Cell Phone Support to Promote Medication Adherence Among Adolescents and Young Adults With Chronic Illness: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Cell Phone Support to Promote Medication Adherence Among Adolescents and Young Adults With Chronic Illness (NCT04241627), a randomized na study. The primary outcome is Self-Reported Medication Adherence.

2. Clinical Question

3. Trial Design

This completed study is registered as a randomized, controlled, parallel-group pilot trial with three arms. The registry lists allocation as randomized and masking as none. The sponsor is Children's Hospital Los Angeles. The study start date is 2020-08-01 and the primary completion date is 2022-08-30. The registry record gives enrollment as 34, while the brief study summary describes a plan for N = 60 participants. These are different record statements; the registry does not explain the difference.

The three arm descriptions are Cell Phone Support, Live Text Support, and Automated Text Reminders. The first two involve an adherence facilitator: phone calls or text messages, respectively, with support delivered on weekdays for 12 weeks. The automated reminder arm uses a fixed text-message template. The study summary describes a comparison with usual care, but the detailed arm description names automated reminders. The registry record does not resolve this difference in wording.

The summary describes a pilot intended to examine medication adherence and illness self-management across varied health conditions, as well as participants' perceptions of the facilitator and communication mode. It says questionnaires and focus groups would be used. The posted primary outcome is self-reported medication adherence at 12 weeks. Although the record indicates two outcome measures, no secondary outcome results are posted in the information available in the registry record. The protocol details, randomization procedure, allocation ratio, and trial-specific statistical analysis plan are not reported in the registry record.

For the primary outcome, the reported analysis population is limited to participants with post-treatment self-report data. The number randomized to each arm and the number of participants with missing outcome data are not reported in the registry record. The arm-level counts shown with the primary outcome should therefore be read as the analyzed group counts for that endpoint, not as a complete account of enrollment or follow-up.

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

Analysis population for the primary outcome, as defined in the registry: Only participants with post-treatment self-report data were analyze for this primary outcome.

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 Self-Reported Medication Adherence, measured over 12 weeks.

The primary endpoint is Self-Reported Medication Adherence at 12 weeks. It measures the percentage of doses taken out of 100%, as reported by the adolescent or young adult using a visual analogue scale. This is a continuous measure: each participant's reported adherence can take values across a scale rather than being restricted to a yes-or-no outcome.

Medication adherence is relevant to a study of support intended to help participants manage medication-taking. A self-report measure can capture participants' own assessment of their behavior, but it is not a direct record of medication ingestion. The registry record does not describe validation against dispensing records, electronic monitoring, or another adherence measure. Nor does it report the instrument's exact response anchors or the method used to combine individual responses into the group summaries.

The posted outcome reports a mean and standard deviation for each arm among those with post-treatment self-report data. A mean gives the group average on the reported scale; the standard deviation describes the spread of participant values around that average. The comparison is between mean adherence in Live Text Support and Cell Phone Support. The outcome description and results do not answer whether adherence changed from baseline, because a baseline value or change-from-baseline analysis is not reported in the registry record.

7. Results Posted in the Registry

• Live Text Support: mean 84.80 versus 86.55 on control; difference -1.75 (95% CI -23.63 to 20.13), standardized effect d = -0.07; z-test p = 0.875.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous, and the registry reports a mean and standard deviation for each arm. In general, a mean is the arithmetic average of the observed values, while a standard deviation describes how dispersed those values are around the average. A smaller standard deviation indicates values tend to be more tightly grouped; a larger one indicates greater spread. These summaries do not show the full distribution, and with small analyzed groups a few individual values can have substantial influence on the mean.

What does the mean difference represent?

The posted comparison is Live Text Support against Cell Phone Support. The mean difference is -1.75 on the adherence percentage scale. It represents the difference between the two reported group averages, with the comparison oriented so that a negative value corresponds to a lower reported average in Live Text Support. It is a group-level contrast, not an estimate of the change experienced by each individual participant. The registry record does not report a comparison between either facilitator-delivered support arm and Automated Text Reminders in the primary outcome results.

How should the confidence interval be understood?

In general, a confidence interval describes the uncertainty around an estimated effect under the statistical method used to construct it. The interval posted for this mean difference runs from -23.63 to 20.13. It includes zero, the value corresponding to no difference in means, and also includes differences on either side of zero. Its breadth means the estimate is not precise enough to pin down a narrow range of plausible differences. The registry record does not identify the specific interval method, so further assumptions about its construction are not warranted.

