Study of Subcutaneous Immune Globulin in Patients Requiring IgG Replacement Therapy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Study of Subcutaneous Immune Globulin in Patients Requiring IgG Replacement Therapy (NCT00542997), a non-randomized phase 3 study. The primary outcome is Total Serum IgG Trough Levels.

2. Clinical Question

The study asked whether serum IgG trough levels during treatment with subcutaneous IgPro20 could be described alongside the levels documented during each participant’s pre-study IgG treatment. It also assessed efficacy, tolerability, safety, and pharmacokinetics in people with primary humoral immunodeficiency who required IgG replacement therapy.

The question is descriptive: the record specifies how levels were assembled and compared, but does not report a numerical treatment contrast, uncertainty interval, or test result. The pre-study observations came from each person’s prior treatment rather than from a group allocated to a control intervention. Consequently, the comparison can describe levels across the two periods, but it does not by itself separate treatment-period differences from other changes over time.

3. Trial Design

This was a Phase 3, multicentre study with non-randomized allocation, no masking, and a single-group model. The registry records enrollment of 51 and lists the study status as completed. The recorded start was 2007-09 and primary completion was 2009-08. The sponsor was CSL Behring.

The intervention was human normal immunoglobulin for subcutaneous administration, identified as IgPro20. The population was people with primary immunodeficiency requiring IgG replacement therapy. Conditions listed in the registry were common variable immunodeficiency, X-linked agammaglobulinemia, and autosomal recessive agammaglobulinemia.

The primary outcome compared levels measured during IgPro20 treatment with documented pre-study trough levels from IgG treatment received before enrollment. Pre-study treatment could be subcutaneous or intravenous. This is not a randomized, concurrent comparison: participants were not allocated between IgPro20 and a separate control intervention. The registry does not report a masking procedure or a randomized allocation method; it identifies the study as unmasked and non-randomized.

The registry defines the primary analysis population as the intention-to-treat population, including subjects treated with IgPro20 during the efficacy period, which started with Week 12. It does not report the number in that population. It also notes that pre-study trough levels were unavailable for 2 subjects in the ITT population.

The study’s listed secondary outcomes concern serious bacterial infections, infection episodes, time away from work, school, or normal activities due to infection, hospitalization days due to infection, and antibiotic use for infection prophylaxis and treatment. The detailed protocol, the rationale for the design, and a statistical analysis plan are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: Screening took place 1 to 4 weeks prior to the first IgPro20 infusion.

Wash in / Wash Out Period

Reasons for not completing this period:

Efficacy Period

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Intention-to-treat (ITT) population analysis. The ITT population included all subjects who were treated with IgPro20 during the efficacy period (starting with Week 12). For 2 subjects in the ITT population, the pre-study treatment IgG trough levels were not available.

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 Total Serum IgG Trough Levels, measured over Up to 6 months prior to first IgPro20 treatment (Pre-study treatment) and Week 12 to 17 (IgPro20 treatment).

The primary endpoint is total serum IgG trough level, measured in g/L. A trough level is a measurement taken at the low point of a dosing interval; in general, it is used to describe the amount of a circulating substance remaining before a subsequent dose. The registry uses trough levels to compare IgG exposure during steady-state IgPro20 treatment with levels documented during pre-study replacement therapy.

For IgPro20, the registry description says that 6 consecutive trough values, obtained before infusions 12 to 17, were combined into a median for each subject. Those subject-level medians were then summarized across subjects using descriptive statistics. For pre-study treatment, the same procedure was applied using the 3 most recent IgG trough values at least 5 g/L, obtained before the first IgPro20 infusion and within the period up to 6 months before it. The registry labels the outcome as a mean with standard deviation, while its description specifies the use of subject-level medians as the values being summarized.

This endpoint is relevant to the study’s stated objective because it describes IgG levels during treatment and permits comparison with each person’s documented pre-study levels. It is a laboratory measure, not a direct measure of infections or day-to-day functioning. The registry record does not report the numerical trough-level estimates, their standard deviations, or a numerical comparison between periods.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The study is described as non-randomized and single-group. Its primary comparison uses IgG trough measurements during treatment and measurements documented before study treatment. This structure is different from a randomized comparison, in which allocation creates concurrent groups intended to be comparable on average. In general, a pre-study comparison can describe change across periods, but differences may also reflect factors that changed over time. The registry record does not report an analysis intended to isolate the effect of treatment from such factors.

