A Study Evaluating the Efficacy and Impact on Health-related Quality of Life of Levocetirizine in Adults With Seasonal Allergic Rhinitis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study Evaluating the Efficacy and Impact on Health-related Quality of Life of Levocetirizine in Adults With Seasonal Allergic Rhinitis (NCT00653224), a randomized phase 4 study. The primary outcome is Mean 24-hour Reflective Total 5 Symptoms Score (T5SS) Over the Total Treatment Period (14 Days).

2. Clinical Question

The primary measure combines ratings for rhinorrhea, sneezing, nasal congestion, itchy nose, and itchy eyes. Each symptom contributes a score from 0 (none) to 3 (severe), giving a total score from 0 to 15. The reported group means describe the average score over the treatment period; a lower score is a lower measured symptom burden on this scale.

The registry record also lists quality-of-life outcomes measured with the Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ), including overall score and domains such as activities and sleep. These outcomes address a different aspect of the study objective than the symptom score. The record identifies the intervention, comparator, population, and measured outcomes, but details of participant eligibility beyond the stated age and condition are not reported in the registry record.

3. Trial Design

This completed Phase 4 study was randomized, quadruple-masked, placebo-controlled, and used a parallel-group design. The registry record lists an enrollment of 580. Participants were assigned to levocetirizine or matched placebo; the intervention was levocetirizine 5 mg once daily for 2 weeks. The study objective included both symptom outcomes and rhinitis-related quality of life.

The primary endpoint was the mean 24-hour reflective T5SS over the total treatment period of 14 days. The endpoint description defines T5SS as the sum of five individual symptom ratings, each scored from 0 to 3. The primary population is described as participants in the intent-to-treat population with available T5SS over the total treatment period. The reported primary group summaries include 292 participants in the placebo group and 285 in the levocetirizine group.

The registry record lists quality-of-life outcomes using the RQLQ at endpoint and at week 1 and week 2, along with several domain-specific measures. It lists 89 posted secondary outcomes and 90 outcome measures and analyses in total. The available detailed secondary results include overall RQLQ change at endpoint, week 1, and week 2.

The registry record does not report the original sample-size justification, the intended statistical analysis plan in full, the randomization procedure, or how masking was implemented. Details of the trial's own approach to missing outcome data and multiplicity are not reported in the registry record. The reported analysis method for the primary comparison is ANCOVA, described as a mean difference in final values.

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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Number of participants from the Intent to treat (ITT) population with available T5SS over the Total Treatment Period

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 Mean 24-hour Reflective Total 5 Symptoms Score (T5SS) Over the Total Treatment Period (14 Days), measured over Over the total treatment period (14 days).

The primary endpoint is the mean 24-hour reflective Total 5 Symptoms Score over the 14-day treatment period. T5SS adds ratings for rhinorrhea, sneezing, nasal congestion, itchy nose, and itchy eyes. Each symptom is scored from 0 (none) to 3 (severe), so the total ranges from 0 to 15. A lower value represents a lower score on the defined symptom scale.

A combined score offers a single continuous summary of several symptoms relevant to seasonal allergic rhinitis. Averaging the score over the treatment period describes the typical reported symptom burden across that interval, rather than focusing on one symptom or one measurement alone. The registry record specifies a 24-hour reflective score, but does not report further details about the timing or collection of daily assessments.

The primary endpoint is useful for comparing group averages, but it does not describe every participant's experience or the distribution of individual changes. Group means and their uncertainty therefore need to be read together. The endpoint definition also does not establish what size of difference would be important to participants; a threshold for clinical importance is not reported in the registry record.

7. Results Posted in the Registry

• Levocetirizine: mean 7.87 versus 8.68 on control; difference -0.81 (95% CI -1.35 to -0.27), standardized effect d = -0.24; z-test p = 0.003.

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.

