Reslizumab to Prevent Post-treatment Eosinophilia in Loiasis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Reslizumab to Prevent Post-treatment Eosinophilia in Loiasis (NCT01111305), a randomized phase 2 study. The primary outcome is Peak Eosinophil Count Post-treatment.

2. Clinical Question

3. Trial Design

This was a phase 2, randomized, parallel-group, placebo-controlled pilot study of reslizumab given before DEC treatment for Loa loa infection. The registry classifies masking as triple and describes the study as double-blind in its official title and summary. It lists enrollment of 31 and a completed status. The study dates recorded are 2010-04 for start and 2016-01 for primary completion.

The active regimen was a single intravenous dose of reslizumab at 1 mg/kg, followed by oral DEC at 9 mg/kg/day for 21 days. The placebo group received a single intravenous placebo dose, followed by the same DEC regimen. The summary says that reslizumab was administered 3 to 7 days before DEC. Both groups therefore received DEC; the randomized contrast is the addition of reslizumab rather than DEC versus no DEC.

The primary outcome population is defined as subjects who received DEC. The endpoint summaries list 4 participants for reslizumab plus DEC and 4 for placebo plus DEC. Enrollment and outcome-summary counts are different, but the reasons for that difference, including any exclusions or unavailable outcome data, are not reported in the registry record. The record does not report the randomization procedure, allocation concealment, or detailed participant flow.

Secondary outcomes named in the record include frequency of adverse events, markers of eosinophil activation, and the proportion of subjects who clear blood microfilariae. The registry lists 4 outcome measures and 1 analysis. Detailed results for the named secondary outcomes are not included in the registry entries used for this interpretation.

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: 31 subjects were enrolled on the screening phase of this protocol, of which 13 had Loa loa infection. Of these 13, 3 were excluded for Loa loa microfilarial loads that were too high, 1 could not comply with the trial time points, and one was lost to followup. This left 8 subjects who were enrolled on the treatment portion of the study.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Subjects who received diethylcarbamazine treatment

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 Peak Eosinophil Count Post-treatment, measured over during the first 7 days of DEC treatment.

The primary endpoint is peak eosinophil count during the first 7 days of DEC treatment, expressed as a percent of the baseline eosinophil count. A value of 100% on this scale would represent a peak equal to baseline; values above or below that reference indicate a peak higher or lower than baseline. This is a general explanation of the scale, not an additional result from the trial.

The endpoint focuses on the early post-treatment period because the study summary describes an IL-5-dependent increase in eosinophilia accompanying reactions to DEC. The stated purpose was to assess whether reslizumab before DEC prevented or reduced that post-treatment eosinophilia. The endpoint is a laboratory measure rather than a direct measure of symptom severity or an adverse clinical event.

The outcome is reported as a geometric mean with a full range for each group. A geometric mean is a summary suited to values that vary multiplicatively; it is not the same as an arithmetic average. The full range gives the lowest and highest observed values but does not show how observations are distributed between those extremes. The outcome summaries apply to participants who received DEC, as defined in the registry record. The record does not report individual values or an additional adjusted estimate for this endpoint.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is summarized with a geometric mean and full range in each arm. The geometric mean is calculated on a multiplicative scale and can be useful when measurements are skewed or when proportional changes are more meaningful than absolute changes. The registry record does not report individual measurements or a standard deviation for this endpoint. The full range is the observed minimum and maximum, so it describes the span of the reported data but not the concentration of observations within that span.

What does the Wilcoxon (Mann-Whitney) test assess?

In general, the Wilcoxon rank-sum test, also called the Mann-Whitney test, compares the ordering of observations between independent groups. It ranks the combined observations and evaluates whether values from one group tend to be higher or lower in rank than values from the other. It does not require the data to follow a normal distribution in the same way as a standard two-sample t-test. Its interpretation as a test of a difference in medians requires additional assumptions about the shapes of the group distributions. More generally, it detects a rank-distribution difference and does not directly test a difference between geometric means.

The record reports this method and p = 0.028. It does not report the test statistic, a confidence interval, or a numerical estimate of the between-group effect from this test. The p-value indicates how unusual a result at least as incompatible with the null hypothesis would be under that hypothesis and the test assumptions. It is not the probability that the null hypothesis is true, and it does not measure the probability that a result is due to chance.

How should the equivalence label be read?

In general, an equivalence analysis asks whether a treatment contrast lies within prespecified bounds considered small enough to count as practically equivalent. That interpretation requires an equivalence margin and an estimate with suitable confidence limits. The registry record labels the analysis as equivalence but does not report the margin, the corresponding contrast, or confidence limits. The reported Wilcoxon p-value alone cannot show that equivalence was established. The record does not explain how the equivalence label relates to the reported test.

Why does over-dispersion matter?

