the listed outcomes. As a result, a coherent overall pattern across all secondary endpoints cannot be established from the registry record. The primary responder-rate result remains the only fully described comparison among the outcome results recorded in the available details.

As a general statistical concern, testing multiple outcomes increases the chance that some results may appear notable by chance if each is assessed separately. The registry record does not report whether multiplicity adjustments were planned or used. Unadjusted secondary results therefore carry less confirmatory weight than a prespecified primary analysis, particularly when complete results and adjustment details are unavailable. They can inform the broader outcome picture, but they should not be treated as independent confirmation of the primary finding.

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

• Mean Change in the Amplitude (Millivolts) in the Most Severely Affected Motor Nerve During the Efficacy Period
• Mean Change in Grip Strength During the Efficacy Period
• Time to Relapse for Subjects Who Were IGIV-C Responders or IGIV-C Rescue Successes, During the Randomized Withdrawal Period

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is binary at the participant level: each person either meets the responder definition or does not. The registry reports responder percentages and a chi-squared analysis for the comparison between randomized groups. The posted counts are 32 responders among 59 participants in the IGIV-C group and 12 among 58 in the placebo group. The percentage values in the record are 54.2% and 20.7%, respectively.

What does a risk difference describe?

The recalculated risk difference is 0.336, with a 95% confidence interval from 0.171 to 0.500. A risk difference compares the event proportions by subtraction and expresses the contrast on the absolute scale. Here, the event is meeting the sustained INCAT responder definition. The estimate is based on the posted group counts and is unadjusted; it is not the sponsor’s model-based or adjusted estimate. The registry record gives a chi-squared result rather than a reported risk-difference estimate.

As a general statistical explanation, an absolute contrast is often useful because it keeps the comparison tied to the outcome frequency in the study groups. It does not replace looking at each group’s rate, and it does not convey the distribution of score changes within responder and nonresponder groups.

What does the chi-squared test assess?

The registry reports a chi-squared analysis with p < 0.001. In general, a chi-squared test for two groups and a binary outcome assesses whether the observed distribution of responses is compatible with equal response proportions, under the test’s assumptions. The p-value measures compatibility with that null hypothesis; it is not the probability that the null hypothesis is true, nor is it the probability that the observed difference arose “by chance” in an unrestricted sense.

The registry record does not report further test details, including whether any continuity adjustment was used. It also does not provide an adjusted primary analysis estimate in the posted result. Consequently, the registry’s test and the simple unadjusted risk-difference calculation answer closely related but not identical reporting questions: one supplies the sponsor’s test result, and the other gives an absolute effect estimate and interval derived from the posted summary counts.

What does the confidence interval add?

As a general explanation, a confidence interval communicates uncertainty in an estimated contrast under a statistical procedure. The 95% interval for the recalculated primary risk difference is 0.171 to 0.500. Its endpoints express a range of effect values compatible with the data and calculation method at that confidence level. The interval does not mean that 95% of individual outcomes fall inside it, and it does not account for unreported design or analysis choices.

Intervals are useful because the same p-value can accompany different degrees of precision and different effect sizes. The risk-difference interval conveys both direction and uncertainty on the absolute scale. It is unadjusted and should be interpreted alongside the sponsor’s own chi-squared analysis, the endpoint definition, and the limitations of the registry entries.

Why can response rates lose information?

As a general statistical point, converting a numerical score change into responder versus nonresponder categories can make a result easier to communicate, but it discards information about the size of changes within each category. Participants just meeting the threshold and those with larger improvements are both counted as responders. The registry’s response definition adds a maintenance requirement through Week 24, but the binary classification still does not show the full distribution of INCAT score changes.

The threshold is at least 1 point improvement in the adjusted score, and the improvement must be maintained through the end of Week 24. The registry record does not report the detailed adjustment procedure or additional sensitivity analyses for alternative response definitions. Results based on the recorded definition should therefore be understood as specific to that threshold and timing.

Why does over-dispersion matter in some outcome models?

As a general explanation, over-dispersion occurs when the variation in count data exceeds what a simple count model expects. It can make standard errors too small if the extra variability is ignored. The primary endpoint in this trial is a binary responder outcome, not a count outcome, so over-dispersion is not the central issue for the reported primary comparison. The registry record does not identify an over-dispersion model for this endpoint.

