North Carolina Genomic Evaluation by Next-generation Exome Sequencing, 2: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for North Carolina Genomic Evaluation by Next-generation Exome Sequencing, 2 (NCT03548779), a randomized na study. The primary outcome is Initial Patient Pediatric Quality of Life (Peds QL) Score.

2. Clinical Question

3. Trial Design

NCGENES 2 is recorded as a randomized, double-masked, parallel study, with a 2x2 factorial design described in the study summary. The stated comparisons concern first-line exome sequencing versus usual care and participant pre-visit preparation versus no pre-visit preparation. The primary outcome results are presented for four combinations of those components: pre-visit preparation with exome sequencing, pre-visit preparation with usual care, no preparation with exome sequencing, and no preparation with usual care.

The registry record lists enrollment of 548 and a completed study. The recorded study dates are 2018-09-28 for the start and 2023-09-08 for primary completion. The sponsor is the University of North Carolina, Chapel Hill. The record lists phase as NA.

The primary outcome analysis is among parent or caregiver participants, rather than a summary of every enrolled participant. The caregiver counts contributing to the primary measure range from 61.0 to 72.0 across the four groups. These counts do not equal the overall enrollment because the primary measure has its own analysis population. The registry record does not explain the difference between overall enrollment and the numbers contributing to this outcome.

The study summary describes the broader aim as assessing clinical utility, including diagnostic efficacy, management planning, medical outcomes, and patient and family well-being. It also describes collection of patient-reported outcomes and clinical data. The primary result is narrower: an initial caregiver-reported quality-of-life score measured before clinic visit 1. It does not by itself represent all the outcomes or aims described for the study.

The registry record does not report the original sample-size justification, the detailed allocation procedure, or how masking was implemented. The factorial design is stated, but the available primary comparisons are contrasts of individual groups against one reference group. They do not report separate factorial main effects or an interaction estimate.

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.

Only the first 6 of 8 groups are shown.

Clinical Study

Health Care Records Analysis

Analysis population for the primary outcome, as defined in the registry: This analysis is conducted among the parent/caregiver participants only.

5. Baseline Characteristics

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

Population: 274 dyads were randomized to the four study groups

Only the first 6 of 9 groups are shown.

6. Primary Endpoint

The registry lists the primary outcome as Initial Patient Pediatric Quality of Life (Peds QL) Score, measured over 4-6 weeks prior to clinic visit 1.

The primary endpoint is the initial Patient Pediatric Quality of Life score, abbreviated Peds QL in the registry record. It is a continuous score on a 0-100 scale, measured 4-6 weeks prior to clinic visit 1. The analysis population is parent or caregiver participants only, and the reported summary is the mean with standard deviation.

The measure is based on the 23-item PedsQL Core Scales, covering physical, emotional, social, and school functioning. The record describes developmentally appropriate questionnaires for ages 2-4, 5-7, 8-12, and 13-18, designed for parent proxy report. Items are answered on a 0-4 scale, reversed scored, and transformed to a 0-100 scale. Higher scores indicate better health-related quality of life. The questionnaire is described as self-administered at home.

A patient- or caregiver-reported measure can capture aspects of health and functioning that may not be represented by clinical or diagnostic outcomes alone. In this study, the initial score characterizes caregiver reports before clinic visit 1. It is not a measure of whether a diagnosis was made, whether management changed, or whether later outcomes improved. The registry record identifies it as the primary outcome but does not report a rationale for selecting this specific measure or time point.

7. Results Posted in the Registry

• Parent/Caregiver Pre-visit Prep + Exome: mean 64.37 versus 65.83 on control; difference -1.46 (95% CI -8.10 to 5.18), standardized effect d = -0.08; z-test p = 0.666.
• Parent/Caregiver No Pre-visit Prep + Exome: mean 60.04 versus 65.83 on control; difference -5.79 (95% CI -11.81 to 0.23), standardized effect d = -0.33; z-test p = 0.059.
• Parent/Caregiver No Pre-visit Prep + Usual Care: mean 63.39 versus 65.83 on control; difference -2.44 (95% CI -8.44 to 3.56), standardized effect d = -0.13; z-test p = 0.426.

