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 RN624 In Adult Patients With Chronic Low Back Pain (NCT00584870), a randomized phase 2 study. The primary outcome is Change From Baseline in Daily Average Low Back Pain Intensity (LBPI) Score at Week 6.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00584870 |
| Phase | Phase 2 |
| Condition | Low Back Pain |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Quadruple |
| Enrollment | 220 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
Adults with chronic low back pain. The registry record gives an enrollment of 220, but does not provide the arm-level counts for the primary endpoint in the information available for this analysis.
Intervention
RN624, also identified in the record as PF-04383119. The adverse-event grouping uses the name tanezumab. Dose and treatment schedule details are not reported in the registry record.
Comparator
Placebo and naproxen. The study is described as placebo- and active-controlled, allowing RN624 to be evaluated against both a non-active comparator and an active comparator.
Primary question
What was the change from baseline in daily average low back pain intensity at Week 6, and how did the RN624 outcome compare with placebo and naproxen? The numerical results and treatment contrasts are not reported in the registry record.
The registry record describes a Phase 2 randomized study in adults with chronic low back pain. Its stated objective was to evaluate the analgesic efficacy of RN624 compared with placebo and compared with naproxen. The primary endpoint was change from baseline in daily average low back pain intensity at Week 6.
The clinical question therefore has two comparator parts: whether the recorded Week 6 pain-intensity change differed between RN624 and placebo, and whether it differed between RN624 and naproxen. The record identifies both comparisons as objectives, but the numerical arm results, estimated contrasts, confidence intervals, and significance tests are not reported in the registry record. No direction or size of a treatment effect can be established from the information available for this analysis.
The study also listed secondary measures covering pain intensity at multiple weeks, average pain over several intervals, brief pain inventory scores, and reductions in pain intensity. Those additional measures could describe different time points and aspects of pain, but their numerical results are not included in the information. The study question is consequently clear at the level of design and endpoint definition, while its answer cannot be reconstructed from the endpoint description alone.
3. Trial Design
This was a Phase 2, randomized, double-blind, placebo- and active-controlled, multicenter, parallel-group study. The registry lists quadruple masking. Those terms describe the trial structure as recorded; details about which roles were masked and how masking was maintained are not reported in the registry record.
The trial compared PF-04383119 (RN624) with placebo and naproxen in adults with chronic low back pain. The registry’s adverse-event grouping calls the RN624 arm “Tanezumab.” The treatment dose, route and schedule for each arm are not reported in the registry record, apart from the primary-population definition’s mention of a Day 1 intravenous infusion for tanezumab or placebo. The arm descriptions contain no further treatment details.
The registry-recorded enrollment is 220. This is an enrollment entry, not a substitute for the number analyzed at a particular endpoint or time point. The primary-outcome population is described as randomized participants who received the Day 1 infusion, while “number analyzed” refers to those evaluable for the measure at the specified time point. Arm-level primary-endpoint counts are not reported in the registry record.
The study is marked completed. Its recorded start date is 2007-07-05 and its primary completion date is 2008-09-02. The primary endpoint was assessed at Week 6, with baseline and Week 6 identified in its timeframe. Secondary outcomes included measures at Week 1, 2, 4, 6, 8 and 12, as well as averages over specified week ranges. The analysis plan, allocation ratio, randomization method, and details of follow-up are not reported in the registry record. The record does not give enough information to infer how the study was powered or how its planned comparisons were handled statistically.
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: Participants underwent a 5-day initial pain assessment period prior to study treatment.
Overall Study
| Stage | Tanezumab | Naproxen | Placebo |
|---|---|---|---|
| STARTED | 88 | 89 | 43 |
| Treated | 88 | 88 | 41 |
| COMPLETED | 59 | 64 | 25 |
| NOT COMPLETED | 29 | 25 | 18 |
Reasons for not completing this period:
| Reason | Tanezumab | Naproxen | Placebo |
|---|---|---|---|
| Adverse Event | 4 | 3 | 2 |
| Lost to Follow-up | 4 | 1 | 1 |
| Lack of Efficacy | 7 | 14 | 8 |
| Withdrawal by Subject | 10 | 5 | 3 |
| Protocol Violation | 1 | 1 | 2 |
| Did not met entrance criteria | 1 | 0 | 0 |
| Other | 2 | 0 | 0 |
| Randomized but not treated | 0 | 1 | 2 |
Analysis population for the primary outcome, as defined in the registry: ITT population included all randomized participants who received the Day 1 intravenous infusion (either tanezumab or placebo infusion). Here 'number analyzed' signifies participants who were evaluable for this measure at given time points.
