Body Composition in Infants With Klinefelter Syndrome and Effects of Testosterone Treatment: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Body Composition in Infants With Klinefelter Syndrome and Effects of Testosterone Treatment (NCT02408445), a randomized phase 4 study. The primary outcome is Change in Body Fat Percent Z-score.

2. Clinical Question

The study concerns whether body composition changes over a short period differ between the randomized groups. Its primary outcome is an age- and sex-normed z-score for body-fat percentage, so the comparison concerns change relative to the reference growth pattern rather than body-fat percentage alone. The registry description also identifies motor skills and hormone measures as areas of interest. The posted comparative results include motor assessments and penile-length change as secondary outcomes.

The clinical question is specific to infants with Klinefelter syndrome and to the recorded treatment and follow-up period. It does not establish what happens beyond the study period, or whether findings apply to other populations. The registry record does not report a broader population description or additional eligibility details in the outcome information.

3. Trial Design

This is a completed, randomized, single-masked, parallel-group Phase 4 study sponsored by the University of Colorado, Denver. The registry record lists enrollment of 20 and two groups: testosterone treatment and no treatment. The posted primary outcome summaries contain 10 participants in each group. The testosterone group received testosterone cypionate by intramuscular injection; the comparator group was not to receive testosterone during the study period.

The primary outcome was assessed at baseline and 3 months. The record describes body-fat percentage measurement by air displacement plethysmography using a PEA POD, followed by calculation of age- and sex-normed z-scores. Secondary outcome timeframes include 3 months for the motor measures and baseline and 3 months for penile-length change. The record also lists hormone outcomes, including serum LH, FSH, total testosterone, inhibin B, AMH, and leptin.

The registry lists the study as starting on 2015-05-08, with primary completion on 2018-01-31, and status as completed. The meaning of “single” masking—such as which participants or study personnel were masked—is not reported in the registry record. Details of allocation concealment, adherence, and the handling of treatment changes are also not reported in the registry record. The original sample-size justification and the trial’s planned statistical analysis are not reported in the registry record. Therefore, the design features that can be described are those recorded for the randomization, masking category, parallel-group structure, assigned groups, and outcomes.

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

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Change in Body Fat Percent Z-score, measured over Baseline and 3 months.

The primary endpoint is change in body-fat percentage z-score from baseline to 3 months. Body-fat percentage is measured using air displacement plethysmography with a PEA POD. The registry says the z-score is age- and sex-normed: zero corresponds to the mean of the reference, while negative and positive values lie below and above that mean. The endpoint is therefore expressed relative to the reference distribution rather than as a raw percentage of body mass.

The registry’s interpretation of change is tied to expected growth. If an infant follows the normal growth curve, the z-score change is 0. A positive change indicates a gain in body fat above the growth typically expected; a negative change indicates a gain that is less than typically expected. This standardization is useful when the outcome is expected to change with age, because the comparison focuses on relative position against an age- and sex-based reference over the study period.

The endpoint is a continuous measure, and the posted group summaries are means with standard deviations. It captures change over the stated follow-up, not body composition across later childhood or adulthood. The registry record does not report additional details about measurement quality, assessor procedures, or how missing endpoint measurements were handled.

7. Results Posted in the Registry

• No Treatment: mean 0.92 versus -0.12 on control; difference 1.04 (95% CI 0.48 to 1.60), standardized effect d = 1.64; z-test p = <0.001.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Change in Raw Score on the Alberta Infant Motor Scale

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • No Treatment: mean 8.90 versus 10.50 on control; difference -1.60 (95% CI -6.95 to 3.75), standardized effect d = -0.26; z-test p = 0.558.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between No Treatment and the control. The interval gives the range of effects that remain compatible with the data.

Change in Total Motor Standard Score on the Peabody Developmental Motor Scales 2

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • No Treatment: mean 2.00 versus 2.80 on control; difference -0.80 (95% CI -7.03 to 5.43), standardized effect d = -0.11; z-test p = 0.801.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between No Treatment and the control. The interval gives the range of effects that remain compatible with the data.

