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 Validation of TearLab Osmometer - Human Factor Usability Report (NCT00731484), a registered phase not stated study. The primary outcome is Tear Osmolarity in Human Measured by TearLab System.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00731484 |
| Phase | Phase not stated |
| Condition | Dry Eye Syndromes |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 233 |
| Arms in the primary outcome | n/a |
| Lead sponsor | TearLab Corporation |
| Results posted | Yes |
2. Clinical Question
Population
The registered population includes healthy normal volunteers and subjects diagnosed with moderate or severe chronic dry eye disease and/or Sjögrens Syndrome. The arm description says subjects should present the general population. The record does not report how many participants belonged to each health-status category or give further eligibility details.
Intervention
The study objective was to assess the OcuSense TearLab™ osmolarity test when performed in physician office laboratories by health care professionals. The device uses a laboratory-on-a-chip to collect and analyze a tear sample. The objective also refers to contrived tear samples, but the primary outcome describes measurement in human subjects.
Comparator
No gold-standard method was used to establish dry eye status, and the record does not describe a comparator test for the primary outcome. It also states that the study was not set up as a randomized comparison. The registry record therefore does not support interpreting its arms as a like-for-like control comparison.
Primary question
The central question was whether the TearLab system could measure tear osmolarity in human subjects. This is a measurement-performance question. It is not a test of whether the device correctly identifies dry eye against an independent reference standard, nor is it a treatment-effect question.
The study is titled “Validation of TearLab Osmometer - Human Factor Usability Report.” Its objective focuses on test performance when health care professionals use the system in physician office laboratories. The registered primary outcome is tear osmolarity measured by the TearLab system at a single visit, at the time of testing.
The participant description spans healthy normal volunteers and people with specified chronic dry-eye diagnoses and/or Sjögrens Syndrome. Although the registry gives an enrollment of 233 and describes the subjects as representing the general population, it does not report the number in each diagnostic category or how the measured values were distributed across those categories. It also does not set out a separate clinical question for each category.
In particular, the study description says that no gold-standard method was used to establish dry eye status. Without an independent reference standard, the registered outcome cannot by itself tell readers how accurately the device classifies people as having or not having dry eye. The stated question is narrower: whether the instrument can measure tear osmolarity in human subjects under the described use conditions.
3. Trial Design
The registry record identifies this as a completed study, with enrollment of 233. The recorded start is 2008-07 and the primary completion is 2009-03. The study is categorized as “other,” rather than as a randomized comparison. The record states that allocation was not stated and that the arms are not a like-for-like control comparison.
The objective was to validate the performance of the OcuSense TearLab™ osmolarity test when used in physician office laboratories by health care professionals. The objective refers to human tear fluid collected from volunteer subjects and to contrived tear samples. The arm description names “Volunteer Patients/Subjects” and says those subjects should present the general population. The registry does not report how the human-subject measurements and contrived samples were divided or analyzed.
The primary outcome is tear osmolarity measured by the TearLab System, at a single visit and at the time of testing. The outcome description says the device uses a laboratory-on-a-chip that simultaneously collects and analyzes the electrical impedance of a 50 nL tear sample from the inferior lateral meniscus. The stated measurement is reported in mOsm/L in the outcome description; the unit field is written as mOsms/L.
The registry lists one outcome measure and zero analyses. That means the posted registry record does not include an analysis entry for the outcome; it does not establish that no analysis was performed outside the registry. The protocol, detailed statistical analysis plan, eligibility criteria, assignment process and methods for handling repeated or unusable measurements are not reported in the registry record.
Planning calculations associated with the results use assumptions of two-sided significance level 0.05, equal allocation between two arms and a normal approximation. Those are planning assumptions for illustrative calculations, not evidence that the study itself had two randomized arms or was designed using those assumptions. The registry record does not report a sample-size justification or an allocation scheme.