Change From Baseline in Overall Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Score at Endpoint During the Two-week Treatment 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:
  • Levocetirizine: mean -1.31 versus -0.93 on control; difference -0.38 (95% CI -0.57 to -0.19), standardized effect d = -0.33; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Levocetirizine than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change From Baseline in Overall Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Score at Week 1

• 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:
  • Levocetirizine: mean -0.94 versus -0.60 on control; difference -0.34 (95% CI -0.51 to -0.17), standardized effect d = -0.34; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Levocetirizine than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Change From Baseline in Overall Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Score at Week 2

• 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:
  • Levocetirizine: mean -1.34 versus -0.95 on control; difference -0.39 (95% CI -0.58 to -0.20), standardized effect d = -0.34; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Levocetirizine than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The detailed secondary results include overall RQLQ change at endpoint, week 1, and week 2. Across these measures, the posted mean changes are more negative in the levocetirizine group than in the placebo group. The sponsor-reported ANCOVA comparisons for each of these listed overall RQLQ outcomes have p < 0.001. This direction is broadly consistent with the primary comparison's lower average symptom score in the levocetirizine group, while addressing quality of life rather than the primary symptom scale.

The registry record lists 89 posted secondary outcomes, including RQLQ domain measures, but the detailed results available for interpretation are not the full set of those outcomes. The overall pattern in the listed measures should not be assumed to represent every secondary endpoint. Differences in outcome definitions, measurement times, and domains can make findings complementary rather than interchangeable.

Secondary outcomes generally carry less weight than a prespecified primary outcome when many outcomes are examined. In general, testing more outcomes creates more opportunities for apparently notable findings by chance. Adjustments for multiple testing, a prespecified testing hierarchy, or other safeguards can help manage that issue, but whether such methods were used is not reported in the registry record. The secondary results are therefore useful context, but their p-values should not be treated as independent confirmation without knowing the multiplicity plan.

The registry record does not report a threshold for a meaningful RQLQ change. The numerical direction and statistical results alone cannot establish how important the differences are to participants. Nor do these secondary findings establish a separate effect for every RQLQ domain or every listed time point.

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

• Change From Baseline in Overall Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Score at Endpoint During the Two-week Treatment Period
• Change From Baseline in Overall Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Score at Week 1
• Change From Baseline in Overall Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Score at Week 2
• Change From Baseline in Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Activities Score at Endpoint During the Two-week Treatment Period
• Change From Baseline in Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Activities Score at Week 1
• Change From Baseline in Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Activities Score at Week 2
• Change From Baseline in Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Sleep Score at Endpoint During the Two-week Treatment Period
• Change From Baseline in Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) Sleep Score at Week 1

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: it is a score averaged over a treatment period. The registry record reports group means and standard deviations, which describe the central value and the spread of participant scores in each group. The simple recalculation compares those means without covariate adjustment. It is useful as a transparent summary of the posted data, but it is not a substitute for the sponsor's reported analysis.

What does the mean difference represent?

The recalculated mean difference is defined as the levocetirizine group mean minus the placebo group mean. Its estimate is -0.81 points. Because lower T5SS values indicate lower scores on the specified symptom scale, the negative sign indicates a lower average score in the levocetirizine group. It does not describe the score of a typical individual, nor does it show how many participants experienced a particular degree of change.

The recalculation uses the posted means, standard deviations, and group sizes. The reported standard deviations describe variation among participants, while the estimated standard error describes uncertainty in the estimated group means and their difference. A standard error is not the spread of individual scores. The recalculated standard errors for the placebo and levocetirizine means are 0.201 and 0.188, respectively.

Why is there also an ANCOVA result?

The registry record reports ANCOVA for the primary analysis, with the result described as a mean difference in final values. ANCOVA is a general statistical method that compares group outcomes while accounting for specified covariates. Accounting for covariates can change the estimated contrast and its uncertainty compared with a simple comparison of group means. The covariates included, model specification, and detailed assumptions are not reported in the registry record, so the adjusted estimate cannot be reconstructed from the posted summary statistics alone.

The sponsor-reported ANCOVA difference is -0.89, with a 95% confidence interval from -1.33 to -0.45 and p < 0.001. The recalculated unadjusted estimate is -0.81, with a recalculated interval from -1.35 to -0.270 and p-value 0.003. Each answers a related but not identical statistical question because the methods differ. The registry record does not indicate a discrepancy between the posted analysis and the recalculation.

How should p-values be understood?

A p-value describes how unusual data at least as incompatible with a specified null model would be if that model and the analysis assumptions were correct. It is not the probability that the null hypothesis is true, and it does not measure the size or importance of an effect. The unadjusted p-value of 0.003 and the sponsor's p < 0.001 are tied to their respective analyses. Neither alone establishes the clinical importance of the estimated difference.

