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 FDG PET/MRI Evaluation of Facet Joint Pain (NCT02921490), a na na study. The primary outcome is Facet Joint High Grade FDG Activity Concordance to Pain.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT02921490 |
| Phase | NA |
| Condition | Low Back Pain |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 10 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Mayo Clinic |
| Results posted | Yes |
2. Clinical Question
Population
People recruited for a study concerning low back pain and lumbar facet joints. The registry record does not report further eligibility details or a fuller description of the participant population.
Intervention
FDG PET/MR examination of the lumbar spine. The study examines FDG activity and MRI signal around facet joints.
Comparator
There is no separate control arm or randomized comparator. All recruited patients are described as undergoing the imaging examination in a single study arm.
Primary question
How concordant are high-grade FDG scores with clinical impression of facet joint pain? The registry names concordance correlation coefficient as the primary outcome measure, but does not report a numerical coefficient or its uncertainty.
The study addresses an assessment problem: facet joint changes on anatomical imaging may not correspond closely to pain, while selecting a joint or patient for a procedure can be difficult. Its exploratory aim is to examine whether FDG PET activity and MRI signal changes around facet joints relate to clinical assessment and might inform later evaluation of imaging biomarkers.
This is an imaging assessment question rather than a treatment comparison. The registry record does not describe an intervention intended to relieve pain, a usual-care control group, or a comparison of clinical outcomes between assigned treatments. It therefore cannot answer whether PET/MRI-guided care improves pain or other patient outcomes. It also does not report a specific threshold for a clinically meaningful degree of concordance.
3. Trial Design
NCT02921490, titled “FDG PET/MRI Evaluation of Facet Joint Pain,” is listed as a completed, single-group study sponsored by Mayo Clinic. The registry reports an enrollment of 10 and describes all recruited patients as receiving FDG PET/MR of the lumbar spine. The listed intervention is an FDG PET/MR examination.
The study is exploratory and focuses on imaging biomarkers around lumbar facet joints. It is not described as a randomized trial: allocation is listed as not applicable, and the design is single group. Masking is listed as none. There is consequently no separate randomized treatment arm against which to estimate a between-group effect. The imaging observations are intended to be considered in relation to clinical impression, rather than as evidence from a blinded treatment comparison.
The record gives a start date of 2016-09 and a primary completion date of 2018-11, with status recorded as completed. The primary outcome timeframe is 2 years. The registry does not report further details about visit schedules, image interpretation procedures, assessor qualifications, or how clinical impressions were established.
The study description frames the work as groundwork for a larger prospective study evaluating whether imaging biomarkers can predict response. That future-study rationale is not itself evidence that prediction was established in this study. The record does not report protocol details for any planned validation, sample-size justification, or an analysis plan. Accordingly, the design supports a focused exploratory description of imaging and clinical concordance, but the available registry information does not establish how precisely the association was estimated or how broadly it can be applied.
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 | PET/MR Recipients |
|---|---|
| STARTED | 10 |
| COMPLETED | 10 |
| NOT COMPLETED | 0 |
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 | PET/MR Recipients |
|---|---|---|
| Participants analysed | 10 | |
| Age, Continuous | years | 63 (50 to 79) |
| Sex: Female, Male: Female | Participants | 7 |
| Sex: Female, Male: Male | Participants | 3 |
| Race and Ethnicity Not Collected | Participants | — |
| Region of Enrollment: United States | Participants | 10 |
| Number of patients with back pain | Participants | 10 |
6. Primary Endpoint
The registry lists the primary outcome as Facet Joint High Grade FDG Activity Concordance to Pain, measured over 2 years.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | concordance correlation coefficient |
| Endpoint classification | not reduced to a single comparison |
The primary outcome is titled “Facet Joint High Grade FDG Activity Concordance to Pain.” Its measurement is identified as a concordance correlation coefficient, with the description specifying concordance of high-grade FDG scores with clinical impression. In practical terms, this endpoint is intended to describe how closely the imaging-based FDG assessment aligns with the clinical assessment of facet joint pain.
A concordance measure is useful when the question is whether two assessment approaches give compatible information, rather than whether one treatment outperforms another. It focuses attention on agreement between the imaging scores and clinical impression. This is relevant to the study’s exploratory purpose because imaging findings that align with clinical assessment could merit further evaluation as candidate biomarkers.