Change in Penile Length

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • No Treatment: mean -0.30 versus 0.90 on control; difference -1.20 (95% CI -1.68 to -0.72), standardized effect d = -2.17; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for No Treatment than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The secondary outcome results span different domains: motor development, penile-length change, and hormone-related measures listed in the registry. The posted comparative summaries for the motor measures have estimates with substantial uncertainty and intervals that include zero. The penile-length contrast is more clearly separated from zero in the posted comparison. This broad pattern does not mirror a uniform difference across every measured domain, and the primary body-fat result should not be treated as evidence that all secondary outcomes changed in the same way.

Secondary outcomes can add context to a primary result, but they answer additional questions and often involve different measurement scales and biological domains. Their estimates should be considered alongside their intervals rather than ranked only by p-values. In particular, a result whose interval includes zero is not proof that the groups were equivalent; it indicates uncertainty about the direction and size of the contrast in the posted data.

The registry lists additional hormone and motor outcomes, but the available posted comparative summaries do not give detailed estimates for every listed measure. The record also does not report a multiplicity adjustment or a prespecified hierarchy for interpreting secondary outcomes. When multiple outcomes are examined, the chance of at least one apparently notable result can increase. Unadjusted secondary findings therefore carry less weight than a result from a clearly designated primary outcome, especially when the statistical plan and reporting approach are not described.

These outcomes can be useful for generating questions for further research, but they do not establish a single coherent effect across all measured outcomes. Their interpretation remains constrained by the limited group size, the stated follow-up, the intervals’ precision, and the absence of reported details on missing measurements and analysis populations.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Serum Luteinizing Hormone (LH)
• Serum Follicle Stimulating Hormone (FSH)
• Serum Total Testosterone
• Serum Inhibin B (INHB)
• Serum Anti-Mullerian Hormone (AMH)
• Leptin
• Change in Raw Score on the Alberta Infant Motor Scale
• Change in Score on the Movement Assessment of Infants (MAI)

9. Statistical Interpretation

10. Statistical Methods Explained

What does a mean difference express?

A mean difference compares the average outcome in one group with the average in another. The direction depends on which group is subtracted from which. For the primary outcome, the posted contrast is no treatment minus testosterone treatment. A positive estimate therefore means the no-treatment group had the higher mean change in z-score. The group means and contrast refer to the same continuous outcome, but answer different questions: the means describe each group, while the contrast describes their separation on the outcome scale.

Because the endpoint is a change in a z-score, its unit is a score on a scale rather than a percentage-point change in body-fat percentage. The registry defines the reference: zero change corresponds to following the expected growth curve, while positive and negative changes have the interpretations stated in the endpoint description. A difference between group mean changes is not itself a claim about every participant’s change.

What does a standard deviation describe?

A standard deviation describes how spread out participant values are around the group mean. It is a measure of observed variability, not a measure of how precisely the mean is estimated. A group can have a mean that is estimated with uncertainty even when its standard deviation is known; the uncertainty in the mean also depends on the number of observations. The posted primary summaries report a standard deviation for each group. The standard deviations should not be read as ranges containing all participants or as confidence intervals.

How should the confidence interval be read?

A confidence interval gives a range of values for the group difference that are compatible with the observed data under the method’s assumptions. It communicates both the estimated direction and the precision of the estimate. An interval that includes zero does not rule out a group difference, and an interval that excludes zero indicates that the posted data are not compatible with a zero difference at the corresponding conventional two-sided level, under the analysis assumptions. Neither feature establishes clinical importance.

For the primary outcome, the interval is above zero for the stated contrast. For some secondary comparisons, the interval crosses zero; for another, it lies below zero. These interval patterns matter because a point estimate alone does not show how uncertain a result is. The intervals are attached to the contrast as reported and should not be confused with the spread of individual values.

What does the p-value add?

A p-value assesses how unusual data at least as inconsistent with a specified null hypothesis would be if that hypothesis and the analysis assumptions held. It is not the probability that the null hypothesis is true, nor the probability that the result occurred by chance. The primary posted p-value is unadjusted. The registry record does not report whether the trial’s planned analysis included adjustment for multiple outcomes or other analyses, so the posted p-value should not be treated as a multiplicity-adjusted result.

