The Developmental Effects of NICU Positioning: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Developmental Effects of NICU Positioning (NCT01628510), a randomized na study. The primary outcome is NICU Network Neurobehavioral Scale (NNNS).

2. Clinical Question

3. Trial Design

The study is listed as a randomized, single-masked, parallel-group trial. Randomization means that assignment to the positioning groups was intended to occur by chance, while a parallel-group design means participants were assigned to one group rather than crossing between both positioning approaches. The record labels the masking as single but does not say who was masked or how masking was maintained. Further details of randomization and masking are not reported in the registry record.

The registry lists an enrollment of 100 and a completed status. The recorded start was 2011-01, and primary completion was 2011-12. These dates describe the registry entry; details of recruitment, follow-up, and whether all enrolled participants contributed to each outcome are not reported in the registry record.

The arms were traditional NICU positioning and Dandle Roo/Dandle Wrap. For the primary outcome, the posted arm summaries include 44 participants in the traditional-positioning group and 48 in the Dandle group. These are the reported outcome group sizes, not a statement about the disposition of everyone enrolled. Reasons that the reported outcome counts differ from the enrollment figure are not reported in the registry record.

The primary outcome was the NNNS asymmetry score at 35 to 41 weeks, described as term equivalent and prior to NICU discharge. The record also names the Bayley Scales of Infant Development-3rd Edition (BSID-III) as a secondary outcome. The registry lists two outcome measures, but only one secondary outcome is named in the record. The phase is listed as not applicable. The sponsor is Washington University School of Medicine.

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: All eligible infants were recruited. Those whose parents signed informed consent were randomized to either traditional positioning or Dandle Roo positioning.

Overall Study

Reasons for not completing this period:

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 NICU Network Neurobehavioral Scale (NNNS), measured over 35 to 41 weeks (term equivalent); prior to NICU discharge.

The primary endpoint is the NNNS asymmetry summary score. The NNNS assesses neonatal behavior and responses, including elicited reflexes and observed behavior. The record describes a set of summary scores for different constructs; the primary posted result concerns asymmetry rather than the other NNNS constructs.

The score was assessed between 35 and 41 weeks postmenstrual age, described in the record as term equivalent and before NICU discharge. The stated scale range for asymmetry is 0 to 16. Higher asymmetry scores mean more asymmetry, so the direction of the score has a specific interpretation: a lower group mean represents less measured asymmetry on this scale, not necessarily a broader developmental advantage.

Neurobehavioral assessment near term-equivalent age provides a standardized way to describe behavior and reflex-related constructs in this population. It is the outcome selected for the primary comparison in this registry record. The record says that the summary scores are analyzed for associations with subsequent developmental outcome, but it does not report the relationship between the posted asymmetry result and later development. The assessment is not itself a report of long-term developmental outcomes.

The arm results are presented as means and standard deviations, which summarize the average score and the spread of scores within each group. The score is one component of a broader assessment; the posted primary result should therefore be read specifically as a comparison of mean asymmetry scores, not as a complete account of neonatal neurobehavior or later development.

7. Results Posted in the Registry

• Dandle Roo/Dandle Wrap: mean 2.56 versus 3.10 on control; difference -0.54 (95% CI -1.36 to 0.28), standardized effect d = -0.27; z-test p = 0.197.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: each infant has a numerical asymmetry score, and the registry reports a mean and standard deviation for each arm. A mean describes the arithmetic average of observed scores within a group. A standard deviation describes how dispersed the scores are around that group's mean. These summaries are useful for comparing average outcomes, while also conveying that individual scores need not be close to the average.

What does the mean difference represent?

The posted mean difference is -0.54 for Dandle Roo/Dandle Wrap relative to traditional positioning. The direction follows the order of the comparison: the Dandle group mean is compared with the traditional-positioning group mean. A negative value therefore indicates a lower sample mean in the Dandle group. Because higher NNNS asymmetry scores mean more asymmetry, this direction corresponds to a lower average measured asymmetry score in that group. It does not, by itself, establish a causal effect or determine the importance of the difference.

The standard deviations are 2.1 for traditional positioning and 1.9 for Dandle Roo/Dandle Wrap. These values describe variation among the observed scores within the respective groups. They are not standard errors, and they do not describe the uncertainty in the difference directly. The standard error of a group mean concerns the precision of that estimated mean; uncertainty in the between-group estimate is represented by its confidence interval.

