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 Circadian Brown Adipose Tissue Metabolism (NCT02285270), a na na study. The primary outcome is Change in Maximum Standardized Update Value (SUVmax) in Brown Adipose Tissue FDG Uptake in the Neck or Upper Chest on Evening and Imaging Compared to Morning Imaging.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02285270 |
| Phase | NA |
| Condition | Healthy |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 10 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of Pennsylvania |
| Results posted | Yes |
2. Clinical Question
Population
Healthy volunteers. The registry lists 10 participants enrolled and gives the condition as Healthy. The primary outcome description says no patients were analyzed because none showed FDG uptake in brown adipose tissue.
Intervention
FDG PET/CT, a diagnostic test/procedure used to image uptake of the glucose analog F-18 FDG. The study aimed to generate pilot data about possible circadian variation in brown adipose tissue activation in healthy humans.
Comparator
Morning imaging was compared with evening imaging, with the primary endpoint describing the evening imaging in relation to the morning imaging. The registry identifies a single-group assignment, not separate intervention and control arms.
Primary question
Does maximum standardized uptake value, or SUVmax, in brown adipose tissue in the neck or upper chest change between morning and evening imaging at an approximately 12-hour timeframe? The registry reports no analyzed patients for this endpoint because no patient showed brown adipose tissue FDG uptake.
3. Trial Design
This was a completed pilot study of circadian variation in brown adipose tissue metabolism in healthy volunteers. The official title describes an investigation of circadian variations in brown adipose tissue metabolism, and the stated purpose was to generate pilot data on potential circadian variation in brown fat activation in healthy humans. The registry lists 10 participants enrolled. The sponsor was the University of Pennsylvania.
The design is recorded as a single-group assignment, with FDG PET/CT listed as the diagnostic test or procedure. Allocation is recorded as NA and masking as none. The registry does not describe a randomized treatment comparison or a separate control group. Morning and evening imaging are the comparison occasions stated for the primary endpoint; they should not be mistaken for independently randomized arms.
The study started in 2014-03, reached primary completion in 2015-04, and is recorded as completed. The phase is listed as NA. The registry record does not report a sample-size justification, detailed imaging schedule, or fuller protocol description. The stated timeframe for the primary endpoint is approximately 12-hours.
The primary outcome concerns change in SUVmax in brown adipose tissue FDG uptake in the neck or upper chest on evening imaging compared with morning imaging. The primary outcome description also states that no patients were analyzed because no patient showed FDG uptake in brown adipose tissue. Thus, enrollment does not mean that an analyzable primary endpoint was obtained for those participants.
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 | Single Group Assignment |
|---|---|
| STARTED | 10 |
| COMPLETED | 5 |
| NOT COMPLETED | 5 |
Reasons for not completing this period:
| Reason | Single Group Assignment |
|---|---|
| Lost to Follow-up | 1 |
| Physician Decision | 3 |
| Determined to be ineligible | 1 |
Analysis population for the primary outcome, as defined in the registry: No patients were analyzed since no patient showed uptake of FDG in brown adipose tissue.
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 | Single Group Assignment |
|---|---|---|
| Participants analysed | 10 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 10 |
| Age, Categorical: >=65 years | Participants | 0 |
| Gender: Female | Participants | 0 |
| Gender: Male | Participants | 10 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 10 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 1 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 1 |
| Race (NIH/OMB): White | Participants | 8 |
| Race (NIH/OMB): More than one race | Participants | 0 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
6. Primary Endpoint
The registry lists the primary outcome as Change in Maximum Standardized Update Value (SUVmax) in Brown Adipose Tissue FDG Uptake in the Neck or Upper Chest on Evening and Imaging Compared to Morning Imaging, measured over ~12-hours.
| Element | Registry entry |
|---|---|
| Result type | N/A |
| Measure of spread | not applicable |
| Unit | not stated |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the change in maximum standardized uptake value, or SUVmax, for FDG uptake in brown adipose tissue in the neck or upper chest. It compares evening imaging with morning imaging over an approximately 12-hour timeframe. SUVmax is a PET imaging measure representing the highest standardized tracer uptake value in the assessed tissue. As a maximum, it characterizes the peak measured uptake rather than the total amount of brown adipose tissue or its average uptake.