A small p-value does not describe the size or practical importance of a difference. The estimate and confidence interval are needed to understand direction and precision. Conversely, a larger p-value for a secondary comparison does not prove equivalence or no effect; an interval that includes zero can still cover effects in either direction.

Why does randomization matter?

Random allocation is intended to make assigned groups comparable on average with respect to measured and unmeasured characteristics, so that a group contrast can be interpreted as a comparison of assigned strategies. In a study of this size, chance imbalance can still occur. The registry identifies the study as randomized but does not report the sequence-generation or allocation-concealment procedures. It also does not report an analysis population or enough detail to establish how participants were handled after randomization.

The parallel design assigns participants to one of the two groups for the study comparison. Single masking is recorded, but the identity of the masked party is not reported in the registry record. These missing design details limit assessment of potential bias; they do not change the arithmetic meaning of the posted means, contrasts, or intervals.

What can be inferred from the posted summaries?

The posted calculations compare group summaries without an adjustment described in the registry record. They are useful for reading the recorded difference and its uncertainty, but are not a substitute for participant-level analyses or a prespecified analysis plan. The registry record lists no reported analyses in the secondary-outcome entries. It does not report how missing measurements, protocol deviations, or multiple comparisons were addressed. Those omissions matter when judging how robustly the reported comparisons represent the trial’s intended analysis.

General statistical interpretation also depends on assumptions, including the suitability of the method for the distribution and design of the data. The registry record does not provide diagnostics or distributional details that would allow those assumptions to be assessed. The summaries should therefore be read as evidence about the recorded group outcomes, with the stated precision, rather than as a complete diagnostic evaluation.

11. Confidence Intervals and Precision

For the primary mean difference, the posted estimate is 1.04, with a 95% confidence interval from 0.483 to 1.597. Since the contrast is no treatment minus testosterone treatment, the positive interval places the estimated difference in the direction of a greater mean z-score change in the no-treatment group. The interval does not cross zero, so the posted comparison supports a positive difference under its analysis assumptions. The interval still spans a range of possible differences; it does not identify one exact value.

Confidence intervals express precision as well as direction. A narrower interval would indicate greater precision on the same scale, while a wider interval would leave more uncertainty about the size of the contrast. The primary interval is accompanied by group standard deviations and a small recorded group size in each arm, so the mean difference should not be mistaken for a precise description of every infant’s response. Individual outcomes may vary around group means.

The secondary intervals illustrate why point estimates alone are insufficient. The motor-outcome intervals include zero and extend in both directions, so the posted summaries do not tightly determine the direction of those group contrasts. The penile-length interval lies below zero for the no-treatment-minus-testosterone comparison. These distinctions describe statistical precision, not clinical importance, and the secondary findings warrant caution because the registry does not report a multiplicity strategy.

A confidence interval is not a prediction interval for an individual, nor does it state the probability that the true difference lies inside the particular interval. It reflects uncertainty under the method used to calculate it. Further details about the trial’s analysis plan and missing-data handling are not reported in the registry record, which limits assessment of whether the interval captures all relevant sources of uncertainty.

12. 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.

The sample-size figures are planning illustrations based on fractions of the observed effect, not the trial’s original design calculations. For these continuous outcomes, the figures are participants per arm, not total events. The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is the stated fraction of the observed effect. The trial’s own original sample-size assumptions are not reported in the registry record.

The 80% power column gives the number of participants per arm estimated to provide an 80% chance of detecting the specified effect if that effect and the planning assumptions were correct. The 90% power column uses a higher chance of detection, so it generally requires more participants per arm. These are design-planning quantities, not descriptions of what happened in the completed trial.

Rows for 100%, 75%, and 50% of the observed effect illustrate how the planning figures change when the effect targeted is smaller. Smaller effects are harder to distinguish from random variation, so they require more participants under the same assumptions. The estimates are tied to the observed effects, which may be unstable in a small study; they should not be treated as guaranteed requirements for a future trial.

