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 Retrospective Study of the Effectiveness and Safety of Niacin and Steroid Eye Drops for Retinal Vein Occlusions (NCT00500045), a na phase 2, phase 3 study. The primary outcome is An Improvement in Vision in the the Treatment Patients, as Measured by an Increase of 15 Letters on the Early Treatment Diabetic Retinopathy Study (EDTRS) Vision Chart..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00500045 |
| Phase | Phase 2, Phase 3 |
| Condition | Central Retinal Vein Occlusion, Branch Retinal Vein Occlusion |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 36 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Palo Alto Medical Foundation |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns people with retinal vein occlusions. The registry names central retinal vein occlusion and branch retinal vein occlusion as conditions; its summary also includes hemi-retinal retinal vein occlusion. The record does not describe eligibility criteria, baseline vision, or other characteristics of the population enrolled.
Intervention
The intervention is listed as nicotinic acid, with the treatment arm described as oral niacin. The study summary describes a proposed approach combining niacin with prednisolone acetate steroid eye drops. It presents niacin as intended to encourage collateral vessel formation and the steroid drops as intended to reduce vascular leakage and macular edema. These are the proposed rationales, not findings from reported study results.
Comparator
No concurrent comparator is specified. The design is recorded as single group, allocation is listed as not applicable, and the study is not a randomized comparison. Repeated intravitreal triamcinolone acetonide is mentioned in the summary as the commonly used approach the investigators hoped to replace, not as a study arm for a like-for-like comparison.
Primary question
The stated primary endpoint asks whether treatment patients had an increase of 15 letters on the Early Treatment Diabetic Retinopathy Study (EDTRS) Vision Chart at one year. The registry reports 0 participants analyzed and says no study data are available for any results modules. Consequently, the record does not establish how many participants met the endpoint or how vision changed during the study.
3. Trial Design
The registry describes a retrospective study and records a single-group model. It lists allocation as not applicable and masking as none. These features mean the record does not describe a randomized, masked comparison between treatment and control groups. The listed phases are phase 2 and phase 3, but the registry does not explain how those phase labels relate to the retrospective, single-group design.
The study concerns central, hemi-retinal, and branch retinal vein occlusions, although the conditions list names central and branch retinal vein occlusion. The treatment arm is described as oral niacin, and the intervention is listed as nicotinic acid. The study summary discusses niacin together with topical prednisolone acetate; the registry does not provide further details about how this proposed combination was administered or how exposure was documented.
The registry lists enrollment as 36. That figure does not indicate how many people had usable endpoint measurements: the primary outcome description explicitly reports 0 participants analyzed. The stated primary endpoint timeframe is one year, but the record does not report follow-up completeness, visit timing, or the number of participants assessed at that time.
The record status is terminated. It says the principal investigator retired and left the institution, attempts to contact the investigator were unsuccessful, and no study data are available for any results modules. The registry does not report the reason for termination beyond that description, or the operational details of the study design, recruitment, treatment, or data collection.
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
| Stage | Treatment |
|---|---|
| STARTED | 0 |
| COMPLETED | 0 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: 0 participants analyzed for the overall number of participants analyzed. The PI has retired and left the institution. Efforts were made to contact the PI but were unsuccessful. No study data are available for any results modules.
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: 0 participants analyzed for the overall number of baseline participants. The PI has retired and left the institution. Efforts were made to contact the PI but were unsuccessful. No study data are available for any results modules.
| Characteristic | Unit | Treatment |
|---|---|---|
| Participants analysed | 0 | |
| Age, Categorical: <=18 years | — | |
| Age, Categorical: Between 18 and 65 years | — | |
| Age, Categorical: >=65 years | — | |
| Sex: Female, Male: Female | — | |
| Sex: Female, Male: Male | — | |
| Region of Enrollment: United States | participants | — |
6. Primary Endpoint
The registry lists the primary outcome as An Improvement in Vision in the the Treatment Patients, as Measured by an Increase of 15 Letters on the Early Treatment Diabetic Retinopathy Study (EDTRS) Vision Chart., measured over one year.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is described as an improvement in vision among treatment patients, measured by an increase of 15 letters on the Early Treatment Diabetic Retinopathy Study (EDTRS) Vision Chart. The listed assessment timeframe is one year. The registry does not report an endpoint unit beyond the chart-letter criterion, additional scoring details, or whether the criterion was intended as an exact increase or a minimum increase.