FDG is a positron-emitting glucose analog. The study description explains that brown adipose tissue can use glucose as an energy source and that FDG PET/CT can image brown fat metabolism through FDG uptake. Comparing imaging at different times of day was intended to assess whether uptake varied in a way consistent with a circadian pattern. This makes the endpoint a measurement of tracer uptake, not a direct measurement of heat production or a clinical outcome.
The registry states that no patients were analyzed for the primary endpoint because no patient showed FDG uptake in brown adipose tissue. It therefore does not report an estimated change in SUVmax, an uncertainty interval, or a statistical test result for the primary comparison.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a pilot investigation of possible time-of-day variation in brown adipose tissue metabolism among healthy volunteers. Its primary question was framed as a comparison of SUVmax on evening and morning imaging. However, the registry explicitly states that no patients were analyzed for the primary endpoint because no patient showed FDG uptake in brown adipose tissue. The key statistical point is therefore not the size or direction of an estimated morning-to-evening change: the record gives no analyzed primary-endpoint estimate to interpret.
The enrollment figure is 10, but enrollment alone does not establish that 10 participants contributed data to the primary comparison. The registry's statement about no patients analyzed for that outcome means that a primary-endpoint result is unavailable in this record. The reason given is absence of detectable FDG uptake in brown adipose tissue, not a reported numerical comparison with an estimated effect.
The record lists three outcome measures and names two secondary outcomes: correlation between cortisol level and brown adipose tissue FDG uptake, and change in total brown adipose tissue FDG uptake measured as total segmented fat volume times mean SUV. It lists zero analyses. The registry does not report estimates or inferential results for those secondary outcomes. Their presence as outcome descriptions should not be read as evidence that results were obtained.
No confidence interval or p-value for the primary endpoint is reported in the registry record. A confidence interval would ordinarily communicate the range of effect sizes reasonably compatible with the data under a statistical model; without an analyzed endpoint estimate and interval, the precision of a morning-to-evening contrast cannot be assessed. Likewise, the record does not establish whether any observed difference would be small, large, or consistent across participants.
The safety record lists 10 at risk for serious adverse events and 0 affected; it also lists 10 at risk for other adverse events and 0 affected. These counts are descriptive safety reporting, not evidence about the primary imaging question. Deaths are not reported in the registry record. Taken together, the posted results provide study context and endpoint availability information, but no analyzed primary comparison from which to estimate circadian variation.
9. Statistical Methods Explained
Statistical interpretation depends on distinguishing the study question, the measurement, and the data available for analysis. The question was whether brown adipose tissue FDG uptake differed between morning and evening imaging. The measurement chosen for the primary endpoint was SUVmax in brown adipose tissue in the neck or upper chest. The registry's primary outcome description says that no patients were analyzed because none showed FDG uptake in brown adipose tissue. Consequently, the record does not give an estimated time-of-day contrast for this endpoint.
What an endpoint estimate would represent
In general, an endpoint estimate summarizes the observed contrast using a defined measurement and comparison. For this study, an estimate would have needed to describe the morning-to-evening change in SUVmax. An estimate is distinct from a hypothesis about the direction of change and from the study's rationale. The background describes interest in possible circadian variation, but a scientific motivation does not establish an observed effect.
The registry does not report a primary-endpoint estimate, a standard error, a confidence interval, or a p-value. A confidence interval is a way of conveying statistical uncertainty around an estimate under specified assumptions. It helps readers assess how precisely the data locate the effect. If no estimate and interval are reported, the size and precision of the proposed contrast cannot be evaluated from the registry results.
Why measurement availability matters
For an imaging outcome, an analysis requires a usable measurement for the participants included in that analysis. The record states that no patients were analyzed for the primary endpoint because no patient showed brown adipose tissue FDG uptake. It does not describe a numerical SUVmax contrast or how measurements below a detection threshold, if any, were handled. The detailed acquisition procedures and the threshold or operational definition used to identify uptake are not reported in the registry record. No particular measurement failure or protocol deviation should be inferred beyond the stated absence of uptake and the lack of an analyzed primary outcome.
More generally, an analysis restricted to participants with measurable uptake could answer a different question from one that includes all enrolled participants. The registry does not report a separate analysis population or a plan for handling unavailable primary measurements. It is therefore not possible to determine from this record how such decisions were specified or whether any alternative endpoint analysis was performed.
