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 The Role of Parathyroid Hormone (PTH) in Low Bone Mass in Anorexia Nervosa (NCT00759772), a randomized phase 2 study. The primary outcome is Percent Change in Lumbar Spine Bone Mineral Density.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00759772 |
| Phase | Phase 2 |
| Condition | Anorexia Nervosa, Osteoporosis |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Single |
| Enrollment | 23 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Massachusetts General Hospital |
| Results posted | Yes |
2. Clinical Question
Population
The trial concerned people with anorexia nervosa and low bone mass. The registry summary describes investigation in women with anorexia nervosa; detailed eligibility criteria and participant characteristics are not reported in the registry record. The trial also lists osteoporosis as a condition.
Intervention
One group received teriparatide. The registry identifies it as a drug intervention, but the dose, administration schedule, and other treatment details are not reported in the registry record.
Comparator
The comparison group received placebo. The registry does not describe the placebo or report additional details about how it was administered.
Primary question
The primary question was whether the mean percent change in lumbar spine bone mineral density from baseline to 6 months differed between the teriparatide and placebo groups. The result is a comparison of a continuous measure over the stated treatment period, not a direct measure of fractures or other clinical events.
The registry identifies one primary outcome measure: percent change in lumbar spine bone mineral density between baseline and 6 months. It reports a mean for each arm and a standard error for each mean. The arm means describe the observed changes, while the comparison asks how far apart those group means were. Statistical results can describe the strength and precision of evidence for a difference in this outcome, but they do not by themselves establish the practical or clinical importance of that difference.
The record identifies the study as randomized and single-masked. Which people were masked is not reported in the registry record. It also does not report detailed eligibility rules, how treatment was assigned, or whether other aspects of care were identical between groups. Those details matter when assessing how closely the comparison isolates the intervention, so they cannot be assumed from the available description.
3. Trial Design
This was a randomized, single-masked, parallel-group phase 2 trial sponsored by Massachusetts General Hospital. The registry lists an enrollment of 23 and describes two drug interventions: teriparatide and placebo. The posted outcome results give an analysis group size of 12 for teriparatide and 11 for placebo. The record is marked completed. It lists a start of 2008-09 and a primary completion date of 2016-02-22.
In a parallel-group design, participants are assigned to one of the study groups and outcomes are compared across groups. Randomization is intended, as a general design principle, to reduce systematic differences between groups at the point of assignment. The registry does not report the randomization sequence, allocation concealment procedures, or the details of who was masked. The arm descriptions contain no further treatment information.
The primary outcome was percent change in lumbar spine bone mineral density from baseline to 6 months, during the treatment period. The registry states that all participants were included in the analysis under an intention-to-treat description. It does not explain how that analysis handled missing outcome measurements or departures from assigned treatment. The original sample-size justification and the trial’s own design assumptions are not reported in the registry record.
The record lists one outcome measure and one posted analysis. It does not list secondary posted outcomes. That means the posted results address a focused outcome, but the available record does not establish whether additional outcomes were measured, whether other analyses were planned, or whether any results were not posted. Such details should not be inferred from the number of posted outcome measures alone.
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 | Teriparatide | Placebo |
|---|---|---|
| STARTED | 12 | 11 |
| COMPLETED | 12 | 11 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: All participants were included in analysis (intention to treat).
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 | Teriparatide | Placebo | Total |
|---|---|---|---|---|
| Participants analysed | 12 | 11 | 23 | |
| Age, Continuous | years | 47.6 (SD 9.6) | 47.1 (SD 7.6) | 47.3 (SD 8.5) |
| Sex: Female, Male: Female | Participants | 12 | 11 | 23 |
| Sex: Female, Male: Male | Participants | 0 | 0 | 0 |
| Region of Enrollment: United States | participants | 12 | 11 | 23 |
6. Primary Endpoint
The registry lists the primary outcome as Percent Change in Lumbar Spine Bone Mineral Density, measured over Baseline and 6 months.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Error |
| Unit | percentage of change |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is percent change in lumbar spine bone mineral density between baseline and 6 months. Bone mineral density is a continuous measure: it can take a range of values rather than being classified only as an event that did or did not occur. The registry reports the mean percent change in each study arm, along with a standard error for each mean.
As a general statistical rationale, a continuous endpoint can retain information about the size and direction of measured changes across participants. Comparing group means provides a summary of the difference in average change between the assigned groups. The lumbar spine measure is used in this trial to examine change in bone density over the treatment period. It is not the same endpoint as fracture occurrence, bone strength in every anatomical location, or a broader clinical outcome.