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 | General Population |
|---|---|
| STARTED | 233 |
| COMPLETED | 233 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Healthy normal volunteers as well as subjects diagnosed with moderate or severe chronic dry eye disease and/or Sjögrens Syndrome
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.
| Characteristic | Unit | General Population |
|---|---|---|
| Participants analysed | 233 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 191 |
| Age, Categorical: >=65 years | Participants | 42 |
| Age, Continuous | years | 47.8 (SD 18.0) |
| Sex: Female, Male: Female | Participants | 159 |
| Sex: Female, Male: Male | Participants | 74 |
| Region of Enrollment: United States | participants | 233 |
6. Primary Endpoint
The registry lists the primary outcome as Tear Osmolarity in Human Measured by TearLab System, measured over Single visit, at time of tear osmolarity testing..
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Full Range |
| Unit | mOsms/L |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is “Tear Osmolarity in Human Measured by TearLab System.” It concerns the numerical tear-osmolarity measurement made by the device, rather than a diagnosis, symptom change or clinical event. The registered timeframe is a single visit, at the time of tear-osmolarity testing. The outcome description says the system collects and analyzes the electrical impedance of a 50 nL tear sample from the inferior lateral meniscus.
The outcome is recorded as a mean, with full range as the stated dispersion. In general, a mean describes the central value of a set of measurements, while the full range describes the lowest-to-highest spread. Considering both can help readers distinguish a typical measurement from the breadth of observed values. A mean alone can hide substantial variation, and a range alone does not show where most observations lie. These are general statistical points; the registry record does not give the observed mean or range values.
The endpoint is relevant to the stated measurement-performance objective because it directly records what the device measured in human subjects. It does not, on its own, establish whether those measurements are accurate relative to a reference method, or whether the values distinguish people with dry eye from those without it. The registry explicitly says no gold-standard method was used to establish dry eye status and that diagnostic performance was not the study’s purpose. The numerical endpoint results are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a device-measurement study, not a randomized trial of a treatment. Its primary question concerns whether the TearLab system could measure tear osmolarity in human subjects when used by health care professionals in physician office laboratories. That objective should guide interpretation: the registered outcome is a measurement, not evidence about treatment benefit or harm.
The primary outcome is defined as a mean tear-osmolarity measure with full range as its dispersion, taken at a single visit at the time of testing. However, the registry record does not report the observed mean or the endpoints of the range. It therefore does not permit a numerical assessment of the central measurement, its spread, or the precision of an estimate. It also does not report an uncertainty interval for the outcome. A confidence interval, in general, describes the statistical uncertainty around an estimate; without a reported interval or the underlying data, readers cannot evaluate that uncertainty from this record.
The registry states that there was no gold-standard method for establishing dry eye status and that the trial was not set up to evaluate diagnostic performance. Consequently, the outcome cannot be read as a measure of sensitivity, specificity, classification accuracy or agreement with an independent reference test. Those quantities require an appropriate reference or comparison framework, which is not described. The stated goal is to determine whether the device could measure tear osmolarity, rather than whether it can diagnose dry eye.
The record identifies an enrollment of 233 and a general-population description for the volunteer subjects. It also identifies healthy normal volunteers and subjects diagnosed with moderate or severe chronic dry eye disease and/or Sjögrens Syndrome as the population for the primary outcome. It does not report group-specific counts, outcome summaries by health status, or an analysis comparing those categories. No subgroup contrast should be inferred from the population description alone.
The study is not described as randomized, allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. Accordingly, a difference between any listed groups would not automatically have a causal interpretation, even if group-level values were available. The registry record does not provide those values or an analysis entry.
Planning illustrations use an observed effect and specified assumptions, including two-sided significance level 0.05, equal allocation between two arms and a normal approximation. Such calculations describe hypothetical planning requirements under those assumptions; they are not observed power and do not establish the original study’s design rationale. The sample-size justification and the original statistical plan are not reported in the registry record.