The registry record does not report the numerical coefficient, a confidence interval, or a p-value for this primary outcome. It also does not specify how “high grade” was defined, how clinical impression was operationalized, or whether concordance was assessed at the patient or facet-joint level. Those details matter for interpreting the coefficient: the unit of analysis, scoring rules, and handling of multiple joints can affect what an agreement estimate represents. Without the reported endpoint result and these methods, the registry description establishes the intended measurement but not the magnitude or precision of concordance.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The central statistical feature of this study is its single-group design. All recruited patients were to undergo FDG PET/MR of the lumbar spine, and the primary question concerns the agreement of high-grade FDG scores with clinical impression. This is an exploratory assessment of a possible imaging marker, not a randomized comparison of treatments. No treatment effect relative to a control group can be inferred from this design.
The registry record reports enrollment of 10. That gives important context for the scale of the study, but enrollment alone does not establish how many participants contributed to the primary analysis, how many facet joints were assessed, or whether all observations were evaluable. Those analysis details are not reported in the registry record. A small enrollment can make estimates sensitive to individual observations, but the extent of that sensitivity cannot be quantified without the endpoint data.
The registry identifies a concordance correlation coefficient as the primary outcome but does not report the coefficient itself. It also does not report an uncertainty interval or a significance test for this endpoint. As a result, the posted registry information cannot show whether the imaging scores aligned closely or weakly with clinical impression, nor how precisely the degree of alignment was estimated. A title or stated objective is not a numerical finding.
The study rationale notes that structural imaging findings can correlate poorly with pain and discusses limited earlier evidence about MRI signal and FDG-PET inflammatory changes. Those statements motivate the research question; they are not results from this study. Likewise, the stated intention to generate information for planning a larger prospective study does not establish that the imaging biomarkers predict response to treatment.
The adverse-event figures are separate from the primary endpoint. The registry lists 0 participants affected by serious adverse events and 1 affected by other adverse events among 10 at risk in the PET/MR recipient group. These counts should be read as safety reporting for the recorded group, not as an efficacy comparison or as evidence of a causal relationship. The record does not provide event descriptions or further context for interpreting them.
Overall, the registry gives a concise description of an exploratory imaging study and its intended measure, but it does not provide the primary numerical result needed to judge concordance. Conclusions about the strength, precision, or predictive value of the imaging signal would go beyond the posted results.
9. Statistical Methods Explained
The study’s primary endpoint is an agreement question. It asks whether high-grade FDG scores correspond with clinical impression, and the registry names a concordance correlation coefficient as the measure. This differs from a treatment comparison, where the main estimand would typically be a contrast between treatment groups. Here, the described design has a single group receiving imaging, so the relevant statistical task is to characterize how two forms of assessment relate.
What does a concordance measure describe?
In general, concordance measures how closely paired assessments agree. Agreement is not identical to association: two measures can move together while differing systematically in their values. Concordance methods are intended to reflect closeness as well as co-movement, although the precise interpretation depends on the chosen method and the data structure. The registry record does not provide a coefficient estimate, confidence interval, or details about the scoring and pairing procedures, so the magnitude and precision of agreement cannot be assessed from the record.
Interpretation also depends on what makes up an observation. A participant may have more than one facet joint assessed, but the registry does not report whether the analysis used patient-level or joint-level observations, or how any clustering was handled. In general, multiple observations from the same person are not necessarily independent. Statistical methods that account for such dependence may be needed to avoid overstating the amount of information. Whether this issue arose in the analysis is not reported in the registry record.
Why do uncertainty intervals matter?
In general, a confidence interval describes a range of values compatible with the observed data under the assumptions of the analysis. It helps readers judge precision, not just the direction or size of a point estimate. A point estimate without an interval can conceal substantial uncertainty, particularly in exploratory work with limited enrollment. The registry does not report an interval for the primary endpoint, so its precision cannot be evaluated from the posted record.
A p-value, when reported, addresses compatibility between data and a specified null model under its assumptions. It does not measure clinical importance, the probability that a hypothesis is true, or the probability that the observed result arose by chance. The record does not report a primary-endpoint p-value or a hypothesis-testing plan. It would therefore be inappropriate to infer statistical significance or absence of significance.
How should planning illustrations be understood?
In general, sample-size calculations use assumptions about the effect to detect, variability, significance level, allocation, and statistical model. A planning illustration based on an observed effect is hypothetical: it asks how much information might be needed under stated assumptions to detect an effect of a chosen size. It is not observed power and does not describe the probability that the completed study detected a true effect. The registry’s stated planning assumptions use 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 the observed effect. Those assumptions do not match the described single-group imaging design, which has no two-arm allocation. Any such illustration should therefore be understood as a generic planning scenario rather than a feature of the observed design.