The stated measurement period is baseline and 6 months. The record does not report a longer-term outcome period or a threshold for deciding what size of change would be clinically important. It also does not report further details about measurement procedures. Consequently, the statistical comparison can be interpreted as a comparison of the posted mean changes over the specified period, while the meaning of that change beyond the measured endpoint remains limited by the information in the registry record.
7. Results Posted in the Registry
- Teriparatide: mean 5.60 versus 0.20 on control; difference 5.40 (95% CI 2.51 to 8.29), standardized effect d = 1.49; z-test p = <0.001.
Mean difference: Teriparatide
95% CI: 2.51 to 8.29
Recalculated from the posted summary statistics
8. Statistical Interpretation
The reported mean percent change in lumbar spine bone mineral density was 5.6 in the teriparatide group, with a standard error of 1.3 and 12 participants, and 0.2 in the placebo group, with a standard error of 0.7 and 11 participants. These are group-level summaries of the change from baseline to 6 months. They do not describe every participant’s result, and the standard errors describe uncertainty around the estimated means rather than the spread of individual outcomes.
An unadjusted recalculation from the posted summary statistics gives a mean difference of 5.4 percentage points, with interval bounds of 2.506 and 8.294. The recalculated unadjusted p-value is <0.001. The confidence level for the interval is not reported in the registry record. These recalculations are not the sponsor’s own analysis. The sponsor reported a two-sided t-test with p < 0.01 and described the comparison as a superiority analysis. Because the recalculated result differs from the sponsor’s analysis, the sponsor’s own analysis takes precedence.
Both the sponsor’s p-value and the recalculated p-value indicate evidence against an equal-means null hypothesis under their respective analyses. A p-value is a measure of how compatible the observed data are with a statistical null model; it is not the probability that the null hypothesis is true and does not measure clinical importance. The distinction between the sponsor’s result and the recalculation matters: the recalculated estimate and interval are useful as an unadjusted check based on posted summaries, but they do not replace the trial’s reported analysis.
The interval bounds from the recalculation are above zero, which is consistent with a positive difference in the direction of a higher mean change in the teriparatide arm. That statement concerns the endpoint and time period as recorded. It is not evidence about longer-term effects, fracture outcomes, or other outcomes that were not posted. The record gives no threshold for a clinically important difference, so statistical evidence alone cannot establish whether the estimated difference is clinically meaningful.
The observed group sizes are small, and the precision of the results should be judged from the uncertainty around the estimates rather than from the p-value alone. The reported standard errors differ between arms, and the group means are estimates based on 12 and 11 participants. The registry does not report participant-level distributions, baseline outcome values, missing-measurement details, or adjustment variables. Those omissions limit assessment of the robustness and context of the comparison. The outcome analysis is described as intention to treat, but the handling of incomplete observations is not stated.
In short, the posted arm means show a larger average 6-month increase in the teriparatide group than in the placebo group, and the sponsor reports a statistically significant two-sided comparison. The unadjusted recalculation also indicates a difference but does not match the sponsor’s p-value. The sponsor’s analysis is the primary reported result, while the recalculation should be read as a separate summary-statistic-based check, not as a replacement or independent confirmation.
9. Statistical Methods Explained
The primary measure is continuous, and the registry reports it as a mean with a standard error in each arm. The sponsor’s reported method is a two-sided t-test. A t-test compares group means while accounting for uncertainty in the estimates; a two-sided test assesses evidence for a difference in either direction, rather than presuming in advance that only one direction is relevant. The registry does not report further details about the sponsor’s implementation of the test, including any adjustment or additional model terms.
What do the means and standard errors describe?
The mean is the average percent change in lumbar spine bone mineral density among the participants represented in the arm summary. The teriparatide mean is 5.6 and its standard error is 1.3; the placebo mean is 0.2 and its standard error is 0.7. A standard error describes the uncertainty in an estimated mean. It is not the same as the standard deviation, which describes variation among individual observations. Individual-level variation cannot be recovered from these arm summaries alone without additional assumptions.
General statistical explanation: standard errors tend to be smaller when an estimate is more precise and larger when it is less precise. They are affected by the amount of information and by variation in the observations. The registry does not give the individual observations or the standard deviations for the endpoint, so the observed variation among participants cannot be described directly from the reported standard errors.
What does the mean difference represent?