How should the p-value be read?

The unadjusted p-value is 0.197. In general, a p-value is calculated under a specified null model and describes how unusual the observed data, or data more extreme, would be if that model held. It is not the probability that the null model is true. It does not measure the size or clinical importance of an effect, and it does not account for every design or analysis limitation.

Here, the record labels the value unadjusted. No multiplicity adjustment is described for this comparison. The p-value should be considered together with the estimated mean difference and its confidence interval rather than as a stand-alone verdict. The confidence interval crosses zero, consistent with the lack of clear evidence against an equal-means model in this unadjusted comparison.

Why does the confidence interval matter?

In general, a confidence interval gives a range of values compatible with the data and the statistical procedure used to calculate it. Its width conveys precision: a wider interval represents less precise estimation than a narrower interval, all else equal. An interval that crosses zero for a mean difference includes no difference as one compatible value. It can also include differences in either direction, so the estimate should not be reduced to a binary conclusion.

The reported interval extends on both sides of zero. The lower and upper limits are posted with the comparison, and the interval is the key summary of uncertainty around the -0.54 estimate. The interval does not mean that there is a particular probability that the true value lies within those fixed limits; the usual confidence interpretation concerns the behavior of the method over repeated samples under its assumptions.

What assumptions and analysis details are known?

The record posts arm means, standard deviations, group sizes, a mean difference, a confidence interval, and an unadjusted p-value. The statistical analysis plan, model details, treatment of missing values, and analysis population are not reported in the registry record. Consequently, the posted summary comparison cannot be used to infer whether covariates were considered in another analysis or how any such analysis was conducted. The registry lists zero analysis entries, although it also posts an arm comparison and its summary statistics.

General statistical considerations are relevant when interpreting a continuous endpoint. A mean comparison is most informative when the summary adequately represents the score distributions and when the assumptions of the inferential method are appropriate. The record does not provide score distributions, diagnostics, or an explanation of the method used to calculate the comparison. It is therefore not possible to assess those details from the registry record.

Randomization can reduce systematic differences between groups on average, but it does not guarantee that groups are identical in a particular trial. Baseline characteristics are not reported in the outcome information, so the extent of any observed baseline imbalance cannot be assessed. The record does not report whether the posted result follows an intention-to-treat approach or another analysis population.

The calculation of group summaries and the choice of inferential method are distinct. Means and standard deviations describe the posted observations; the p-value and interval rely on an inferential procedure. Without the analysis plan and model details, interpretation should stay with the reported estimates and their stated uncertainty rather than attributing a particular method or adjustment to the investigators.

10. Confidence Intervals and Precision

The mean difference is -0.54, with a confidence interval that crosses zero. This interval indicates that the estimate is not very precise relative to the range of values compatible with the reported data and method. In particular, the data do not isolate a difference in one direction: the interval includes zero and extends into positive as well as negative values.

In general, a confidence interval is a range produced by a statistical procedure to express uncertainty about an estimated quantity. A narrower interval generally represents greater precision, while a wider interval leaves more possible values compatible with the data. This does not mean every value in the interval is equally plausible, and it does not give the probability that the true effect lies inside the particular observed interval.

The reported group standard deviations, 2.1 for traditional positioning and 1.9 for Dandle Roo/Dandle Wrap, provide context about the spread of observed scores. The reported outcome group sizes are 44 and 48, respectively. Precision depends on both variability and the amount of information available, as well as the analysis method. The registry record does not report the original analysis plan or the method used to construct the interval, limiting further assessment of its assumptions.

The p-value of 0.197 is consistent with uncertainty in the estimated difference, but it is not a measure of precision by itself. The confidence interval is more informative about the range and direction of values compatible with the estimate. The posted results do not establish that the groups have equal means; rather, the interval leaves equality among the possibilities while also allowing nonzero differences.

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.

The sample-size figures are planning illustrations based on the observed effect, not the trial's original design assumptions. They give participants per arm, not total participants or total events. The planning assumptions are a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation. Each planning scenario targets a stated fraction of the observed effect.

For planning based on 100% of the observed effect, the figures are 215 participants per arm for 80% power and 288 participants per arm for 90% power. For planning based on 75% of the observed effect, they are 383 participants per arm for 80% power and 512 participants per arm for 90% power. For planning based on 50% of the observed effect, they are 860 participants per arm for 80% power and 1,151 participants per arm for 90% power.

