Aminotransferase Trends During Prolonged Acetaminophen Dosing: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Aminotransferase Trends During Prolonged Acetaminophen Dosing (NCT00743093), a randomized phase 4 study. The primary outcome is The Proportion of Subjects Treated With Long-term Acetaminophen (4 g/Day) That Develops Persistent ALT Elevations..

2. Clinical Question

3. Trial Design

This was a randomized, quadruple-masked, parallel-group phase 4 trial. The registry lists an enrollment of 398 and identifies Denver Health and Hospital Authority as the sponsor. Its status is completed. The study start is recorded as 2008-08 and primary completion as 2011-08. The registry record does not explain the masking roles or give details about the randomization process, allocation concealment, or the number assigned to each arm.

The study compared acetaminophen at 4 grams/day with placebo. The brief summary describes monitoring healthy people taking the maximum labeled daily dose for 16 to 40 days. Participants whose liver tests remained normal after 16 days completed their study participation. Those who developed abnormal liver tests continued their assigned study drug and were monitored for up to an additional 24 days. The summary also states that participants would be told to stop the study drug if test results indicated more than a minor increase; further operational details are not reported in the registry record.

The primary measure concerned persistent ALT elevation at Day 40. ALT was measured on Day 0 and Day 16 for all participants. If ALT was elevated at Day 16, measurements continued every three days until the elevation resolved or Day 40. The record also lists a secondary outcome concerning detectable serum acetaminophen-cysteine adduct concentrations at 1, 2, and 3 days after starting maximal recommended acetaminophen dosing. Numerical results for that secondary outcome are not reported in the registry record.

The enrollment figure is not the same as the stated primary-analysis population: the record says that only trial completers were included and early withdrawals were excluded. The number completing, and the arm-specific counts completing, are not reported in 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.

Before assignment: 398 subjects were consented for the study. Of these, 122 were excluded for not meeting full eligibility criteria. 276 eligible subjects were assigned to treatment groups, of which 252 completed all study requirements.

Base Study Period

Extended Dosing Period

Analysis population for the primary outcome, as defined in the registry: The total number of subjects completing the trial was used for analysis. Subjects who withdrew early were not included.

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: Baseline characteristics were collected on all subjects at screening and included: race, ethnicity, gender, age, weight, and height. The number of participants included in the analysis (276) is based on the safety population, which includes any subject that took at least one dose of study medication.

6. Primary Endpoint

The registry lists the primary outcome as The Proportion of Subjects Treated With Long-term Acetaminophen (4 g/Day) That Develops Persistent ALT Elevations., measured over serial samples for 16-40 days.

The primary endpoint concerns the number or proportion of participants with a persistent ALT elevation after prolonged dosing. The endpoint description defines persistence as an ALT elevation that had not resolved by study Day 40. ALT was measured at baseline, Day 0, and Day 16 for all participants. Participants with an elevated ALT at Day 16 continued to have measurements every three days until the elevation resolved or the Day 40 endpoint was reached.

ALT is a liver enzyme measured in blood. In general, tracking ALT over time can describe changes in a laboratory marker during exposure and whether an observed elevation resolves or persists. This endpoint therefore focuses on the course of a laboratory finding during the study period, rather than on a clinical diagnosis or a patient-reported outcome. The registry record does not provide a threshold for an elevated ALT, beyond its definition of persistence as unresolved at Day 40, and does not report how the laboratory measurements were summarized across participants.

The endpoint title refers to a proportion, while the listed unit and parameter describe a number of participants. That presentation makes the intended outcome recognizable but leaves the precise reported measure unclear. No numerical primary-outcome result, uncertainty interval, or between-arm estimate is reported in the registry record. The stated analysis population included trial completers; early withdrawals were excluded. The number of participants contributing to that analysis is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record identifies a randomized, parallel-group trial with quadruple masking. Randomization is intended, in general, to create groups that are comparable on average at the start of a study. Masking is intended to limit the influence of knowledge about assignment on study conduct or assessment. The registry record does not describe who was masked, how the random sequence was generated, how assignments were concealed, or whether masking was maintained.

What the endpoint definition captures

The primary endpoint is a laboratory outcome defined by persistence: an ALT elevation had to remain unresolved at Day 40. All participants had ALT measured on Day 0 and Day 16. Those with an elevated ALT at Day 16 continued to have ALT measured every three days until resolution or Day 40. This schedule describes repeated measurement for a subset of participants, rather than an outcome measured identically at every visit for everyone. The registry record does not report a numerical result, the threshold used to classify ALT as elevated, or how results from the repeated measurements were incorporated into an arm-level analysis.

The outcome title refers to a proportion, but its listed unit is participants and its parameter is NUMBER. A count is the number of participants meeting a definition; a proportion relates that count to a specified denominator. In general, reporting both the event count and its denominator makes the result interpretable. The registry record does not give the primary endpoint count or denominator by arm, so neither an arm-specific estimate nor an unadjusted comparison can be described.