The recalculated mean difference is 5.4, with the teriparatide group’s mean change compared with the placebo group’s mean change. It is expressed in the endpoint’s percentage-change scale. This is an unadjusted comparison based on the posted summary statistics, not a covariate-adjusted estimate. The recalculated interval bounds are 2.506 and 8.294. The confidence level for that interval is not reported in the registry record, and the registry’s sponsor analysis does not give an estimated difference or interval bounds.
A confidence interval is generally a range of values compatible with the data under a specified statistical procedure. Its width conveys precision: narrower intervals indicate greater precision than wider intervals under the same method and confidence level. The recalculated interval is not the sponsor’s interval, and its confidence level is not stated in the registry record. It should therefore be interpreted as a recalculated uncertainty summary, with that limitation in mind.
How should the p-values be understood?
The sponsor reports p < 0.01 from a two-sided t-test. The summary-statistic recalculation gives p < 0.001. These values are not identical, which is why the recalculation should not be presented as the trial’s primary analysis. The registry does not explain the source of the discrepancy. The sponsor’s own analysis takes precedence. A p-value is conditional on the statistical model and its assumptions; it is not a measure of effect size, a probability that the result will be replicated, or a measure of clinical importance.
General statistical explanation: a two-sided test evaluates departures from the null in either direction. It is distinct from a confidence interval, though tests and intervals can be related when they use the same assumptions and confidence level. The registry does not report a confidence level for the recalculated interval, so an exact test-interval correspondence should not be assumed from the record.
What do the standardized summaries add?
The recalculation also gives a pooled standard deviation of 3.632 and a standardized effect size, d, of 1.487. A standardized effect expresses a difference relative to a pooled measure of spread, which can help describe the magnitude on a scale that is less tied to the endpoint’s original units. These are recalculated summaries, not results reported by the sponsor. Their interpretation depends on the calculation and assumptions used, and a standardized effect does not indicate clinical importance by itself.
General statistical explanation: when outcomes are continuous, variation may not be identical across groups, and some designs or data features may require methods that allow unequal variances or other departures from a simple model. The registry does not report diagnostics or a detailed statistical plan that would allow assessment of such issues. Over-dispersion is more commonly discussed for count outcomes, where observed variability exceeds what a simple count model expects; it is not a basis for adding an unreported adjustment to this continuous endpoint.
The record does not report whether the sponsor assessed model assumptions, used an alternative analysis, or conducted sensitivity analyses. It also does not report an interim-analysis plan or a detailed pre-specified analysis plan. The reported two-sided t-test and the summary-statistic recalculation are therefore the methods that can be described from the registry entry, without inferring further procedures.
10. Confidence Intervals and Precision
The sponsor’s analysis reports p < 0.01, but it does not report an estimated mean difference or confidence interval. The unadjusted recalculation gives a mean difference of 5.4 and interval bounds of 2.506 and 8.294. Those bounds provide an uncertainty summary for the recalculated estimate, not for an estimate explicitly reported by the sponsor. The confidence level is not reported in the registry record, so the interval should not be assigned a confidence percentage that the record does not state.
The interval’s positive lower bound is consistent with a difference favoring a larger mean percent change in the teriparatide arm under the recalculation’s assumptions. Its width indicates that the estimate is not exact: a range of values remains compatible with the summary statistics under the interval procedure. The interval does not establish a clinical-importance threshold, and no such threshold is reported in the registry record.
The arm means are accompanied by standard errors of 1.3 for teriparatide and 0.7 for placebo. Standard errors quantify uncertainty in the arm means; they do not show the full spread of participant outcomes. The posted group sizes are 12 and 11. With these small group sizes, the estimate’s precision should be considered alongside the interval and the limitations of a summary-statistic recalculation, rather than inferred from a p-value alone.
The registry does not report the sponsor’s interval, a confidence level for the recalculated interval, or participant-level results. It also does not give enough detail to independently assess all modeling choices. These missing details limit comparisons of precision across analyses and prevent a fuller evaluation of how sensitive the result is to statistical assumptions.
11. Planning a Similar Trial: Sample Size
This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.
| Effect to detect | Participants per arm, 80% power | Participants per arm, 90% power |
|---|---|---|
| 100% of the observed effect | 8 | 10 |
| 75% of the observed effect | 13 | 17 |
| 50% of the observed effect | 29 | 39 |
The planning figures are participants per arm, not total events. They are illustrations based on the observed effect, rather than the trial’s original sample-size plan. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to the stated fraction of the observed effect. The trial’s own original design assumptions and sample-size justification are not reported in the registry record.