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.

Initial Average Peds QL Score for "Missing School for Not Feeling Well"

• 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:
  • Parent/Caregiver Pre-visit Prep + Exome: mean 70.80 versus 80.60 on control; difference -9.80 (95% CI -21.42 to 1.82), standardized effect d = -0.39; z-test p = 0.098.
  • Parent/Caregiver No Pre-visit Prep + Exome: mean 65.50 versus 80.60 on control; difference -15.10 (95% CI -25.76 to -4.44), standardized effect d = -0.61; z-test p = 0.005.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Parent/Caregiver Pre-visit Prep + Exome and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Parent/Caregiver No Pre-visit Prep + Exome than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Final Average Peds QL Score for "Missing School for Not Feeling Well"

• 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:
  • Parent/Caregiver Pre-visit Prep + Exome: mean 77.10 versus 82.60 on control; difference -5.50 (95% CI -21.83 to 10.83), standardized effect d = -0.24; z-test p = 0.509.
  • Parent/Caregiver No Pre-visit Prep + Exome: mean 78.90 versus 82.60 on control; difference -3.70 (95% CI -17.67 to 10.27), standardized effect d = -0.16; z-test p = 0.604.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Parent/Caregiver Pre-visit Prep + Exome and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Parent/Caregiver No Pre-visit Prep + Exome and the control. The interval gives the range of effects that remain compatible with the data.

Initial Average Peds QL Score for "Missing School for Doctors Visit"

• 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:
  • Parent/Caregiver Pre-visit Prep + Exome: mean 59.70 versus 65.00 on control; difference -5.30 (95% CI -17.96 to 7.36), standardized effect d = -0.19; z-test p = 0.412.
  • Parent/Caregiver No Pre-visit Prep + Exome: mean 54.90 versus 65.00 on control; difference -10.10 (95% CI -22.08 to 1.88), standardized effect d = -0.37; z-test p = 0.098.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Parent/Caregiver Pre-visit Prep + Exome and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Parent/Caregiver No Pre-visit Prep + Exome and the control. The interval gives the range of effects that remain compatible with the data.

The registry record lists 35 outcome measures and posts 15 secondary outcomes. The available secondary summaries include initial and final caregiver-reported scores related to missed school and work effects. Across the reported comparisons, estimates for initial outcomes generally point toward lower means in the compared groups than in the pre-visit preparation plus usual-care reference group. One initial comparison has an unadjusted interval that does not include zero; the other posted initial comparisons and the posted final comparisons have intervals that include zero. This pattern is descriptive and does not establish a consistent secondary-outcome effect.

The primary outcome is also an initial caregiver-reported Peds QL score, but it summarizes a broader quality-of-life measure rather than a single item about school absence. The secondary findings therefore add context about specific reported impacts; they do not substitute for the primary outcome or resolve its uncertainty. The record does not report a combined analysis relating these secondary measures to the primary score.

Unadjusted secondary results carry less weight when many outcomes and comparisons are examined. General statistical context: the more separate statistical tests conducted, the greater the chance that at least one result may appear unusual by chance, even if no underlying differences exist. The registry record does not report a multiplicity adjustment or a prespecified hierarchy for interpreting secondary outcomes. It is therefore inappropriate to treat an isolated unadjusted result as decisive evidence, especially without an analysis plan and a clear account of which outcomes were designated in advance.

The registry record does not give a complete set of results for all listed secondary outcomes in the material available for these summaries. Nor does it report analyses that combine the secondary outcomes or account for repeated measurements. The observed pattern should be read as exploratory context around the primary result, rather than as a broad conclusion about caregiver or family well-being.