What does the endpoint summary represent?

The registry’s primary outcome is a continuous laboratory measure: total serum IgG trough level in g/L. The description first combines repeated measurements within each subject. During IgPro20 treatment, 6 consecutive trough values obtained before infusions 12 to 17 were reduced to a subject-level median. Pre-study levels were handled using the 3 most recent values at least 5 g/L, collected before the first IgPro20 infusion and up to 6 months before it. The resulting subject-level summaries were then described across subjects.

In general, this kind of aggregation prevents a subject with more recorded measurements from automatically contributing more independent observations to the group summary. It also compresses information: variation from one measurement to another within a person is not represented in the same way as it would be in a model using all measurements. The registry describes the aggregation and says the summaries were descriptive. It does not report a repeated-measures model, an adjustment model, or a detailed inferential procedure.

The outcome is labeled as a mean with standard deviation. In general, the mean is the arithmetic average, while the standard deviation describes how dispersed values are around that average. The description’s reference to subject-level medians means those medians are the observations being summarized across subjects. The registry does not report the numerical mean or standard deviation, so readers cannot assess the distribution or the amount of between-subject variability from the record.

What would uncertainty estimates add?

In general, a confidence interval communicates the range of values reasonably compatible with an estimate under the assumptions of the analysis. A narrow interval indicates greater precision than a wide interval, although precision alone does not establish clinical importance or freedom from bias. The registry record does not report a confidence interval for the primary outcome or a numerical estimate from which its precision can be assessed. It also does not report a p-value or a hypothesis test for this outcome. The endpoint’s measurement definition should therefore not be mistaken for an inferential result.

Standard deviation and standard error have different roles. In general, standard deviation describes variability among observations, while standard error describes uncertainty in an estimated summary under a statistical model. The primary outcome is labeled with standard deviation; a standard error is not reported in the registry record. No additional uncertainty measure for the primary comparison is reported there.

Why does repeated measurement matter?

Measurements from the same person are usually related rather than independent. In general, ignoring that dependence can make uncertainty estimates misleading. The registry’s stated approach reduces repeated measurements to a subject-level median before descriptive summarization. It does not report whether analyses of other outcomes used a method accounting for repeated observations, or how those outcomes were modeled.

The method also distinguishes the steady-state treatment period from the pre-study period. The IgPro20 summary uses measurements before infusions 12 to 17, and the registry labels this treatment window as Week 12 to 17. For pre-study treatment, it uses recent trough values meeting the stated threshold, obtained before the first IgPro20 infusion. These are different observation windows and data sources. The record does not report further detail about measurement comparability, assay procedures, or how incomplete series were handled.

How should the planning calculations be understood?

The sample-size assumptions describe a planning illustration based on the observed effect, not the original trial design. The stated assumptions include a two-sided significance level of 0.05, equal allocation between two hypothetical arms, and a normal approximation; the effect to detect is defined as a stated fraction of the observed effect. Such calculations are prospective illustrations of the sample size that might be needed under assumed conditions. They are not observed power, and they do not establish that the study was designed or conducted using those assumptions.

That distinction matters for this study because its recorded design is a non-randomized, single-group study, while the planning assumptions describe equal allocation between two arms. A hypothetical two-arm calculation does not turn the actual design into a randomized two-arm comparison. The registry does not report the investigators’ sample-size justification, any protocol-based target, or a statistical plan explaining how the planning assumptions relate to the study.

In general, sample-size calculations depend on the outcome’s variability, the effect one aims to detect, the significance level, and the allocation and analysis assumptions. A planning illustration based on an observed effect is especially dependent on that effect estimate. The numerical primary result and the scenario-specific sample-size values are not reported in the registry record, so the planning calculations cannot be independently interpreted from the recorded information alone.

