This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for The Effect of Xiidra on Comfort and Dryness in Symptomatic Contact Lens Wearers (NCT04297618), a na phase 4 study. The primary outcome is Difference in Contact Lens-related Discomfort at 12 Weeks Compared to Baseline.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04297618 |
| Phase | Phase 4 |
| Condition | Dry Eye |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 45 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Waterloo |
| Results posted | Yes |
2. Clinical Question
Population
Symptomatic contact lens wearers with dry eye. The study enrolled 45 participants. The primary endpoint description notes that 2 participants discontinued before the study could be completed.
Intervention
Participants used Xiidra, identified as lifitegrast 5.0% ophthalmic solution. The registry describes the same study drops being used over the 12-week study.
Comparator
There was no separate control group. The study is recorded as single-group, with allocation listed as not applicable and masking listed as none. Baseline is the reference point for the primary endpoint, not a concurrent comparison group.
Primary question
How did participants’ contact lens-related discomfort scores at 12 weeks compare with their baseline scores? The registry defines the measure but does not report the score values or the change estimate.
This is a within-study question about reported discomfort over time among participants using Xiidra. It is not a randomized comparison of Xiidra against another treatment or against a control group. Consequently, even if a before-and-after change were reported, the design alone would not separate change associated with the intervention from changes that might occur over time or from other influences.
The discomfort measure is a participant rating on a scale from 0, meaning no discomfort, to 100, meaning maximal discomfort. The registry specifies baseline and 12 weeks as the assessment time points and identifies the median and full range as the intended summary. However, the median scores, ranges, and a numerical comparison are not reported in the registry record. The central clinical question is therefore identifiable, but its result cannot be evaluated from the posted registry information.
3. Trial Design
The registry identifies this as a Phase 4 study with a single-group model. It lists enrollment as 45 and the status as completed. The recorded study start date is 2021-07-07, and the primary completion date is 2024-04-18. The sponsor is the University of Waterloo.
All participants were assigned the same study drops, Xiidra, over the 12-week study. Allocation is recorded as not applicable, and masking is recorded as none. There is no separate comparator group in the design. The primary endpoint uses participants’ baseline scores as a reference for comparison with their 12-week scores; this is a repeated assessment within the study group, not a controlled treatment contrast.
The registry’s primary endpoint description says that 2 participants discontinued before the study could be completed. It does not explain why they discontinued or how their data were handled in the endpoint analysis. The record also lists adverse-event risk groups of 42 after Xiidra was dispensed and 43 before it was dispensed. The reasons for the differing group counts are not reported in the registry record, and those counts should not be treated as an explanation of the primary endpoint analysis population.
The design can describe reported scores over time among participants in the study, but without a control group it cannot directly estimate how scores would have changed over the same period in the absence of the intervention. The registry record does not report a protocol-level statistical plan, details of recruitment, or a sample-size justification. The completed status indicates the study’s registry status, but does not itself establish that every planned analysis or outcome result is available in the 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: Out of the 45 participants that were enrolled, 43 met the inclusion critieria, and 42 were dispensed with the study treatment.
Overall Study
| Stage | Xiidra Treatment |
|---|---|
| STARTED | 42 |
| COMPLETED | 40 |
| NOT COMPLETED | 2 |
Reasons for not completing this period:
| Reason | Xiidra Treatment |
|---|---|
| Adverse Event | 1 |
| Withdrawal by Subject | 1 |
Analysis population for the primary outcome, as defined in the registry: 2 participants discontinued before the study could be completed.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
Population: All suitable participants who were eligible to take part in the study.
| Characteristic | Unit | Xiidra Treatment |
|---|---|---|
| Participants analysed | 43 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 42 |
| Age, Categorical: >=65 years | Participants | 1 |
| Age, Continuous | years | 30.7 (SD 11.8) |
| Sex: Female, Male: Female | Participants | 36 |
| Sex: Female, Male: Male | Participants | 7 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: Canada | participants | 43 |
6. Primary Endpoint
The registry lists the primary outcome as Difference in Contact Lens-related Discomfort at 12 Weeks Compared to Baseline, measured over Baseline and 12 weeks.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | Full Range |
| Unit | score on a scale |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is titled Difference in Contact Lens-related Discomfort at 12 Weeks Compared to Baseline. Participants rate their contact lens-related discomfort on a scale from 0, no discomfort, to 100, maximal discomfort. The assessment time points are baseline and 12 weeks. The registry specifies the median as the summary measure and the full range as the measure of spread.
