Navigator II Continuous Glucose Monitor Home Use Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Navigator II Continuous Glucose Monitor Home Use Study (NCT01455064), a registered phase not stated study. The primary outcome is Clarke Error Grid Analysis.

2. Clinical Question

The study was framed as a home-use performance evaluation of an investigational continuous glucose monitoring system in people with diabetes. Its primary endpoint concerns how sensor results compare with a blood glucose reference when categorized using the Clarke Error Grid. The question is therefore about the distribution of results across specified accuracy and acceptability zones, not about a treatment effect against a randomized control group.

The registry record does not report the percentages in either zone grouping, the number of sensor results contributing to those percentages, or an uncertainty estimate. It is therefore not possible to describe the observed level of agreement or its precision from the registry record. The clinical question can be identified, but its numerical answer is not reported in the registry record.

3. Trial Design

The record describes a completed home-use evaluation of the FreeStyle Navigator II Continuous Glucose Monitoring System, sponsored by Abbott Diabetes Care. Enrollment was 31. The study began in 2011-10, and primary completion was in 2011-12. The stated purpose was to evaluate system performance in a home-use environment over a 15 day period in people with diabetes.

The listed group is an observational group for people with type 1 or type 2 diabetes using MDI or a pump. The record does not describe a randomized allocation, and its notes caution that this is not a randomized comparison and that the arms are not a like-for-like control comparison. No comparator arm or allocation procedure is reported in the registry record. The system is listed as a device intervention.

The primary outcome is Clarke Error Grid Analysis, expressed as a percentage of results, with a timeframe of 15 days sensor wear. Its description identifies the proportions in Zone A and Zones A and B compared with blood glucose reference. The registry record lists one outcome measure and no analyses. It does not report the outcome values or an analysis population description beyond noting that a participant who withdrew because of a mild reaction to the sensor adhesive contributed data up to withdrawal.

The record does not report the protocol’s intended sample-size justification, a statistical analysis plan, or the procedures used to select or summarize sensor readings. The enrollment count describes the number enrolled; it should not be read as the number of valid sensor observations or as evidence of a particular level of statistical precision.

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

Analysis population for the primary outcome, as defined in the registry: One subject was withdrawn due to a mild reaction to the sensor adhesive. This subject's data was included in the study up to the point of withdrawal.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Clarke Error Grid Analysis, measured over 15 days sensor wear.

The primary endpoint uses the Clarke Error Grid to classify continuous glucose monitoring results against a blood glucose reference. The registry describes two summaries: the percentage of results in Zone A, called clinically accurate, and the percentage in Zones A and B together, called clinically acceptable. These summaries address how often readings fall within categories defined by the grid rather than reporting a single average difference between sensor and reference measurements.

In general, a categorical accuracy summary can make the distribution of measurement errors easier to interpret by distinguishing categories with different clinical meanings. The Zone A percentage focuses on the category described as clinically accurate. Combining Zones A and B gives a broader summary using the record’s stated clinically acceptable grouping. Neither summary, on its own, conveys every aspect of measurement performance: the category totals do not reveal the size or direction of individual errors, and their interpretation depends on the classification method and reference measurements.

The registry record gives the endpoint definition and timeframe, but not either percentage, the number of readings analyzed, or an uncertainty interval. The endpoint’s numerical findings and precision are therefore not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a percentage based on classifying continuous glucose monitoring results against blood glucose reference using the Clarke Error Grid. The record describes the percentage in Zone A and the percentage in Zones A and B combined. It does not report the calculated percentages, the number of underlying readings, or the statistical procedure used to produce them.

What does a percentage endpoint describe?

In general, a percentage expresses the share of observations that meet a stated criterion. For this endpoint, the criterion is membership in a specified Error Grid zone. The unit is listed as percentage of results, so the summary concerns readings rather than directly representing a percentage of participants. A reading-based percentage and a participant-based percentage answer different questions: the former weights readings, while the latter would summarize participant-level outcomes. The registry record does not say whether each participant contributed the same number of readings or how repeated readings were incorporated.

The two zone summaries have related but distinct interpretations. The Zone A summary is limited to the category described as clinically accurate. The combined Zones A and B summary includes the broader grouping described as clinically acceptable. Neither percentage is reported in the registry record. The record also does not give the counts that would allow a reader to see how many readings fell inside or outside either grouping.

Why does uncertainty matter?

In general, an estimate from a sample has uncertainty because a different sample or set of measurements could yield a different estimate. A confidence interval is a range constructed by a statistical procedure to express uncertainty around an estimate under its assumptions. A narrow interval typically indicates greater precision than a wide interval, but it does not by itself establish that the design or measurements are unbiased. No confidence interval or other uncertainty estimate for the primary endpoint is reported in the registry record.