For time-to-event outcomes, the assumptions describe total events using a Schoenfeld method; for other outcomes, they describe participants per arm. This distinction concerns what a planning output counts, not what was observed in this study. The listed primary endpoint is continuous, and no time-to-event primary endpoint is identified in the record.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("IgPro20", "Pre-study IgG Treatment")
n   <- c(46, 44)
m   <- c(8.1, 7.49)
sp  <- c(1.44, 1.57)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  IgPro20  46  8.100  1.440  7.672  8.528
CARM  Pre-study IgG Treatment  44  7.490  1.570  7.013  7.967

11. Multiplicity, Missing Data and Analysis Populations

The registry identifies 11 outcome measures and lists secondary outcomes related to serious bacterial infections, infection episodes, time away from work, school, kindergarten, day care, or normal activities because of infection, hospitalization days due to infection, and antibiotic use for infection prophylaxis and treatment. It names a primary outcome and several secondary outcomes, but the statistical analysis plan is not reported in the registry record.

When a study evaluates multiple outcomes, the chance of finding at least one apparently unusual result can increase if many separate tests are conducted. In general, a multiplicity strategy can specify which outcomes are confirmatory, how tests are ordered, or how significance thresholds are adjusted. The registry does not report whether any such approach was planned or used. It reports 0 analyses in the record, so there are no recorded analysis results from which to assess how outcomes were tested or interpreted.

The primary analysis population is defined as the ITT population: subjects treated with IgPro20 during the efficacy period starting with Week 12. For 2 subjects in that population, pre-study treatment trough levels were unavailable. The registry does not report whether those observations were excluded from the primary comparison, imputed, or handled by another method. It also does not report other missing-data patterns, reasons for missingness, or sensitivity analyses.

A secondary outcome refers to serious bacterial infections in both ITT and PPE populations. The registry does not report the definition of the PPE population. The number analyzed for each outcome, the analysis populations for the other secondary outcomes, and any rules for handling incomplete follow-up are not reported in the registry record. These omissions limit assessment of which participants and observations contributed to each result.

12. 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: diarrhoea (2.0%), pneumonia (2.0%), pyrexia (2.0%), bronchiolitis (2.0%), appendicitis (2.0%).

The registry reports an all-treated group of 51 at risk for serious adverse events, with 5 affected. For other adverse events, it reports 51 at risk and 50 affected. These are separate registry counts for the categories described; they should not be combined into a new total or interpreted as a comparison between treatment groups.

The serious adverse event terms listed include diarrhoea, pneumonia, pyrexia, bronchiolitis, appendicitis, and sciatica, each reported as 2.0%. These percentages are the registry’s stated figures. The record does not provide further context in the posted safety summary about event timing, recurrence, severity grading, or causal attribution. A term appearing in a serious-event list does not, by itself, establish that treatment caused the event.

The study is single-group and non-randomized, so these safety figures do not provide a concurrent control rate. The death entry is not reported in the registry record. The counts describe what the registry records for the treated group; they do not establish how the figures would compare with another treatment or with no treatment.

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

The registry record establishes the study’s design, population, intervention, and intended primary measurement. It describes a comparison between IgG trough levels during steady-state IgPro20 treatment and trough levels from pre-study IgG replacement. The primary measurement is a laboratory marker, summarized using subject-level medians before descriptive statistics are applied.

However, the record does not report numerical results for the primary outcome. It therefore does not establish the average or spread of the levels, the direction or size of a difference between periods, or the precision of any estimate. A clinical or statistical conclusion about the primary outcome cannot be drawn from the outcome definition alone.

The design also shapes what a comparison can mean. Because the study is non-randomized and single-group, its pre-study measurements are not a concurrent randomized control. In general, an observed difference between periods could reflect treatment-period changes as well as other changes over time or differences in measurement circumstances. The registry does not report an analysis that would distinguish among these possibilities.

The adverse event counts and listed serious-event terms describe events recorded among treated subjects. They are not comparative estimates of risk, and the record does not establish whether a listed event was caused by treatment. Likewise, the presence of secondary outcome definitions does not supply results for infections, hospitalizations, activity limitations, or antibiotic use. Numerical results for those outcomes are not reported in the registry record.