General statistical context: over-dispersion occurs when observed variability is greater than expected under a model's assumptions. If a model assumes less variability than the data contain, its standard errors may be too small and its confidence intervals too narrow, making evidence appear more precise than it is. This concern is most relevant to model-based analyses of counts or rates. The primary result is reported using a rank-based test and descriptive geometric means; the registry record does not report a fitted count model or an over-dispersion assessment. The range summaries nevertheless show why describing variability matters: a single central summary cannot capture the full spread of individual observations.

What does a confidence interval contribute?

In general, a confidence interval gives a range of effect estimates compatible with the data and a specified statistical procedure. It communicates precision as well as direction and can help readers assess which effect sizes remain plausible. A p-value does not provide that interval information. No confidence interval for the primary between-group contrast is reported in the registry record, so the precision of the treatment contrast cannot be judged from an interval estimate. The ranges reported for each group are not confidence intervals; they describe observed values, not uncertainty around a treatment effect.

What can a planning calculation say?

In general, sample-size planning calculations describe the number of participants per arm needed to detect an assumed effect under stated design and statistical assumptions. They are planning illustrations, not observed power and not evidence that a study was adequately powered. The record's stated planning assumptions use a two-sided significance level of 0.05, equal allocation, a normal approximation, and effects defined as fractions of the observed effect. The numerical planning results are not reported in the registry record. They should not be confused with the outcome group sizes or with a retrospective claim about the probability that this trial detected an effect.

10. Analyses Reported by the Sponsor

The registry reports the sponsor's comparison as a Wilcoxon (Mann-Whitney) test with p = 0.028. The primary outcome is also presented descriptively as group geometric means and full ranges. These summaries show the observed endpoint values, while the reported test evaluates the rank ordering of observations between groups. The test result does not supply a direct estimate of a geometric-mean contrast or a confidence interval for that contrast.

A separate recalculated comparison estimate and its uncertainty are not reported in the registry record. The registry entries therefore do not allow a numerical comparison between the sponsor's test and an independently recalculated inferential result. The registry does not flag a discrepancy between the sponsor analysis and a recalculation. The equivalence label remains difficult to interpret because the registry record does not report an equivalence margin or confidence limits. The sponsor analysis is the inferential result reported in the record, but its scope is limited to the stated test and endpoint.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 4 outcome measures and 1 analysis. It also names secondary outcomes concerning adverse-event frequency, eosinophil activation markers, and microfilarial clearance. The record does not report a multiplicity adjustment, a hierarchy among outcomes, or a prespecified strategy for interpreting multiple tests. When several outcomes are tested, the chance of at least one apparently unusual result can increase unless the analysis plan accounts for that multiplicity. This is general statistical context; the registry does not say whether any adjustment was planned or used.

The primary outcome population is described as subjects who received DEC. The arm summaries report 4 participants in each group. The record does not report whether participants were analyzed according to randomized assignment, whether any participants were excluded after randomization, or how missing primary outcome values were handled. It also does not report the reasons for the difference between enrollment of 31 and the outcome-summary counts. No missing-data method, imputation procedure, or sensitivity analysis is reported in the registry record.

These omissions matter because analysis populations and missing outcomes can affect interpretation of a randomized comparison. An analysis restricted to participants who received treatment may differ from an analysis that retains all randomized participants, particularly if treatment receipt or outcome availability is related to prognosis. The registry record does not provide enough information to determine whether that concern applies. It also does not report interim analyses or a detailed statistical analysis plan, so their use or absence cannot be inferred.

The record identifies a single reported analysis, but does not establish whether that was the only analysis conducted. The number of posted analyses should not be treated as proof that no other comparisons were considered. Readers should interpret the p-value alongside the limited outcome sample, the unreported missing-data details, and the absence of stated multiplicity procedures.

12. 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 0% reporting threshold.

Most frequent non-serious adverse event terms

For serious adverse events, the registry reports 0 affected participants in the reslizumab plus DEC group and 0 in the placebo plus DEC group. It reports 0 deaths in each group. The serious-event groups each list 4 participants at risk. No serious adverse-event terms are listed.

For other adverse events, the registry reports 4 affected participants in each group, with 4 at risk in each group. These counts describe participants recorded as affected; the record does not provide event-level descriptions, severity details, timing, or the number of events per participant. The figures therefore do not permit a detailed comparison of the types or burden of non-serious events.

Zero reported serious events in these outcome groups means none were recorded among the participants listed at risk; it does not establish that serious events cannot occur or that the regimens have equivalent safety. With a small number of participants in the posted safety summaries, the absence of an observed serious event gives limited information about uncommon harms. The registry record does not report a formal safety comparison or confidence intervals.

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

The posted result describes lower peak eosinophil summaries relative to baseline in the reslizumab plus DEC group than in the placebo plus DEC group. The reported group geometric means are 61.0% and 245.6% of baseline, respectively, and the registry reports p = 0.028 from a Wilcoxon (Mann-Whitney) comparison. The reported ranges also describe the observed spread within each group. These statistics concern the primary laboratory endpoint during the first 7 days of DEC treatment.

