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 Study of an Implantable Device for Lowering Intraocular Pressure in Glaucoma Patients Undergoing Cataract Surgery (NCT01085357), a randomized na study. The primary outcome is Proportion of Eyes With ≥ 20% Decrease in Intraocular Pressure (IOP) From Baseline to the Hypotensive Medication-free 24-month Postoperative Examination Using Non-responder Imputation for Missing Data.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01085357 |
| Phase | NA |
| Condition | Primary Open Angle Glaucoma (POAG), Cataract |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 897 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Transcend Medical, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned patients with primary open-angle glaucoma and cataract who were undergoing cataract surgery. The primary outcome used the intent-to-treat population and counted one study eye per subject. The primary outcome description identifies eyes as non-responders under specified circumstances, including continued ocular hypotensive medication use, an IOP-affecting secondary procedure, CyPass explantation or repositioning, or an attempted but incomplete implantation.
Intervention
The intervention was the CyPass Micro-Stent placed at the conclusion of cataract surgery. The trial asked whether adding this device changed outcomes related to intraocular pressure, while also assessing safety and effectiveness.
Comparator
The comparator was cataract surgery alone, without CyPass implantation at the conclusion of surgery. Both groups therefore underwent cataract surgery; the randomized contrast concerned the addition of the implant.
Primary question
The primary endpoint was the percentage of eyes with at least a 20% decrease in IOP from baseline to the hypotensive medication-free 24-month postoperative examination. IOP was measured by Goldmann applanation tonometry. The posted proportions were 72.5% for CyPass plus cataract surgery and 58.0% for cataract surgery alone. These are observed endpoint summaries; the registry record does not report an inferential comparison for this count outcome.
The practical statistical question is whether the proportion meeting this prespecified response definition differed between the randomized groups, while recognizing how medication use, subsequent procedures, implant removal or repositioning, and incomplete implantation were handled. The registry record also lists mean IOP change and the proportion of eyes within a specified IOP range as secondary outcomes. Those measures offer related but distinct descriptions of postoperative pressure: one expresses average change, while the other classifies eyes against a range. Neither should be treated as interchangeable with the primary responder definition.
3. Trial Design
The study was prospective, randomized, comparative, multicenter, and parallel-group. It enrolled 897 participants according to the registry record. The two groups were CyPass Micro-Stent plus cataract surgery and cataract surgery alone. The record describes the study as single-masked but does not identify who was masked. The study phase is recorded as not applicable.
The primary analysis population is described as intent-to-treat. The primary endpoint was reported for 374.0 eyes in the CyPass group and 131.0 eyes in the cataract-surgery-only group. These are the outcome denominators recorded for that endpoint and should not be read as the total enrollment. The registry record does not explain the difference between the enrollment figure and the endpoint denominators, or provide a participant flow account that would clarify exclusions or missing observations.
The study began in 2009-09, had primary completion in 2015-03, and is recorded as completed. The registered purpose was to evaluate the safety and efficacy of CyPass for lowering IOP in patients with glaucoma undergoing cataract surgery. The listed conditions were primary open-angle glaucoma and cataract.
The randomized parallel comparison supports interpreting differences between groups as contrasts of the assigned strategies, subject to the outcome definitions and available follow-up. The registry record does not report details of sequence generation, allocation concealment, the identity of the masked parties, or procedures used to maintain masking. It also does not report a sample-size justification, a detailed statistical analysis plan, or interim analyses. Those design details therefore cannot be assessed from the record summarized in the posted results.
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: of the 897 enrolled, 392 participants were exited prior to randomization as ineligible/withdrew consent. This reporting group includes all randomized participants (505).