The secondary motor-nerve amplitude outcome is continuous and is reported as a mean with standard deviation. Its registry analysis is ANCOVA, with p = 0.542. The posted summary-based recalculation gives a mean difference of 0.22 and a confidence interval from -0.536 to 0.976, with an unadjusted p-value of 0.569. These values illustrate that a secondary analysis may use a different model and scale from the primary binary endpoint. The record does not provide enough detail to reconstruct the ANCOVA model or its adjustment variables.

Across the analyses, distinguish the registry’s reported tests from simple unadjusted recalculations based on posted summary statistics. The latter can help describe an effect and its uncertainty, but they do not replace the sponsor’s analysis or recover information absent from the registry record.

11. Confidence Intervals and Precision

The primary recalculated risk difference is 0.336, with a 95% confidence interval from 0.171 to 0.500. The interval lies above zero, indicating that the posted rates are compatible with a positive difference under this calculation. Its width also matters: the estimate is not precise enough to identify one exact risk difference. The endpoints express statistical uncertainty around the group contrast, rather than uncertainty about whether any particular participant responded.

As a general explanation, a confidence interval gives a range of values that are compatible with the data and method at a stated confidence level. Its interpretation depends on the calculation assumptions. This interval is an unadjusted recalculation from posted summary counts; it does not incorporate adjustments that are not reported in the registry record. It should be read with the sponsor’s chi-squared result, p < 0.001, rather than treated as a substitute for that analysis.

The group percentages are 54.2% for IGIV-C and 20.7% for placebo, based on 59 and 58 participants, respectively. Sample size, the number of observed responses, and the chosen method all contribute to precision. The record does not provide a detailed account of missing primary outcome data, so the interval does not resolve uncertainty about unreported missing-data handling.

For the secondary motor-nerve amplitude comparison, the recalculated mean difference is 0.22, with a confidence interval from -0.536 to 0.976. This interval includes zero. The registry’s ANCOVA p-value is 0.542, while the unadjusted recalculated p-value is 0.569. These secondary statistics have a different outcome scale and analysis method from the primary comparison, and should not be conflated with the primary responder-rate precision.

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 figures are planning illustrations based on the observed effect, not the trial’s original design calculation. For these comparisons, the figures are participants per arm, not total event counts. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect used for each illustration is the stated fraction of the observed effect.

The 80% power column gives the number of participants per arm that the planning calculation estimates would be needed to have an 80% chance of detecting the selected effect under those assumptions, if the effect and assumptions were correct. The 90% power column expresses the corresponding planning target for a 90% chance. These are design calculations, not descriptions of the probability that the completed trial produced a positive result. They are not observed power.

Rows using 100% of the observed effect use the full estimated effect as the target. Rows using 75% or 50% of that effect examine planning for smaller target effects. Smaller effects require more participants to distinguish them from random variation under the same assumptions, so the required per-arm figures increase as the target effect becomes smaller.

The original trial’s own sample-size justification and design assumptions are not reported in the registry record. These illustrations therefore should not be taken as evidence about how the trial’s actual enrollment target was chosen, nor as a retrospective judgment about whether the completed enrollment was adequate. They show how hypothetical future planning requirements change with the chosen effect size and power target, while holding the stated calculation assumptions fixed.

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 = 0.207; treatment proportion p₁ = 0.542; average p̄ = 0.375.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6845 = 1.3416.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6421 = 0.5404.
4. n = (1.3416 + 0.5404)² / (0.3355)² = 31.5, rounded up to 32 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 <- 0.206896551724138                          # control proportion
p1 <- 0.542372881355932                          # 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(220740)
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 = 32 (80% power), 42 (90% power)
 75% of observed effect: n per arm = 54 (80% power), 72 (90% power)
 50% of observed effect: n per arm = 114 (80% power), 152 (90% power)
power.prop.test: 31.5 
Simulated power at n = 32 per arm: 0.816 (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 is a chi-squared comparison of the two treatment groups and reports p < 0.001. The simple recalculation from the posted responder counts gives a risk difference of 0.336, a 95% confidence interval from 0.171 to 0.500, and an unadjusted p-value of <0.001. The sponsor’s result and the unadjusted recalculation therefore point in the same inferential direction in the posted record.