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.
Population: Intent to treat (ITT) population included all randomized participants who received the Day 1 intravenous infusion (either tanezumab or placebo infusion).
| Characteristic | Unit | Tanezumab | Naproxen | Placebo | Total |
|---|---|---|---|---|---|
| Participants analysed | 88 | 88 | 41 | 217 | |
| Age, Continuous | years | 49.5 (SD 14.7) | 52.1 (SD 14.8) | 52.2 (SD 15) | 51.1 (SD 14.8) |
| Sex: Female, Male: Female | Participants | 53 | 42 | 23 | 118 |
| Sex: Female, Male: Male | Participants | 35 | 46 | 18 | 99 |
6. Primary Endpoint
The registry lists the primary outcome as Change From Baseline in Daily Average Low Back Pain Intensity (LBPI) Score at Week 6, measured over Baseline, Week 6.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was change from baseline in daily average low back pain intensity at Week 6, expressed in units on a scale. Pain intensity was assessed with an 11-point numeric rating scale, from 0 (no pain) to 10 (worst possible pain). Participants rated their average low back pain during the past 24 hours.
Baseline was defined as the mean of scores over the 5-day period before randomization. The post-baseline weekly score was calculated from the mean of scores over the 7 days before and including the day at the end of the corresponding week. The primary measure therefore compares a pre-randomization average with an average representing the period ending at Week 6, rather than relying on a single day’s rating.
Change from baseline is used to describe how the recorded pain score differs from the participant’s baseline value. Comparing the mean change between randomized groups can summarize the relative pattern in this continuous outcome. The record identifies the endpoint as a mean and its dispersion as standard deviation, but the numerical group means, standard deviations, treatment contrasts, and uncertainty estimates are not reported in the registry record. The endpoint definition explains what was intended to be measured; it does not, by itself, establish whether or how the groups differed.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The primary endpoint is defined in sufficient detail to understand the intended measurement: daily average low back pain intensity on an 11-point scale, with change from baseline assessed at Week 6. The trial objective identifies RN624 comparisons with both placebo and naproxen. However, the registry record information available for this analysis does not include the numerical results for those comparisons.
In particular, no Week 6 arm means, standard deviations, numbers analyzed, between-group differences, confidence intervals, or p-values are reported in the registry record. Without these, it is not possible to describe the observed direction or magnitude of the primary outcome, assess its precision, or determine whether a reported statistical test met a chosen threshold. The design and endpoint description cannot be used to infer those results.
The registry lists 22 outcome measures and one analysis, while the primary outcome has several categories or time points and is not reduced to one comparison in the available summary. This matters for interpretation: a single headline estimate would not necessarily capture all the planned or reported contrasts. The complete outcome-level results and the analysis details would be needed to identify which contrasts were tested and how their uncertainty should be read. Those details are not reported in the registry record.
Some contextual information is available. The study was randomized, masked, parallel-group, and included placebo and naproxen comparators. The primary endpoint’s scale and time window are described, and the record defines the intended analysis population. These features help frame what evidence the trial was designed to collect. They do not replace results or establish that the measured outcome favored any arm.
The safety entries report serious adverse events in the naproxen group and none in the listed tanezumab and placebo groups. Those counts are descriptive and cannot be interpreted as a complete comparison of safety without considering event definitions, observation periods, participant exposure, and the detail of reporting. Death counts are not reported in the registry record. The listed other adverse events are common within each group, but the record does not establish causality.
Accordingly, the defensible conclusion is limited: the registry describes a randomized Phase 2 trial and a specified Week 6 pain-intensity endpoint, but the primary numerical comparison is not reported in the registry record. No conclusion about the size, precision, or statistical significance of the primary treatment effects follows from the endpoint description or study design alone.