Overall Study
| Stage | CyPass Micro-Stent + Cataract Surgery | Cataract Surgery Only |
|---|---|---|
| STARTED | 374 | 131 |
| COMPLETED | 355 | 125 |
| NOT COMPLETED | 19 | 6 |
Reasons for not completing this period:
| Reason | CyPass Micro-Stent + Cataract Surgery | Cataract Surgery Only |
|---|---|---|
| Adverse Event | 1 | 1 |
| Subject Decision | 4 | 3 |
| Investigator Decision | 1 | 1 |
| Death | 11 | 1 |
| Lost to Follow-up | 2 | 0 |
Analysis population for the primary outcome, as defined in the registry: Intent-to-treat (ITT)
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 randomized participants (Intent-to-Treat)
| Characteristic | Unit | CyPass Micro-Stent + Cataract Surgery | Cataract Surgery Only | Total |
|---|---|---|---|---|
| Participants analysed | 374 | 131 | 505 | |
| Age, Continuous | years | 70.3 (SD 8.45) | 70.2 (SD 8.17) | 70.3 (SD 8.37) |
| Sex: Female, Male: Female | Participants | 197 | 72 | 269 |
| Sex: Female, Male: Male | Participants | 177 | 59 | 236 |
6. Primary Endpoint
The registry lists the primary outcome as Proportion of Eyes With ≥ 20% Decrease in Intraocular Pressure (IOP) From Baseline to the Hypotensive Medication-free 24-month Postoperative Examination Using Non-responder Imputation for Missing Data, measured over Baseline; Month 24 postoperative.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of eyes |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint asks whether an eye achieved at least a 20% reduction in intraocular pressure from baseline to the hypotensive medication-free Month 24 postoperative examination. IOP is fluid pressure inside the eye, measured in this study using Goldmann applanation tonometry and expressed in millimeters of mercury. The endpoint converts a continuous pressure measurement into a responder classification: an eye either meets the stated reduction threshold or does not.
A responder outcome can be clinically interpretable because it expresses the proportion of eyes reaching a prespecified degree of change rather than only the average change across a group. It also makes the outcome sensitive to the response threshold chosen. Eyes with changes on opposite sides of that threshold are classified differently even if their measured changes are close. This general feature of binary endpoints means the proportion does not describe the size of the reduction among responders, nor the full distribution of IOP changes.
The registry record specifies non-responder imputation for missing data and classifies eyes as non-responders in several circumstances, including continued use of ocular hypotensive medication, IOP-affecting secondary surgery, CyPass explantation or repositioning, and attempted but incomplete implantation. These rules make the endpoint a composite of pressure response and treatment or procedure status. The posted outcome is therefore not simply the percentage of eyes with a measured pressure decrease; it is the percentage satisfying the response definition under the specified handling rules.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary outcome proportions were 72.5% in the CyPass Micro-Stent plus cataract surgery group and 58.0% in the cataract-surgery-only group. These figures describe the percentage of eyes meeting the registry's responder definition at the medication-free Month 24 examination. The endpoint denominators were 374.0 and 131.0, respectively. The record does not provide a confidence interval, p-value, or sponsor-reported inferential comparison for this primary count outcome. A formal claim about statistical evidence for a between-group difference cannot be based on these proportions alone.
The primary result should be read in light of its definition. A response required at least a 20% IOP reduction, and non-responder imputation classified specified medication and procedure circumstances as failures to meet the endpoint. Thus the proportion combines measured pressure response with treatment and post-randomization event rules. It is not a direct summary of average IOP change, and it does not show how far responders moved beyond the threshold.
The secondary mean-change outcome gives a different summary. Mean IOP change was -7.0 mmHg in the CyPass group and -5.3 mmHg in the cataract-surgery-only group, with standard deviations of 4.53 and 3.95. An unadjusted recalculation from the posted summary statistics estimates a mean difference of 1.7 mmHg for cataract surgery alone relative to CyPass plus cataract surgery, with a reported recalculated confidence interval from 0.882 to 2.517 and p < 0.001. In direction, the more negative mean change is in the CyPass group. This is a simple unadjusted recalculation, not a registry-reported analysis; no sponsor-reported analysis is listed for this secondary outcome. The interval and p-value therefore should not be confused with an adjusted or prespecified sponsor analysis.
