This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Inpatient Clinical Trial of NAC (NCT03581084), a na phase 4 study. The primary outcome is Forced Expiratory Volume in One Second (FEV1) Measurement.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT03581084 |
| Phase | Phase 4 |
| Condition | Asthma |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 1 |
| Arms in the primary outcome | n/a |
| Lead sponsor | University of California, San Francisco |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns people with asthma. The registry record describes an inpatient clinical trial and lists an enrollment of 1. It does not report further eligibility details or describe the enrolled participant’s characteristics. The study’s summary also refers to identifying a subgroup with a mucus profile using CT lung imaging, but the record does not report how that subgroup was defined or whether the participant had that profile.
Intervention
The intervention was N-acetylcysteine, or NAC, described as an inhaled medication intended to break down mucus. The stated research aim was to assess its effect on lung function, with CT lung imaging also included in the study description. The registry identifies NAC as the drug intervention. It does not report a detailed treatment schedule or dose.
Comparator
There was no separate comparison group. The registry identifies the study as single-group, with all participants receiving the same treatment, and lists allocation as not applicable. The record therefore does not describe a randomized contrast between NAC and placebo, usual care, or another treatment. A change from before to after treatment, if measured, would not by itself provide the same control for time trends or other influences as a concurrent comparison group.
Primary question
The primary outcome was post-treatment Forced Expiratory Volume in One Second (FEV1), measured via spirometry and reported in liters at the end of the one week treatment period. The intended question was whether lung function, as represented by FEV1, changed after NAC treatment. The registry record does not report a numerical FEV1 result, a baseline value, or a statistical estimate of change. A secondary outcome was a CT scan mucus score. The record does not report an analysis of that outcome.
3. Trial Design
The registry describes NCT03581084, titled Inpatient Clinical Trial of NAC, as a phase 4, single-group study in asthma. The sponsor is the University of California, San Francisco. The intervention is N-acetylcysteine (NAC), listed as a drug. The study summary states that all participants would receive the same treatment. There is no separate control arm in the registry description, and allocation is listed as not applicable.
The record lists enrollment of 1. It identifies the study as unmasked, meaning masking is listed as none. The registry records a start date of 2018-07-06 and a primary completion date of 2018-07-13. The study status is terminated. The reason for termination is not reported in the registry record, so the status alone does not explain why the study ended or whether the planned study procedures were completed.
The primary outcome was post-treatment FEV1, measured by spirometry in liters at the end of the one week treatment period. A CT scan mucus score is listed as a secondary outcome. Although two outcome measures are indicated in the record, a numerical result is not reported for the primary endpoint, and no analysis is listed. No detailed description of the treatment dose, administration schedule, eligibility criteria, or assessment procedures is reported in the registry record.
This design can describe observations made in the treated participant, but it does not provide a concurrent untreated or alternative-treatment group. As a result, any post-treatment observation cannot isolate an effect of NAC from other explanations using a between-group comparison. The record also does not report a prespecified statistical analysis plan, so the intended method for analyzing the outcomes is not available.
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
| Stage | N-acetylcysteine |
|---|---|
| STARTED | 1 |
| COMPLETED | 1 |
| NOT COMPLETED | 0 |
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.