9. Statistical Methods Explained
What does a mean change describe?
The primary outcome is a continuous measure summarized as a mean. A group mean describes the average recorded change among the participants included in that analysis. It can be useful for comparing groups, but it does not show the spread of individual responses or imply that each participant changed by the same amount. The registry identifies standard deviation as the measure of dispersion, but the numerical means and standard deviations are not reported in the registry record.
A treatment comparison generally focuses on the difference between group summaries, rather than interpreting a within-group change in isolation. A group’s change from baseline can reflect more than the study treatment, including the passage of time and other influences. Randomized between-group comparisons are intended to help distinguish the treatment-group pattern from those shared influences. The numerical contrasts needed to make that comparison are not reported in the registry record.
How should uncertainty be assessed?
A confidence interval is a general statistical way to express uncertainty around an estimated effect. Its range indicates which effect sizes are reasonably compatible with the data under the method used. A narrow interval indicates greater precision than a wide interval, while an interval spanning effects on different sides of no difference can leave the direction uncertain. This is a general explanation, not a description of an interval reported for this trial: no confidence interval for the primary comparison is reported in the registry record.
A p-value, when reported, addresses how compatible the data are with a specified null hypothesis under the statistical model. It does not measure the probability that the null hypothesis is true, nor does it convey the clinical importance or precision of an effect by itself. No primary-outcome p-value is reported in the registry record. The analysis method and test assumptions are also not reported in the registry record.
What does the randomized design contribute?
Random allocation is intended to make treatment groups comparable on average with respect to both measured and unmeasured characteristics. Masking is intended to limit the influence of treatment knowledge on care, assessment, or reporting, depending on which people are masked. The registry describes randomized allocation, quadruple masking, and a parallel-group model. It does not report the randomization procedure or specify the roles covered by masking, so more detailed claims about these procedures are not warranted.
The primary population is defined as all randomized participants who received the Day 1 intravenous infusion of tanezumab or placebo. The record also clarifies that the number analyzed at a time point means those evaluable for the measure then. This distinction is important: an intended analysis population and the number with usable endpoint data need not be identical. Arm-specific evaluable counts and the handling of missing endpoint observations are not reported in the registry record.
How should planning illustrations be read?
Sample-size planning illustrations use assumptions and are not observed trial outcomes. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is defined as a stated fraction of the observed effect. For time-to-event tables, the stated quantity is total events, while other illustrations give participants per arm. These are planning conventions, not evidence that the trial had a particular power or that an effect was observed with a particular precision.
The effect estimate on which an illustration is based, the numerical illustration outputs, and the trial’s own sample-size justification are not reported in the registry record information available for this analysis. The illustrations therefore cannot establish the study’s original design rationale or be treated as observed power. In general, a planning calculation depends on the effect size and assumptions chosen; changing those assumptions changes the planning result. No additional calculation can be reconstructed from the endpoint definition alone.
Why can over-dispersion matter?
Over-dispersion is a general concern when observed variability exceeds what a statistical model assumes. A model that understates variability can produce confidence intervals that are too narrow and tests that appear more decisive than warranted. The primary endpoint is a continuous mean outcome, and the record identifies standard deviation as its dispersion measure. The statistical model and its diagnostics are not reported in the registry record, so there is no basis to claim that over-dispersion was assessed or was present. This general issue should not be confused with a finding about this trial.
10. Multiplicity, Missing Data and Analysis Populations
The record lists 22 outcome measures, including a primary Week 6 pain-intensity change and secondary outcomes at multiple weeks, over several week ranges, and using several pain-related measures. When many outcomes, time points, or treatment contrasts are considered, the chance of at least one apparently notable result can increase. General approaches to address this include prespecifying a hierarchy or adjusting statistical tests, but the registry record does not report a multiplicity strategy. It is therefore not possible to determine whether or how the study controlled for multiple comparisons.
The record notes that the primary outcome has several categories or time points and is not reduced to one comparison in the available summary. The actual numerical estimates and tests for the relevant categories or comparisons are not reported in the registry record. No single result should be inferred from the objective or from the list of outcomes.