In general, p-values can be affected by sample size and analysis choices. A small p-value can accompany a modest estimated difference, and a larger p-value can occur when estimates are imprecise. Interpretation therefore depends on the estimate, its interval, the outcome's scale, and the study context, not on a threshold alone.

What do the group counts and standard deviations add?

The primary summaries use 292 placebo participants and 285 levocetirizine participants. The means are 8.68 and 7.87, and the standard deviations are 3.44 and 3.17. Standard deviations help show that individual scores vary around each group mean. Since the groups have appreciable within-group variation, the mean contrast should be understood as a difference in averages, not as a uniform difference across participants.

General statistical practice distinguishes random variation from possible sources of bias. Randomization is intended to support a fair comparison of assigned groups, but it does not resolve every concern about outcome measurement, missing data, or analysis decisions. The registry record identifies randomized allocation and masking but does not report all implementation details or a complete statistical analysis plan. Those omissions limit assessment of how each methodological choice was made.

Finally, the primary endpoint is one of many outcomes listed in the record. When many outcomes or analyses are examined, the chance of at least one apparently notable result can increase. Statistical adjustment or a prespecified hierarchy can address this issue in some settings, but the registry record does not report whether or how multiplicity was handled. Accordingly, secondary findings should be read as supportive context rather than treated as independent confirmation without qualification.

11. Confidence Intervals and Precision

A confidence interval describes a range of effect estimates compatible with the observed data and the assumptions of the analysis. It conveys uncertainty around an estimate rather than a guarantee that the true effect lies within the particular interval. A narrower interval indicates greater statistical precision; a wider interval indicates less precision. Neither width nor location alone determines clinical importance.

For the recalculated unadjusted primary mean difference, the estimate is -0.81 points and the interval runs from -1.35 to -0.270. The interval lies on the negative side, consistent with a lower mean T5SS in the levocetirizine group under this comparison. The sponsor's ANCOVA estimate is -0.89, with a 95% confidence interval from -1.33 to -0.45. The sponsor's interval is reported for the adjusted analysis; the recalculated interval comes from the simple comparison of summary statistics.

The two intervals are broadly consistent in direction, but their limits differ because the estimates arise from different methods. The registry record does not report enough information about the ANCOVA model to reproduce its interval. Precision is also not the same as certainty about how the result would apply outside the studied participants, or about the clinical importance of the difference.

As a general point, intervals can help distinguish a precisely estimated small effect from a less precisely estimated larger effect. Here, the estimated difference is modest relative to the reported standard deviations, which describe variation among participants. The registry record does not report a threshold for a meaningful change on the T5SS scale, so the intervals cannot by themselves determine whether the estimated difference is important to patients.

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 illustrations are expressed as participants per arm, because the primary outcome is continuous and the planning assumptions specify equal allocation between the two arms. They are not totals across both arms and are not counts of events. The registry record's original sample-size justification and design assumptions are not reported; the illustrations are instead based on the observed effect.

The listed 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 as the stated fraction of the observed effect. The rows therefore show planning for 100%, 75%, and 50% of the observed effect, with separate columns for 80% and 90% power.

In plain terms, 80% power means that if the assumed effect and planning model were correct, a study of the listed size would have an 80% chance of detecting an effect at the chosen significance level. The 90% column describes a higher chance of detection under the same assumptions and generally calls for a larger planned sample. These are design-planning quantities, not guarantees about a future study's result.

Smaller effects are harder to distinguish from random variation, so planning to detect a smaller fraction of the observed effect requires more participants per arm. The figures are illustrative: they do not establish what the original investigators planned or whether the original trial was designed around the observed result. This is not observed power; observed power is not a useful substitute for interpreting the estimated effect and its confidence interval.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -0.810; pooled standard deviation σ = 3.309.
2. n = 2 × (1.96 + 0.842)² × 3.309² / -0.810² = 262.0, rounded up to 263 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -0.81                      # observed difference in means
sigma <- 3.30939773845701                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(653224)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 263 (80% power), 351 (90% power)
 75% of observed effect: n per arm = 466 (80% power), 624 (90% power)
 50% of observed effect: n per arm = 1,049 (80% power), 1,404 (90% power)
power.t.test: 263 
Simulated power at n = 263 per arm: 0.803 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The sponsor-reported primary analysis used ANCOVA and gave a mean difference in final values of -0.89, with a 95% confidence interval from -1.33 to -0.45 and p < 0.001. The recalculation uses the posted arm means, standard deviations, and participant counts, without adjustment. It gives a mean difference of -0.81, an interval from -1.35 to -0.270, and an unadjusted p-value of 0.003.

