Feasibility Study Comparing Standard FBT and Guided Self-Help FBT for Adolescent Anorexia Nervosa: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Feasibility Study Comparing Standard FBT and Guided Self-Help FBT for Adolescent Anorexia Nervosa (NCT04957498), a randomized na study. The primary outcome is Treatment Acceptability Ratings.

2. Clinical Question

The registry describes a feasibility study of conducting a randomized controlled trial comparing standard FBT with guided self-help FBT. Its stated focus is a parent-only guided self-help approach for adolescents with anorexia nervosa. The primary outcome is treatment acceptability, not a direct measure of symptom change or a test of whether one treatment is more effective.

The treatment descriptions differ in delivery format and therapist contact. Standard FBT is described as therapist sessions; FBT-GSH includes online materials and parent coaching sessions. The registry does not provide numerical results for the acceptability ratings, so the direction or size of any difference between arms cannot be determined from the registry record.

The study record lists an enrollment of 40 and a randomized, parallel design. Its primary question is therefore best understood as whether acceptability ratings were assessed across these two approaches in the planned feasibility comparison. The registry record does not report an estimate comparing the arms, uncertainty around such an estimate, or a statistical test for the primary question.

3. Trial Design

This completed study is titled as a feasibility study comparing standard Family Based Treatment and Guided Self-Help Family Based Treatment for adolescent anorexia nervosa. It is registered as randomized, with a parallel-group model and single masking. The record does not identify who was masked, so the meaning of single masking cannot be specified more narrowly.

The registry lists an enrollment of 40. It identifies Stanford University as the sponsor and anorexia nervosa as the condition. The recorded study start date is 2019-08-01, the primary completion date is 2021-06-18, and the current status is completed. The phase is listed as NA.

In the FBT arm, treatment is described as up to 15 sessions, each lasting 50-60 minutes, with a trained therapist. In the FBT-GSH arm, parents have access to a website containing educational videos, readings, discussion groups, and journals, and may receive up to 12 coaching sessions lasting 20-30 minutes with a trained therapist. These are descriptions of the assigned interventions in the registry, not evidence about how much treatment participants actually received.

In general, random allocation is intended to create groups whose baseline characteristics are comparable on average, while a parallel design assigns participants to one arm rather than having each participant receive both approaches. These design features help define a comparison, but do not by themselves establish that the groups were balanced in this study or that a particular analysis was conducted.

The record does not report details of the randomization procedure, allocation concealment, the identity of the masked party, or participant flow by arm. It also does not report a statistical analysis plan or a trial-specific sample-size justification. Those omissions limit how fully the conduct and planned analysis can be evaluated from the registry record.

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: Since this is a feasibility study, all enrolled and randomized participants are analyzed together to report the rate that they were recruited to the 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 Treatment Acceptability Ratings, measured over Session 1 and Session 8 (approximately 5 minutes to complete questionnaire).

The primary outcome is Treatment Acceptability Ratings. The registry describes it as a score on a scale and reports the mean and standard deviation as the summary measures. Parents completed the Cooperation and Helpfulness sub-scales of the Helping Alliance Questionnaire after session 1 and session 8; the questionnaire is described as taking approximately 5 minutes to complete.

Both sub-scales use a Likert response scale anchored from Strongly feels it's true (+3) to Strongly feel it's not true (-3). The registry gives the Cooperation total-score range as -18 to 18. Its Helpfulness range is written as 15- to 15, leaving the lower bound unclear in the record. The registry states that higher scores indicate a better outcome and that an average score was calculated when more than one parent responded.

Acceptability is useful in a feasibility study because it describes parents’ reported views of the treatment experience. In general, such ratings can help characterize whether an approach is acceptable to participants and families; they do not, on their own, establish clinical benefit, completion, or feasibility across all aspects of a trial. The registry record does not report the observed means or standard deviations for either sub-scale or either assessment time.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a randomized, parallel-group study with single masking. It does not report the sequence-generation method, allocation concealment, who was masked, or the statistical analysis plan. Those details should not be inferred from the design labels alone.

What does a mean and standard deviation describe?

The primary outcome is continuous, and the registry identifies the mean and standard deviation as its summary statistics. In general, the mean is the arithmetic average of observed scores. The standard deviation describes how spread out those scores are around the mean. The two summaries answer different questions: the mean describes the central level of ratings, while the standard deviation describes variation among ratings. A standard deviation is not the same as the standard error, which describes the estimated precision of a sample statistic.