| Characteristic | Unit | N-acetylcysteine |
|---|---|---|
| Participants analysed | 1 | |
| Age, Categorical: <=18 years | Participants | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 0 |
| Age, Categorical: >=65 years | Participants | 1 |
| Sex: Female, Male: Female | Participants | 1 |
| Sex: Female, Male: Male | Participants | 0 |
| Ethnicity (NIH/OMB): Hispanic or Latino | Participants | 0 |
| Ethnicity (NIH/OMB): Not Hispanic or Latino | Participants | 1 |
| Ethnicity (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Race (NIH/OMB): American Indian or Alaska Native | Participants | 0 |
| Race (NIH/OMB): Asian | Participants | 0 |
| Race (NIH/OMB): Native Hawaiian or Other Pacific Islander | Participants | 0 |
| Race (NIH/OMB): Black or African American | Participants | 0 |
| Race (NIH/OMB): White | Participants | 0 |
| Race (NIH/OMB): More than one race | Participants | 1 |
| Race (NIH/OMB): Unknown or Not Reported | Participants | 0 |
| Region of Enrollment: United States | Participants | 1 |
| Forced Expiratory Volume in One Second (FEV1) Measurement | liters | .85 |
| Mean Number of Mucus Plugs | number of mucus plugs | 11 (6 to 16) |
6. Primary Endpoint
The registry lists the primary outcome as Forced Expiratory Volume in One Second (FEV1) Measurement, measured over end of the one week treatment period.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | liters |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is Forced Expiratory Volume in One Second (FEV1), reported in liters. FEV1 is the volume of air exhaled during the first second of a forced breathing maneuver, measured by spirometry. It is used as a lung-function measure and is relevant to the study’s stated aim of assessing whether inhaled NAC affects lung function.
The registry specifies a post-treatment FEV1 measurement at the end of the one week treatment period. It does not report a baseline FEV1 value, the participant’s post-treatment value, or a calculated change between measurements. It also does not report a confidence interval or other measure of uncertainty. Without those values, the direction and magnitude of the observed FEV1 result cannot be described from the registry record.
In general, a single post-treatment measurement describes lung function at that assessment time. If the question is whether lung function changed during treatment, a baseline measurement and a clearly defined comparison are also important. Even a before-and-after change in one participant would not, by itself, separate a treatment effect from ordinary variation, measurement conditions, or changes over time. The registry lists a CT scan mucus score as a secondary outcome, but does not report its result.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record gives limited information for interpreting the primary outcome. It identifies post-treatment FEV1 as the endpoint and specifies spirometry, liters, and the end of the one week treatment period. It does not report the numerical FEV1 measurement, a baseline measurement, or an estimated change. No confidence interval, p-value, or analysis of FEV1 is listed. The record therefore does not establish the direction, size, or precision of an observed lung-function result.
The enrollment was 1, and the design was single-group. These features sharply limit what can be concluded from any individual observation. A measurement after treatment would describe the participant at that time, but without a comparator it would not show what would have happened over the same period without NAC or under another treatment. In general, a control group helps distinguish treatment-related differences from time trends, measurement variability, and other influences. The record does not support a controlled estimate of treatment effect.
The study status is terminated, but the reason for termination is not reported in the registry record. That status should not be taken as an explanation for the missing outcome value or as evidence about why the study stopped. Similarly, the registry’s stated research aim and planned endpoint describe what the investigators sought to examine; they do not substitute for a reported result.
The registry lists a CT scan mucus score as a secondary outcome, but does not report a result or analysis for it. It lists no analyses. Details such as the analysis population, handling of missing measurements, and any prespecified statistical model are not reported in the registry record. This means readers cannot determine whether an outcome was measured but omitted, whether an analysis was planned but not completed, or whether another reporting circumstance applies.
The posted safety information lists serious adverse event figures for the NAC group, including angina as the top serious term. Those entries describe events recorded in this small study; they do not establish that NAC caused an event. The safety entries and the absent FEV1 result answer different questions: the former summarize recorded adverse events, while the latter leaves the primary lung-function outcome uninterpretable from the registry record.
Any sample-size figures associated with this record are planning illustrations based on the observed effect, not evidence of the precision of a result or of observed power. The registry’s planning assumptions describe a hypothetical two-arm calculation, whereas the actual study is listed as single-group. Such calculations cannot create a control comparison or replace a reported outcome estimate. No treatment-effect estimate can be inferred from the planning exercise alone.
