Remote Home Prothrombin Time (PT)/International Normalized Ratio (INR) Monitoring and Patient Management System: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Remote Home Prothrombin Time (PT)/International Normalized Ratio (INR) Monitoring and Patient Management System (NCT00978445), a randomized na study. The primary outcome is Time Spent Per PT/INR Monitoring Encounter.

2. Clinical Question

The trial concerns time spent on PT/INR monitoring encounters under a remote home protocol and a standard protocol involving clinic INR testing and caregiver interaction. The registry identifies venous thromboembolism as the condition and describes long-term anticoagulation management as the clinical context. It explains that anticoagulation requires monitoring of PT/INR to guide treatment, and that the home system was intended to support testing, patient questions, scheduling, and dosage management.

The primary endpoint is encounter time, measured in minutes. The registry describes measurement once per week during a 12 week study. Its stated comparison is the time spent measuring coagulation under the standard protocol versus the home protocol. This is an operational question about the monitoring process; it is not, by itself, a measure of anticoagulation control, clinical events, or patient satisfaction.

The registry also lists quality-of-life measures as a secondary outcome, including patient satisfaction and anticoagulation satisfaction instruments. Numerical results for that outcome are not reported in the registry record. The main posted numerical outcome is the mean time per monitoring encounter for each protocol.

3. Trial Design

The registry classifies this as a randomized crossover trial with no masking. It lists the study status as completed and records enrollment of 25. The study start is recorded as 2009-09 and primary completion as 2010-08. The phase is listed as not applicable. The sponsor is ZIN Technologies, Inc.

A crossover design assigns participants to experience more than one monitoring condition, with the sequence varying between groups. The registry names the sequences Home/Standard and Standard/Home. Its descriptions refer to home and clinic INR procedures and caregiver interaction, but the wording does not clearly resolve every detail of how each protocol was delivered in each period. The registry record does not report period-specific timing, washout procedures, or other details needed to characterize the conduct of the crossover more fully.

Because a crossover design can allow each participant to contribute observations under both conditions, the relation between measurements within the same participant matters statistically. The posted outcome rows give a mean and standard deviation for each protocol, with 22 observations reported for each. They do not provide participant-level paired measurements or explain how the observations relate across periods. Accordingly, the summaries alone do not establish whether the comparison accounted for pairing, sequence, or period.

The intervention is named the vMetrics protocol. The arm descriptions state that participants received the vMetrics protocol at home and in a clinical setting, while also describing standard and home procedures in different orders. This phrasing is not fully clear, so the distinction between the intervention system and the standard monitoring procedure should be read cautiously. No further operational detail is reported in the registry record.

The registry lists two outcome measures and one posted secondary outcome. There are no posted analyses for the primary comparison. The record does not report the randomization method, allocation concealment, a detailed statistical analysis plan, or whether any interim analyses were conducted. These design and analysis details are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: Clear enrollement criteria were created only real exclusion was if physician did not believe patient could perform protocol and if outside of age criteria.

Overall Study

Analysis population for the primary outcome, as defined in the registry: through minimum power study

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 Time Spent Per PT/INR Monitoring Encounter, measured over Once per week during 12 week study.

The primary endpoint is time spent per PT/INR monitoring encounter, expressed in minutes. The registry describes it as minutes spent measuring coagulation time of blood under the standard and home protocols. It specifies measurement once per week during a 12 week study and identifies the summary statistic as the mean, with standard deviation as the measure of spread.

Encounter time is a process measure: it describes the duration associated with monitoring rather than the quality of anticoagulation control or the occurrence of clinical outcomes. It can be useful when comparing the practical burden of alternative monitoring workflows. In general, a time measure may also reflect several components of care, such as testing and interaction with a caregiver; the registry does not define exactly which activities were timed or how timing began and ended.

The posted means are 19.4 minutes for the home protocol and 47.0 minutes for the standard protocol. The corresponding standard deviations are 2.3 and 2.6. These summaries describe the reported encounter times, but do not show the distribution of participant-level changes or the uncertainty around a protocol comparison. No confidence interval, test statistic, or p-value for the primary endpoint is posted.

The registry’s timeframe includes recurring monitoring during the study, but it does not explain whether the posted summary combines repeated measurements, how many measurements contributed for each participant, or how missing measurements were handled. Those details affect the interpretation of a mean in a crossover study and are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary measure as continuous and summarizes it with a mean and standard deviation. A mean gives the arithmetic average of measured encounter times. A standard deviation describes how dispersed individual measurements are around that average. It is not the same as the uncertainty of the mean or of a difference between protocols.

What does a confidence interval add?

In general, a confidence interval gives a range of values compatible with the data and the analysis assumptions, expressing uncertainty around an estimate. A narrow interval indicates greater precision than a wide interval, while an interval spanning values with different practical implications may leave the result inconclusive. The registry record does not report a confidence interval for the primary comparison, so its precision cannot be read directly from the posted means and standard deviations.

Why does the crossover structure matter?