Overall, the posted record establishes the study’s measurement focus, population description, endpoint definition and basic status. It does not provide the numeric outcome results needed to assess how the measurements behaved, nor does it provide a reference-standard comparison needed to evaluate diagnostic accuracy. These limits constrain what can be concluded from the registry entry.
9. Statistical Methods Explained
What is the outcome measuring? The primary outcome is a tear-osmolarity measurement made with the TearLab system. The outcome description specifies that the device collects and analyzes the electrical impedance of a 50 nL tear sample from the inferior lateral meniscus. In general, a measurement endpoint is most informative when the quantity, measurement method, timing and summary are clearly defined. Here, the registry describes the quantity, device and single-visit timing, and identifies the summary as a mean with full range for dispersion.
The unit is written as mOsms/L in the outcome unit field and mOsm/L in the outcome description. The record does not explain the difference in wording. This inconsistency does not supply grounds to alter the reported unit or infer an alternative measurement scale.
What do mean and full range convey? In general, a mean condenses a group of measurements into a central summary. It can be useful for comparing or describing measurements, but it can be influenced by extreme observations and does not show the shape of the underlying distribution. The full range records the lowest and highest values, giving a sense of the total span. It is sensitive to extreme observations and does not indicate how densely values are concentrated between its endpoints. Because the registry gives neither the mean nor the range endpoints, these concepts explain the intended summaries but cannot be used to characterize the actual results.
A broader spread can arise for several reasons, including real differences among the people measured, variation in sample collection, or variation in measurement. This is a general measurement principle, not a finding about this study. The registry does not report repeated-measurement data, a reliability analysis, or separate estimates of within-person and between-person variability. Therefore, it does not allow those sources of variation to be distinguished.
Why does the reference standard matter? A measurement study and a diagnostic-accuracy study answer different questions. A measurement study can describe whether an instrument yields readings in the intended setting. Diagnostic accuracy asks how well a test identifies a target condition, ordinarily by comparing test classifications with an accepted reference standard. General measures such as sensitivity and specificity require that reference framework and defined classification thresholds. The registry says no gold-standard method was used to establish dry eye status and explicitly states that diagnostic performance was not the objective. Diagnostic accuracy cannot therefore be inferred from the registered endpoint.
Agreement is also distinct from the ability to produce a measurement. In general, evaluating agreement between methods requires paired readings and an appropriate comparison of their differences or concordance. The registry does not describe a reference measurement method or report paired method-comparison results. A claim of agreement with another instrument would go beyond the information in the record.
How should planning calculations be read? The planning illustrations are based on an observed effect and state assumptions of a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation. They describe hypothetical participant requirements for detecting a specified fraction of the observed effect under those assumptions. They are not the study’s observed results, do not establish that the original study had two comparable arms, and are not observed power. A planning calculation is conditional on its assumptions; changing the assumed effect or allocation can change the planning requirement. The registry record does not report the original sample-size justification, nor does it explain a protocol-based target enrollment.
For a continuous outcome, a normal approximation may be used in planning when the method’s assumptions are judged suitable. In general, the distribution of measurements, variability and analysis design matter to whether such an approximation is reasonable. The registry record does not report enough distributional detail or an analysis plan to evaluate those assumptions for the study’s actual outcome analysis. The planning assumptions should therefore be understood as features of the illustrative calculations, not confirmed features of the original protocol.
What does over-dispersion mean in general? For count data, over-dispersion means that observed variability exceeds what a chosen model expects. Ignoring it can make standard errors too small and confidence intervals too narrow. This is a general concept and is not an identified feature of this trial: the registered primary endpoint is a continuous measurement summarized by a mean and full range, and the record does not describe a count outcome or an over-dispersion analysis.
What can an uncertainty interval add? In general, a confidence interval conveys a range of values compatible with an estimate under the method’s assumptions. A narrow interval indicates greater precision than a wide interval, but neither one alone establishes that an estimate is accurate or clinically meaningful. The registry record does not include a confidence interval for the primary outcome or a statistical analysis entry. No interval or precision estimate should be inferred from the enrollment count alone.