What does the p-value tell the reader?

The posted unadjusted p-value is 0.875. In general, a p-value describes how unusual data at least as incompatible with a specified null hypothesis would be if that hypothesis and the statistical model were correct. It is not the probability that the null hypothesis is true, and it is not the probability that the result occurred by chance. Because the value is unadjusted, it does not account for any multiplicity from testing multiple outcomes or comparisons. The registry record does not report a testing hierarchy or multiplicity adjustment plan.

Why does variation matter?

When participant values vary substantially, the group mean is estimated less precisely for a given number of observations. In general, over-dispersion means that variability is greater than a model expects; accounting for it can matter because underestimating variability may make uncertainty appear too small. The registry reports standard deviations but does not identify an over-dispersion model or report that one was used. These standard deviations help readers see that participants' self-reported adherence values were spread out, but they do not by themselves identify why participants differed.

What analysis population is represented?

The registry states that only participants with post-treatment self-report data were analyzed for the primary outcome. The displayed arm counts are 11, 10, and 8 for Cell Phone Support, Live Text Support, and Automated Text Reminders, respectively. Those endpoint counts do not disclose how many participants were randomized, completed follow-up, or lacked data in each arm. The missing-data method, if any, is not reported in the registry record. In general, restricting an analysis to participants with observed outcomes can affect interpretation if data availability is related to the outcome or to group assignment.

What can be concluded from a pilot comparison?

A pilot can provide descriptive information about recruitment, implementation, and outcome measurement, as well as preliminary estimates. The record labels this study a pilot and reports small analyzed groups for the primary endpoint. The registry record does not report a trial-specific sample-size justification, the intended primary analysis method, or whether any interim analyses were planned. The posted results should therefore be interpreted as preliminary estimates with appreciable uncertainty, not as a definitive estimate of a treatment effect. The sample-size illustrations are planning calculations based on the observed effect, not observed power or a report of the original study design.

10. Confidence Intervals and Precision

The primary comparison estimates a mean difference of -1.75 for Live Text Support versus Cell Phone Support. The reported 95% confidence interval extends from -23.63 to 20.13. Because the interval includes zero, the posted estimate is compatible with no difference as well as with differences favoring either group. The interval is wide, so the data do not locate the mean difference precisely. The point estimate alone should not be read as a reliable indication of the true size or direction of a difference.

Precision is influenced by the amount of information in the analysis and by variability in the outcome. The primary comparison uses 10 participants in Live Text Support and 11 in Cell Phone Support. The reported standard deviations are 31.07 and 17.58, respectively. The registry record does not report a confidence interval for each arm's mean, and it does not provide individual-level data or further distributional summaries. The confidence interval for the comparison is the most direct posted description of uncertainty about the difference between these two means.

A confidence interval is not a range containing a fixed proportion of individual participants' adherence values. In general, it describes uncertainty in an estimated group contrast under the method used. It also does not assign a probability to each possible true value after the data have been observed. The registry record does not identify the exact method used for this interval. The results therefore support a cautious reading: the observed difference is small in absolute point-estimate terms, while the uncertainty spans considerably larger differences in both directions. This precision does not resolve how the approaches compare in a larger or different population.

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 comparison between Live Text Support and Cell Phone Support, not the original trial's design. They are participants per arm, not total events. The stated calculation assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The calculation uses a target effect set to a stated fraction of the observed effect. The registry record does not report the trial's own original sample-size assumptions or justification.

For planning for 100% of the observed effect, the illustration gives 3,178 participants per arm for 80% power and 4,254 participants per arm for 90% power. For planning for 75% of the observed effect, it gives 5,650 participants per arm for 80% power and 7,563 participants per arm for 90% power. For planning for 50% of the observed effect, it gives 12,711 participants per arm for 80% power and 17,016 participants per arm for 90% power.

In general, power is the probability that a planned study will detect a specified effect under its assumptions if that effect is present. The 80% and 90% columns therefore describe different planning targets: the 90% target requires more participants per arm than the 80% target for the same assumed effect. Smaller effects need more participants to detect, which is why the planning figures increase as the assumed effect becomes a smaller fraction of the observed one. These calculations are not observed power. They are illustrations tied to this pilot's observed estimate and stated planning assumptions, not evidence that the original trial was designed with those sample sizes.