Both estimates point in the same direction and are similar in size, but they are outputs from different methods. ANCOVA may account for covariates specified in the analysis; the registry record does not report those covariates or enough model detail to reproduce the sponsor's result. The simple recalculation is therefore best read as a check on the unadjusted summaries, not as a correction of the sponsor's analysis.

The registry record does not indicate a discrepancy between the reported and recalculated analyses. The sponsor analysis remains the trial's reported analysis, while the recalculation offers a transparent comparison based only on group-level summary statistics. Differences between the two results should not be attributed to a particular modeling choice without the missing analysis details.

15. Multiplicity, Missing Data and Analysis Populations

The registry record lists many outcomes and analyses: 90 outcome measures and analyses in total, including 89 posted secondary outcomes. Examining multiple outcomes can increase the chance that at least one result appears statistically notable even when there is no underlying difference for that outcome. This general issue is known as multiplicity. It matters when interpreting secondary p-values, especially if the analysis plan does not specify which results are confirmatory and how testing across outcomes is handled.

Whether the trial used a multiplicity adjustment, a prespecified hierarchy, or another approach is not reported in the registry record. The posted p-values should therefore be interpreted in the context of that missing information. The primary endpoint is the study's designated primary outcome in the registry record, but details about any formal testing sequence are not reported.

The primary population is described as participants from the intent-to-treat population with available T5SS over the total treatment period. This wording indicates that the summarized endpoint required available measurements, but it does not explain how unavailable measurements were handled or why they were unavailable. Methods such as imputation, model-based handling, or sensitivity analyses are not reported in the registry record and should not be assumed.

The registry record does not report the numbers of participants with missing primary outcome data, reasons for missingness, or analyses testing the effect of missing data assumptions. Although enrollment is 580 and the primary arm summaries list 292 and 285 participants, those counts alone do not explain participant flow or missingness. The detailed analysis population definitions for all secondary outcomes are also not reported.

These gaps limit assessment of whether the estimates are robust to missing data and how strongly secondary evidence should be weighted. They do not change the numerical results that are posted, but they narrow the conclusions that can be drawn about analysis choices and the completeness of outcome information.

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 2% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: cellulitis (0.4%).

The registry record reports serious adverse events for 0 of 293 participants at risk in the placebo group and 1 of 285 participants at risk in the levocetirizine group. It lists cellulitis at 0.4% among the top serious-event terms. The record does not specify the group for that term in the information available, so it should not be attributed to one arm on that basis alone.

Other adverse events are reported for 12 of 293 participants at risk in the placebo group and 13 of 285 participants at risk in the levocetirizine group. These figures are participant counts, not measures of event severity beyond the separate serious-event category. The registry record does not provide further detail about event definitions, duration, relatedness to treatment, or the full event listings in the information available.

Deaths are not reported in the registry record. The event counts are descriptive and should be read with their group denominators and the limited reporting detail in mind. They do not establish that an event was caused by a study treatment, nor do these counts alone support broad safety conclusions.

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

The posted primary results show a lower mean T5SS over the treatment period in the levocetirizine group than in the placebo group. The simple unadjusted mean difference is -0.81 points, and the sponsor-reported ANCOVA estimate is -0.89. Both analyses have intervals on the negative side, with the sponsor analysis reporting a 95% confidence interval from -1.33 to -0.45. These are group-level comparisons on a symptom score ranging from 0 to 15.

The finding describes the estimated difference in average scores, not an individual participant's likely response. The standard deviations indicate variation within both groups, and the registry record does not report a threshold defining a clinically meaningful change. Statistical evidence against a no-difference model does not, by itself, establish how important the size of the estimated difference is to participants.