The calculations answer related questions but are not interchangeable. The registry’s chi-squared test reports a significance test; the recalculation adds an absolute risk-difference estimate and interval derived from the summary counts. The recalculation does not reproduce an analysis with covariate adjustment or any other details not encoded in those counts.

For the secondary motor-nerve amplitude outcome, the registry reports ANCOVA with p = 0.542. The unadjusted recalculation from group means and standard deviations gives a mean difference of 0.22, an interval from -0.536 to 0.976, and p = 0.569. Differences between these p-values can arise because the analyses use different information or assumptions; the registry record does not provide enough model detail to identify the precise reason. The sponsor’s reported analysis remains the registry’s own analysis, while the recalculation is a transparent, unadjusted summary-based comparison.

15. Multiplicity, Missing Data and Analysis Populations

The primary efficacy population is defined as all randomized subjects, and the primary endpoint is described as the comparison of responder rates during the efficacy period. The registry record does not report a detailed missing-data method for participants without an evaluable Week 24 response. It also does not report whether missing values were imputed, counted as nonresponse, or handled by another procedure. Without those details, the effect of missing outcome data on the responder percentages cannot be assessed from the record.

The study description says that participants who deteriorated or showed no improvement between day 16 and month 6 would receive the alternate study drug for an additional 6 months. The registry record does not explain how such switching was incorporated into the primary analysis, whether the switch affected response classification, or how outcomes after switching were analyzed. This leaves some uncertainty about the relationship between the treatment pathway and the endpoint estimand.

Three secondary outcomes are listed in addition to the primary endpoint. Multiplicity adjustment, a hierarchy for testing, or another strategy for controlling the overall false-positive risk is not reported in the registry record. The posted secondary analyses should therefore be read as exploratory or supportive unless additional analysis details establish otherwise. The record does not report a full statistical analysis plan that would clarify which secondary tests were confirmatory.

The registry record does not report interim analyses or stopping rules. It also does not report detailed subgroup analyses or sensitivity analyses for the primary endpoint. These omissions do not establish that such procedures were absent; they mean that their use is not documented in the registry record. A complete evaluation of the analysis strategy would require those details, including the planned handling of missing data, switching, multiplicity, and any interim monitoring.

16. 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: headache (1.8%), myalgia (1.1%), demyelinating polyneuropathy (1.1%), back pain (1.1%), asthma (1.1%).

For serious adverse events, the record lists 6 affected participants among 113 at risk in the IGIV-C safety group and 8 among 95 at risk in the placebo safety group. These denominators differ from the primary efficacy group sizes of 59 and 58. The registry record does not explain the reason for the safety denominators or provide a participant-flow account linking them to the randomized population.

The record also lists other adverse events affecting 81 of 113 participants in the IGIV-C group and 25 of 95 in the placebo group. These are distinct figures from the serious adverse event counts and should not be combined with them. The registry identifies headache at 1.8%, and myalgia, demyelinating polyneuropathy, back pain, asthma, and medical observation for asthma at 1.1% each among the top serious adverse event terms. The record does not assign these listed terms to a specific treatment group in the available details.

Death counts are not reported in the registry record. These event counts alone do not establish comparative safety, explain severity or duration, or show how events were judged related to treatment. They should be read as descriptive registry figures, with attention to the different safety denominators and the limits of the available event detail.

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

The posted primary results show a higher percentage of participants meeting the sustained INCAT responder definition in the IGIV-C group than in the placebo group during the six-month efficacy period. The recalculated risk difference and its confidence interval describe the size and precision of that contrast, while the registry’s chi-squared test reports p < 0.001. Together, these statistics indicate a clear difference in the recorded responder rates under the analyses described.

The result is specific to a particular definition: at least 1 point improvement in the adjusted INCAT score, maintained through the end of Week 24. It does not describe all score changes, every aspect of neurological function, or outcomes beyond the recorded period. A binary response classification also does not show how much participants improved once they crossed the response threshold.

The result does not establish the effect of treatment for every person with CIDP, or in populations and settings not represented by the trial. The registry record does not provide subgroup results to support claims about particular participant characteristics. Nor does the primary endpoint answer questions about the listed secondary outcomes that lack numerical results in the record.