In general, power is the chance that a planned study will detect an effect of the assumed size under the model and design assumptions, if that effect is present. The 80% and 90% columns represent different target chances of detecting the assumed effect. Higher target power requires more participants under the same other assumptions. Smaller effects are harder to distinguish from random variation, so planning for a smaller fraction of the observed effect requires more participants per arm.

These figures are not observed power. They are conditional planning illustrations based on this trial's observed estimate, and the original trial's sample-size justification and design assumptions are not reported in the registry record. They should not be read as evidence about what power the completed trial actually had or as a definitive sample-size recommendation for another study.

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 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 = -0.540; pooled standard deviation σ = 1.998.
2. n = 2 × (1.96 + 0.842)² × 1.998² / -0.540² = 214.9, rounded up to 215 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 <- -0.54                      # observed difference in means
sigma <- 1.99805460941943                     # 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(1628510)
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 = 215 (80% power), 288 (90% power)
 75% of observed effect: n per arm = 383 (80% power), 512 (90% power)
 50% of observed effect: n per arm = 860 (80% power), 1,151 (90% power)
power.t.test: 215.9 
Simulated power at n = 215 per arm: 0.800 (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. Multiplicity, Missing Data and Analysis Populations

The registry record names the NNNS asymmetry score as the primary outcome and the BSID-III as a secondary outcome. It also states that the NNNS includes multiple summary constructs, with each analyzed for associations with subsequent developmental outcome. The record does not report how many hypotheses were included in the investigators' analysis plan, whether outcomes or comparisons were prioritized beyond the primary designation, or whether any multiplicity adjustment was planned or applied. The posted p-value is described as unadjusted.

Multiplicity matters because testing multiple outcomes or hypotheses can increase the chance of obtaining at least one apparently notable result by chance. In general, an adjustment can address this issue, but the appropriate approach depends on the analysis plan and the scientific questions. Since those details are not reported in the registry record, the degree to which multiplicity was considered cannot be determined from the posted information.

Missing-data handling is also not reported in the registry record. The enrollment figure is 100, while the primary outcome summaries list 44 participants in the traditional-positioning arm and 48 in the Dandle arm. These outcome counts do not explain the status of all enrolled participants. Reasons for absent outcome data, if any, and the method used to handle missing observations are not reported. The record does not state whether missing outcomes were imputed or whether analyses used only observed scores.

The analysis population is not reported in the registry record. In particular, it does not specify whether the comparison followed assignment regardless of adherence, included only participants with measured outcomes, or used another population definition. The registry indicates zero analysis entries even though a summary comparison and p-value are posted. This limits the detail available about the inferential analysis and its relationship to the original plan.

14. 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 5% reporting threshold.

The registry reports serious adverse events, other adverse events, and deaths by arm. For Dandle Roo/Dandle Wrap, the record lists 48 at risk for serious adverse events and 48 at risk for other adverse events; both event counts are 0, and deaths are 0. For traditional NICU positioning, it lists 44 at risk for each adverse-event category; both event counts are 0, and deaths are 0.

These are the event figures recorded for the groups and categories listed. A zero count means that no events in that category were reported in the registry data for the stated group; it does not prove that an event is impossible or that all possible harms were captured. The record does not provide adverse-event definitions, collection procedures, follow-up duration for safety, or details of how events were assessed.

The figures should be interpreted as registry safety reporting rather than as a complete assessment of risk. The at-risk counts attached to the safety categories are the relevant reported denominators. No serious adverse-event terms are listed. The registry information does not support a broader comparison of safety beyond the recorded counts.

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

The posted primary result describes average NNNS asymmetry scores near term-equivalent age in the two positioning groups. The Dandle Roo/Dandle Wrap group had a mean score of 2.56, and the traditional-positioning group had a mean of 3.1. The reported mean difference was -0.54, favoring a lower observed group mean in the Dandle arm on this particular score. Higher scores represent more asymmetry.

The confidence interval crosses zero, and the unadjusted p-value is 0.197. These results leave substantial uncertainty about the size and direction of the underlying mean difference. The observed estimate alone does not establish that the positioning methods differ, and the uncertainty does not establish that they are equivalent. The record does not report an equivalence or non-inferiority framework.

The outcome is a specific neurobehavioral summary score measured during a defined period before NICU discharge. It is not a direct measure of every aspect of development, and it is not the same as a later developmental assessment. Although the BSID-III is named as a secondary outcome, its result is not reported in the outcome information described by this record. The primary result therefore cannot answer what happened on that secondary measure.