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

• Initial Average Peds QL Score for "Missing School for Not Feeling Well"
• Final Average Peds QL Score for "Missing School for Not Feeling Well"
• Initial Average Peds QL Score for "Missing School for Doctors Visit"
• Final Average Peds QL Score for "Missing School for Doctors Visit"
• Initial Amount of Work Missed Because of Child's Condition or Treatments Score
• Final Amount of Work Missed Because of Child's Condition or Treatments Score
• Initial Difficulty With Finishing Normal Work (Including Both Work Outside of the Home and Housework) Because of Child's Condition or Treatments Score
• Intermediate Difficulty With Finishing Normal Work (Including Both Work Outside of the Home and Housework) Because of Child's Condition or Treatments Score

9. Statistical Interpretation

10. Statistical Methods Explained

What does a mean difference describe?

A mean is the arithmetic average of the recorded scores in a group. The primary outcome is continuous, so the registry reports each group’s mean and standard deviation. The mean difference contrasts a group’s average with the average in the selected reference group. In these comparisons, the reference is parent or caregiver participants assigned to pre-visit preparation plus usual care. A negative contrast means the compared group had a lower observed mean; because higher Peds QL scores indicate better health-related quality of life, a lower score points in the direction of lower reported quality of life on this measure. That direction alone does not establish a causal effect or a clinically important difference.

What does the standard deviation add?

The standard deviation describes the spread of individual scores around a group mean. It is not the uncertainty interval for the mean and does not indicate how much the mean would vary across repeated samples. The reported standard deviations show that individual caregiver scores vary within each group. General statistical context: when measurements are dispersed, a mean can be estimated less precisely than when observations cluster more closely, all else being equal. Group size also affects precision. The registry reports standard deviations and participant counts, but it does not give a clinical threshold for interpreting the size of a score difference.

How should the intervals and p-values be read?

An interval around a mean difference describes uncertainty about the contrast under the statistical procedure used. General statistical context: intervals that include zero are compatible with a zero mean difference at the interval’s stated confidence level, as well as with nonzero differences within the interval. The registry record does not state the confidence level for the posted interval bounds, so no confidence percentage is assigned. The intervals for all three primary contrasts include zero.

A p-value summarizes how compatible the observed data are with a specified null model, under the assumptions of the analysis. It is not the probability that the null hypothesis is true, and it does not measure the probability that a result will replicate. The listed p-values are unadjusted. They should not be read as correcting for the number of outcomes or comparisons in the study. In general, a p-value also does not describe the size or practical importance of a difference; the estimate and interval are needed for that.

Why distinguish the displayed contrasts from factorial effects?

The study summary describes a 2x2 factorial design, with sequencing and pre-visit preparation as the two components. A factorial analysis can estimate the average contribution of each component across levels of the other component and can assess whether the components’ effects depend on one another. The primary results available in the registry instead compare each of three combinations against pre-visit preparation plus usual care. These group-versus-reference contrasts are not the same as reported factorial main effects or an interaction. The registry record does not report those factorial estimates or the model used to obtain them.

The presented mean differences, intervals, and p-values are unadjusted recalculations from the posted group summaries. The record contains no associated reported analyses for these outcomes. An unadjusted calculation uses the group-level means, standard deviations, and counts without a reported covariate adjustment. It can help readers understand the direction and precision of a simple contrast, but it does not reveal whether the study’s intended analysis used additional modeling, missing-data methods, or other adjustments. Those details are not reported in the registry record.

Why can over-dispersion matter?

General statistical context: over-dispersion means that observed variability is greater than a statistical model assumes. If a model underestimates variability, standard errors may be too small and uncertainty may appear narrower than it should. The primary outcome is summarized as a continuous score with standard deviations, and no over-dispersion assessment is reported. The general issue is relevant when choosing a model, but there is no basis in the registry record to say that over-dispersion occurred in this analysis.

What do the planning calculations represent?