The primary population is described as randomized participants who received the Day 1 infusion. For a given time point, the number analyzed means those evaluable for that measure. The arm-level counts with evaluable Week 6 data, reasons for missing observations, and methods used to address missing data are not reported in the registry record. In general, missing outcome data can affect a comparison if missingness is related to treatment or the unobserved outcome; the direction and extent of any such influence depend on the circumstances and analysis method. Those details cannot be evaluated.
The registry also does not report whether an intention-to-treat analysis, imputation, sensitivity analysis, or a prespecified primary statistical model was used. The population definition should therefore be read as a description of who was intended to contribute, not as a complete account of the analysis procedures.
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 |
|---|---|---|---|
| Tanezumab | 0 | 88 | 0.0% |
| Naproxen | 2 | 88 | 2.3% |
| Placebo | 0 | 41 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 2% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Tanezumab | 44 of 88 |
| Naproxen | 45 of 88 |
| Placebo | 27 of 41 |
Most frequent serious adverse event terms
| Event term | Organ system | Tanezumab | Naproxen | Placebo |
|---|---|---|---|---|
| Atrial fibrillation | Cardiac disorders | 0 of 88 | 1 of 88 | 0 of 41 |
| Syncope vasovagal | Nervous system disorders | 0 of 88 | 1 of 88 | 0 of 41 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Tanezumab | Naproxen | Placebo |
|---|---|---|---|---|
| Headache | Nervous system disorders | 10 of 88 | 5 of 88 | 8 of 41 |
| Arthralgia | Musculoskeletal and connective tissue disorders | 13 of 88 | 6 of 88 | 0 of 41 |
| Upper respiratory tract infection | Infections and infestations | 4 of 88 | 4 of 88 | 2 of 41 |
| Influenza | Infections and infestations | 3 of 88 | 5 of 88 | 1 of 41 |
| Nasopharyngitis | Infections and infestations | 2 of 88 | 6 of 88 | 1 of 41 |
| Back pain | Musculoskeletal and connective tissue disorders | 3 of 88 | 5 of 88 | 1 of 41 |
| Myalgia | Musculoskeletal and connective tissue disorders | 7 of 88 | 0 of 88 | 2 of 41 |
| Pain in extremity | Musculoskeletal and connective tissue disorders | 4 of 88 | 2 of 88 | 2 of 41 |
| Urinary tract infection | Infections and infestations | 3 of 88 | 4 of 88 | 0 of 41 |
| Contusion | Injury, poisoning and procedural complications | 1 of 88 | 6 of 88 | 0 of 41 |
Serious events with the highest arm-level rate: atrial fibrillation (1.1%), syncope vasovagal (1.1%).
The registry lists serious adverse events for three groups: tanezumab, naproxen, and placebo. The serious-event counts are 0 among 88 at risk in the tanezumab group, 2 among 88 at risk in the naproxen group, and 0 among 41 at risk in the placebo group. These are descriptive counts in the registry record. They do not, on their own, establish that a treatment caused an event or that one group’s safety profile differs from another’s.
The record lists atrial fibrillation and syncope vasovagal among the top serious terms, each at 1.1%. It does not provide group-specific attribution for those terms in the information available for this analysis. Death counts are not reported in the registry record.
The other adverse-event counts are 44 among 88 at risk for tanezumab, 45 among 88 at risk for naproxen, and 27 among 41 at risk for placebo. These entries should be distinguished from serious adverse events. The registry does not provide, in the available information, event-level detail, exposure-adjusted rates, or a complete account of severity and duration. The counts therefore describe what was recorded, rather than providing a full comparative safety analysis.
12. What the Result Does, and Does Not, Mean
The registry record establishes that a randomized, masked, parallel-group Phase 2 study was conducted to compare RN624 with placebo and naproxen in adults with chronic low back pain. It specifies a Week 6 change-from-baseline endpoint based on daily average pain intensity and describes how the baseline and weekly scores were formed. These are useful details about the trial question and measurement.
They do not establish the outcome of the trial. The numerical primary results, between-group estimates, confidence intervals, and p-values are not reported in the registry record information available for this analysis. Consequently, it is not possible to say whether the average pain-intensity change differed between groups, how large any difference was, or how precisely it was estimated. Nor can a statistical or clinical interpretation be inferred from the fact that the trial was completed or that results were collected.