The result does not establish the size of a precise treatment effect because the registry record does not report a between-group estimate with a confidence interval. It does not establish equivalence: although the analysis is labelled equivalence, no equivalence margin or supporting confidence limits are reported. Nor does the primary endpoint by itself show how participants felt, whether clinical reactions were prevented, or whether microfilariae were cleared.

The trial's secondary outcomes include adverse-event frequency, markers of eosinophil activation, and microfilarial clearance, but detailed results for these measures are not reported in the registry record. The available safety figures report no serious adverse events or deaths in the listed outcome groups, while other adverse events were recorded for all participants in each of those groups. These counts are not a full account of event type, severity, or timing.

The study is described as a pilot, and the primary endpoint summaries include 4 participants per group. The results therefore offer a limited view of the observed laboratory outcome in this trial. They do not settle how the result would generalize to other patients, settings, or treatment regimens. A statistical comparison can indicate a difference in observed data under its assumptions, but it does not alone establish clinical importance or the broader balance of benefits and harms.

14. Why This Trial Matters Statistically

This trial illustrates how clinical questions can be translated into a laboratory endpoint with a defined time window and reference value. Peak eosinophil count during the first 7 days of DEC treatment, expressed as a percent of baseline, links the question to a measurable post-treatment response. Expressing the outcome relative to baseline also gives a clear reference scale, while the geometric mean summarizes the group values on a multiplicative scale.

It also shows why the choice of statistical method and the reported estimand matter. The registry provides geometric means and ranges but reports a rank-based Wilcoxon comparison. Those methods summarize different features of the data: the means describe group centers on a transformed scale, whereas the rank test evaluates ordering between groups. A p-value should not be mistaken for an effect size, and a rank-based result does not automatically provide evidence of equivalence.

The small outcome groups make uncertainty and reporting especially important. Full ranges reveal observed variability, but they are not substitutes for confidence intervals around a treatment contrast. Missing details about participant flow, missing outcomes, multiplicity, and the equivalence margin further limit interpretation. These are not merely technical omissions: they affect what readers can conclude from the posted analysis and what questions remain open.

Finally, the record demonstrates the distinction between a biological endpoint and broader clinical outcomes. Eosinophil counts, adverse events, and microfilarial clearance are related but not interchangeable outcomes. A result for one cannot stand in for all the others. Clear endpoint-specific interpretation helps keep statistical evidence aligned with the question actually analyzed.

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 outcome summaries include 4 participants in each group, although the registry lists enrollment of 31. The record does not explain the difference, describe participant flow, or report why outcome data are unavailable for participants not represented in the primary summaries. The outcome population is described as subjects who received DEC, but the registry does not specify the analysis population in enough detail to determine how it relates to randomization.

The primary results are reported as geometric means and full ranges, without individual participant data or a confidence interval for the between-group contrast. The reported Wilcoxon (Mann-Whitney) p-value does not quantify the effect's precision or directly test the geometric means. The equivalence label is not accompanied by an equivalence margin, an equivalence estimate, or confidence limits, so the basis for an equivalence interpretation is not reported.

The registry does not report missing-data procedures, sensitivity analyses, multiplicity handling, or a detailed statistical analysis plan. The summary lists secondary outcomes, but their detailed results are not included in the record details available for interpretation. Safety counts give affected participants and participants at risk but not event descriptions, severity, or timing for other adverse events.

Generalizability is also limited by the pilot nature of the study and the small outcome groups. The registry summary describes adults with Loa loa infection and 0-5000 microfilariae/mL, and the tested regimen includes a specific reslizumab dose, timing, and DEC course. The record does not establish whether findings apply beyond that population and regimen. Detailed eligibility criteria, randomization procedures, allocation concealment, and the rationale for the planned enrollment are not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Reslizumab to Prevent Post-treatment Eosinophilia in Loiasis — NCT01111305.
• Registry record last updated 2022-01-27; status last verified 2017-10.
• Results first posted 2017-06-01.
• 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 record describes a completed phase 2 randomized, placebo-controlled, parallel-group pilot study of reslizumab before DEC treatment for loiasis. It lists enrollment of 31, triple masking, and a primary endpoint of peak eosinophil count during the first 7 days of DEC treatment as a percent of baseline. The primary outcome population is subjects who received DEC.

The posted geometric means are 61.0% of baseline for reslizumab plus DEC and 245.6% for placebo plus DEC, with full ranges of 42.7 to 104.0 and 175.0 to 372.0. Each group has 4 participants in the outcome summary. The reported Wilcoxon (Mann-Whitney) comparison has p = 0.028. The registry does not report a confidence interval for the group contrast or the margin needed to interpret the equivalence label.

Secondary outcomes concern adverse events, eosinophil activation, and microfilarial clearance. The safety figures list 0 serious adverse events and 0 deaths in each group, and other adverse events in 4 participants in each group. Further details on outcome availability, missing-data handling, and secondary results are not reported in the registry record.