The planning illustrations use the observed group differences as reference effects and show participant requirements under stated assumptions. They are not the study’s original design justification. The registry record lists a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. The displayed fractions are 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. General statistical context: if a smaller difference is the target while the other planning assumptions remain fixed, more participants are generally required to distinguish it from random variation with the same power. The original design assumptions and any original sample-size rationale are not reported in the registry record.

11. Confidence Intervals and Precision

The intervals for the primary mean differences communicate uncertainty about the comparisons, not uncertainty about every individual score. For pre-visit preparation plus exome versus pre-visit preparation plus usual care, the difference is -1.46, with bounds of -8.097 and 5.177. For no preparation plus exome versus the reference group, it is -5.79, with bounds of -11.81 and 0.226. For no preparation plus usual care versus the reference group, it is -2.44, with bounds of -8.442 and 3.562. Each interval includes zero, and each also permits a range of negative differences.

General statistical context: a confidence interval gives a range of values compatible with the data and the interval procedure, conditional on its assumptions. Wider intervals indicate less precision than narrower intervals. The confidence level associated with these posted bounds is not reported in the registry record, so it cannot be stated. The intervals do not mean that every value inside them is equally plausible, and they do not guarantee that the true value lies within the bounds.

The group standard deviations are substantial relative to the observed mean differences, and the outcome counts vary across groups. Both the variability of scores and the amount of information available influence precision. The estimates should therefore be considered alongside their intervals rather than interpreted from the point estimates alone. In particular, an interval that includes zero does not demonstrate equivalence; an equivalence conclusion would require a defined margin and an analysis designed for that question. Neither is reported in the registry record.

The listed intervals and p-values are unadjusted recalculations from posted summary statistics. No adjusted primary analysis is reported in the registry record. Thus, the stated precision reflects these simple contrasts and should not be mistaken for a full account of uncertainty under an unreported analysis plan.

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 planning figures are participants per arm for 80% power and participants per arm for 90% power. These are participant counts for the continuous-outcome comparisons, not total event counts. The planning assumptions listed in the registry record are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning scenario targets the stated fraction of the observed effect: 100%, 75%, or 50%. The original trial’s own sample-size assumptions and justification are not reported in the registry record.

In plain language, the 80% power column gives the number of participants per arm estimated to provide an 80% chance of detecting the specified effect under the planning assumptions, if that effect is present. The 90% power column gives the corresponding planning count for a 90% chance. Power is a property of a planned design under assumptions, not a measure of whether the observed result is true or important.

Within a comparison, the smaller-effect scenarios require more participants per arm than the scenario targeting the full observed effect. This follows because a smaller difference is harder to distinguish from random variation when score variability is otherwise similar. The planning estimates are tied to the observed effect in this study and should not be treated as a recommendation for another study without considering its population, outcome, and design. These figures are not observed power.

The planning displays give separate estimates for each comparison and effect fraction. Their purpose is to illustrate how sample requirements change with the target effect and desired power. They do not establish that the completed study was designed with these calculations, and they do not replace the unreported original sample-size rationale.

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 = -1.460; pooled standard deviation σ = 19.259.
2. n = 2 × (1.96 + 0.842)² × 19.259² / -1.460² = 2,731.4, rounded up to 2,732 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 <- -1.45999999999999                      # observed difference in means
sigma <- 19.2587311068552                     # 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(3548779)
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 = 2,732 (80% power), 3,657 (90% power)
 75% of observed effect: n per arm = 4,856 (80% power), 6,501 (90% power)
 50% of observed effect: n per arm = 10,926 (80% power), 14,627 (90% power)
power.t.test: 2732.4 
Simulated power at n = 2,732 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.

14. Multiplicity, Missing Data and Analysis Populations

The study record lists many outcome measures, including a primary endpoint and multiple secondary outcomes. It does not report how the analysis accounted for testing multiple outcomes or comparisons. This matters because, in general, conducting many tests increases the chance that some results will appear notable by chance. The secondary p-values are unadjusted, and no multiplicity correction, testing hierarchy, or other family-wise error strategy is described in the registry record. The primary results should also be interpreted in the context of the broader outcome set, rather than as if they were the only analyses conducted.