A discomfort rating captures the participant’s own experience, which is relevant because discomfort is subjective. Comparing scores within a participant over time can describe whether reported discomfort changed during the study. The median describes the middle of the observed scores and is less influenced by unusually high or low values than the arithmetic mean. The full range gives the lowest and highest observed values, although it does not show how scores are distributed between those extremes. These are general statistical interpretations of the listed summaries, not evidence about the study’s observed outcome.
The registry record does not report the baseline or 12-week medians, their ranges, or a numerical difference between time points. It also does not report a confidence interval or a significance test for this endpoint. The endpoint’s definition is available, but its observed result and precision are not reported in the registry record. Therefore, the size and direction of any change cannot be determined from the posted information.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies a clinically understandable question: whether contact lens-related discomfort ratings at 12 weeks differed from baseline among participants using Xiidra. It specifies the rating scale, assessment times, and intended summaries. It does not provide the observed scores, the estimated change, or a measure of uncertainty. As a result, the primary endpoint cannot be interpreted as showing improvement, worsening, or no change on the basis of the posted results.
The study’s single-group design matters for interpretation. Baseline scores allow a within-group comparison over time, but there is no concurrent control group to show what might have happened over the same period without the study intervention. A change in a before-and-after comparison, if available, would not by itself establish that the intervention caused that change. This is a general limitation of an uncontrolled before-and-after design, not a claim about the actual outcome in this study.
The record lists enrollment as 45 and notes that 2 participants discontinued before the study could be completed. It does not state whether endpoint data from those participants were available, whether they were included in an analysis, or how any missing measurements were handled. The participant count used for the primary endpoint analysis is not reported in the registry record. The adverse-event risk groups have their own listed counts, but those do not establish the analysis population for the comfort endpoint.
The safety entries are descriptive counts. The record lists no serious adverse events in the groups recorded before or after Xiidra was dispensed, while separately recording other adverse events and deaths. These entries should be read in their stated timing groups and should not be treated as a comparison of treatment with control. The registry does not report the details needed to assess individual events, their relationship to the intervention, or the completeness of safety follow-up.
Overall, the posted information supports a description of the study question, design, endpoint definition, and recorded safety counts. It does not support a quantitative conclusion about the primary comfort outcome or a causal estimate of treatment effect. Absence of a result in the registry record is not evidence that the study found no change; it means the result is not reported there.
9. Statistical Methods Explained
The registry identifies the primary summary as a median with a full range. It does not report an inferential method for testing or estimating the baseline-to-12-week change. The explanations below describe general statistical concepts; they do not assert that a particular method was used in this study.
What does the median describe?
The median is the midpoint of a set of ordered observations: half the observations are at or below it and half are at or above it. It can be useful for rating scales when the distribution is skewed or when a small number of extreme values could pull the mean away from the typical observation. A median alone does not describe all aspects of the data. The registry also specifies the full range, which identifies the lowest and highest observed scores but does not show how concentrated or dispersed the remaining scores are.
For a before-and-after study, it is important to distinguish summaries at each time point from a summary of individual change. The difference between group medians is not necessarily the same as the median of participants’ paired differences. A paired analysis uses each participant’s observations together and can account for the fact that measurements from the same person are related. The registry’s endpoint title refers to a difference, but the record does not describe the precise calculation or analysis used for that endpoint. It does not report a numerical change estimate.
What would a confidence interval add?
In general, a confidence interval expresses uncertainty around an estimated quantity under the assumptions of the method used. It helps readers assess which effect sizes are reasonably compatible with the data and analysis, rather than relying only on a single estimate. A narrow interval indicates greater precision than a wide interval, while an interval that includes values on both sides of no change may be compatible with more than one interpretation. These are general principles. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be assessed.