The 80% power column gives the planned number of participants per arm under those assumptions for an analysis with an 80% chance of detecting the specified effect if that effect were the true one. The 90% power column gives the corresponding number per arm for a 90% chance under the same planning framework. These are design calculations, not descriptions of what happened in the trial. They do not show the probability that the observed result is true, and they are not observed power.
The planning illustrations consider 100%, 75%, and 50% of the observed effect. For 100% of the observed effect, the figures are 8 participants per arm for 80% power and 10 for 90% power. For 75% of the observed effect, they are 13 per arm and 17 per arm. For 50% of the observed effect, they are 29 per arm and 39 per arm. Smaller effects need more participants to detect under the same assumptions, which is why the planning figures rise as the target effect becomes smaller.
These figures depend on an effect estimated from a small trial, so they should not be read as a guarantee that a future study of those sizes would achieve the stated power. The assumed effect may not match the effect in another study, and the simple planning assumptions may not match a future design. The registry does not report the assumptions used to plan the original trial.
12. How the Sample Size Is Derived
Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z1−α/2 = 1.960) and the desired power (z1−β = 0.842 for 80% and 1.282 for 90%).
Formula
n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.
Worked calculation for this trial
- Observed difference Δ = 5.400; pooled standard deviation σ = 3.632.
- n = 2 × (1.96 + 0.842)2 × 3.6322 / 5.4002 = 7.1, rounded up to 8 participants per arm for 80% power.
The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).
R code
alpha <- 0.05
z_a <- qnorm(1 - alpha / 2) # two-sided
delta <- 5.4 # observed difference in means
sigma <- 3.63173840048038 # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))
# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")
# Simulation: exact two-sample t-test using simulated means and variances
set.seed(759772)
n <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n)) # difference in sample means
s2 <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1)) # pooled sample variance
tstat <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))
Output from running the code
100% of observed effect: n per arm = 8 (80% power), 10 (90% power)
75% of observed effect: n per arm = 13 (80% power), 17 (90% power)
50% of observed effect: n per arm = 29 (80% power), 39 (90% power)
power.t.test: 8.2
Simulated power at n = 8 per arm: 0.789 (20000 replicates)The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.
13. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| t-test, 2 sided | not reported | < 0.010 |
The sponsor’s posted analysis compares the teriparatide and placebo groups using a two-sided t-test and reports p < 0.01. The registry describes the analysis as a superiority analysis, but does not report a sponsor-estimated mean difference or interval bounds. That is the trial’s own reported inferential result.
A separate unadjusted recalculation from the posted arm summary statistics gives a mean difference of 5.4, interval bounds of 2.506 and 8.294, and p < 0.001. The recalculation is not identical to the sponsor’s reported p-value. The registry does not explain why the results differ. In light of that discrepancy, the sponsor’s own analysis takes precedence; the recalculated result should be treated as a supplementary check rather than as a correction or replacement.
The recalculation uses posted summary statistics and is not an adjusted analysis. It does not provide details absent from the registry, such as participant-level values, handling of missing observations, or the sponsor’s exact analysis procedures. The confidence level for the recalculated interval is not reported in the registry record. Readers should therefore keep the two analyses distinct and avoid combining their estimates as if they were a single analysis.
14. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure and one posted analysis. It reports the primary endpoint as percent change in lumbar spine bone mineral density from baseline to 6 months. No secondary outcomes are posted. A single posted outcome does not establish that only one outcome was measured or analyzed during the trial; the record does not report whether there were other planned or collected outcomes that were not posted.
The registry does not report a multiplicity strategy, such as whether adjustments were planned for testing multiple outcomes, time points, or analyses. It also does not provide enough information to establish whether the sponsor’s reported analysis followed a pre-specified statistical plan. The full statistical analysis plan and any interim-analysis procedures are not reported in the registry record. Without those details, it is not possible to assess whether the reported test was selected before results were known or how any additional analyses were handled.
The primary population is described as all participants included in an intention-to-treat analysis. That description indicates the intended analysis population, but it does not explain how participants with missing endpoint measurements were handled. The registry does not report the amount or pattern of missing outcome data, any imputation method, or sensitivity analyses for missingness. It also does not report whether all randomized participants had measurements at baseline and 6 months.
General statistical explanation: missing outcome data can affect an estimate if the participants with observed measurements differ systematically from those without them. An intention-to-treat label alone does not specify how missing measurements were addressed, so it cannot resolve that question. Similarly, multiplicity adjustments are relevant when several statistical claims are tested; the registry’s limited list of posted outcomes does not provide enough information to determine whether multiplicity was an issue in the full trial analysis.