9. Statistical Methods Explained
The registry describes a single-group study with NAC and no separate comparator. This is a design description, not a statistical test. It tells the reader that all participants were assigned to the same treatment in the study summary, while allocation is listed as not applicable. With no concurrent control group, the record cannot provide a randomized between-group estimate of the difference between NAC and another condition. General statistical interpretation must therefore distinguish a measurement after treatment from evidence that treatment caused a change.
The primary endpoint is post-treatment FEV1 measured by spirometry and expressed in liters. A statistical analysis of repeated measurements might compare a participant’s value before treatment with a value after treatment, but the registry does not report a baseline value or a change estimate. It also does not report the actual post-treatment value. Consequently, it is not possible to describe an observed difference, calculate its uncertainty, or assess whether it is compatible with a range of effects. No such calculation should be inferred from the endpoint description alone.
A confidence interval, in general, expresses the uncertainty around an estimated quantity under the assumptions of the analysis. A narrow interval indicates greater statistical precision, while a wide interval indicates less precision. It does not resolve limitations in the study design, and it cannot be interpreted without a reported estimate and method. No confidence interval for FEV1 is reported in the registry record. Likewise, no p-value or inferential analysis is listed, so there is no reported hypothesis-test result to interpret.
The record lists no analyses. It does not report a statistical model, a test, covariate adjustments, or an analysis population. It also does not report whether any interim analyses were planned or conducted, or the protocol’s statistical decision criteria. The absence of these details means the intended analysis cannot be reconstructed from the registry entry. It would be inappropriate to assume a particular model or to treat a generic method as the study’s actual analysis.
In general, the choice of statistical method depends on the endpoint, the number and timing of measurements, the study design, and features of the data. A single post-treatment value, a paired before-and-after comparison, and a comparison between treatment groups answer different statistical questions. These approaches cannot be treated as interchangeable. The record specifies the endpoint timing but does not give enough measurement or analysis detail to identify which inferential approach, if any, was used.
The registry also includes planning illustrations based on the observed effect. Their stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is expressed as a fraction of the observed effect. These are assumptions for hypothetical planning calculations, not a description of the actual single-group study. In particular, equal allocation between two arms does not mean that the enrolled study had two arms. The planning assumptions should be read as illustrations of sample size under a hypothetical design, not as evidence that the actual trial had a comparator.
Sample-size calculations ask how many participants per arm a hypothetical study might require under specified assumptions. They depend on the effect used for planning and on choices such as the significance level, allocation, and statistical model. A planning illustration based on an observed effect is not observed power. It does not indicate the probability that this study detected an effect, nor can it compensate for the absence of a reported estimate. The registry does not report the trial’s own sample-size justification, so the planning assumptions should not be attributed to the study’s original design.
Dispersion and variability also matter in general. If outcomes vary more widely than a model assumes, estimates may be less precise than a simple model suggests. This is one reason statistical methods need to match the data structure and endpoint. However, the registry does not report a dispersion estimate or an analysis model for FEV1, and there is no basis for diagnosing over-dispersion in this outcome from the information recorded. It is a general statistical consideration, not a finding about this study.
The study includes a CT scan mucus score as a secondary outcome. The record does not report its numerical result, analytic method, or relationship to FEV1. No inference about concordance between the lung-function measure and imaging outcome can be made. Nor does the registry record state whether the secondary outcome was analyzed, whether it was prespecified in a protocol, or how its scale was handled statistically.
When multiple outcomes or comparisons are analyzed, general statistical practice considers whether the chance of false-positive findings across analyses should be controlled or otherwise addressed. The registry record does not report a multiplicity strategy. Since no analyses are listed, it is not possible to determine how many tests were performed or whether any adjustment was used. It would be inaccurate to assume either that multiplicity was addressed or that a particular adjustment was required by the study plan.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies FEV1 as the primary outcome and a CT scan mucus score as a secondary outcome. It does not report an analysis for either outcome. No multiplicity procedure or strategy for interpreting results across outcomes is reported in the registry record. In general, when several outcomes or comparisons are tested, the chance of at least one apparently unusual result can increase; methods for addressing that concern depend on the planned analyses. Here, the analysis details needed to assess that issue are not reported.