Visual acuity expressed through chart letters provides a standardized way to record vision rather than relying only on a broad clinical description. Turning a change into a threshold outcome can make a particular degree of improvement straightforward to count, but it also discards information about changes that fall short of or exceed that threshold. A full analysis would ordinarily need to describe the number meeting the criterion and the number assessed, along with uncertainty around the estimated proportion. No such results are available in the registry record.
The endpoint is a measure of vision, not a direct measurement of retinal thickness or vascular leakage. The registry lists a decrease in retinal thickness as a secondary outcome, but it does not report results for that outcome either. With 0 participants analyzed, the posted record cannot show whether the primary endpoint was reached or how precisely any treatment-related change was estimated.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central statistical fact is that the registry reports 0 participants analyzed for the primary outcome and states that no study data are available for any results modules. It therefore supplies no observed count of participants who achieved the stated vision threshold, no estimate of the endpoint, and no measure of its uncertainty. The enrollment listing of 36 does not fill that gap: enrollment and an analyzed endpoint population are different quantities.
The design is recorded as single group, with no allocation to a comparator. Even if outcome measurements had been available, a before-and-after change in a single group would not by itself isolate the effect of treatment. Changes could also reflect the course of the condition, other care, the way participants entered the study, or differences in measurement and follow-up. A concurrent control group can help address some of these alternative explanations; none is described in this record.
The endpoint is framed as an increase of 15 letters at one year. Without participant-level or aggregate outcome data, the registry cannot establish how often this threshold was reached, whether the measurement was complete, or how variable the changes were. It also cannot support an estimate of the size of a treatment effect or a confidence interval. A confidence interval is a general statistical way to express the uncertainty around an estimate; it cannot be interpreted when the underlying estimate and analyzed data are unavailable.
The adverse-event record lists 0 at risk and 0 events in its displayed group. Those entries should not be read as evidence that no adverse events occurred. In the context of the registry's statement that 0 participants were analyzed and that no study data are available, the entries do not supply an evaluable safety result.
The registry status is terminated, and the outcome description explains that the principal investigator retired and could not be contacted. This limits what can be recovered from the posted record; it does not explain the clinical outcomes. The record therefore documents a research question, a design description, an enrollment listing, and the absence of analyzed results, rather than evidence for or against the treatment approach.
9. Statistical Methods Explained
What can a single-group study estimate?
A single-group study can describe outcomes observed among people receiving the intervention, if usable measurements are collected and reported. For a threshold endpoint, a report would generally give the number meeting the criterion and the number assessed, together with an estimate of the proportion and an uncertainty interval. Those summaries distinguish the observed result from the precision with which it is known. The registry record gives no analyzed endpoint data, so none of these quantities can be evaluated.
A within-group change is not the same as a treatment effect relative to an untreated or alternatively treated group. To estimate a comparative effect, researchers need a defined contrast between groups or a suitable design that makes the comparison credible. Here, the model is single group, allocation is not applicable, and the record describes no control arm. A change in vision, if reported, could be described for that group, but it could not automatically be attributed to niacin or the steroid drops.
How should the threshold endpoint be understood?
The primary outcome uses a letter-based vision measure and a specified threshold: an increase of 15 letters. Such a threshold converts a measurement into a category, such as meeting or not meeting the criterion. This can make the outcome easier to interpret than an unstructured description, but it reduces detail. People with different amounts of change can fall into the same category, and changes close to the threshold may be classified differently despite being similar in magnitude.
For a binary outcome, the denominator matters as much as the count meeting the criterion. The number assessed at the relevant time should be distinguished from the number initially enrolled, because participants can lack follow-up measurements. The record reports enrollment as 36 but reports 0 participants analyzed for the primary outcome. It does not provide reasons for non-analysis, follow-up status, or endpoint values. As a result, neither a response proportion nor its uncertainty can be calculated from the posted results.