The record can thus be read as an account of a study question and measurement strategy, with some safety counts, rather than as a complete quantitative report of the primary comparison. It does not support a claim about the magnitude, precision, or causal interpretation of the primary outcome. Those limits concern what is recorded, not a judgment about the underlying treatment.

14. Why This Trial Matters Statistically

This study is statistically notable for comparing repeated laboratory measurements during treatment with measurements collected before treatment in the same study population. The registry does not describe a randomized, concurrent control group. That distinction is central to interpretation: a within-person comparison can show how recorded values across periods relate, but it does not have the same protection against time-related differences as a randomized comparison.

The measurement strategy also raises an important design issue in longitudinal data. Several trough values were collected for each subject, then reduced to a subject-level median before descriptive summarization. In general, repeated observations within a person are correlated; a method that acknowledges this dependence is important when estimating uncertainty. Aggregating the measurements is one way to create subject-level summaries, but it also means that variation among a person’s repeated values is not directly represented in the final group summary in the same way as the spread between subjects.

Missing pre-study trough levels for 2 subjects in the ITT population make reporting of analysis populations and missing-data handling especially relevant. Those details, together with numerical results and uncertainty estimates, are not reported in the registry record. Their absence prevents assessment of how robust the primary comparison is to incomplete baseline information.

The record also makes clear why an endpoint description, a safety listing, and a statistical result are different kinds of evidence. The endpoint definition explains what was intended to be measured; the safety figures count reported events; neither supplies the missing numerical primary comparison. The planning assumptions likewise describe a hypothetical calculation rather than the study’s actual randomized design or observed power.

For biostatistical interpretation, the key lesson is to keep the design, measurement process, analysis population, missingness, and reported estimates distinct. The record provides useful detail on the first parts of that chain, but leaves the primary numerical result and several analysis details unreported.

15. 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 limitation for interpreting efficacy is that numerical results for the primary endpoint are not reported in the registry record. The record therefore does not allow readers to assess the observed trough levels, their between-subject variability, the comparison between treatment periods, or the precision of an estimate.

The study is identified as non-randomized, unmasked, and single-group. Pre-study measurements provide a historical, within-person reference rather than a concurrent randomized comparator. This design cannot by itself exclude time-related changes or differences between pre-study and treatment-period measurements as explanations for a period comparison. The registry does not report additional design or analysis information that would address these concerns.

For 2 subjects in the ITT population, pre-study trough levels were unavailable. The record does not report how this missing information was handled, whether other measurements were missing, or whether sensitivity analyses were conducted. The number contributing to each outcome analysis and the definition of the PPE population are also not reported in the registry record.

The registry describes aggregating repeated trough values to subject-level medians and then summarizing those values descriptively. It does not report numerical summaries, uncertainty estimates, a detailed inferential method, or an analysis plan. It also does not report measurement-assay details or enough information to assess the comparability of measurements across periods.

Safety reporting includes group counts and selected serious adverse event terms, but the record does not provide further context on timing, recurrence, or causal assessment in the safety summary. As a single-group study, it also lacks a concurrent control rate for interpreting those counts. These limitations restrict interpretation of both the primary outcome and the safety information recorded.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Study of Subcutaneous Immune Globulin in Patients Requiring IgG Replacement Therapy — NCT00542997.
• Registry record last updated 2011-09-01; status last verified 2011-08.
• Results first posted 2011-03-15.
• 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.

19. Record Summary

The registry identifies NCT00542997 as a completed Phase 3, multicentre, non-randomized, unmasked, single-group study of subcutaneous IgPro20 in people requiring IgG replacement therapy for primary immunodeficiency. Enrollment was 51. The recorded study start was 2007-09, and primary completion was 2009-08.

The primary outcome was total serum IgG trough level in g/L, comparing steady-state IgPro20 measurements with documented pre-study IgG trough levels. The registry describes subject-level aggregation of repeated values and identifies the ITT population as treated subjects during the efficacy period starting with Week 12. Pre-study levels were unavailable for 2 subjects in that population.

Safety counts and selected serious adverse event terms are recorded. Numerical primary outcome results, a statistical analysis plan, missing-data methods, and the definition of the PPE population are not reported in the registry record.