For general sample-size planning, smaller target effects usually require more information to distinguish them from random variation, all else equal. The effect-size assumptions and model must be clinically and scientifically defensible; planning from an unstable exploratory estimate can be misleading. The registry does not report a study-specific sample-size justification or the inputs used to plan enrollment. Nor does it provide numerical planning outputs in the record, so no number of participants required for a future study can be interpreted from these registry entries.
What limits interpretation of the analysis?
The registry record lists 8 outcome measures and no analysis entries. That does not establish which analyses were performed, which outcomes were analyzed, or whether any results were omitted. The outcome listing by itself cannot substitute for a prespecified statistical analysis plan. Details such as handling of missing observations, adjustment for multiple outcomes, analysis population, and any subgroup analyses are not reported.
In general, exploratory studies can generate hypotheses and help refine measurement procedures, but estimates from them may be unstable and need independent evaluation. If several imaging features, clinical assessments, or anatomical units are examined, selective emphasis on the most favorable association can exaggerate apparent evidence. Prospective specification of the endpoint, scoring rules, analysis unit, and missing-data approach can reduce ambiguity. Whether such procedures were used in this study is not reported in the registry record.
The primary endpoint is a measure of concordance with clinical impression, not a direct measure of future treatment response. A claim that imaging predicts response would require an outcome definition, temporal relationship, and predictive analysis beyond the endpoint described in the registry. The record’s stated motivation for later research should therefore be separated from evidence about prediction in the present study.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 8 outcome measures, while no analysis entries are listed. It does not report how many outcomes were prespecified as primary or secondary in the protocol, how the outcomes were prioritized, or whether statistical tests were adjusted for multiplicity. The named primary endpoint is concordance of high-grade FDG activity with pain, but the record does not establish how other measures were treated in the analysis.
In general, examining several outcomes or imaging features creates multiple opportunities to observe an apparently notable result. When many tests are conducted, a nominal significance threshold can produce more false-positive findings across the set unless the analysis plan accounts for multiplicity or the exploratory nature is made clear. Adjustment is not always necessary for exploratory work, but readers need to know what was tested and how results were selected. Those details are not reported in the registry record.
Missing-data procedures are also not reported. The record does not describe whether imaging or clinical assessments were incomplete, how unavailable observations were handled, or whether reasons for missingness were recorded. Without those details, it is not possible to determine whether the primary analysis used all enrolled participants or a subset, or whether missing observations could have affected the result.
The analysis population is not described, and no endpoint analysis result is posted in the registry record. Therefore, enrollment should not be treated as the number analyzed for the primary endpoint. A complete interpretation would require the analysis denominator, exclusions or unevaluable observations, analysis methods, and any sensitivity analyses, if conducted. These items are not reported in the registry record.
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 |
|---|---|---|---|
| PET/MR Recipients | 0 | 10 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| PET/MR Recipients | 0 of 10 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 1% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| PET/MR Recipients | 1 of 10 |
Most frequent non-serious adverse event terms
| Event term | Organ system | PET/MR Recipients |
|---|---|---|
| IV site swelling | Blood and lymphatic system disorders | 1 of 10 |
For the PET/MR recipients group, the registry lists 10 participants at risk for serious adverse events and 0 affected by serious adverse events. It lists 10 at risk for other adverse events and 1 affected by other adverse events. These are recorded participant counts, not rates calculated.
The registry record does not identify the other adverse event, describe its severity or timing, or provide further information about how events were collected. It also does not state whether an event was judged related to the imaging examination. The counts therefore describe the safety entries as recorded, without establishing cause or providing enough detail to assess the nature of the event.
These figures should not be interpreted as evidence that the examination is risk-free, nor as a comparison with another procedure or group. The study has a single group and the posted record does not provide a comparator for safety. A count of 0 serious adverse events is a report for this study record, not proof that serious events cannot occur. The safety information is also distinct from the primary question about concordance between imaging scores and clinical impression.
12. What the Result Does, and Does Not, Mean
The study asks whether high-grade FDG activity around lumbar facet joints is concordant with clinical impression of pain. It documents an exploratory single-group imaging design, identifies the intended primary measure as a concordance correlation coefficient, and reports enrollment of 10. The registry status is completed, and the primary endpoint timeframe is 2 years.