The two secondary outcomes address related but nonidentical questions. Mean change summarizes average movement from baseline, while the other listed endpoint concerns the proportion of eyes whose postoperative IOP fell within the stated range. The registry record provides a numerical secondary comparison for mean change, but does not provide a numerical result for the range-based endpoint in the posted results. The secondary findings should not be used to substitute for a missing inferential analysis of the primary responder endpoint.
Overall, the posted primary proportions are descriptively higher in the implant group, and the recalculated secondary mean-change comparison favors a larger average reduction in that group. Precision and inferential strength differ across these outcomes: the primary result lacks a reported uncertainty estimate, and the secondary comparison is an unadjusted recalculation. The registry record also does not report whether these secondary analyses were prespecified in a multiplicity plan. These limitations temper how strongly the results can be interpreted as a unified statistical conclusion.
9. Statistical Methods Explained
What does the primary proportion represent?
A proportion is the number of observations meeting a definition divided by the number assessed under that outcome. Here, the outcome is expressed as a percentage of eyes that met the specified IOP reduction rule. Each eye is classified as a responder or non-responder for this endpoint. Unlike a mean, a proportion does not preserve the amount of change for each eye; it records whether the threshold was crossed. The responder threshold and the handling of intercurrent events therefore shape the meaning of the reported percentage.
The registry record identifies the primary population as intent-to-treat and says one study eye contributed to the analysis. It also specifies non-responder imputation for missing data, with named medication, surgery, and implant-related circumstances treated as non-response. Imputation is an analysis rule used when the outcome cannot be treated as an ordinary observed measurement. In this case, the listed rules are part of the endpoint definition, not merely a neutral way to fill in an absent pressure reading. The record does not provide a separate sensitivity analysis showing how alternative missing-data assumptions would affect the primary result.
How should the mean-change comparison be read?
The secondary mean-change outcome reports the average difference between baseline IOP and the medication-free Month 24 examination, with baseline-value imputation for missing data. The posted mean changes are -7.0 mmHg for CyPass plus cataract surgery and -5.3 mmHg for cataract surgery alone. Negative change indicates a decrease from baseline. The associated standard deviations, 4.53 and 3.95, describe variation in individual changes around each group mean; they are not confidence intervals for the mean.
The recalculated comparison is an unadjusted difference in means, expressed as cataract surgery alone relative to the CyPass group. Its estimate is 1.7 mmHg, and the recalculated confidence interval is reported from 0.882 to 2.517, with p < 0.001. A confidence interval describes a range of values compatible with the data and the calculation assumptions; it conveys uncertainty in the estimated contrast. A p-value measures how unusual data at least this discrepant from a null comparison would be under that null model and its assumptions. Neither statistic establishes the importance of an effect by itself. These values are recalculations from posted summary statistics, and the registry record does not list a sponsor-reported analysis for this endpoint.
The recalculation uses the posted means, standard deviations, and outcome denominators and treats the comparison as unadjusted. It does not account for covariates, stratification, clustering, or a more complex analysis unless those features are explicitly part of the calculation; the registry record does not report such an adjusted model. The results should therefore be described as an unadjusted recalculated comparison, not as the trial's own reported inferential result.
Why do the endpoints use different summaries?
The primary endpoint is binary, while mean change is continuous. A binary endpoint can be easy to interpret as a percentage meeting a rule, but it discards information about the size of changes and can depend heavily on the selected threshold. A continuous endpoint retains more information about the observed magnitude of change, but a group mean can conceal differences in spread or in the shape of the outcome distribution. Agreement in the direction of these summaries can be informative, but it does not make them equivalent evidence or remove uncertainty about either analysis.