A significance test, if used, would address a different question from the size and precision of the change. A p-value does not measure the probability that the intervention works, nor does it show whether an observed difference is important to participants. The registry record does not report a p-value or identify a primary-endpoint significance test. No conclusion about statistical significance can therefore be drawn from the posted information.
Why does the single-group design affect the analysis?
Measurements from the same participant over time are usually dependent rather than independent. General methods for repeated measurements preserve that pairing or otherwise account for within-person correlation. Treating baseline and follow-up observations as if they came from unrelated groups can misrepresent uncertainty. The record does not state whether the analysis accounted for pairing, which test or model was used, or whether any covariates were included.
Even a method that correctly handles paired observations would estimate change over time within the study group, not a controlled contrast against an untreated or alternatively treated group. Without a concurrent comparator, the statistical analysis cannot by itself distinguish an intervention-associated change from other explanations for change over time. This is a design limitation, not a defect that can be resolved by selecting a different test after the fact.
Do over-dispersion methods apply?
Over-dispersion is a general concern for some count-data models when the observed variability exceeds what the model assumes. It can make standard errors too small if not addressed. The primary endpoint is a discomfort rating summarized by a median and range, not a count outcome. The registry does not identify a count-data model for this endpoint, so there is no basis for saying that over-dispersion was relevant to its analysis. This general concept should not be mistaken for a method reported for this study.
For safety counts, denominators and the way events are counted matter. A count of affected participants is not interchangeable with a count of event episodes, and one participant may potentially contribute more than one event. The registry lists affected counts and risk groups but does not give event narratives or explain all counting conventions. Those entries are therefore best read as descriptive registry counts, without calculating comparative risks or inferring a model-based treatment effect.
In short, the registry supplies the endpoint definition and descriptive summaries it intended to use, but does not report enough statistical detail to reproduce or evaluate an inferential analysis. The analysis method, handling of paired scores, uncertainty estimates, and any adjustments are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The record lists 2 outcome measures and 2 analyses. It does not provide enough detail to determine how the outcomes relate to one another, which analyses correspond to which outcomes, or whether any were designated as secondary or exploratory beyond the primary endpoint identified in the record. The analysis details and a plan for controlling the chance of false-positive findings across multiple tests are not reported in the registry record. No multiplicity adjustment should be assumed.
Missing-data handling is also unclear. The primary endpoint description notes that 2 participants discontinued before the study could be completed, but does not state whether their baseline or follow-up scores were available, whether they were included in the analysis, or how missing measurements were treated. It does not identify an imputation method or explain assumptions about why data might be missing. The primary endpoint analysis population is not reported in the registry record.
These omissions limit interpretation of both the result and its precision. If participants with missing follow-up scores differed from those with complete scores, the analyzed observations might not represent the experience of everyone enrolled. That is a general possibility, not a claim that such a difference occurred in this study. The registry does not provide enough information to assess it. Similarly, without the outcome-specific analysis plan, readers cannot determine whether the reported analysis—if available elsewhere—was selected in advance or how multiple outcomes were handled.