However, the numerical result for the primary endpoint is not reported in the registry record. No coefficient, confidence interval, or p-value is posted. The record therefore does not establish the strength of agreement, its precision, or whether a particular level of agreement was observed. It also does not provide the endpoint details needed to determine exactly how scores and clinical impressions were paired and analyzed.
The study’s rationale discusses challenges in assessing facet joint pain and the possibility that imaging biomarkers could help guide later research. Those aims do not amount to evidence that PET/MRI improves clinical decisions, predicts treatment response, or changes patient outcomes. A relationship between imaging findings and clinical impression would not by itself show that using the scan to make decisions leads to better outcomes.
Because there is no randomized comparator, this record cannot support a causal contrast between imaging-guided and non-imaging-guided care, or between treatments. The adverse-event counts describe the recorded PET/MR recipient group only; they do not establish comparative safety. The record can be read as documentation of an exploratory question and study design, but the posted results are insufficient to judge the primary association or its clinical implications.
13. Why This Trial Matters Statistically
Facet joint pain poses a measurement challenge: anatomical changes and pain do not necessarily align, while clinical selection of a target for treatment can be difficult. This study is statistically relevant because it frames the imaging question as concordance between a biomarker assessment and clinical impression, rather than assuming that an image finding is itself a definitive measure of pain.
That distinction matters for study design. An agreement endpoint can assess whether two ways of evaluating a clinical problem provide compatible information. It does not by itself establish that either assessment is correct, or that one can predict response to treatment. Later studies would need to define the clinical outcome of interest and test prediction or decision impact directly.
The exploratory, single-group structure is suited to describing a candidate association, but it limits what can be concluded. There is no randomized comparison, and the registry record does not report the primary numerical estimate or its precision. The enrollment of 10 underscores that the study is presented as early-stage work, but the number alone cannot tell readers how many observations were available for analysis or how reliable any estimate would be.
For biostatistical interpretation, the missing endpoint result, analysis details, and multiplicity and missing-data procedures are central rather than incidental. They determine whether the intended measure can be interpreted, how uncertain it is, and whether selective analysis could influence the apparent pattern. By stating the question and design but not reporting the primary result, the record highlights both the potential role of imaging biomarkers and the need for transparent reporting before their value can be assessed.
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 main limitation of the registry record is that it does not report a numerical result for the named primary endpoint. Without a concordance estimate and an uncertainty interval, the central study question cannot be answered from the posted information. The record also does not report a p-value or enough endpoint detail to reproduce or fully interpret the intended calculation.
The study is described as a single-group examination with no randomized comparator. It can therefore address an association between imaging and clinical impression as described, but not comparative treatment effects or the impact of imaging on care. The record does not report whether the analysis was at the participant or facet-joint level, how high-grade FDG activity was defined, how clinical impression was assessed, or how repeated measurements within a participant were handled.
Enrollment is listed as 10, but the number included in the primary analysis is not reported. The registry also does not report exclusions, incomplete imaging or assessments, missing-data methods, or an analysis population. It lists 8 outcome measures without analysis entries, and does not describe multiplicity procedures or a study-specific sample-size justification.
Finally, the registry’s stated rationale includes the possibility that imaging biomarkers could inform a larger study of response prediction. No predictive result is reported for this study. The recorded dates and completed status describe registration information, but do not resolve the absent endpoint result or methodological detail.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: FDG PET/MRI Evaluation of Facet Joint Pain — NCT02921490.
- Registry record last updated 2020-02-19; status last verified 2020-02.
- Results first posted 2020-02-19.
- 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
NCT02921490 is a completed, exploratory, single-group study titled “FDG PET/MRI Evaluation of Facet Joint Pain,” sponsored by Mayo Clinic. The registry lists enrollment of 10, a start date of 2016-09, and primary completion in 2018-11. All recruited patients are described as receiving FDG PET/MR of the lumbar spine.
The primary outcome is concordance of high-grade FDG activity with clinical impression, measured by a concordance correlation coefficient, with a timeframe of 2 years. The numerical primary result and its uncertainty are not reported in the registry record. The safety entries list 0 participants affected by serious adverse events and 1 affected by other adverse events in the PET/MR recipient group. The record does not describe the other event or report a comparative safety group.
The design supports an exploratory imaging-assessment question, not a randomized treatment comparison. Further analysis details, including the analysis population, missing-data procedures, and multiplicity approach, are not reported in the registry record.