Statistical evidence of a difference is not the same as proof of a particular mechanism, a complete account of benefit and harm, or a judgment about treatment choice. The safety figures are descriptive and have limitations, including different denominators and limited detail about event attribution. The registry record also does not document the complete missing-data, multiplicity, or treatment-switching analysis methods.

Accordingly, the defensible statistical reading is bounded: the recorded primary endpoint favored a higher response percentage in the IGIV-C group in this randomized comparison, with uncertainty quantified by the reported recalculated interval. The record does not, by itself, settle questions beyond that endpoint, population, timeframe, and analysis.

18. Why This Trial Matters Statistically

This trial illustrates why a registry result is more informative when the outcome definition, group rates, effect estimate, and uncertainty are read together. A responder percentage is easy to understand at a glance, but its meaning depends on the threshold and timing used to define response. Here, response required at least 1 point improvement in adjusted INCAT score that persisted through Week 24.

The primary comparison also illustrates the difference between a test result and an effect estimate. The chi-squared p-value addresses compatibility with a null comparison, while the recalculated risk difference expresses the absolute contrast and the confidence interval communicates uncertainty in that estimate. Neither statistic alone captures all aspects of the outcome or trial conduct.

The registry includes multiple secondary outcomes, but detailed numerical results are not reported for all of them. This makes completeness and multiplicity important statistical considerations: isolated secondary findings should not automatically be treated as confirmation, especially when the planned testing strategy is not documented.

Finally, the record demonstrates why population and analysis details matter. The primary analysis population is defined, but missing-data handling, switching, and the original sample-size justification are not reported. Safety denominators also differ from primary efficacy denominators. These details shape what can be inferred from a trial record and distinguish a narrowly supported comparison from broader conclusions not established by the posted results.

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 registry record does not report the original sample-size justification or the assumptions used to set enrollment. The sample-size illustrations based on the observed effect are not a substitute for that design information. The record also does not provide an interim-analysis plan or a full statistical analysis plan.

Missing-data handling for the primary endpoint is not reported. This is relevant because the response classification requires a maintained improvement through Week 24, and the record does not describe how unavailable or incomplete assessments were treated. The treatment-switching plan for participants who deteriorated or showed no improvement is described, but its relation to the primary analysis is not explained.

The primary result is based on a binary responder definition and does not show the full distribution of INCAT changes. The adjustment procedure for the INCAT score is not described in sufficient detail to reconstruct it. The registry record also does not report subgroup or sensitivity analyses that could show how robust the primary finding is to alternative assumptions or participant categories.

Although three secondary outcomes are listed, numerical results are not reported for grip strength or time to relapse in the registry record. Multiplicity handling for the secondary analyses is also not reported. This limits the ability to assess the consistency of results across outcomes or the confirmatory status of any secondary finding.

Safety counts use denominators different from those for the primary efficacy comparison, and the registry record does not explain that difference. Death counts are not reported. The record’s serious adverse event terms are not attributed to a treatment group in the available details. These limitations mean that the safety summary is descriptive and incomplete for comparative interpretation.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Immune Globulin Intravenous (IGIV) For Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) — NCT00220740.
• Registry record last updated 2016-03-23; status last verified 2016-02.
• Results first posted 2015-09-10.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

23. Record Summary

The registry record describes a completed Phase 3 randomized parallel-group study of IGIV-C versus placebo in participants with CIDP. Enrollment was 117. The primary efficacy endpoint compared the percentage of responders during a six-month efficacy period, with response defined as at least 1 point improvement in adjusted INCAT score maintained through Week 24.

The posted responder rates were 54.2% for IGIV-C and 20.7% for placebo. The registry’s chi-squared analysis reports p < 0.001. The unadjusted recalculated risk difference is 0.336, with a 95% confidence interval from 0.171 to 0.500.

The record lists three secondary outcomes, but numerical results are not reported for all of them. Safety counts are available, though their denominators differ from the primary efficacy group sizes and the record does not provide all details needed for comparative interpretation. Missing-data handling, multiplicity methods, interim analyses, and the original sample-size justification are not reported in the registry record.