For repeated sensor readings, an important general consideration is dependence among observations from the same person. Readings from one participant can share characteristics, so treating each reading as unrelated to every other reading may underestimate uncertainty. Methods that account for clustering or summarize data at participant level can address this dependence in different ways. The registry record does not report which approach, if any, was used. It also does not state how reference measurements and sensor readings were matched over time.

What can the enrollment count establish?

Enrollment of 31 describes the number of participants enrolled, not the number of endpoint observations. It does not by itself show how many participants contributed to the reported endpoint, how many readings were usable, or how precisely the percentages could be estimated. The record notes that a participant withdrew following a mild sensor adhesive reaction and that the participant’s data were included up to withdrawal. It does not explain how the reduction in available observations after withdrawal was handled in the endpoint calculation.

The record lists no analyses, and numerical outcome results are not reported. As a result, there is no posted estimate from which to assess the observed effect or its uncertainty. In general, a statistical analysis plan would specify the analysis population, treatment of repeated measurements and missing data, and any inferential procedures. These details are not reported in the registry record and should not be inferred from the endpoint description.

How should planning illustrations be read?

In general, sample-size calculations are prospective planning exercises based on assumptions about the effect to detect, variability, significance level, power, and design. The assumptions described for planning illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the target effect is expressed as a fraction of an observed effect. These are assumptions for illustrations, not evidence that the trial used a two-arm randomized design or that its protocol specified those choices. The registry record describes an observational group and does not state an allocation procedure.

Such planning illustrations are not observed power and do not replace an estimate with a confidence interval. The stated conventions distinguish participant counts per arm from event totals for time-to-event calculations, but no endpoint result or observed effect is reported in the registry record. Without a reported estimate, a reader cannot use the record to evaluate the assumptions’ relevance to this trial. Any sample-size figures should therefore be understood as planning scenarios rather than observed trial findings or a reconstruction of the trial’s design justification.

Overall, the endpoint is identifiable, while the analytic details needed to evaluate its calculation and precision are not. Statistical interpretation would require the outcome percentages, the denominator of readings, the handling of within-participant dependence and missing readings, and the method used to form uncertainty estimates. These details are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure, the Clarke Error Grid Analysis endpoint, and no analyses. That record does not establish whether the study protocol designated this endpoint as the sole primary analysis, whether additional outcomes were assessed outside the registry listing, or whether multiple statistical tests were planned. A multiplicity adjustment or testing hierarchy is not reported in the registry record.

In general, multiplicity arises when several outcomes, comparisons, subgroups, or repeated tests are examined. Conducting many tests can increase the chance of at least one apparently notable result arising by chance. A prespecified analysis plan can clarify which questions are primary and how multiple tests will be interpreted. The registry record does not report enough information to determine whether multiplicity was relevant or how it would have been handled.

Missing-data procedures and the primary analysis population are also not reported in the registry record. The record notes that one participant withdrew due to a mild reaction to the sensor adhesive and that the participant’s data were included up to withdrawal. This does not specify how readings after withdrawal were treated, whether other readings were unavailable, or whether the analysis used all available readings or a defined subset. It also does not state whether the endpoint was summarized at the reading level or participant level.

In general, missing observations can affect an estimate when the availability of measurements is related to participant characteristics, device use, or the measurement itself. Statistical methods may make different assumptions about why data are missing; those assumptions cannot be checked from a withdrawal note alone. The registry record does not describe an imputation method, a sensitivity analysis, or a rule for excluding incomplete records. These omissions limit assessment of how the reported endpoint, if available, would represent the enrolled participants.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The registry record lists 0 serious adverse events among 31 participants in the observational group. It lists 4 other adverse events among 31 participants. These are counts recorded for the group; they do not give the timing, duration, severity details for the other events, or causal relationship to the device. The record does not list serious adverse event terms, and deaths are not reported in the registry record.

The record separately notes that one participant was withdrawn because of a mild reaction to the sensor adhesive, with that participant’s data included up to the point of withdrawal. It does not explicitly link that note to a particular entry among the other adverse events, so the two details should not be combined or treated as independent counts beyond what is stated.

In general, adverse event counts describe events recorded during a study and do not by themselves establish whether an intervention caused an event. Their interpretation depends on definitions, observation time, completeness of reporting, and the study design. The registry record does not provide the detailed event listings or follow-up information needed to assess those features. The absence of listed serious events in this group should therefore be read as a registry count, not as proof that serious events cannot occur.

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

The registry record establishes that the study was a completed home-use evaluation of the FreeStyle Navigator II Continuous Glucose Monitoring System in people with diabetes, with enrollment of 31 and a primary endpoint based on the Clarke Error Grid over 15 days sensor wear. It identifies the intended measurement comparison: continuous glucose monitoring results against blood glucose reference, summarized for Zone A and Zones A and B together.