Missing-data handling is also not reported in the registry record. The entry does not say whether the FEV1 measurement or CT score was missing, whether an outcome was collected but not posted, or how missing measurements would have been handled in an analysis. The absence of a numerical endpoint result should not be equated with proof that a measurement was missing; the record does not establish the reason a result is unavailable.
The analysis population is not reported in the registry record. The entry does not describe an intention-to-treat population, a per-protocol population, or another analysis set. It also does not explain how participants were included or excluded from any analysis. Because no analyses are listed, there is no reported denominator for an efficacy analysis beyond the trial’s enrollment listing.
These omissions limit reproducibility and interpretation. Without an analysis plan, a description of missingness, and a defined analysis population, readers cannot tell which observations were included or how the intended conclusions were to be drawn. They also cannot determine whether the primary and secondary outcomes were handled according to a prespecified hierarchy. The record does not report interim analyses or a multiplicity adjustment, and neither should be assumed.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| N-acetylcysteine | 1 | 1 | 100.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| N-acetylcysteine | 0 of 1 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| N-acetylcysteine | 1 of 1 |
Most frequent serious adverse event terms
| Event term | Organ system | N-acetylcysteine |
|---|---|---|
| Angina | Cardiac disorders | 1 of 1 |
Most frequent non-serious adverse event terms
| Event term | Organ system | N-acetylcysteine |
|---|---|---|
| Headache | General disorders | 1 of 1 |
Serious events with the highest arm-level rate: angina (100.0%).
The registry lists the NAC group with 1 at risk and 1 affected for serious adverse events, and 1 at risk and 1 affected for other adverse events. It lists 0 deaths. Angina is the top serious adverse event term, reported as 100.0%. These are the posted safety figures for this study; they should be read as registry entries rather than as a comparative estimate of risk.
With an enrollment of 1 and no control group, these entries cannot show whether the event frequency differs from what would occur without NAC or with another treatment. A serious adverse event recorded during a study does not, by itself, establish that the study drug caused it. The registry record does not report a causal assessment, event timing, or additional clinical details that would support such an interpretation.
The 100.0% figure is the registry’s reported proportion for the listed serious term; it does not provide evidence about how often angina would occur in a larger population. The small study and absence of a comparator make the safety information descriptive and highly limited. The recorded deaths figure is 0, but that entry should not be interpreted as a broad estimate of mortality risk.
12. What the Result Does, and Does Not, Mean
This record documents an inpatient, phase 4, single-group study of NAC in asthma, with post-treatment FEV1 as the primary outcome and a CT scan mucus score as a secondary outcome. It records enrollment of 1 and a terminated status. The stated research aim was to examine lung function and use CT imaging to identify a subgroup with a mucus profile. These details describe the study’s purpose and design; they do not establish an effect of NAC.
The registry does not report a numerical FEV1 result, a baseline value, or an estimate of change. It also lists no analyses. Therefore, the posted record does not establish whether FEV1 increased, decreased, or stayed similar after treatment, and it does not quantify the precision of any outcome estimate. The CT mucus score result is also not reported. A statistical conclusion about either endpoint cannot be drawn from the information in the record.
The single-group design has no concurrent comparator. In general, an observation after treatment cannot by itself distinguish a treatment effect from changes over time, measurement variability, or other influences. The available record also cannot show how a participant’s outcome would compare with an outcome under an alternative treatment or no treatment. No causal treatment-effect conclusion follows from the design description alone.
The safety entries record serious and other adverse events in the NAC group, and angina is listed as the top serious term. Those entries are not a controlled comparison and do not establish causation. The absence of deaths in the record is a descriptive entry for this study, not a precise estimate of risk in a broader population.