What does uncertainty mean?
In general, a confidence interval describes the range of values compatible with an estimate under the assumptions of the statistical method. A narrow interval indicates greater precision than a wide interval, while neither width nor location alone establishes causation. Intervals depend on both the estimate and the amount and structure of the data. Since no primary outcome data are reported, there is no estimate around which an interval could be formed. No confidence interval or inferential result should be inferred from the enrollment listing or from the study's stated objective.
Likewise, a significance test would require an explicitly defined hypothesis, an analysis population, a statistical method, and observed data. The registry does not report an analysis plan, a test result, or a p-value. The presence of a sample-size planning illustration does not supply evidence about the outcome, and a planning calculation is not observed power. No actual sample-size estimate or result can be interpreted from the information available in the registry record.
Why does the comparator matter?
The registry's sample-size illustration describes assumptions of a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It also describes planning for a stated fraction of an observed effect. These are planning assumptions, not evidence that the trial used a two-arm design: the registered model is single group and allocation is not applicable. The record does not explain the relationship between the illustration and the study's actual design. It does not report the observed effect needed to interpret planning scenarios.
A comparison with a concurrent group can help separate an intervention-associated difference from changes that might occur without the intervention. Without that comparison, the study cannot establish a comparative treatment effect through randomization. Randomization is not described, and masking is listed as none. These design features should be kept distinct from statistical precision: even a precise estimate of a single-group outcome would not, on its own, resolve confounding or establish what would have happened under another treatment.
What can be said about safety?
Safety analysis requires a defined population at risk, a period of observation, and recorded events. The adverse-event listing contains zero entries for participants at risk and event counts, while the primary outcome text says no study data are available for any results modules. That combination is not a basis for estimating the frequency of harms. It also does not show that adverse events were actively assessed or that none occurred. The record does not describe event definitions, severity grading, attribution, or duration of safety follow-up.
Overall, the statistical methods needed to quantify the primary outcome are not reported because the underlying outcome data are absent. General concepts such as confidence intervals, binary-outcome denominators, and comparative estimands explain what a complete analysis would address; they do not fill in missing study findings.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists a primary vision outcome and a secondary outcome described as a decrease in retinal thickness. It also reports two outcome measures, but the record does not provide results for either measure. The registry does not report whether there were additional planned endpoints, multiple time points, subgroup analyses, or a strategy for handling multiple statistical tests. A multiplicity adjustment or hierarchy among outcomes is therefore not reported in the registry record.
The primary outcome description states that 0 participants were analyzed and that no study data are available for any results modules. It does not state how many participants had missing measurements, why any data were unavailable, whether participants discontinued, or how missing observations were to be handled. There is no reported imputation method, sensitivity analysis, or comparison of participants with and without observed outcomes.
Analysis populations are also not described. The registry does not say whether the intended analysis population included all enrolled participants, only those receiving treatment, or only those with available outcome measurements. The enrollment listing of 36 is not a substitute for a documented analysis population. Without denominators, endpoint values, and a missing-data plan, neither the impact of missingness nor the robustness of an outcome estimate can be assessed.
The adverse-event record's zeros do not resolve these issues. They coexist with the statement that no study data are available and should not be treated as complete follow-up or a confirmed absence of events. The record does not describe the completeness of safety monitoring or the population included in a safety analysis.
11. What the Result Does, and Does Not, Mean
The registry record establishes that a retrospective study of niacin for retinal vein occlusions was registered as a single-group study, lists enrollment as 36, and specifies a vision endpoint based on an increase of 15 letters at one year. It also states that 0 participants were analyzed for the primary outcome and that no study data are available for any results modules. The posted record therefore does not provide an outcome estimate.
It does not show how many participants experienced the specified improvement, how much vision changed, or whether retinal thickness decreased. It cannot establish the precision of an effect estimate because no effect estimate or uncertainty interval is reported. The zeros in the adverse-event listing do not establish that the intervention was free of adverse events, given the explicit absence of study data.
The record also does not establish a comparison with repeated intravitreal triamcinolone acetonide. That approach appears in the study summary as the commonly used treatment the investigators hoped to improve upon, not as a comparator arm. With no concurrent comparison described, the study design would not by itself distinguish treatment-associated change from other explanations even if within-group outcome data were available.