The record also does not identify which people were masked, describe allocation concealment, or give a detailed analysis population definition beyond the intention-to-treat statement. These are gaps in the available reporting, not evidence that a particular procedure was or was not used.
15. 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 |
|---|---|---|---|
| Teriparatide | 2 | 12 | 16.7% |
| Placebo | 3 | 11 | 27.3% |
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 |
|---|---|
| Teriparatide | 12 of 12 |
| Placebo | 9 of 12 |
Most frequent serious adverse event terms
| Event term | Organ system | Teriparatide | Placebo |
|---|---|---|---|
| Hospitalization or exacerbation | Psychiatric disorders | 2 of 12 | 3 of 11 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Teriparatide | Placebo |
|---|---|---|---|
| Injection site ecchymoses, bruising, erythema | Skin and subcutaneous tissue disorders | 8 of 12 | 9 of 12 |
| Headache | Nervous system disorders | 6 of 12 | 5 of 12 |
| Lightheadedness | Nervous system disorders | 4 of 12 | 6 of 12 |
| Muscle pain/spasm | Musculoskeletal and connective tissue disorders | 3 of 12 | 4 of 12 |
| Nausea | Gastrointestinal disorders | 1 of 12 | 5 of 12 |
| Vomiting | Gastrointestinal disorders | 1 of 12 | 3 of 12 |
| Elevated 24hr urine calcium | Endocrine disorders | 3 of 12 | 1 of 12 |
| Elevated serum calcium | Endocrine disorders | 3 of 12 | 0 of 12 |
Serious events with the highest arm-level rate: hospitalization or exacerbation (27.3%).
The registry lists serious adverse events in 2 of 12 participants at risk in the teriparatide group and 3 of 11 participants at risk in the placebo group. These are counts of participants affected as reported in the safety record. The registry does not describe the seriousness criteria, event collection period, or whether a participant could contribute more than one event to the counts.
For other adverse events, the registry lists 12 at risk and 12 affected in the teriparatide group, and 12 at risk and 9 affected in the placebo group. The placebo safety denominator for other adverse events is listed as 12, whereas the posted primary outcome group size for placebo is 11. The record does not explain this difference, so the safety counts should be read using their own listed denominators rather than assumed to match the outcome analysis group sizes.
The registry identifies Hospitalization or exacerbation as a serious adverse-event term at 27.3%, without specifying an arm in that entry. Death counts are not reported in the registry record. These figures describe the safety information posted in the registry; they do not establish whether an event was caused by an intervention. The record does not provide enough detail about event definitions, timing, or attribution to support broader conclusions about comparative safety.
16. What the Result Does, and Does Not, Mean
The posted primary outcome means show a 5.6 percent change in lumbar spine bone mineral density in the teriparatide group and a 0.2 percent change in the placebo group over baseline to 6 months. The sponsor reports a two-sided t-test with p < 0.01. The summary-statistic recalculation gives a mean difference of 5.4, interval bounds of 2.506 and 8.294, and p < 0.001, but it differs from the sponsor’s reported analysis. The sponsor’s result takes precedence.
These results describe a group-average change in one measured endpoint during the stated treatment period. They do not say that every participant experienced the group average, and the registry does not report the distribution of individual changes. The endpoint is bone mineral density at the lumbar spine; it is not a direct count of fractures or a measure of all aspects of bone strength. No fracture result or other secondary outcome is posted.
A statistically significant test does not, by itself, establish clinical importance. The registry does not report a threshold for a clinically important change, and the sponsor does not provide an effect estimate with interval bounds. The recalculated interval is an unadjusted summary-statistic result, and its confidence level is not reported in the registry record. These considerations limit how specifically the magnitude and precision can be characterized.
The record describes a randomized phase 2 trial with 12 participants in the teriparatide outcome group and 11 in the placebo outcome group. Its results should be interpreted in that trial context. The registry does not provide detailed eligibility criteria, baseline participant characteristics, treatment administration details, or longer-term outcome results. It therefore does not establish how well these findings apply to people outside the study or what the outcome would be beyond 6 months.
The appropriate statistical reading is narrow: the posted means differ in the direction of a larger average change for the teriparatide arm, and the sponsor reports a statistically significant superiority comparison. The record does not establish the practical importance of that difference, effects on unposted outcomes, or longer-term outcomes. These results describe the posted comparison and should not be extended beyond its population, endpoint, and follow-up period.