The registry record also lists a secondary proportion of eyes with postoperative IOP at least 6 and at most 18 mmHg, using Goldmann tonometry at the medication-free Month 24 examination and non-responder imputation. This is another binary summary, but its classification rule differs from the primary percentage-reduction threshold. The record does not provide a numerical result for that outcome in the posted results, so its pattern cannot be evaluated from the available statistics.
What do the planning illustrations mean?
The posted planning illustration uses the observed secondary mean-change effect as its starting point, with two-sided significance level 0.05, equal allocation, and a normal approximation. It gives participants per arm for 80% power and for 90% power at 100%, 75%, and 50% of the observed effect. The corresponding figures are 105 and 140 for planning for 100% of the observed effect; 186 and 249 for planning for 75% of the observed effect; and 419 and 560 for planning for 50% of the observed effect.
These are planning illustrations, not the enrollment target used to design this trial and not observed power. They show how the required planned group size changes under the stated assumptions when the effect to detect is smaller or larger. In general, detecting a smaller effect with a given power and significance level requires more participants per arm. The registry record does not report the trial's own sample-size justification, so the planning figures cannot be taken as evidence about the design rationale or adequacy of enrollment.
General statistical interpretation also depends on assumptions. A normal approximation simplifies the calculation, and equal allocation is a planning choice in the illustration; neither establishes the analysis method used by the sponsor. For count outcomes, over-dispersion is a general concern when variability exceeds that expected under a simple count model, and model choice can then affect uncertainty estimates. No model-based comparison for the primary count endpoint is reported in the registry record, so this concern cannot be assessed against a sponsor analysis.
10. Multiplicity, Missing Data and Analysis Populations
The primary endpoint uses non-responder imputation. The record specifies that an eye is a non-responder when ocular hypotensive medication use was not terminated, an IOP-affecting secondary surgical procedure occurred, CyPass was explanted or repositioned, or implantation was attempted but not completed. The primary endpoint is consequently defined by both pressure response and these post-randomization circumstances. This approach is explicit in the registry record, but the record does not report sensitivity analyses using alternative assumptions for missing outcomes or intercurrent events.
For the secondary mean-change outcome, the record specifies baseline-value imputation for missing data. This differs from the primary endpoint's non-responder approach and can affect the interpretation of the two summaries. The registry record does not report additional sensitivity analyses or explain how many observations were missing under either approach. The outcome denominators are reported, but a detailed flow of randomized participants through follow-up and analysis is not reported in the registry record.
The registry record lists a primary endpoint and secondary outcomes, but does not report a multiplicity adjustment, a hierarchy for interpreting outcomes, or an analysis plan establishing which comparisons were confirmatory. When multiple outcomes or comparisons are examined, the chance of a nominally notable result can increase. Without a reported plan, the recalculated secondary p-value should be interpreted as unadjusted and exploratory in that respect, rather than as evidence that accounts for all outcome testing.
The primary count endpoint has no posted confidence interval or p-value, and the registry record reports no analyses for it. The numerical mean-change comparison is a recalculation from summary statistics, rather than a sponsor-reported result. The record also does not report interim analyses, the detailed statistical plan, or a sample-size justification. These omissions limit assessment of prespecification, missing-data robustness, and the intended inferential framework; they should not be filled in by assumption.