The record does not report a detailed statistical analysis plan, the model for the primary endpoint, covariate adjustment, or whether assumptions were checked. It does not report how missing observations were handled, whether an imputation procedure was used, or whether sensitivity analyses assessed the consequences of missing data. Counts differ across outcomes and groups, and the final outcome summaries have fewer participants than the initial summaries. The reason for these differences and the patterns of missingness are not reported in the registry record; the counts alone cannot show whether missingness was random or related to participant characteristics or outcomes.

The primary outcome population is specified as parent or caregiver participants only. The record does not describe a broader intention-to-treat analysis population for this endpoint, how participants were retained in analyses after randomization, or how any departures from assigned groups were addressed. Details of the allocation sequence and the implementation of masking are also not reported. The study summary describes a factorial design, but separate main-effect and interaction analyses are not reported for the primary outcome.

These omissions limit the ability to assess whether the posted simple comparisons match the study’s intended analyses. They do not show that a particular method was or was not used outside the registry record. They indicate that the corresponding analysis details are not reported in the registry record.

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 serious adverse event terms

Serious events with the highest arm-level rate: septic shock (1.4%).

The serious adverse event summary is reported for child groups, while the primary quality-of-life outcome is analyzed among parent or caregiver participants. In the child pre-visit preparation plus usual-care group, 1 serious adverse event was recorded among 70 participants at risk, and 1 death was recorded. The other listed child groups each had zero serious adverse events and zero deaths. The record lists no other adverse events in these groups.

The serious event term listed is septic shock, with a reported frequency of 1.4%. This is a descriptive registry entry. The record does not state whether the serious event or death was considered related to the study intervention, and the listed term should not be taken as evidence of causation. Event counts also do not, by themselves, establish comparative safety; they describe what was recorded in the listed groups during the reporting period.

The registry record does not provide further clinical detail about the event, the death, or their timing. The figures should therefore be read as a brief accounting of reported serious events, other adverse events, and deaths, not as a complete clinical assessment or a comparison adjusted for differences between groups.

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

The primary result describes caregiver-reported quality of life before clinic visit 1. The mean score in the pre-visit preparation plus usual-care reference group was 65.83. The other group means were 64.37, 60.04, and 63.39. The unadjusted mean differences against the reference group were negative, but their intervals all include zero. The posted data therefore leave uncertainty about the size and direction of the underlying group differences.

These numbers do not establish that any study component improves or worsens health-related quality of life. They do not establish equivalence between groups, since no equivalence margin or equivalence analysis is reported. They also do not indicate whether an observed score difference would matter to participants: the registry record does not report a threshold for clinical importance. The p-values are unadjusted and should not be read as probabilities that a treatment effect exists or does not exist.

The primary measure is one part of a larger study that the registry describes as addressing diagnostic efficacy, management planning, medical outcomes, and patient and family well-being. A baseline caregiver-reported Peds QL score does not answer all of those questions. It is measured before clinic visit 1 and does not, by itself, describe change after results are returned or show whether diagnoses or medical management differed between groups.

The study’s factorial structure also calls for care in interpreting the group contrasts. The results compare each of three combinations with one reference combination. They do not report the average contribution of exome sequencing across preparation groups, the average contribution of preparation across sequencing groups, or whether those components interact. Those distinct questions are not answered by the listed contrasts.

In general, randomized comparisons can help distinguish intervention effects from differences that existed before assignment, but interpretation still depends on the analysis population, missing-data handling, outcome selection, and analysis methods. Several of those details are not reported in the registry record. The appropriate reading is therefore limited to the posted group summaries and their unadjusted comparisons, without a broader claim about treatment benefit, diagnostic utility, or medical outcomes.