The stated rationale for combining niacin with prednisolone acetate is a proposed mechanism: niacin was intended to encourage collateral vessel formation, while the steroid drops were intended to reduce leakage and macular edema. Those aims are not findings. The unavailable results mean that neither the proposed clinical benefit nor the safety of the approach can be judged from this registry record.
12. Why This Trial Matters Statistically
This study raises a useful statistical distinction between a research question and evidence that can answer it. The registry identifies a concrete vision endpoint and a proposed treatment approach, but the outcome description reports 0 participants analyzed and no study data available for results. Without outcome observations, there is no estimate to interpret, no uncertainty to quantify, and no basis for comparing observed experience with the study's intended effect.
The design information also matters. A single-group study is different from a randomized comparison, and a treatment rationale is different from a demonstrated treatment effect. Even complete descriptive follow-up in a single group would not automatically identify what would have happened under another approach. Clear reporting of the comparison, analysis population, outcome denominators, and follow-up would be essential to understand what a study can establish.
The registry also illustrates why enrollment should not be confused with analysis. An enrollment listing does not tell readers how many people contributed data to a specific outcome. The stated absence of analyzed participants is critical to interpreting both efficacy and safety; the displayed zero event counts cannot be read as a verified absence of harm.
Finally, the record describes an interruption in access to study information after the principal investigator retired and could not be contacted. Transparent reporting of study status and missing results helps readers distinguish a completed analysis with an uncertain finding from a study for which results are unavailable. In this case, the statistical conclusion is limited to that absence: the registered question remains unanswered in the posted results.
13. 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 main limitation is the absence of analyzable results. The registry explicitly reports 0 participants analyzed for the primary outcome and says no study data are available for any results modules. There are no reported endpoint counts, measurements, estimates, or uncertainty intervals with which to assess the vision outcome or the listed retinal-thickness outcome.
The design is recorded as retrospective and single group, with allocation not applicable and no masking. No like-for-like control comparison is described. The study summary mentions repeated intravitreal triamcinolone acetonide as a treatment approach the investigators hoped to improve upon, but it is not listed as a comparator arm. The registry does not describe a plan to address confounding, selection into treatment, or differences in care.
Details needed to assess the study population and execution are not reported in the registry record. These include eligibility criteria, baseline characteristics, treatment duration and adherence, outcome assessment procedures, follow-up completeness, and reasons for missing data. The record does not describe an analysis population or a missing-data strategy. It also does not explain how the phase 2 and phase 3 labels apply to this retrospective, single-group study.
The safety record lists zero participants at risk and zero events, but the lack of study data prevents interpreting those entries as a reliable safety finding. The registry does not report the safety observation period, event definitions, or completeness of monitoring. The terminated status and the account of the investigator's retirement and unsuccessful contact attempts further limit the information available for evaluating methods and findings.
14. Related Tutorials
15. Related Statistical Calculators
16. Sources
- ClinicalTrials.gov: Retrospective Study of the Effectiveness and Safety of Niacin and Steroid Eye Drops for Retinal Vein Occlusions — NCT00500045.
- Registry record last updated 2019-11-13; status last verified 2019-10.
- Results first posted 2019-11-13.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
17. Record Summary
The registry record concerns a retrospective study of niacin for central, hemi-retinal, and branch retinal vein occlusions. It lists phase 2 and phase 3, a single-group design, no masking, and enrollment of 36. The treatment arm is described as oral niacin; the study summary discusses niacin with prednisolone acetate steroid eye drops.
The primary outcome is an increase of 15 letters on the Early Treatment Diabetic Retinopathy Study (EDTRS) Vision Chart at one year. A decrease in retinal thickness is listed as a secondary outcome. The record status is terminated. It reports 0 participants analyzed for the primary outcome and states that the principal investigator retired, contact attempts were unsuccessful, and no study data are available for any results modules.
Accordingly, no efficacy or safety estimate can be drawn from the posted results. The record does not provide a comparator group, outcome counts, or an analysis plan.