17. Why This Trial Matters Statistically
This trial illustrates why the sponsor’s analysis and a recalculation from summary statistics should be kept separate. The sponsor reports a two-sided t-test with p < 0.01, while the unadjusted recalculation gives p < 0.001. The record does not explain the discrepancy. A recalculation can be a useful check on the posted summaries, but a discrepancy is a reason to preserve the distinction between the reported analysis and the supplementary calculation rather than treating them as interchangeable.
It also illustrates the difference between statistical evidence and precision. A p-value summarizes compatibility with a null model, while an estimated difference and interval communicate magnitude and uncertainty. The sponsor’s result does not include an estimated difference or interval bounds. The recalculated difference and interval add a summary of magnitude and uncertainty, but they are not the sponsor’s own estimates and the interval confidence level is not reported.
The arm sizes, 12 and 11, are important context for interpreting the uncertainty. A statistically significant comparison can still have limitations in precision and generalizability, particularly when the number of participants is small. The record does not give a clinical-importance threshold, participant-level distributions, or detailed missing-data procedures, so a p-value cannot answer those questions.
The endpoint is also important to keep in view. The result concerns lumbar spine bone mineral density change between baseline and 6 months, not fractures or a broad measure of clinical benefit. One posted outcome and one posted analysis do not reveal the full set of outcomes or analyses that may have been considered. The record’s omissions leave uncertainty about multiplicity and analysis choices. Together, these points show why interpretation depends on the endpoint, the reported analysis, and the quality and completeness of statistical reporting—not on statistical significance alone.
18. 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 trial’s posted outcome groups are small: 12 participants for teriparatide and 11 for placebo. The registry does not report a sponsor-estimated effect size or interval bounds, and the unadjusted recalculation differs from the sponsor’s p-value. The source of that discrepancy is not explained. The sponsor’s analysis takes precedence, but the lack of detail makes it harder to reconcile the two results.
The primary endpoint covers change in lumbar spine bone mineral density from baseline to 6 months. Longer-term outcomes are not reported, and the registry does not post fracture outcomes or secondary results. The record gives no threshold for a clinically important difference, so the clinical relevance of the estimated change cannot be determined from the statistical results alone.
Details needed to assess the trial population and treatment are limited. Eligibility criteria, baseline characteristics, teriparatide dose and schedule, placebo details, and the identity of the masked parties are not reported in the registry record. The record also does not describe the randomization sequence or allocation concealment. No conclusion about these procedures should be drawn from their absence in the registry entry.
The analysis is described as intention to treat, but missing-measurement counts, handling methods, and sensitivity analyses are not reported. The statistical analysis plan, the trial’s original sample-size justification, any interim analyses, and a multiplicity strategy are also not reported. The recalculated interval’s confidence level is not stated. These limitations affect assessment of precision, robustness, and the extent to which the posted result reflects the planned analysis.
The safety record lists a placebo denominator of 12 for other adverse events, while the primary outcome results list 11 participants in the placebo group. The registry does not explain the difference. Serious-event definitions, timing, and attribution are not described in enough detail to interpret the counts beyond the recorded figures.
19. Related Tutorials
20. Related Statistical Calculators
21. Sources
- ClinicalTrials.gov: The Role of Parathyroid Hormone (PTH) in Low Bone Mass in Anorexia Nervosa — NCT00759772.
- Registry record last updated 2017-05-11; status last verified 2017-04.
- Results first posted 2017-03-28.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
22. Record Summary
NCT00759772 is a completed randomized, single-masked, parallel-group phase 2 trial sponsored by Massachusetts General Hospital. It lists teriparatide and placebo as the interventions and an enrollment of 23. The record gives a start of 2008-09 and a primary completion date of 2016-02-22.
The primary outcome is percent change in lumbar spine bone mineral density from baseline to 6 months. The reported arm means are 5.6 for teriparatide and 0.2 for placebo. The sponsor reports a two-sided t-test with p < 0.01. An unadjusted recalculation gives a mean difference of 5.4, with interval bounds of 2.506 and 8.294, and p < 0.001; the recalculation differs from the sponsor analysis, which takes precedence.
The registry describes the primary analysis as intention to treat, but does not report detailed missing-data handling, the original sample-size justification, or a full statistical plan. No secondary outcomes are posted. Safety counts are listed in the record, with a denominator difference for placebo other adverse events that is not explained.