Nor do these summaries establish why any difference occurred. The study is randomized, but details of masking, adherence, missing data, analysis population, and the statistical plan are not reported. Those omissions constrain interpretation of the causal comparison. The posted adverse-event counts are zero for the listed categories, but they do not establish the absence of all possible harms or replace a detailed safety assessment.

In short, the record gives an estimate of the difference in mean asymmetry scores and communicates uncertainty around that estimate. It does not establish a definitive developmental benefit, harm, or equivalence for either positioning approach, and it should not be generalized beyond the outcome, assessment period, and information recorded.

16. Why This Trial Matters Statistically

This trial illustrates why a point estimate and its uncertainty need to be read together. The mean difference is -0.54, which indicates the direction and magnitude of the observed contrast, while the confidence interval crossing zero shows that the data are compatible with no group mean difference as well as with differences in either direction. A single p-value cannot convey this range of uncertainty as clearly.

It also highlights the distinction between a measured endpoint and a broad clinical concept. The primary outcome is one NNNS construct, asymmetry, scored at a specific developmental period. Statistical interpretation should remain tied to that outcome rather than expanding the result into a claim about all neurodevelopment or later development. The named secondary outcome is not accompanied by a reported result in this record.

Sample-size planning provides another useful statistical lesson. The registry lists illustrations for detecting different fractions of the observed effect, with progressively larger participant requirements for smaller effects and for higher power targets. These are planning calculations, not evidence that the completed trial had a particular observed power or that its original design used these assumptions.

Finally, the record demonstrates the importance of transparent reporting beyond headline estimates. Details about the analysis plan, missing data, analysis population, multiplicity, and outcome assessment procedures affect how readers evaluate the comparison. Their absence does not erase the reported result, but it limits how fully its statistical foundations and generalizability can be assessed.

17. 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 registry record gives limited information about eligibility, participant characteristics, and the clinical setting beyond premature infants receiving NICU positioning. Baseline characteristics are not reported in the outcome information, so the comparability of the groups on measured or prognostic factors cannot be assessed. The descriptions of both positioning approaches are truncated, leaving their exact implementation unclear.

Masking is listed as single, but the record does not identify who was masked or describe how masking was maintained. It also does not report adherence, crossovers, co-interventions, or protocol deviations. These details matter when interpreting a randomized comparison, especially when the intervention involves positioning practices and outcome assessment includes observed behavior.

The primary outcome group counts are 44 for traditional positioning and 48 for Dandle Roo/Dandle Wrap, while the enrollment figure is 100. The record does not explain this difference or report reasons for missing outcome measurements. It also does not identify the analysis population or how missing observations were handled. As a result, the possibility and consequences of incomplete outcome data cannot be evaluated from the registry record.

The statistical analysis plan, method for the confidence interval and p-value, and multiplicity strategy are not reported. The record indicates zero analysis entries even though it posts an unadjusted comparison. No detailed results are listed for the named BSID-III secondary outcome. These reporting gaps limit assessment of prespecification, selective reporting, and the broader pattern of results.

Finally, the primary endpoint concerns NNNS asymmetry near term-equivalent age. The record does not report follow-up results connecting this score to later development. The posted endpoint therefore supports interpretation only of the measured score at the stated timeframe, not long-term outcomes.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: The Developmental Effects of NICU Positioning — NCT01628510.
• Registry record last updated 2018-02-27; status last verified 2018-01.
• Results first posted 2015-04-13.
• 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.

21. Record Summary

NCT01628510 is a completed randomized, single-masked, parallel-group trial titled “The Developmental Effects of NICU Positioning.” It compared Dandle Roo/Dandle Wrap with traditional NICU positioning for premature infants. The registry lists enrollment of 100, a start of 2011-01, and primary completion of 2011-12.

The primary outcome was the NNNS asymmetry score measured at 35 to 41 weeks, before NICU discharge. The reported mean difference was -0.54, with an unadjusted p-value of 0.197 and a confidence interval that crosses zero. The record also names the BSID-III as a secondary outcome, but does not report its result in the posted outcome information.

Serious adverse events, other adverse events, and deaths are recorded as zero in both arms. Details about missing data, analysis populations, multiplicity, and the original statistical plan are not reported in the registry record.