The adverse-event risk groups list counts of 42 after Xiidra was dispensed and 43 before dispensing. The reason for the differing counts and their relationship to endpoint participation are not reported. These safety denominators should not be substituted for a missing endpoint analysis population.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Ocular Adverse Events (After Xiidra Was Dispensed) | 0 | 42 | 0.0% |
| Systemic Adverse Events (After Xiidra Was Dispensed) | 0 | 42 | 0.0% |
| Ocular Adverse Events (Before Xiidra Was Dispensed) | 0 | 43 | 0.0% |
| Systemic Adverse Events (Before Xiidra Was Dispensed) | 0 | 43 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Ocular Adverse Events (After Xiidra Was Dispensed) | 0 of 42 |
| Systemic Adverse Events (After Xiidra Was Dispensed) | 0 of 42 |
| Ocular Adverse Events (Before Xiidra Was Dispensed) | 1 of 43 |
| Systemic Adverse Events (Before Xiidra Was Dispensed) | 0 of 43 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Ocular Adverse Events (After Xiidra Was Dispensed) | 3 of 42 |
| Systemic Adverse Events (After Xiidra Was Dispensed) | 6 of 42 |
| Ocular Adverse Events (Before Xiidra Was Dispensed) | 1 of 43 |
| Systemic Adverse Events (Before Xiidra Was Dispensed) | 0 of 43 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Ocular Adverse Events (After Xiidra Was Dispensed) | Systemic Adverse Events (After Xiidra Was Dispensed) | Ocular Adverse Events (Before Xiidra Was Dispensed) | Systemic Adverse Events (Before Xiidra Was Dispensed) |
|---|---|---|---|---|---|
| Bacterial conjunctivitis | Eye disorders | 2 of 42 | 0 of 42 | 0 of 43 | 0 of 43 |
| COVID | Infections and infestations | 0 of 42 | 2 of 42 | 0 of 43 | 0 of 43 |
| Irritated, red eye & purulent discharge | Eye disorders | 1 of 42 | 0 of 42 | 0 of 43 | 0 of 43 |
| Watery eye | Eye disorders | 1 of 42 | 0 of 42 | 0 of 43 | 0 of 43 |
| Leukocytoclastic vasculitis | Vascular disorders | 0 of 42 | 1 of 42 | 0 of 43 | 0 of 43 |
| Sinus infection | Respiratory, thoracic and mediastinal disorders | 0 of 42 | 1 of 42 | 0 of 43 | 0 of 43 |
| Ear infection | Ear and labyrinth disorders | 0 of 42 | 1 of 42 | 0 of 43 | 0 of 43 |
| Dryness around periorbital eyelid skin | Skin and subcutaneous tissue disorders | 0 of 42 | 1 of 42 | 0 of 43 | 0 of 43 |
| Corneal sterile infiltrates | Eye disorders | 0 of 42 | 0 of 42 | 1 of 43 | 0 of 43 |
| Infiltrative keratitis | Eye disorders | 0 of 42 | 0 of 42 | 1 of 43 | 0 of 43 |
The registry separates adverse-event entries by timing relative to when Xiidra was dispensed and by ocular or systemic category. For serious adverse events, it records 0 affected among 42 at risk after dispensing, and 0 affected among 43 at risk before dispensing. It lists no serious adverse-event terms. These are descriptive entries in the registry, not a comparison between randomized groups.
For other adverse events, the registry records 3 affected in the ocular group after dispensing and 6 in the systemic group after dispensing. Before dispensing, it records 1 affected in the ocular group and 0 in the systemic group. The record lists 0 deaths after dispensing and 1 death in the ocular group before dispensing; it lists 0 deaths in the systemic group before dispensing. A death is recorded separately from the serious-adverse-event affected counts in these entries.
The timing categories describe whether Xiidra had been dispensed; they do not establish the cause of an event. The registry record does not provide event descriptions, an assessment of relatedness, or further context for the death. Counts should not be interpreted as proof that an event was caused by, or unrelated to, the intervention. Nor do the entries establish how completely events were collected during follow-up.
12. What the Result Does, and Does Not, Mean
The registry record establishes that the study examined contact lens-related discomfort before and after a 12-week period in which participants used Xiidra. It defines the discomfort scale and identifies the median and full range as the intended summaries. This makes the endpoint question clear, but the result itself is not reported in the registry record.
Without baseline and follow-up scores or an estimated change, readers cannot determine the direction, magnitude, or precision of any difference in discomfort. There is no reported confidence interval or p-value to assess uncertainty or statistical evidence. The absence of those statistics in the record does not mean that the scores did not change; it means the posted information does not show whether they changed.
The study design also limits what any within-group change could establish. There is no separate comparator group, and masking is recorded as none. A before-and-after association would not by itself show that Xiidra caused the change. Other influences over time cannot be separated from the intervention using this design alone. This is a general interpretation of the design, not a finding about what happened to participants.
The adverse-event entries provide counts by timing and category, including no recorded serious adverse events in the listed groups and a death recorded before Xiidra was dispensed. They do not establish causality or provide enough event detail for a fuller safety assessment. The registry does not report the primary outcome results, the handling of missing endpoint data, or the analysis methods needed to judge the precision of the primary comparison.