17. Why This Trial Matters Statistically

This study is statistically notable for combining two components in a factorial design: exome sequencing and pre-visit preparation. That design can address more than one question within a single trial, but the conclusions depend on matching the analysis to the design. The available primary comparisons use the pre-visit preparation plus usual-care group as a common reference. They are informative as group contrasts, but they do not present the separate factorial effects or interaction that would help describe the components across the full design.

The primary outcome also illustrates the distinction between a point estimate and its precision. The observed mean differences are negative, while all three intervals include zero. Readers can see both the direction of the posted estimates and the uncertainty around them, rather than relying on a single p-value. The caregiver-reported outcome adds a perspective on well-being that is different from diagnostic or clinical measures, though the initial measurement alone cannot establish later change.

The registry record includes several secondary outcomes and a larger set of listed measures. This makes transparent reporting of the analysis plan, missing-data handling, and multiplicity approach especially relevant. Without those details, unadjusted secondary findings should be treated cautiously, and readers cannot determine how the reported results relate to any prespecified hierarchy or comprehensive analysis.

Finally, the record provides planning illustrations based on observed effects while not reporting the trial’s original sample-size rationale. Keeping these distinct helps prevent a retrospective calculation from being mistaken for the basis of the trial’s design. Together, these features make the study useful for understanding how design, outcome choice, and uncertainty shape interpretation of clinical research results.

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 primary measure is restricted to parent or caregiver participants and captures an initial report 4-6 weeks prior to clinic visit 1. It does not directly describe the child’s clinical status, diagnostic findings, or subsequent change. The registry record does not report a threshold for meaningful change on the scale, limiting interpretation of the practical importance of the observed mean differences.

The listed contrasts are unadjusted comparisons of each study group against one reference group. Although the study summary describes a 2x2 factorial design, the record does not report factorial main effects or an interaction estimate for the primary outcome. It also does not provide the full statistical model, covariate adjustment, or confidence level for the posted interval bounds. As a result, these contrasts cannot establish the overall effect of either component averaged across the other component.

The primary counts range from 61.0 to 72.0, and the posted secondary results show different counts by outcome and group. The registry record does not explain missing observations, attrition, analysis-population rules, or sensitivity analyses. It is not possible to determine from the counts alone why participants did not contribute to each measure or whether missingness could affect the comparisons.

The record also does not report the original sample-size rationale, detailed multiplicity handling, or the broader analysis plan. Secondary outcomes are numerous, while the available analyses are unadjusted; isolated secondary findings consequently warrant caution. These are limitations of what the registry record reports and do not establish that additional analyses were not conducted elsewhere.

Finally, the reported safety summary is brief and does not provide event-level clinical context or causal attribution. The primary outcome findings and safety counts address different participant groups, so they should not be combined into a single assessment of benefit and risk.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: North Carolina Genomic Evaluation by Next-generation Exome Sequencing, 2 — NCT03548779.
• Registry record last updated 2025-05-13; status last verified 2024-02.
• Results first posted 2025-05-13.
• 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.

22. Record Summary

NCGENES 2 is listed as a completed, randomized, double-masked, parallel study sponsored by the University of North Carolina, Chapel Hill, with enrollment of 548. Its summary describes a 2x2 factorial evaluation of exome sequencing and participant pre-visit preparation.

The primary outcome is the initial parent or caregiver Peds QL score, collected 4-6 weeks prior to clinic visit 1. Higher scores indicate better health-related quality of life. The registry reports group means and standard deviations and unadjusted comparisons against the pre-visit preparation plus usual-care group. All three primary comparison intervals include zero.

The registry record also lists secondary outcomes and a brief child safety summary. It does not report the original sample-size rationale, the detailed analysis plan, multiplicity handling, or missing-data methods. The posted results support interpretation of the stated group summaries and unadjusted contrasts, but not broader conclusions about factorial effects or the study’s full clinical aims.