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 |
|---|---|---|---|
| CyPass Micro-Stent + Cataract Surgery | 53 | 374 | 14.2% |
| Cataract Surgery Only | 13 | 131 | 9.9% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| CyPass Micro-Stent + Cataract Surgery | 101 of 374 |
| Cataract Surgery Only | 39 of 131 |
Most frequent serious adverse event terms
| Event term | Organ system | CyPass Micro-Stent + Cataract Surgery | Cataract Surgery Only |
|---|---|---|---|
| Pneumonia | Infections and infestations | 4 of 374 | 2 of 131 |
| Knee arthroplasty | Surgical and medical procedures | 3 of 374 | 1 of 131 |
| Cardiac failure congestive | Cardiac disorders | 2 of 374 | 1 of 131 |
| Hip fracture | Injury, poisoning and procedural complications | 2 of 374 | 1 of 131 |
| Osteoarthritis | Musculoskeletal and connective tissue disorders | 3 of 374 | 0 of 131 |
| Pancreatic carcinoma | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 2 of 374 | 1 of 131 |
| Cardiac failure | Cardiac disorders | 2 of 374 | 0 of 131 |
| Sepsis | Infections and infestations | 2 of 374 | 0 of 131 |
| Cerebrovascular accident | Nervous system disorders | 0 of 374 | 2 of 131 |
| Dizziness | Nervous system disorders | 2 of 374 | 0 of 131 |
Most frequent non-serious adverse event terms
| Event term | Organ system | CyPass Micro-Stent + Cataract Surgery | Cataract Surgery Only |
|---|---|---|---|
| BCVA loss => 10 letters read at/after 3 month postoperative visit | Eye disorders | 33 of 374 | 20 of 131 |
| Worsening in visual field MD by => 2.5 dB as compared with preoperative | Nervous system disorders | 25 of 374 | 13 of 131 |
| AC cell and flare requiring steroid treatment at/after 30 days postoperative | Eye disorders | 32 of 374 | 5 of 131 |
| Secondary ocular surgical intervention | Eye disorders | 20 of 374 | 7 of 131 |
| Worsening in any ocular symptom by ≥ 2 points to severe/very severe at/after 3 months postoperative | Eye disorders | 21 of 374 | 4 of 131 |
Serious events with the highest arm-level rate: pneumonia (1.5%), cerebrovascular accident (1.5%), osteoarthritis (0.8%), knee arthroplasty (0.8%), cardiac failure congestive (0.8%).
The posted safety counts show 53 serious adverse events among 374 participants at risk in the CyPass plus cataract surgery group, and 13 among 131 at risk in the cataract-surgery-only group. The corresponding counts for other adverse events are 101 among 374 at risk and 39 among 131 at risk. These are counts reported for each group; they are not, by themselves, adjusted comparisons or evidence that an event was caused by the assigned intervention.
The listed serious adverse event terms include pneumonia and cerebrovascular accident at 1.5% each, and osteoarthritis, knee arthroplasty, congestive cardiac failure, and atrial fibrillation at 0.8% each. The record does not assign these listed term percentages to a particular treatment group in the information, so they should not be interpreted as arm-specific rates. Death counts are not reported in the registry record.
Adverse-event counts need context, including how events were defined, collected, coded, and attributed, as well as the duration of observation. Those details are not reported in the registry record. The figures support a descriptive reading of recorded events only; they do not provide a complete comparative safety analysis or establish causation.
12. What the Result Does, and Does Not, Mean
The primary result describes the proportion of eyes meeting a particular IOP response definition at the medication-free Month 24 postoperative examination. The posted percentage is higher in the CyPass plus cataract surgery group than in the cataract-surgery-only group. This is a descriptive contrast, not a reported test of statistical significance: the registry record does not provide a primary confidence interval or p-value for the two proportions.
The result does not show the full distribution of IOP changes, the size of change among responders, or how close non-responders came to the threshold. The endpoint also treats medication use, subsequent IOP-affecting procedures, implant removal or repositioning, and incomplete implantation according to its non-responder rules. Interpretation therefore depends on this composite definition. The endpoint should not be reduced to an unqualified statement about pressure measurements alone.
The mean-change result offers a related summary and its unadjusted recalculation indicates a difference between group means. It remains a secondary result, and its inferential statistics were recalculated rather than reported as the sponsor's own analysis. The other listed secondary endpoint has no numerical result in the registry record. Thus the available outcomes do not provide a complete set of confirmatory analyses or a reported multiplicity framework.
The results do not establish the size of any effect in settings beyond the studied population and follow-up definition, nor do they settle whether observed differences are clinically important. The registry record does not report a prespecified clinical-importance threshold. The results also do not support causal attribution of the adverse events from counts alone. A careful reading distinguishes what is posted—the endpoint percentages, the secondary mean summaries, and the adverse-event counts—from what is not reported, including the primary inferential comparison, detailed analysis plan, and sensitivity analyses.