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 = -1.750; pooled standard deviation σ = 24.898.
2. n = 2 × (1.96 + 0.842)² × 24.898² / -1.750² = 3,177.6, rounded up to 3,178 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 <- -1.75                      # observed difference in means
sigma <- 24.8983915143127                     # 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(4241627)
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 = 3,178 (80% power), 4,254 (90% power)
 75% of observed effect: n per arm = 5,650 (80% power), 7,563 (90% power)
 50% of observed effect: n per arm = 12,711 (80% power), 17,016 (90% power)
power.t.test: 3178.6 
Simulated power at n = 3,178 per arm: 0.797 (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 identifies two outcome measures, but it posts no secondary outcome results. The available primary-outcome results include a pairwise comparison of Live Text Support with Cell Phone Support. The record does not describe a prespecified hierarchy of outcomes or comparisons, nor does it report a plan for controlling the chance of false-positive findings when multiple hypotheses are tested. The posted p-value is explicitly unadjusted. Without a multiplicity plan, it should be read as pertaining to that comparison alone rather than as an adjusted summary across all outcomes or arms.

The registry lists zero analysis entries, despite the posted pairwise result. It does not explain this difference in record structure, and it does not provide a complete statistical analysis plan. Methods for modeling the outcome, adjusting for baseline values, handling covariates, or addressing repeated measurements are not reported in the registry record. The study summary mentions questionnaires and focus groups, but qualitative findings or analyses are not posted in the results.

For the primary endpoint, only participants with post-treatment self-report data were analyzed. The record does not state how many participants in each randomized arm were missing this outcome, why data were missing, or whether participants who did not provide an outcome differed from those who did. An imputation method, sensitivity analysis, or missing-data assumption is not reported in the registry record. In general, an analysis limited to observed outcomes may be biased if the likelihood of reporting an outcome is related to adherence or to the assigned condition; the record does not provide enough information to assess that possibility.

The analysis population is therefore narrower than a clearly documented full randomized population: the primary result describes participants with observed post-treatment self-reports. The registry record does not report an intention-to-treat analysis or the number originally assigned to each arm. These omissions limit assessment of how missing data, multiple comparisons, and analysis choices affect the posted estimate.

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 0% reporting threshold.

The registry lists serious adverse events, other adverse events, and deaths separately for each arm. For Cell Phone Support, the record gives 11 participants at risk for serious events and 11 at risk for other events, with zero events in each category and zero deaths. For Live Text Support, it gives 12 at risk for serious events and 12 at risk for other events, with zero events in each category and zero deaths. For Automated Text Reminders, it gives 11 at risk for serious events and 11 at risk for other events, with zero events in each category and zero deaths.

These figures describe the recorded event counts for the groups and categories listed. They do not establish that no symptoms or other health events occurred; the registry reports zero events in the serious and other adverse-event fields. The number at risk for these fields differs from the primary endpoint analysis counts for some arms. The registry record does not explain the difference, define the event-collection procedures in detail, or provide event terms. No serious-event terms are listed. With these group sizes and the information recorded, the figures should be read as a limited safety summary rather than as a precise estimate of event risk.

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

The posted primary result is a preliminary comparison of self-reported medication adherence at 12 weeks among participants with post-treatment data. The Live Text Support mean was 84.8 and the Cell Phone Support mean was 86.55; the estimated mean difference was -1.75. The confidence interval, from -23.63 to 20.13, shows substantial uncertainty around that estimate. The result does not provide a precise estimate of how these two approaches compare, and it does not establish that one approach is better or worse.

The outcome is self-reported and the analysis excludes participants without post-treatment self-report data. The registry record does not report a baseline-adjusted comparison, a missing-data analysis, or secondary outcome findings. Thus, the posted result does not tell readers whether adherence changed from baseline, how the arms compare on illness self-management or appointment adherence, or how participants perceived the facilitator. The study summary describes those as areas of interest, but results for them are not posted in the registry record.

The trial includes adolescents and young adults with diverse chronic illnesses, but the registry record does not provide condition-specific estimates. A group average from this pilot cannot establish that the result applies equally across conditions or to populations outside the listed age range. Nor can the posted comparison show how a particular participant would respond. It is a statistical description of group-level outcomes under the study conditions, not a basis for individual medical decisions.