How estimates and uncertainty would be read

In general, an estimated difference between groups summarizes the observed contrast in an outcome, while a confidence interval describes the range of values compatible with the data under the analysis assumptions. A narrower interval indicates greater precision; a wider interval indicates more uncertainty. A significance test addresses compatibility with a specified null hypothesis, but a p-value alone does not describe the size or clinical importance of an effect. No primary-outcome estimate, confidence interval, or p-value is reported in the registry record, so these concepts cannot be applied to a posted ALT comparison.

The record states that 0 analyses are listed. That does not establish that no analyses were conducted; it means the registry does not report analysis entries. The statistical model, any adjustment for covariates, the handling of repeated observations, and the method used for a comparison between arms are not reported in the registry record.

What the planning assumptions mean

The record describes planning illustrations based on the observed effect, using a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation. It explicitly characterizes these as planning illustrations, not as the trial’s own design. Such illustrations, in general, show how a hypothetical future study’s required enrollment could depend on the effect size chosen for detection and the assumed error rate. They are not observed power and do not establish that the completed trial was designed with those assumptions. No numerical planning results are reported in the registry record, and the primary outcome has several categories or time points, so it is not reduced to one comparison.

The general principle of over-dispersion is relevant when count variation exceeds what a simple statistical model expects; in that situation, model-based standard errors can be too small if the extra variability is ignored. This is a general statistical consideration, not a reported feature of this study. The registry record does not provide a count model, dispersion estimate, or evidence that over-dispersion was assessed. Nor does it identify a model for the primary endpoint. No modeling choice should therefore be attributed to the trial based on this record.

Why the analysis population matters

The primary outcome description says that the total number of participants completing the trial was used for analysis and that early withdrawals were excluded. In general, excluding participants who withdraw can change the makeup of the analyzed groups if withdrawal is related to assignment or outcome. The size and direction of any such effect cannot be determined without the number and reasons for withdrawals, the outcomes available before withdrawal, and a fuller analysis plan. These details are not reported in the registry record. As a result, the listed enrollment does not identify the primary analysis denominator.

The endpoint also involves follow-up that can stop when an elevation resolves or at Day 40. In general, outcomes observed at different times and repeated measurements may require a clearly specified summary rule. The registry describes the monitoring schedule and the Day 40 definition, but does not report a longitudinal model or a rule for handling measurements that are unavailable. The record therefore supports interpretation of the intended endpoint, but not reconstruction of its analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures and 0 analyses. It identifies a primary ALT outcome and a secondary outcome concerning detectable serum acetaminophen-cysteine adduct concentrations at 1, 2, and 3 days after starting dosing. Numerical results for either outcome, and any reported comparisons, are not reported in the registry record.

Multiplicity arises in general when several outcomes, time points, or statistical comparisons are examined. Without a prespecified testing strategy, repeated testing can increase the chance of a finding that appears notable by chance. The registry record does not report whether a multiplicity adjustment was planned or used, whether the secondary outcome was formally tested, or how the multiple adduct time points were handled. The record also does not report a statistical analysis plan, interim analyses, or a sample-size justification for the trial.

The stated primary analysis included participants who completed the trial; early withdrawals were excluded. The number of completers, withdrawal counts, withdrawal reasons, and the number analyzed in each arm are not reported in the registry record. The record does not describe imputation or other methods for missing observations, and it does not report a sensitivity analysis of the exclusion of early withdrawals. These omissions limit assessment of how representative the analyzed participants were of those enrolled.

In general, missing outcome data can affect both the precision and the interpretation of an estimate, especially when missingness is related to assignment or to the outcome itself. The registry record does not provide enough information to assess whether that concern applied in this trial. The described completer analysis should therefore be distinguished from an analysis of all randomized participants; the record does not report an all-randomized analysis.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 1% reporting threshold.

Most frequent non-serious adverse event terms

The registry’s serious adverse event entries list 0 affected participants in the acetaminophen arm, with 224 at risk, and 0 affected participants in the placebo arm, with 52 at risk. No serious adverse-event terms are listed. These are the serious-event counts and denominators reported in the registry record; they should not be interpreted as the primary ALT endpoint results.

The registry also lists other adverse events for 147 of 224 participants at risk in the acetaminophen arm and 25 of 52 at risk in the placebo arm. These are counts, not a reported comparison adjusted for differences between groups. The record does not explain the difference between the listed at-risk denominators, the enrolled total of 398, and the primary analysis population of trial completers. The number completing the trial is not reported in the registry record.

In general, a zero count in a posted record means that no affected participants are listed for that event category and denominator. It does not establish that no event of any kind occurred, and it does not indicate the precision of a group comparison by itself. The record does not give further definitions or details for the other adverse-event category. The serious-event counts should be read as registry entries, not as evidence about the frequency of persistent ALT elevation or the secondary adduct outcome.

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

The registry record establishes the question the trial was designed to address: whether prolonged acetaminophen dosing was associated with persistent ALT elevations, compared with placebo, among healthy participants. It describes a monitoring schedule and defines persistence as an elevation unresolved at Day 40. It also records a secondary objective involving detectable acetaminophen-cysteine adduct concentrations after starting dosing.