The registry says that an average score was calculated if more than one parent responded. This describes how parent responses were combined for a participant, but the record does not give further detail about handling multiple parents, incomplete questionnaires, or score availability at each assessment.

What would an arm comparison mean?

In general, a comparison of mean scores between randomized arms estimates the difference in average ratings under the study’s analysis approach. A point estimate alone would not show how precisely the difference was estimated. A confidence interval would convey a range of estimates compatible with the observed data under the model and its assumptions. A p-value, if used, would address how compatible the data are with a specified null hypothesis; it would not measure the probability that the null hypothesis is true.

The registry record does not report a mean difference, confidence interval, or p-value for the primary outcome. Consequently, no numerical treatment contrast or formal test can be interpreted. An absence of a reported test is not a result of a non-significant test.

Why do the two assessment times matter?

Helpfulness and Cooperation were assessed after session 1 and session 8. In general, repeated assessments can describe ratings at different points in treatment, but interpretation depends on how within-participant measurements are handled and what contrast is prespecified. Analyses might focus on ratings at a particular time, change across time, or a difference in trajectories between arms. These are distinct questions. The registry record does not say which contrast was intended or report results for any of them.

The two sub-scales also represent distinct aspects of the questionnaire. A score on one should not be treated as interchangeable with a score on the other. The registry describes higher scores as indicating a better outcome, but does not report how the two sub-scales were combined, if at all.

What does the planning illustration represent?

The registry describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It describes the effect to detect as a stated fraction of the observed effect. This is a planning exercise, not a report of the trial’s own design justification. The registry record does not report a trial-specific sample-size justification, and no planning sample counts or observed-effect estimate are reported in the record.

In general, a sample-size calculation is conditional on its assumptions about the effect to detect, variability, allocation, significance threshold, and analysis method. A planning illustration does not indicate the probability that a completed study found a statistically significant result. It is not observed power, and it cannot substitute for the estimates and uncertainty from the actual analysis.

The record lists seven outcome measures and zero analyses. It does not identify the statistical model, covariates, approach to repeated observations, handling of missing scores, or any multiplicity procedure. These are important details for judging how an analysis was conducted, but they are not reported in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The primary acceptability outcome includes the Helpfulness and Cooperation sub-scales assessed after session 1 and session 8. The registry also lists seven outcome measures overall and indicates that the primary outcome has several categories or time points and was not reduced to one comparison. It does not specify which acceptability contrast, if any, should be treated as the single primary statistical test.

When several outcomes, sub-scales, or time points are examined, the chance of at least one apparently unusual result can increase if each is tested separately. In general, a prespecified analysis plan can clarify which comparisons are primary and whether any adjustment or hierarchy is used. The registry record does not report a multiplicity strategy, so it is not possible to determine whether or how the reported outcomes were intended to account for multiple comparisons.

The primary outcome population is described as intent-to-treat, excluding participants withdrawn from the study per investigator decision. The record does not report how many participants were withdrawn, whether all randomized participants contributed data, or how missing questionnaire responses were handled. It does not report an imputation method, a sensitivity analysis, or whether analyses used all available observations.

In general, missing outcomes can affect both the precision and interpretation of an estimate, particularly if the reasons for missingness differ across arms or relate to participants’ experiences. The registry record does not provide enough information to assess those possibilities. It also does not report the number of completed questionnaires at either assessment time.

11. 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: hospitalization (20.0%).

The registry lists serious adverse event counts separately for the groups labelled FBT-V and GSH-FBT. In the FBT-V group, 1 of 20 participants at risk was affected by a serious adverse event. In the GSH-FBT group, 4 of 20 participants at risk were affected. The registry reports 0 deaths in each group.

For other adverse events, the record lists 0 affected among 20 at risk in each group. The top serious adverse event term is Hospitalization, listed at 20.0%. The record does not provide further detail about the events, their timing, severity, relatedness to treatment, or the denominator used for that term listing. The term listing alone does not establish that every serious adverse event was a hospitalization.

These figures are counts reported in the registry, not a statistical comparison. The record does not report an analysis of between-group safety differences or uncertainty around the counts. In general, event counts describe what was recorded in the study; they do not by themselves establish that an intervention caused an event or rule out events that were not observed in this study.

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

The registry record shows that this was a randomized feasibility study designed to compare standard FBT with guided self-help FBT for adolescents with anorexia nervosa. It identifies parent-rated treatment acceptability as the primary outcome and describes two questionnaire sub-scales assessed after session 1 and session 8. It also records serious and other adverse event counts for the two safety groups.