What the design permits
The study is listed as single-group, with FDG PET/CT as a diagnostic procedure and no masking. Morning and evening are measurement occasions in the endpoint description, not randomized treatment arms. A before-and-after or paired comparison, in general, uses measurements from the same participant at different occasions and can account for stable participant-level characteristics. But the registry does not report a completed paired analysis, a statistical model, or the structure of any analyzed data. No particular test or model should be attributed to the investigators based on the available record.
The trial is not a randomized comparison of a treatment against a control. Its stated aim was to generate pilot data about potential circadian variation. The registry does not report a formal sample-size justification or a planned precision target. Therefore the enrollment figure cannot by itself establish adequate power, and no observed power can be inferred from it.
Planning illustrations are not trial results
General sample-size planning asks how many participants would be needed under specified assumptions to detect a chosen effect with a chosen error rate. The planning assumptions associated with this record describe a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of an observed effect. Those are planning assumptions, not a description of the single-group design. Sample-size illustrations based on such assumptions are hypothetical planning quantities, not observed power and not evidence that this study tested a two-arm comparison.
Because the registry reports no analyzed primary endpoint, an effect derived from primary results is not available in the posted record as described. The registry also does not report the investigators' own sample-size justification. Any planning illustration should therefore be kept separate from the actual enrollment and from the unavailable primary comparison.
Over-dispersion and repeated measurements in general
General statistical methods sometimes need to account for greater variability than a simple model expects; this is called over-dispersion. When present, ignoring it can make uncertainty appear too small. Repeated measurements may also be correlated within a participant, so methods generally need to account for that dependence rather than treating every measurement as independent. These are general methodological considerations only. The registry does not report that over-dispersion was assessed, nor does it identify a repeated-measures model or describe a variance structure.
In short, the registry provides the study aim, design labels, endpoint definition, and a reason no primary patients were analyzed. It does not provide the statistical analysis details or numerical primary outcome results needed to evaluate an estimated circadian contrast.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists three outcome measures: one primary endpoint and two secondary outcomes. The secondary outcomes concern the correlation between cortisol level and brown adipose tissue FDG uptake, and change in total brown adipose tissue FDG uptake measured using total segmented fat volume times mean SUV. The record lists zero analyses, and it does not report results for these outcomes.
When several outcomes are tested, the chance of at least one apparently notable result can increase if each is interpreted without considering the number of tests. General approaches to multiplicity include adjusting testing thresholds or identifying a primary outcome in advance. The registry record does not report a multiplicity adjustment, a hierarchy among secondary outcomes, or a detailed statistical analysis plan. No adjustment method should be assumed.
The primary outcome description states that no patients were analyzed because no patient showed brown adipose tissue FDG uptake. This is an outcome-specific analysis statement; it does not establish how many participants had other measurements available or whether they contributed to secondary outcomes. The record does not report a missing-data method, a flow of participants by analysis population, or reasons for unavailable measurements beyond the stated absence of uptake for the primary endpoint.
Enrollment was 10, but the record does not explain whether every enrolled participant completed all planned procedures or had every planned measurement. It would be inappropriate to treat enrollment as the denominator for every outcome without further information. The registry also does not report whether any interim analyses were planned or performed.
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 |
|---|---|---|---|
| Single Group Assignment | 0 | 10 | 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 |
|---|---|
| Single Group Assignment | 0 of 10 |
The safety record lists 10 participants at risk for serious adverse events and 0 affected. It also lists 10 at risk for other adverse events and 0 affected. These are counts recorded for the single-group assignment. They describe the safety reporting in the registry and should not be interpreted as a comparison between groups, because the design is not a randomized comparison with a separate control arm.
The figures do not explain the duration or completeness of safety follow-up, how events were collected, or whether any events were considered related to the diagnostic procedure. That information is not reported in the registry record. The death count is recorded as null, so deaths are not reported in the registry record; null should not be recast as a reported count of zero.
These safety counts are separate from the primary imaging outcome. The fact that the safety record lists 10 at risk does not mean that 10 participants were analyzed for SUVmax. The primary outcome description explicitly says no patients were analyzed because none showed brown adipose tissue FDG uptake.
12. What the Result Does, and Does Not, Mean
The study was designed to generate pilot data on possible circadian variation in brown adipose tissue activation in healthy humans. It used FDG PET/CT and specified a primary comparison of SUVmax in brown adipose tissue in the neck or upper chest between evening and morning imaging. The registry record also states that no patients were analyzed for this primary endpoint because none showed brown adipose tissue FDG uptake.