The result is best understood as an imprecise preliminary estimate that may inform further research. It neither proves an absence of a difference nor establishes a meaningful difference. The posted safety fields also record zero serious and zero other adverse events in each arm, but their limited detail and small at-risk groups do not support broad conclusions about safety. Clinical interpretation requires evidence beyond this registry record.

16. Why This Trial Matters Statistically

This trial raises several statistical issues that are common in behavioral and digital health research. Its three-arm design compares different modes of support, but the posted primary comparison covers only Live Text Support versus Cell Phone Support. A complete interpretation of the trial's aims would require results for the other relevant comparisons and the additional outcomes described in the study summary. Those results are not reported in the registry record.

The outcome is a continuous self-report measure. Reporting both means and standard deviations helps readers see the average and the degree of variation, rather than relying on a single point estimate. The wide confidence interval for the posted comparison highlights why the size of an observed group difference should be considered together with its precision. The mean difference is an estimate, not a certainty about the underlying contrast.

Missing outcome data also matter. The primary analysis includes only participants with post-treatment self-reports, while the record does not describe missingness by arm or explain its handling. If outcome availability is related to adherence or intervention experience, the observed group summaries might not fully represent the randomized groups. Without a reported analysis plan or sensitivity analyses, readers cannot assess how robust the estimate is to those issues.

Finally, a pilot's descriptive findings and planning calculations should be kept distinct. The registry lists an enrollment of 34, while the study summary describes a planned N = 60. The planning illustrations use the observed effect and explicit assumptions; they do not report the original design rationale or observed power. Distinguishing these purposes helps prevent a small, uncertain pilot estimate from being treated as a definitive answer. The record makes visible the questions that a larger, fully reported analysis would need to address, without resolving them itself.

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 primary outcome is self-reported medication adherence, and the registry does not report corroboration with an objective adherence measure. Self-report may capture participants' own perceptions, but the available record does not establish how closely it reflects medication-taking behavior. The outcome is measured at 12 weeks; a longer-term adherence result is not reported in the registry record.

The primary analysis includes only participants with post-treatment self-report data. Counts of missing outcomes, reasons for missingness, and methods to address missing data are not reported. The analyzed counts are small, and the confidence interval for the main pairwise comparison is wide. The record also does not report baseline outcome values, adjusted estimates, or condition-specific results, limiting assessment of baseline differences and variation across chronic illnesses.

There is a difference between the registry's enrollment of 34 and the study summary's planned N = 60. The record does not explain that difference. The summary describes usual care as the comparator, while the detailed arm description lists Automated Text Reminders. This wording difference is not resolved in the registry record. Masking is listed as none, and the record does not report whether outcome assessment was otherwise protected from knowledge of assignment.

The registry does not report the original sample-size justification, a complete statistical analysis plan, a multiplicity strategy, or reasons for missing data. It lists two outcome measures but posts no secondary results. Together, these limits mean that the available results provide a narrow, preliminary view of the primary self-report comparison rather than a complete account of all trial aims and analyses.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Cell Phone Support to Promote Medication Adherence Among Adolescents and Young Adults With Chronic Illness — NCT04241627.
• Registry record last updated 2024-01-08; status last verified 2024-01.
• Results first posted 2023-06-15.
• 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.

21. Record Summary

NCT04241627 is a completed randomized, parallel-group pilot trial sponsored by Children's Hospital Los Angeles. It concerns cell phone support for medication adherence among adolescents and young adults aged 15-20 years with chronic illnesses. The registry lists enrollment as 34; the study summary describes a planned N = 60. Masking is listed as none.

The primary outcome is self-reported medication adherence at 12 weeks, reported as a percentage of doses taken out of 100%. The posted means are 86.55 for Cell Phone Support, 84.8 for Live Text Support, and 68.75 for Automated Text Reminders. The posted pairwise comparison of Live Text Support with Cell Phone Support gives a mean difference of -1.75, a 95% confidence interval from -23.63 to 20.13, and an unadjusted p-value of 0.875. The primary analysis includes participants with post-treatment self-report data. Secondary outcome results and details of the trial's original statistical plan are not reported in the registry record.