What is not documented? The registry lists one outcome measure and zero analyses. It does not report the outcome’s numerical estimate, the number of usable measurements, missing-data handling, an analysis population, a prespecified model, adjustment variables, interim analyses or multiplicity procedures. Those features are important when judging how results were generated and how much uncertainty remains. Their absence from the registry record does not prove they were absent from all study documents; it means they are not documented in this registry entry.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure and zero analyses. It does not report a statistical analysis plan, the analysis population, or whether the registered endpoint was analyzed as a single prespecified measure or in additional forms. It also does not report interim analyses or a multiplicity strategy.
In general, multiplicity arises when several hypotheses or outcomes are tested. Repeated testing can increase the chance of at least one apparently notable result arising by chance, so a prespecified approach to interpreting multiple tests can matter. The registry record does not say whether any such tests were conducted, and it does not support assuming either that multiplicity was present or that it was controlled.
Missing-data methods are also not reported in the registry record. There is no description of whether any measurements were missing or unusable, how such cases were handled, or whether the analysis included all enrolled subjects. Enrollment of 233 does not by itself establish the number with an available primary measurement. The record also does not define an intention-to-treat, per-protocol or other analysis population.
These gaps limit assessment of possible selection effects, analysis choices and uncertainty. They should be read as omissions from the registry record, not as proof that the study team did not make or document such decisions elsewhere.
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 |
|---|---|---|---|
| General Population | 0 | 233 | 0.0% |
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 |
|---|---|
| General Population | 0 of 233 |
The registry’s adverse-event entry lists a General Population group with 233 at risk for serious adverse events and 0 affected. It also lists 233 at risk for other adverse events and 0 affected. No serious adverse-event terms are listed. The deaths field is null, so a death count is not reported in the registry record.
These figures describe what is entered in the registry, not a comparison between randomized treatment groups. The study is categorized as “other,” and the record says it was not a randomized comparison with like-for-like control arms. The adverse-event entry does not identify a treatment contrast or provide event rates by intervention and comparator.
A reported zero affected is a registry count of zero for the listed category; it is not an estimate proving that the risk is absent. Interpretation also depends on how events were defined, collected and followed. The registry record does not report those details, the safety-monitoring method, or a follow-up period for adverse events. The single-visit timeframe belongs to the primary tear-osmolarity outcome and should not be assumed to define safety follow-up. The safety figures therefore need to be read as limited registry reporting rather than as a comprehensive estimate of risk.
12. What the Result Does, and Does Not, Mean
The registry record describes a completed study intended to validate performance of the OcuSense TearLab™ osmolarity test when used by health care professionals in physician office laboratories. Its primary outcome is a tear-osmolarity measurement in human subjects at a single visit. The stated objective also refers to contrived tear samples. This information clarifies what the study set out to examine and how the registered human measurement was defined.
The record does not report the numerical mean or full range for the primary outcome. It therefore cannot show the actual level or spread of the measured values. It also does not include an analysis entry or uncertainty interval from which to judge precision. The enrollment count alone cannot replace those results.
The study description specifically says that no gold-standard method was used to establish dry eye status and that diagnostic performance was not the purpose. Thus, the record does not establish how well the device classifies dry eye, whether it agrees with an independent reference method, or how measurements differ across the described health-status categories. Those questions require information not reported in the registry record.
The study is not presented as a randomized comparison, and the record cautions that the arms are not like-for-like controls. It should not be interpreted as showing a causal effect of one assigned treatment over another. It is also not evidence about treatment benefit. The registered outcome concerns measurement, not a clinical intervention.
In general, validation evidence is tied to the intended use, operators, sampling conditions and comparison methods examined. The objective names physician office laboratories, health care professionals, human tear fluid and contrived samples, but the registry does not give detailed results by operator, sample type or subject category. Consequently, the entry alone does not support broader claims about performance in settings or circumstances not described in the record.