Accordingly, the record can be used to understand the study’s question, single-group structure, endpoint definition, and listed safety counts. It cannot establish the size or direction of the comfort outcome, whether any change was statistically significant, or whether any change was caused by the intervention.
13. Why This Trial Matters Statistically
This study raises a useful statistical distinction between change within a group and a treatment effect estimated against a comparator. Repeated ratings at baseline and follow-up can describe how participants’ reported discomfort changed over time. That question is not the same as asking whether the change was caused by the intervention. A concurrent comparison group is generally needed to help separate intervention effects from other changes over time.
The endpoint also illustrates why the summary measure and the analysis target should be clear. A median at each visit describes the score distribution at that visit, while a paired change summarizes how scores shifted within participants. Those quantities need not be identical. The registry specifies a median and full range and titles the endpoint as a difference, but the precise calculation and observed result are not reported in the registry record.
Precision is central to interpreting a clinical outcome. An estimate without an uncertainty interval can leave readers unable to distinguish a precisely estimated small change from an imprecisely estimated change. Here, neither the endpoint estimate nor its uncertainty is posted in the registry record. Enrollment and completion status do not substitute for those results.
The record also illustrates why analysis populations, discontinuations, and missing-data methods matter. It notes 2 discontinuations but does not explain how those participants’ endpoint data were handled. This makes it difficult to assess who contributed to the primary analysis or how missing observations might affect interpretation. The safety entries have separate timing-specific counts and should not be conflated with the endpoint population.
These features make the record informative about design and measurement while leaving the central outcome unanswered in the posted information. Transparent reporting of estimates, uncertainty, analysis methods, and missing-data handling would be needed for a fuller statistical assessment.
14. 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 central limitation of the registry record is that it defines the primary endpoint but does not report its observed values or comparison. The baseline and 12-week medians, full ranges, and estimated difference are not reported in the registry record. Neither an uncertainty interval nor a significance test is listed. This prevents assessment of the endpoint’s direction, size, and precision.
The single-group design has no concurrent control, and masking is recorded as none. Consequently, a change over time could not, on design alone, be attributed specifically to the intervention. The registry does not provide information that would resolve this limitation.
The record notes 2 discontinuations before study completion but does not report their reasons, whether follow-up scores were available, or how missing data were handled. The analysis population for the primary endpoint is not reported. The safety groups list 42 at risk after dispensing and 43 before dispensing, but the record does not explain the difference or connect these counts to the primary endpoint population.
The endpoint is based on participant ratings, so it reflects reported discomfort on the specified scale. The registry does not report further information about the rating instrument’s measurement properties or how the endpoint difference was calculated. It also lists 2 outcome measures and 2 analyses without enough detail to assess the analysis plan or any multiplicity approach.
Finally, safety entries are summarized as affected counts without event descriptions or a reported assessment of relatedness. These limitations concern what can be concluded from the registry record; they do not establish that an unreported method or result was absent from other study materials.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: The Effect of Xiidra on Comfort and Dryness in Symptomatic Contact Lens Wearers — NCT04297618.
- Registry record last updated 2025-05-04; status last verified 2024-06.
- Results first posted 2025-05-04.
- 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.
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18. Record Summary
This completed Phase 4 study enrolled 45 participants with symptomatic contact lens wear and dry eye. The registry describes a single group using Xiidra, identified as lifitegrast 5.0% ophthalmic solution, over 12 weeks. Allocation is listed as not applicable, and masking as none. The study start date is 2021-07-07, and the primary completion date is 2024-04-18.
The primary endpoint concerns contact lens-related discomfort at 12 weeks compared with baseline, rated from 0 to 100 and summarized by the median and full range. The record notes that 2 participants discontinued before completion, but does not report the primary endpoint values, estimated change, uncertainty, or analysis method. It lists safety counts separately before and after Xiidra was dispensed, including no serious adverse events in the listed groups and 1 death recorded before dispensing. The posted information describes the study design and endpoint, but does not provide the primary outcome result.