13. Why This Trial Matters Statistically
This trial illustrates why endpoint definition is central to clinical-trial interpretation. The primary endpoint is not simply a mean pressure change: it is a threshold-based responder proportion combined with rules for medication use and post-randomization procedures. A reader must understand those rules before interpreting the percentages. The mean-change secondary outcome supplies another perspective but answers a different statistical question.
It also illustrates the difference between a posted descriptive result and an inferential comparison. The primary proportions are available, but no primary confidence interval or p-value is reported. A numerical difference in percentages does not, by itself, describe the precision of that contrast. The secondary mean-change comparison has recalculated uncertainty statistics, but those are unadjusted and are not a sponsor-reported analysis. Keeping these evidence types distinct helps prevent a secondary calculation from being mistaken for the trial's primary statistical conclusion.
The record also highlights the importance of missing-data rules and multiplicity. Non-responder imputation and baseline-value imputation are used for different outcomes, while no sensitivity analyses or multiplicity strategy are reported. These details affect how confidently outcomes can be compared and how much weight to place on nominal secondary evidence.
Finally, the planning illustration demonstrates a general design principle: sample-size requirements depend on the effect targeted and the assumptions used. Those calculations are not the trial's documented design rationale or observed power. The registry record does not report its own sample-size justification, so planning figures based on the observed secondary effect should remain illustrative rather than retrospective validation.
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 registry record leaves several trial-specific uncertainties. It does not report a primary inferential comparison for the responder proportion, including a confidence interval or p-value. It also does not report a numerical result for the listed secondary endpoint based on the postoperative IOP range. As a result, the available evidence does not support a complete statistical assessment across the registered outcome set.
The outcome denominators are lower than the enrollment figure, but participant flow and reasons for the denominators are not reported in the registry record. The record does not give a detailed account of missing observations, follow-up completeness, or sensitivity analyses for the stated imputation methods. Without these details, the robustness of the results to alternative missing-data assumptions cannot be assessed.
Other design and analysis details are also absent: the identity of the masked parties, allocation concealment, the detailed statistical plan, a sample-size justification, interim analyses, and a multiplicity strategy are not reported in the registry record. The single-masked label alone does not establish how masking was implemented. The mean-change comparison is an unadjusted recalculation, and no sponsor-reported analysis is listed, which limits its role as confirmatory evidence.
The serious adverse event terms are presented without arm-specific term percentages in the reported information, and deaths are not reported in the registry record. The available safety counts also do not establish attribution. These limitations are specific to what the record reports and should be kept separate from conclusions that would require information not present in the registry record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of an Implantable Device for Lowering Intraocular Pressure in Glaucoma Patients Undergoing Cataract Surgery — NCT01085357.
- Registry record last updated 2017-05-15; status last verified 2017-05.
- Results first posted 2016-10-20.
- 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
NCT01085357 is a completed, prospective, randomized, comparative, multicenter, parallel-group study of CyPass Micro-Stent placement at the conclusion of cataract surgery versus cataract surgery alone in patients with open-angle glaucoma undergoing cataract surgery. The registry record describes the study as single-masked and lists enrollment of 897.
The primary endpoint was the proportion of eyes with at least a 20% IOP decrease at the hypotensive medication-free Month 24 examination, using non-responder imputation. The posted proportions were 72.5% for CyPass plus cataract surgery and 58.0% for cataract surgery alone. No primary inferential comparison is reported. Secondary outcomes include mean IOP change and the proportion of eyes within the specified postoperative IOP range; the mean-change comparison is available only as an unadjusted recalculation.
The registry record does not report a detailed statistical plan, sample-size justification, multiplicity strategy, or sensitivity analyses. Safety counts are descriptive and do not establish causal attribution.