What the record does not establish is the numerical performance result. Neither percentage is reported, and there are no posted analyses or precision estimates. Thus, no claim about the amount of agreement, the proportion of readings in either zone, or the certainty of an estimate can be drawn from this registry record. Missing numerical results should not be interpreted as evidence in favor of or against any particular level of performance.

The design context also matters. The record describes an observational group and does not state an allocation procedure or a like-for-like control comparison. The endpoint is therefore described as a measurement-performance summary rather than a randomized treatment contrast. An observational performance evaluation can address the specified comparison with a reference under the study conditions, but the record alone does not establish comparative effects between assigned groups.

In general, a study’s estimate is most informative when its population, measurement methods, analysis rules, and uncertainty are clear. The record identifies the broad population and timeframe, but does not report the number of sensor readings analyzed, the handling of repeated readings or missing data, or the method used to calculate uncertainty. These gaps limit the statistical interpretation of the endpoint even apart from the absent numerical values.

The record notes a mild sensor adhesive reaction that led to withdrawal and states that the participant’s data were included through withdrawal. It also lists 0 serious adverse events and 4 other adverse events in the observational group. Those counts describe the registry’s safety entries; they do not establish causation or characterize risk beyond the study record. Overall, the study question is clear, but the registry record does not provide the results needed to answer it quantitatively.

13. Why This Trial Matters Statistically

This trial is statistically interesting because its primary endpoint is a measurement-agreement summary rather than a conventional comparison of outcomes between randomized groups. The Clarke Error Grid categorizes sensor results relative to blood glucose reference, and the record specifies summaries for Zone A and Zones A and B together. Understanding what a percentage counts—and what it leaves out—is central to interpreting this kind of endpoint.

The outcome is stated as a percentage of results, while enrollment is reported as 31 participants. Those are different units. The number of participants does not reveal the number of readings contributing to a percentage, and multiple readings from the same participant may be related. In general, the choice of analysis unit and treatment of within-participant dependence affect how uncertainty should be estimated. The registry record does not report these analytic details.

The record also illustrates why an endpoint definition is not the same as an endpoint result. It gives a clear description of the intended comparison and timeframe, but the numerical percentages and their precision are not reported. Without them, statistical interpretation cannot proceed from the research question to an estimate of observed performance.

Finally, the record’s observational design description sets limits on the kinds of comparisons it can support. Allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. Planning conventions based on equal allocation between two arms should not be confused with evidence of the actual study design. These distinctions—measurement endpoint versus treatment contrast, participant count versus reading count, and planning assumption versus observed result—are broadly important in clinical biostatistics.

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 specific to this registry record constrain interpretation. The primary endpoint is named and described, but neither of its numerical percentages is reported. There is no confidence interval or other uncertainty estimate. The number of readings contributing to the endpoint is also not reported, so the denominator and measurement-level completeness cannot be assessed.

The record identifies an observational group and states that allocation is not stated. It cautions that the arms are not a like-for-like control comparison. Accordingly, the record does not support treating the evaluation as a randomized comparison. Details of participant selection, system use, reference measurement procedures, and matching of sensor results to the reference are not reported in the registry record.

Although enrollment is 31, the record does not specify how many participants contributed endpoint data or whether all enrolled participants were included in the primary analysis. It notes a withdrawal after a mild sensor adhesive reaction and inclusion of that participant’s data up to withdrawal, but does not explain how unavailable observations were handled. The analysis unit, management of repeated readings, and any methods for accounting for dependence are not reported in the registry record.

The registry lists one outcome measure and no analyses. The statistical plan, sample-size justification, multiplicity procedures, and any interim analyses are not reported in the registry record. Planning assumptions described for illustrative calculations should not be read as the trial’s own design justification or analysis plan.

The adverse event entries provide group counts, but not detailed event terms for the other adverse events, timing, follow-up duration, or causal assessments. These omissions limit interpretation of safety entries. Collectively, the absent numerical endpoint results and analytic details prevent assessment of the endpoint’s magnitude, precision, and robustness from this record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Navigator II Continuous Glucose Monitor Home Use Study — NCT01455064.
• Registry record last updated 2013-07-22; status last verified 2013-05.
• Results first posted 2013-07-22.
• 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.

18. Record Summary

The registry record describes a completed home-use evaluation of the FreeStyle Navigator II Continuous Glucose Monitoring System, sponsored by Abbott Diabetes Care. Enrollment was 31, and the primary endpoint was Clarke Error Grid Analysis over 15 days sensor wear, comparing continuous glucose monitoring results with blood glucose reference. The record specifies percentages for Zone A and Zones A and B together but does not report their numerical results.

The study is listed as observational, with allocation not stated and no like-for-like control comparison. One participant withdrew because of a mild sensor adhesive reaction; the record states that data were included up to withdrawal. It lists 0 serious adverse events and 4 other adverse events among 31 participants. The registry lists one outcome measure and no analyses. The outcome values, uncertainty estimates, and key analysis procedures are not reported in the registry record.