However, no numerical results for the primary acceptability outcome are reported in the registry record, and the record lists zero analyses. The posted results therefore do not establish whether average ratings differed between arms, whether ratings changed over time, or how precisely any comparison was estimated. They also do not establish similarity: absence of a reported comparison is not evidence of equivalence.

The trial title and registry description emphasize feasibility, but the record does not report results on recruitment, retention, treatment completion, or other feasibility outcomes. Nor does it report a statistical analysis plan or trial-specific sample-size justification. The enrollment figure describes the registered enrollment; it should not be mistaken for the number with complete data for every outcome.

In general, acceptability scores provide information about reported experience, while clinical outcomes and broader feasibility measures address different questions. A favorable rating would not, by itself, establish improvement in anorexia nervosa, just as an unreported rating cannot establish poor acceptability. The registry record supports describing the study’s intended comparison and recorded event counts, but not conclusions about comparative treatment effects.

13. Why This Trial Matters Statistically

Feasibility studies can be statistically informative even when their central purpose is not to establish a definitive treatment effect. They can help characterize whether a planned comparison is workable and what outcomes should be measured in a later study. This registry record identifies a randomized comparison of standard FBT and guided self-help FBT and specifies parent-rated acceptability as a primary outcome.

The design also raises questions that matter for analysis: how ratings at two assessment times are compared, whether Helpfulness and Cooperation are treated separately, how missing parent responses are handled, and how multiple outcomes are interpreted. These choices affect what an estimate means and how certain conclusions can be. The registry does not report the planned statistical approach or results needed to answer those questions.

For biostatisticians and clinical researchers, the distinction between a study’s stated aim and its available results is important. A registered randomized design defines an intended comparison, but estimates and uncertainty are needed to interpret observed differences. Likewise, safety counts and acceptability measures describe different dimensions of the study and should not be substituted for one another.

The record’s lack of numerical acceptability results is itself a practical interpretive limitation: readers cannot assess the scale of ratings or their variability. It also illustrates why outcome definitions, analysis populations, missing-data procedures, and reporting of estimates are essential for evaluating a trial, including a feasibility study.

14. 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 does not report the numerical primary outcome results, despite describing the measure, its timing, and the intended summary statistics. It also lists zero analyses. This prevents assessment of the observed acceptability ratings, differences between arms, or precision of any estimate.

The primary population description excludes participants withdrawn by investigator decision, but the record does not report how many participants were withdrawn or how many contributed data at each assessment. Questionnaire completion, missing-data handling, and the treatment of responses from multiple parents are not described beyond the statement that an average was calculated when more than one parent responded.

The record specifies two sub-scales and two assessment times but does not identify the intended primary contrast or a multiplicity approach. It lists seven outcome measures, without reporting the analysis methods, covariate adjustment, or handling of repeated observations. The identity of the party masked under the single-masking designation is also not reported.

The Helpfulness score range is written as 15- to 15, making its lower bound unclear. The record also does not report a trial-specific sample-size justification. These omissions limit interpretation of both the measurement and the planned statistical precision. Finally, the safety record provides event counts but little detail about event characteristics, timing, or relatedness. These are limitations of what is reported in the registry record and do not establish that the underlying study did not collect additional information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Feasibility Study Comparing Standard FBT and Guided Self-Help FBT for Adolescent Anorexia Nervosa — NCT04957498.
• Registry record last updated 2022-06-06; status last verified 2022-05.
• Results first posted 2021-12-13.
• 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.

18. Record Summary

NCT04957498 is a completed randomized, parallel-group feasibility study sponsored by Stanford University. The registry lists an enrollment of 40, anorexia nervosa as the condition, a study start date of 2019-08-01, and a primary completion date of 2021-06-18. The study compares standard Family Based Treatment with Guided Self-Help Family Based Treatment for adolescents aged 12 to 18.

The primary outcome is parent-rated treatment acceptability, measured with the Helpfulness and Cooperation sub-scales of the Helping Alliance Questionnaire after session 1 and session 8. The registry lists seven outcome measures and zero analyses. Numerical results for the primary outcome and a trial-specific statistical analysis plan are not reported in the registry record.

For safety, the record reports serious adverse events in both groups, no deaths, and no other adverse events. It lists Hospitalization as the top serious event term. The available registry entries describe the study design, outcome, and recorded event counts, but do not permit a numerical interpretation of the primary comparison.