That statement means the registry does not provide an analyzed primary comparison. It does not show that morning and evening uptake were equal, nor does it establish the direction or magnitude of a difference. Without a reported estimate and measure of uncertainty, the record cannot indicate how precisely a possible change was assessed.
The study's rationale is that brown adipose tissue uses glucose and that FDG PET/CT can image uptake of a glucose analog. The background also refers to circadian variation observed in mice. Those points explain why the investigators pursued the question; they are not results from the human participants in this record.
The posted enrollment of 10 and the completed status provide information about trial registration and conduct, but neither substitutes for an outcome analysis. The registry lists two secondary outcomes but does not report their estimates or analyses. The safety figures are descriptive counts and do not answer the question about time-of-day variation.
Accordingly, the record documents a pilot research question and an important limitation in primary endpoint availability. It does not establish whether brown adipose tissue FDG uptake varies by time of day in healthy humans, and it does not support a quantitative estimate of such variation.
13. Why This Trial Matters Statistically
This trial is statistically informative partly because it illustrates the difference between enrolling participants and obtaining analyzable data for a prespecified endpoint. The registry records 10 participants enrolled, while the primary outcome description says no patients were analyzed because none showed FDG uptake in brown adipose tissue. For interpretation, endpoint availability is as important as the nominal enrollment count: without an analyzed endpoint, a planned contrast cannot be estimated from the posted results.
The question also involves repeated imaging occasions. In general, measuring the same participant at different times can focus attention on within-person change, while accounting for the fact that repeated observations from one participant are related. The registry identifies morning and evening imaging but does not report an analysis method or a numerical comparison. This distinction keeps the study's scientific question separate from an assumption that a particular statistical approach was used.
The record further distinguishes exploratory intent from confirmatory evidence. The stated aim was to generate pilot data, and the registry lists three outcomes but zero analyses. Without reported estimates, uncertainty intervals, or tests, readers cannot judge the magnitude, precision, or consistency of any time-of-day pattern.
Finally, the study has a single-group diagnostic design, not randomized treatment arms. Any planning exercise framed in terms of two arms should be interpreted as a hypothetical planning illustration, not as a description of the trial's actual design or its observed power. These distinctions are useful whenever registry entries include enrollment, endpoint definitions, and safety counts but do not provide analyzable outcome results.
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 for statistical interpretation is explicit in the primary outcome description: no patients were analyzed because no patient showed FDG uptake in brown adipose tissue. The registry therefore does not report a primary SUVmax contrast, its uncertainty, or a test of morning versus evening imaging. The endpoint cannot be evaluated quantitatively from the posted results.
The record lists 10 participants enrolled, but it does not provide participant flow or explain whether all enrolled volunteers completed imaging. It does not report the number with measurements available for either secondary outcome. Handling of absent or unmeasurable uptake, missing-data methods, and the definition of the analysis population are not reported in the registry record.
The registry describes the endpoint and approximate timeframe but does not report detailed imaging procedures, the operational criteria for identifying uptake, or a statistical analysis plan. It also does not report whether analyses were adjusted for multiple outcomes, whether interim analyses were conducted, or how the sample size was justified. No analysis method should be inferred from the outcome wording alone.
The design is single-group and unmasked, with no randomized control group. Thus, the listed morning and evening occasions do not constitute a randomized treatment comparison. The registry's safety counts also lack reported follow-up details and do not provide a comparative safety estimate. These limitations concern what can be learned from the registry record and do not establish what may or may not exist outside it.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Circadian Brown Adipose Tissue Metabolism — NCT02285270.
- Registry record last updated 2016-12-07; status last verified 2016-10.
- Results first posted 2016-06-17.
- 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
NCT02285270, titled Circadian Brown Adipose Tissue Metabolism, is a completed pilot study sponsored by the University of Pennsylvania. It enrolled 10 healthy volunteers and used FDG PET/CT in a single-group design. The study began in 2014-03 and reached primary completion in 2015-04.
The primary endpoint concerned change in brown adipose tissue SUVmax in the neck or upper chest between evening and morning imaging, at an approximately 12-hour timeframe. The registry states that no patients were analyzed because no patient showed brown adipose tissue FDG uptake. Two secondary outcomes are listed, but the record lists zero analyses and reports no numerical outcome estimates.
Safety reporting lists 10 at risk and 0 affected for serious adverse events, and 10 at risk and 0 affected for other adverse events. Deaths are not reported in the registry record.