This is not observed power. It is a planning illustration using the posted effect estimates and stated assumptions, and it does not reveal the trial’s original rationale for its enrollment.

13. 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 z_1−α/2 = 1.960) and the desired power (z_1−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

1. Observed difference Δ = 1.040; pooled standard deviation σ = 0.635.
2. n = 2 × (1.96 + 0.842)² × 0.635² / 1.040² = 5.9, rounded up to 6 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 <- 1.04                      # observed difference in means
sigma <- 0.635177140646607                     # 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(2408445)
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 = 6 (80% power), 8 (90% power)
 75% of observed effect: n per arm = 11 (80% power), 14 (90% power)
 50% of observed effect: n per arm = 24 (80% power), 32 (90% power)
power.t.test: 7 
Simulated power at n = 6 per arm: 0.727 (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.

14. Multiplicity, Missing Data and Analysis Populations

The registry record does not report a statistical plan for controlling multiplicity. It lists a primary outcome and multiple secondary outcomes, while the posted comparisons include unadjusted p-values. Without a reported strategy—such as a prespecified testing hierarchy or an adjustment method—it is not possible to determine whether the secondary comparisons were intended as confirmatory tests or exploratory analyses. When many outcomes are tested, the chance of a nominally notable result somewhere among them can rise. This is why individual unadjusted secondary results should be interpreted cautiously.

Missing-data methods are not reported in the registry record. The posted arm summaries identify the number of participants contributing to the displayed outcomes, but do not explain whether any enrolled participants lacked measurements, how such cases were handled, or whether the analysis used all randomized participants. The registry record does not report an intention-to-treat, per-protocol, or other analysis population. Without this information, the effect of missing measurements or post-randomization exclusions cannot be assessed from the summaries alone.

The record also does not report imputation methods, sensitivity analyses, or reasons for missing data. If participants with unavailable measurements differed from those with recorded outcomes, a complete-case summary could potentially represent the randomized groups differently. That is a general concern, not evidence that such differences occurred in this trial.

These omissions do not invalidate the posted numerical results, but they limit appraisal of their robustness and of the relationship between the displayed analyses and the study’s intended analysis. The registry record reports no secondary analyses in its analysis entries, and does not supply enough information to reconstruct a full analysis plan.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

The safety figures shown for the testosterone-treatment group record 0 serious adverse events among 10 participants at risk, 5 other adverse events among 10 participants at risk, and 0 deaths. The registry lists no serious adverse-event terms. These counts describe the posted safety record; they do not describe event severity beyond the serious-versus-other categories recorded, or the timing and relationship of events to treatment.

The available safety summary does not provide corresponding adverse-event counts for the no-treatment group. It also does not report event descriptions for the other adverse events, participant-level detail, or an assessment of whether events were considered treatment-related. The absence of reported serious-event terms should not be read as proof that no safety concerns of any kind occurred. It indicates that no serious adverse-event terms are listed in this record.

With a limited number of participants and the recorded follow-up, the figures offer a descriptive account rather than a precise estimate of event risk. The registry safety summary should be interpreted only as the counts it reports, without inferring a comparative safety difference.

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

The posted primary result is a difference in mean change in an age- and sex-normed body-fat z-score between the randomized groups over the stated period. The estimate is positive for the no-treatment-minus-testosterone contrast, and its confidence interval lies above zero. Under the assumptions of the posted comparison, the recorded data therefore support a difference in mean z-score change between groups over this assessment period.

The z-score is a relative measure, not a direct measure of body-fat percentage points. The registry describes a positive change as a gain in body fat above that typically expected with growth, and a negative change as a gain below that expected. The comparison should be interpreted using this definition, rather than as a claim about the amount of fat gained by every participant. The means summarize groups and do not show the distribution of individual responses.

The result does not establish the duration of any observed difference, its relevance to later development, or whether it generalizes beyond the infants enrolled. It does not establish a causal mechanism or settle the meaning of the secondary results. The motor-outcome intervals include zero, whereas the penile-length comparison has an interval below zero for the stated contrast; these are distinct outcomes and have their own uncertainty. The record does not report a multiplicity plan, detailed missing-data methods, or a complete analysis population, all of which affect how broadly the full set of findings can be interpreted.