The termination status does not reveal the reason the study ended. The record does not report a sample-size justification, a detailed statistical plan, or the handling of missing data. Planning calculations based on an observed effect, where included, are hypothetical sample-size illustrations rather than evidence of observed power or a substitute for missing trial results. The appropriate conclusion is that the registry documents the study’s design and selected safety entries but does not provide enough outcome or analysis information to estimate an effect on lung function.
13. Why This Trial Matters Statistically
This study is statistically instructive because its central question concerns a treatment effect, while the registry describes a single-group design without a comparator. In general, treatment-effect questions require a comparison that helps distinguish the effect of treatment from other explanations for an observed outcome. A post-treatment measurement may be clinically meaningful as a description, but it does not alone establish what would have happened under a different condition.
The enrollment listing of 1 also emphasizes the difference between an individual observation and a population-level estimate. Statistical precision depends on the amount and variability of information, as well as the analysis design. With no numerical FEV1 result or uncertainty estimate in the registry record, the reader cannot assess even the precision of the observed endpoint. The absence of an analysis prevents the record from showing how uncertainty was quantified.
The record also illustrates why outcome registration and outcome reporting are separate. Naming FEV1 and a CT mucus score identifies what the study intended to measure, but it does not provide the results or methods needed to evaluate those measurements. The termination status adds context about the study’s status, but without a reported reason it does not explain the absence of an analysis.
Finally, planning calculations should not be confused with evidence from the enrolled study. A hypothetical two-arm sample-size illustration can help explain assumptions for a future design, but it does not turn a single-group study into a comparison or show that an effect was detected. Keeping design, observed data, analysis, and planning assumptions distinct is essential when interpreting a sparse registry record.
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 main trial-specific limitation is the single-group design. There is no concurrent comparator in the registry description, so the record cannot support a controlled estimate of NAC’s effect relative to another condition. The study is also listed as unmasked, with masking reported as none. The registry does not describe procedures that might have reduced measurement or assessment bias.
Enrollment is listed as 1, limiting the amount of information available for describing variability or generalizing beyond the recorded study. The registry does not provide participant characteristics or detailed eligibility criteria, so it is not possible to assess how representative the participant was of the broader asthma population or of the proposed mucus-profile subgroup.
The primary outcome is defined as post-treatment FEV1, but its numerical result is not reported. A baseline value, estimated change, confidence interval, and analysis are also not reported in the registry record. The secondary CT scan mucus score has no posted result or analysis. Thus, the record does not allow an assessment of endpoint magnitude, precision, or consistency across measures.
The study status is terminated, but the reason is not reported. The record does not explain whether the planned measurements were completed, why the study ended, or whether there were deviations from the intended procedures. It also does not report treatment dose or schedule, missing-data handling, an analysis population, a statistical plan, or a sample-size justification. These specific gaps limit interpretation beyond the general constraints of a single-group study.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Inpatient Clinical Trial of NAC — NCT03581084.
- Registry record last updated 2021-10-26; status last verified 2021-09.
- Results first posted 2021-10-26.
- 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.
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18. Record Summary
NCT03581084 is a phase 4, single-group inpatient study of N-acetylcysteine in asthma, sponsored by the University of California, San Francisco. The registry lists enrollment of 1, no masking, and terminated status. The recorded start date is 2018-07-06, and the primary completion date is 2018-07-13.
The primary outcome is post-treatment FEV1, measured by spirometry in liters at the end of the one week treatment period. A CT scan mucus score is listed as a secondary outcome. The registry record does not report numerical results or analyses for these outcomes. It also does not report the reason for termination, the statistical analysis plan, the analysis population, or missing-data procedures.
Safety entries list serious and other adverse events in the NAC group, with angina identified as the top serious term and 0 deaths recorded. These entries are descriptive and do not establish causation or comparative risk. Overall, the record documents the study design and selected safety information but does not provide a numerical primary outcome result from which to estimate lung-function change.