In general, crossover studies collect measurements under different conditions from the same participants. A paired analysis uses the within-participant relationship rather than treating the protocol groups as if they necessarily came from unrelated people. When measurements within a participant are positively associated, analyzing paired changes can yield a different uncertainty estimate from an analysis that ignores pairing. Sequence and period can also matter: measurements may differ over time or because participants experience one condition before another. The registry identifies a crossover model and two sequences, but does not report the method used to account for pairing, sequence, or period.

The reported means and standard deviations are marginal summaries for the protocols. They do not contain the participant-level paired differences or the covariance between repeated measurements. Reconstructing a paired test or interval would require information not present in the registry record. The registry lists no analyses for the outcome, so the sponsor’s inferential analysis is not available in the posted results.

What does the planning illustration represent?

General sample-size planning estimates the number of participants that might be needed under specified assumptions to detect a chosen effect with a chosen statistical power. The planning illustration associated with these results is described as based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation; it considers the stated fraction of the observed effect. Such values are planning illustrations, not observed power and not evidence that the trial was designed with those assumptions. The registry does not report its own sample-size justification, so that justification is not reported in the registry record.

A planning calculation based on an observed effect is especially sensitive to the estimate used as its starting point. In general, an effect estimated imprecisely in a small study may be an unstable basis for planning a future study. Planning results also depend on the target effect and analysis assumptions. The illustration should therefore be understood as conditional guidance, not as a finding about the trial’s ability to detect an effect. No numerical planning outputs are stated in the registry record.

How should the mean and standard deviation be read?

For this continuous endpoint, the mean summarizes typical encounter time on the scale of minutes. The standard deviation describes observed spread, not a range containing a fixed proportion of all values in every dataset. In general, a mean can be affected by unusually long or short observations, and a standard deviation does not show the shape of the distribution. The registry does not provide a distribution plot, median, range, or participant-level values for this endpoint.

The posted values are 19.4 with standard deviation 2.3 for the home protocol, and 47.0 with standard deviation 2.6 for the standard protocol. These summaries support a descriptive comparison of the reported averages. They do not, on their own, account for repeated observations, missing data, or the crossover correlation structure, nor do they provide an uncertainty interval for a protocol effect.

What is not reported about the analysis?

The registry does not state which statistical test or model was planned or used, whether adjustments were made, how repeated weekly measurements were reduced or modeled, or how any departures from the planned analysis were handled. The record also does not provide an analysis population definition. These omissions limit reproducibility and make it difficult to evaluate whether the reported summaries represent all intended observations or a selected subset.

General statistical interpretation therefore separates three things: the observed descriptive summaries, the analysis model used to estimate a protocol contrast, and the uncertainty attached to that contrast. Only the first is available in the posted primary outcome. The stated planning assumptions concern hypothetical future design choices and do not supply the missing inferential analysis for this trial.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and one posted secondary outcome, described as changes in quality of life based on several questionnaires. Numerical secondary results are not reported in the registry record. The record does not explain how outcome multiplicity was addressed, whether any outcomes were designated as key secondary measures, or whether adjustment for multiple comparisons was planned. The approach to multiplicity is therefore not reported in the registry record.

Multiplicity matters in general when several outcomes, time points, or analyses are examined. Repeated opportunities to test hypotheses can increase the chance of finding an apparently notable result by chance. Statistical strategies may prioritize a primary endpoint, adjust inference, or treat secondary analyses as exploratory. No such strategy is described for this trial, so the strength of any secondary finding cannot be evaluated from the record.

The primary outcome rows report 22 observations for each protocol, while enrollment is listed as 25. The record does not describe participant disposition, the amount or pattern of missing outcome data, reasons for missingness, or an imputation method. It also does not state whether the posted summaries use all randomized participants, participants with available measurements, or another analysis population. These details are not reported in the registry record.

Missingness can affect interpretation if participants without recorded times differ systematically from those with recorded times. In a crossover study, missing a measurement in one period can also complicate paired comparisons. These are general concerns, not claims about what happened in this trial. Without details on missing data and analysis populations, the representativeness of the posted summaries cannot be assessed.

The registry reports no primary analyses. It does not report whether any planned analyses were omitted or whether any interim analyses occurred. Those matters are not reported in the registry record.

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.

The registry’s safety summary lists 25 participants at risk for serious adverse events and records 0 affected. It also lists 25 at risk for other adverse events and records 0 affected. These figures describe what the registry reports; they do not provide event-level follow-up details or a time-specific rate.

The death field is not populated with a count, so deaths are not reported in the registry record. No serious adverse event terms are listed. A count of 0 affected in the posted summary means no affected participants are recorded in that field; it should not be expanded into a claim about every possible event, every period of exposure, or safety outside the trial.

In general, adverse-event counts depend on how events were defined, collected, and followed. The registry record does not provide the observation window, event-collection procedures, severity grading, or a breakdown by monitoring protocol or crossover period. It also does not report a comparative safety analysis. The posted safety numbers therefore offer a limited descriptive account and do not establish that the protocols have equivalent safety profiles.