Statistical evidence of a group difference is not the same as evidence of clinical importance. The registry record does not give a threshold for a meaningful change in the z-score, and the posted data do not establish such a threshold. The result is best understood as the measured group contrast, with its confidence interval, for the specified outcome and follow-up—not as a conclusion about every possible outcome or longer-term consequence.

17. Why This Trial Matters Statistically

This trial illustrates how a standardized continuous endpoint can frame growth-related outcomes. Body-fat percentage is measured at two time points, then expressed as an age- and sex-normed z-score. That approach makes the outcome interpretable relative to a reference growth pattern and clarifies why a change of zero has a specific meaning in the registry description.

It also shows why estimates, intervals, and outcome definitions need to be read together. The primary comparison is positive in the stated direction and its confidence interval excludes zero, while the secondary motor comparisons remain imprecise. Looking only at a p-value would obscure the scale and range of plausible differences; looking only at group means would omit the uncertainty around their contrast.

The study’s limited enrollment makes precision and generalizability central statistical considerations. The posted results can describe the observed groups, but they cannot by themselves establish whether the same pattern would recur in a broader population or persist beyond the recorded follow-up. Secondary findings also demonstrate the interpretive challenge of multiple outcomes when the registry does not report a multiplicity strategy.

For biostatisticians and clinical researchers, the record is a useful example of the distinction between a registered design feature, a posted result, and an unreported analysis detail. Randomization and a designated primary endpoint provide a framework for comparison, while missing information about masking, analysis populations, missing data, and the original statistical plan constrains deeper appraisal. Those limits are part of the statistical interpretation, rather than a reason to replace the reported estimates with stronger claims.

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 posted summaries come from a small study, with 10 participants in each group for the primary outcome. Estimates from a study of this size can be sensitive to the outcomes of individual participants, and the reported group summaries do not show participant-level distributions. The confidence interval communicates uncertainty in the primary contrast, but the record does not report other analyses that might test its robustness.

The follow-up for the primary outcome is baseline and 3 months. The result therefore addresses change across that period and cannot describe longer-term trajectories. The registry record does not report the identities of masked parties, allocation-concealment procedures, adherence, treatment deviations, or the analysis population. It also does not report how missing outcome data were handled, whether sensitivity analyses were performed, or whether the posted results correspond to a prespecified analysis.

There are multiple secondary outcomes, but no multiplicity strategy is reported. The record provides comparative summaries for some secondary endpoints, while detailed comparative results for every listed hormone outcome are not included in the posted outcome summaries. This limits a comprehensive evaluation across all outcomes and makes isolated secondary findings less secure than the primary result.

The endpoint is a standardized z-score whose interpretation depends on the reference described in the registry. The record does not provide further information on measurement reliability, assessor procedures, or a threshold for clinical importance. These limitations restrict conclusions about measurement, broader applicability, and the practical meaning of the observed difference; they do not alter the numerical estimates recorded.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Body Composition in Infants With Klinefelter Syndrome and Effects of Testosterone Treatment — NCT02408445.
• Registry record last updated 2020-04-15; status last verified 2020-04.
• Results first posted 2020-04-15.
• 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.

22. Record Summary

The registry record describes a completed, randomized, single-masked, parallel-group Phase 4 study sponsored by the University of Colorado, Denver. It enrolled 20 and compared testosterone cypionate treatment with no testosterone treatment in infant males with Klinefelter syndrome. The primary outcome was change in body-fat percentage z-score from baseline to 3 months.

The posted primary mean difference, defined as no treatment minus testosterone treatment, was 1.04, with a 95% confidence interval from 0.483 to 1.597 and an unadjusted p-value of <0.001. Secondary summaries cover motor outcomes and penile-length change, with differing levels of precision. The registry does not report the original sample-size justification, full analysis plan, multiplicity approach, or missing-data methods.