However, the record does not report a numerical result for the primary endpoint. There is no posted count or proportion of participants with persistent ALT elevation by arm, no reported comparison, and no confidence interval or p-value. The secondary outcome results are also not reported. Consequently, the record does not establish the size, direction, or precision of either outcome comparison. It cannot support a statement that acetaminophen did or did not cause persistent ALT elevations in this trial.

The listed serious adverse event counts are 0 among 224 at risk in the acetaminophen arm and 0 among 52 at risk in the placebo arm. These figures are limited to the registry’s serious-event entries and do not answer the primary endpoint question. Other adverse-event counts are also listed, but the record does not provide enough context to interpret them as a causal comparison or to relate them to ALT outcomes.

In general, a study’s design describes how evidence was intended to be gathered, while its reported results show what was observed. Randomization and masking describe features of the design; they do not substitute for arm-level outcome estimates. Here, the design and outcome definitions are documented, but the main numerical findings are not. The enrollment figure of 398 should not be treated as the primary analysis denominator, because early withdrawals were excluded from the stated analysis population and the number of completers is not reported.

The trial record therefore supports a description of the research question, monitoring plan, and posted safety counts. It does not support a quantitative conclusion about the primary comparison or the adduct outcome.

13. Why This Trial Matters Statistically

This trial raises a useful statistical question about how to define and report a laboratory outcome observed over time. ALT was measured on Day 0 and Day 16 for all participants, while continued measurements were described for participants with an elevated ALT at Day 16. The endpoint then focused on whether an elevation remained unresolved at Day 40. This definition connects a repeated-measurement process to a single persistence classification, but interpretation depends on a clear account of the threshold, measurement schedule, and analysis denominator.

It also illustrates why the distinction between enrollment and analysis population matters. The record lists enrollment of 398, yet says early withdrawals were excluded from the primary analysis. Without the number who completed the trial or arm-specific denominators, readers cannot tell how many participants contributed to the endpoint. In general, reporting both the number meeting the outcome definition and the number analyzed in each group is important for understanding the result and its precision.

The endpoint title uses the language of a proportion, while its listed unit and parameter describe a number of participants. That difference highlights a basic reporting issue: counts and proportions answer related but distinct questions, and a proportion requires a stated denominator. The registry record does not provide the primary result needed to resolve that ambiguity.

Finally, a randomized, masked design and a detailed monitoring schedule do not by themselves permit assessment of the observed outcome. Numerical estimates and uncertainty are needed to describe what the trial found. Because the registry record does not report the primary or secondary outcome results, it is possible to discuss the design and limitations, but not to characterize the size or precision of the outcome comparisons.

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 most important limitation for interpreting the registry record is that it does not report numerical results for the primary ALT endpoint. The endpoint description is detailed enough to identify the intended definition, but there are no arm-specific counts or proportions, denominators, estimates, uncertainty intervals, or statistical comparisons. Results for the listed secondary adduct outcome are also not reported.

The record specifies that early withdrawals were excluded from the primary analysis, but does not state how many participants completed the trial or how many were analyzed in each arm. It does not give withdrawal reasons, the number of missing ALT measurements, or methods for handling missing data. Therefore, the potential effect of restricting the analysis to completers cannot be evaluated from the registry record.

The primary endpoint title describes a proportion, while the listed unit and parameter describe a participant count. The record does not explain that difference, report the threshold for classifying an ALT elevation, or specify how repeated ALT measurements were summarized beyond the persistence definition. It describes additional monitoring for participants with an elevated ALT at Day 16, but does not provide a full statistical analysis method for those measurements.

Although the trial is identified as randomized and quadruple-masked, details of sequence generation, allocation concealment, masking roles, and the randomization ratio are not reported in the registry record. A statistical analysis plan, sample-size justification, interim analyses, and multiplicity procedures are also not reported. The safety entries list different at-risk denominators for the two arms, but the record does not explain those denominators or their relationship to enrollment and completion.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Aminotransferase Trends During Prolonged Acetaminophen Dosing — NCT00743093.
• Registry record last updated 2013-09-18; status last verified 2013-09.
• Results first posted 2013-07-25.
• 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

The registry describes a completed randomized, quadruple-masked, parallel-group phase 4 trial sponsored by Denver Health and Hospital Authority, with enrollment of 398. It compared acetaminophen at 4 grams/day with placebo. The primary endpoint was persistent ALT elevation, defined as an elevation unresolved at Day 40. The stated primary analysis included trial completers and excluded early withdrawals.

The record lists a secondary outcome concerning detectable serum acetaminophen-cysteine adduct concentrations at 1, 2, and 3 days after dosing began. It reports 0 serious adverse events among 224 at risk in the acetaminophen arm and 0 among 52 at risk in the placebo arm. Other adverse-event counts are also listed. Numerical primary and secondary outcome results, the completer count, and detailed statistical methods are not reported in the registry record.