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

The main descriptive result is that the posted average time per encounter is 19.4 minutes for the home protocol and 47.0 minutes for the standard protocol. The registry gives standard deviations of 2.3 and 2.6, respectively, and lists 22 observations for each protocol. This pattern describes the reported monitoring times; it does not by itself answer whether the protocol effect is estimated precisely or whether it would be reproduced in another setting.

No inferential primary comparison is posted. There is no reported confidence interval or p-value, and no analysis method is described. The registry’s means cannot be treated as proof of a statistically established difference. Nor do they establish equivalence: an equivalence conclusion generally requires a prespecified margin and an analysis showing that uncertainty is sufficiently limited relative to that margin. Such information is not reported in the registry record.

The endpoint measures time spent during monitoring encounters. It does not report whether INR values were within a therapeutic range, whether thrombotic or bleeding outcomes differed, or whether anticoagulation management was clinically equivalent. The registry’s brief summary describes an aim to assess efficiency and confirm equivalent care standards, but the posted primary outcome is an encounter-time measure, and the corresponding equivalence analysis is not reported.

The registry lists a quality-of-life secondary outcome but does not report numerical results for it. The posted safety summary records 0 participants affected by serious adverse events and 0 affected by other adverse events among 25 at risk in each category; deaths are not reported in the registry record. These safety entries do not supply a comparison between protocols.

The result is therefore best read as a descriptive account of encounter duration, alongside substantial gaps in inferential and operational detail. The summaries do not show individual paired changes, explain missing measurements, or establish how repeated observations were analyzed. They should not be interpreted as evidence about clinical effectiveness or as a recommendation for patient care.

13. Why This Trial Matters Statistically

This trial is statistically notable because it combines a repeated-measures question with a practical workflow endpoint. In a crossover design, each participant may contribute measurements under more than one protocol. That structure can make within-participant comparisons informative, but it also means the association between measurements and the order of exposure may matter for uncertainty and interpretation.

The registry posts separate means and standard deviations for the home and standard protocols, but no paired comparison or model. For readers, this illustrates why descriptive summaries do not always capture the information needed for inference. In general, a comparison based on paired data can depend on the distribution of within-participant differences, which cannot be recovered from the two marginal means and standard deviations alone.

The endpoint also illustrates the distinction between efficiency and clinical outcomes. Time per encounter can characterize a feature of service delivery, but it does not establish anticoagulation control, clinical safety, or equivalence of care. Claims should stay aligned with the endpoint actually reported.

Finally, the record shows the value of transparent reporting beyond a headline average. A statistical assessment would be easier to interpret with a stated analysis plan, a definition of the analysis population, details on repeated measurements and missing data, and an estimate with its uncertainty. These items are not reported in the registry record. The available summaries still permit a descriptive reading, but not a full evaluation of the precision or robustness of the comparison.

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 principal limitation is the absence of an inferential analysis for the primary outcome. The registry lists no analyses and gives no confidence interval, test result, or model specification. Consequently, the precision of the comparison and the strength of evidence for a protocol effect cannot be assessed from the posted results.

The crossover design raises additional questions that the record does not resolve. It names Home/Standard and Standard/Home sequences but does not clearly document the period structure, timing procedures, or the analysis of sequence and period effects. The primary outcome is described as occurring once per week during a 12 week study, yet the record does not explain how repeated times were combined or modeled. Nor does it report the within-participant association needed to reconstruct a paired comparison.

Enrollment is recorded as 25, while the protocol outcome rows list 22 observations each. The record does not explain participant flow, missing measurements, exclusions, or the analysis population. This limits assessment of whether the summaries represent the randomized population or a subset with available observations.

The endpoint description does not specify the exact activities included in timing, how timing was performed, or whether the measure reflects testing alone or other encounter activities. The arm descriptions also leave some ambiguity about the distinction and ordering of the home and standard procedures. These uncertainties affect the operational meaning of the outcome.

Finally, the registry does not report the trial’s sample-size justification, detailed statistical plan, multiplicity strategy, or interim analyses. The quality-of-life outcome has no numerical result posted. Safety data are limited to summary counts, with deaths not reported and no event terms listed. Each of these omissions narrows what can be concluded from the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Remote Home Prothrombin Time (PT)/International Normalized Ratio (INR) Monitoring and Patient Management System — NCT00978445.
• Registry record last updated 2013-03-21; status last verified 2013-03.
• Results first posted 2013-03-21.
• 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 describes a completed, randomized, unmasked crossover study of the vMetrics remote home PT/INR monitoring and patient management system. It lists venous thromboembolism as the condition, enrollment of 25, and a study start of 2009-09 with primary completion in 2010-08.

The primary endpoint is mean time per PT/INR monitoring encounter, in minutes, measured once per week during a 12 week study. The posted mean is 19.4 with standard deviation 2.3 for the home protocol and 47.0 with standard deviation 2.6 for the standard protocol; each row lists 22 observations. No inferential primary analysis is posted.

The registry lists a quality-of-life secondary outcome without numerical results. Its safety summary records 0 affected by serious adverse events and 0 affected by other adverse events among 25 at risk in each category; deaths are not reported in the registry record. Important analysis, missing-data, and crossover details are also not reported.