The most defensible interpretation is limited: the registry records a study of TearLab tear-osmolarity measurement, with a specified single-visit outcome and a stated measurement-focused objective. The outcome values and analysis details needed to evaluate the magnitude, variability and precision of performance are not reported in the registry record.
13. Why This Trial Matters Statistically
This study is statistically important because it illustrates why the question a study was designed to answer must be separated from a question readers may hope to answer. A device can be studied as a way to obtain a measurement without being evaluated as a diagnostic classifier. The registry explicitly frames the objective around measuring tear osmolarity and says no gold-standard method was used to establish dry eye status. That distinction prevents measurement validation from being mistaken for diagnostic-accuracy evidence.
The endpoint definition also makes clear that summaries are not results. A mean and full range specify ways of describing measurements, but interpretation depends on the observed values and their uncertainty. Those numerical results are not reported in the registry record. Without them, readers cannot assess the actual central value, spread or precision, even though the intended summary is described.
The record further illustrates the importance of distinguishing a trial’s design from a planning calculation. Illustrative sample-size calculations assume equal allocation between two arms, a normal approximation and a stated significance level. The study itself is not described as randomized, allocation is not stated, and the arms are not characterized as like-for-like controls. Planning assumptions should not be retroactively treated as the actual design or as evidence of observed power.
Finally, the absence of analysis details matters to statistical interpretation. The registry lists zero analyses and does not describe missing-data handling, analysis populations, multiplicity procedures or interim analyses. These omissions do not establish that such methods were never used, but they prevent readers from evaluating them from the registry entry. This case therefore highlights the value of transparent reporting of endpoint results, uncertainty and analysis methods alongside a clear statement of the intended measurement question.
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.
Several limitations are specific to the information recorded for this study. First, the primary endpoint is defined, but its numerical mean and full range are not reported in the registry record. The record therefore does not permit readers to judge the magnitude or variability of the actual tear-osmolarity measurements. It also provides no confidence interval or other estimate of precision.
Second, the registry states that no gold-standard method was used to establish dry eye status and that diagnostic performance was not the objective. This rules out treating the registered measurement outcome as evidence of sensitivity, specificity or diagnostic agreement. The population description includes healthy volunteers and subjects with specified diagnoses, but group-specific counts and outcome results are not reported.
Third, this was not a randomized comparison. Allocation is not stated, and the record cautions that the arms are not like-for-like controls. The entry does not provide a comparative analysis that could support a causal contrast. It also does not explain how human tear samples and contrived samples were incorporated into the study’s results.
Fourth, the registry lists zero analyses and does not report the statistical analysis plan, analysis populations, missing-data handling, interim analyses or multiplicity procedures. These omissions limit assessment of the analysis process. They should not be taken as evidence that such procedures did not exist outside the registry.
Finally, the outcome’s unit is written as mOsms/L in one field and mOsm/L in its description, without an explanation. The registry record also does not provide detailed operator, sample-quality, repeatability or safety-follow-up methods. These points restrict the amount of measurement and safety performance that can be independently assessed from this record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Validation of TearLab Osmometer - Human Factor Usability Report — NCT00731484.
- Registry record last updated 2016-04-12; status last verified 2016-02.
- Results first posted 2011-05-03.
- 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
NCT00731484 is a completed study titled “Validation of TearLab Osmometer - Human Factor Usability Report,” sponsored by TearLab Corporation. The registry records a start of 2008-07, primary completion of 2009-03 and enrollment of 233. It describes an objective of validating TearLab tear-osmolarity measurement in physician office laboratories with health care professionals, using human tear fluid and contrived tear samples.
The primary outcome is tear osmolarity measured by the TearLab System at a single visit. The stated summary is a mean with full range as dispersion. The registry lists one outcome measure and zero analyses. It says the study was not designed to assess diagnostic performance, because no gold-standard method was used to establish dry eye status. Numerical outcome results and detailed analysis methods are not reported in the registry record.