The secondary outcomes identify a broad set of additional pain measures and time points. Without their results and the multiplicity approach, they cannot be used to reconstruct an overall conclusion. The adverse-event entries provide selected counts and terms, but they are not a complete basis for causal judgments or comparative safety conclusions. Death counts are not reported in the registry record.
In general, a trial result is interpreted by considering the effect estimate, its uncertainty, the analysis population, missing data, and the planned statistical methods alongside the clinical context. The relevant numerical and methodological detail is not reported in the registry record information available for this analysis. The most that can be concluded is that the study was designed to address the stated comparisons; its primary treatment-effect answer is not available from the recorded details summarized in this analysis.
13. Why This Trial Matters Statistically
This trial is statistically informative as an example of how a registry can describe a research question and measurement framework without supplying enough numerical outcome detail to interpret the treatment comparison. The record identifies randomization, masking, the parallel-group structure, comparators, and the primary endpoint. It also defines the pain scale and the time windows used for baseline and follow-up scoring. Those details clarify what was to be compared.
At the same time, the gap between endpoint specification and reported results is consequential. A mean change endpoint invites interpretation of arm-level means, a between-group contrast, and uncertainty around that contrast. Those numerical results are not reported in the registry record information. Readers therefore cannot evaluate the magnitude or precision of the primary result from the design description.
The study also illustrates why outcome multiplicity and analysis-population detail matter. Its registry entry lists multiple outcomes and time points, and describes evaluability at a time point as the basis for the number analyzed. But the analysis plan, multiplicity strategy, missing-data methods, and endpoint-specific counts are not reported in the registry record. Without them, a complete account of how the evidence was generated is unavailable.
Finally, safety counts require careful reading. Counts by group are useful descriptive information, but they do not alone quantify comparative risk or establish causality. The registry entries do not provide the fuller context needed for such assessments. The statistical lesson is not a treatment conclusion: it is that transparent interpretation depends on both a clearly defined estimand and accessible estimates, uncertainty, and analysis details.
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 central limitation is that numerical primary-endpoint results are not reported in the registry record information available for this analysis. Arm means, standard deviations, evaluable counts, treatment contrasts, confidence intervals, and p-values are not available, preventing assessment of the primary effect’s direction, magnitude, and precision.
The registry describes a population that included randomized participants who received the Day 1 infusion, while defining the number analyzed as those evaluable at a given time point. It does not report endpoint-specific counts, reasons for missing data, or methods for handling missing observations. The effect of missingness on the results therefore cannot be assessed.
The record lists many outcomes and time points, but does not report the statistical analysis plan or any strategy for multiplicity. It also does not report the primary model, test assumptions, or sensitivity analyses. The available study description cannot establish how the stated comparisons were implemented.
Treatment details are limited: arm descriptions are empty, and dose and schedule are not reported in the registry record. The record mentions a Day 1 intravenous infusion for tanezumab or placebo in the population definition, but does not provide further administration details there. Randomization and quadruple masking are recorded, while the procedures and masked roles are not described.
The safety information is also limited to selected counts and terms. Group-specific attribution for the listed serious terms, death counts, and fuller event detail are not reported in the registry record. These limitations prevent a complete efficacy or safety interpretation and should not be filled by assumptions.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: RN624 In Adult Patients With Chronic Low Back Pain — NCT00584870.
- Registry record last updated 2021-07-12; status last verified 2021-06.
- Results first posted 2021-06-16.
- 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
The registry describes NCT00584870 as a completed Phase 2 randomized, double-blind, placebo- and active-controlled, multicenter, parallel-group study in adults with chronic low back pain. It lists an enrollment of 220, quadruple masking, and comparisons of RN624 (PF-04383119) with naproxen and placebo. The recorded start date is 2007-07-05, and the primary completion date is 2008-09-02.
The primary outcome was change from baseline in daily average low back pain intensity at Week 6, measured on an 11-point numeric rating scale. The registry defines the baseline and weekly scoring windows and the intended primary population. It lists 22 outcome measures. Numerical primary comparisons, uncertainty estimates, the analysis plan, multiplicity handling, and missing-data methods are not reported in the registry record information available for this analysis.