The listed overall RQLQ outcomes also show more negative mean changes in the levocetirizine group, with sponsor-reported p-values below 0.001. These results add quality-of-life context, but the registry record lists many secondary outcomes and does not report a multiplicity approach or a threshold for meaningful RQLQ change. They should not be treated as proof of an effect across every listed outcome or domain.

The trial concerns adults 18 years of age and older with seasonal allergic rhinitis and the stated 2-week treatment period. The registry record does not report enough detail about eligibility, missing data, or analysis methods to resolve every question about generalizability and robustness. These results describe the posted trial comparisons; they do not determine outcomes for a particular person or establish effects beyond the population and period represented in the record.

18. Why This Trial Matters Statistically

This trial is statistically instructive because it reports both a continuous primary outcome and a sponsor analysis using ANCOVA, while the posted group means and standard deviations also permit a simple unadjusted comparison. The two approaches estimate related contrasts but rely on different information and methods. Reading them together illustrates why a recalculation from summary statistics can check the direction and rough magnitude without reproducing an adjusted analysis.

The estimated primary difference is small relative to the standard deviations of scores within each group. That contrast between average effect and within-group variation is a useful reminder that statistical evidence about group means does not imply that participants have identical outcomes. The confidence intervals add information about the precision of the estimated average difference, while the p-values address a different question about compatibility with a null model.

The study also lists many secondary outcomes, including several quality-of-life measures. This makes multiplicity a relevant interpretive issue: isolated secondary p-values are harder to weigh without knowing the prespecified testing strategy. The registry record's missing details about multiplicity and missing-data methods show why numerical results should be considered alongside reporting completeness.

Finally, planning illustrations based on the observed effect help explain how target effect size and desired power affect sample-size requirements. They are not a record of the investigators' original design assumptions and are not a measure of the trial's observed power. Keeping those distinctions clear prevents retrospective planning calculations from being mistaken for evidence about how the trial was designed.

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.

The registry record does not report a threshold for clinical importance on the T5SS or RQLQ scales. As a result, the statistical estimates and intervals describe the direction and precision of group differences but do not establish whether their magnitude is meaningful to participants.

The primary population is described as the intent-to-treat population with available T5SS over the treatment period, but missing-data counts, reasons, and handling methods are not reported in the registry record. Enrollment and outcome-summary counts alone do not explain participant flow. Missing-data sensitivity analyses are not reported in the registry record.

The sponsor's primary result is identified as ANCOVA, but the covariates, model specification, and analysis assumptions are not reported in the registry record. The recalculated unadjusted comparison cannot reproduce that adjusted model. The record also does not report the original sample-size justification, so the planning illustrations based on the observed effect should not be read as the trial's design rationale.

The record lists numerous secondary outcomes, but a multiplicity strategy is not reported. Detailed results are available for only some of the listed outcomes, limiting assessment of the complete secondary pattern. In addition, the registry record provides limited detail about eligibility beyond adults 18 years and older with seasonal allergic rhinitis, and about randomization and masking implementation. These gaps constrain evaluation of robustness and generalizability without altering the reported numerical summaries.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: A Study Evaluating the Efficacy and Impact on Health-related Quality of Life of Levocetirizine in Adults With Seasonal Allergic Rhinitis — NCT00653224.
• Registry record last updated 2011-08-31; status last verified 2009-12.
• Results first posted 2009-11-17.
• 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, randomized, quadruple-masked, placebo-controlled, parallel-group Phase 4 study of levocetirizine for seasonal allergic rhinitis. The listed enrollment is 580. The intervention was levocetirizine 5 mg once daily for 2 weeks, compared with matched placebo.

The primary outcome was mean 24-hour reflective T5SS over 14 days. The posted means were 8.68 for placebo and 7.87 for levocetirizine. The sponsor-reported ANCOVA difference was -0.89, with a 95% confidence interval from -1.33 to -0.45 and p < 0.001. Detailed secondary results include overall RQLQ outcomes at endpoint, week 1, and week 2.

Serious adverse events were reported for 0 of 293 placebo participants and 1 of 285 levocetirizine participants. The registry record does not report deaths. Original sample-size assumptions, detailed missing-data methods, and the multiplicity approach are not reported in the registry record.