N-acetylcysteine in Non-Acetaminophen Pediatric Acute Liver Failure: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for N-acetylcysteine in Non-Acetaminophen Pediatric Acute Liver Failure (NCT00248625), a randomized phase 3 study. The primary outcome is Survival.

2. Clinical Question

The question concerns a treatment strategy in a narrowly defined clinical setting: pediatric acute liver failure for which the record describes no antidote or other specific treatment as available. The endpoint therefore counts survival whether it occurred without a transplant or after one. That definition makes the primary outcome broader than spontaneous recovery alone. It asks whether participants were alive at the specified follow-up, rather than whether their liver recovered without transplantation.

The comparison is between the randomized groups, not between participants who did and did not receive a transplant. Transplantation is part of the clinical course and is included in the survival definition; it is also assessed separately as a secondary outcome. The primary result should therefore be read as a comparison of one-year survival under the two assigned strategies. It does not, by itself, isolate the contribution of transplantation or explain why individual participants survived or died.

3. Trial Design

The registry identifies this as a Phase 3, randomized, parallel-group study with 184 participants and a completed status. It lists the University of Pittsburgh as sponsor. The trial compared intravenous N-acetylcysteine with placebo in pediatric acute liver failure not caused by acetaminophen. The brief summary describes a double-blind trial, while the registry classification lists triple masking. The record does not explain how those masking classifications relate to one another.

There were 92 participants in each arm. The N-acetylcysteine arm received 150 mg/kg/d in 5% dextrose, infused over 24 hours for up to 7 consecutive days. The placebo arm received 5% dextrose on the same infusion schedule for up to 7 consecutive days. The registry describes adaptive allocation within strata defined by age—less than 2 years or at least 2 years—and hepatic encephalopathy grade—0-1 or 2-4. It does not report further details about the allocation procedure.

The study start is recorded as 2000-01 and primary completion as 2009-09. Enrollment required participation in the Pediatric Acute Liver Failure Study Registry. The primary survival analysis included all participants enrolled in the study, according to the outcome description. The registry does not report the trial's original sample-size justification, planned statistical analysis details beyond the posted test, or whether interim analyses were conducted.

The record names several secondary outcomes, including spontaneous recovery, transplantation, hospital and ICU stay, organ-system failure, hepatic encephalopathy, and infectious complications. The detailed results available for secondary outcomes cover only some of these measures. Results for the other named outcomes are not reported in the registry record. These gaps limit how much can be concluded about the full set of outcomes, even though the primary endpoint is clearly described.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: All participants who were enrolled in the study were included in the survival analysis

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: All participants who were randomized were included in the baseline analysis.

6. Primary Endpoint

The registry lists the primary outcome as Survival, measured over One year following randomization.

The primary endpoint is survival one year after randomization. It counts participants who survived without a transplant together with participants who survived following transplantation. The registry states that all enrolled participants were included in the survival analysis. In the posted counts, 68 of 92 participants in the N-acetylcysteine group and 76 of 92 in the placebo group met the survival outcome.

This endpoint captures an outcome that matters directly to participants and families: whether the child was alive at follow-up. Including survival after transplantation recognizes that survival can occur through more than one clinical pathway. A separate secondary outcome addresses spontaneous recovery, which is narrower because it distinguishes survival without transplantation. These measures answer related but different questions and should not be treated as interchangeable.

As a general statistical point, a binary survival status at a fixed follow-up is easy to interpret as a count of participants meeting the outcome. The registry also reports a log-rank comparison, a method that uses information about the timing of events over follow-up. The record does not provide event-time summaries or further endpoint details, so the exact handling of follow-up and censoring cannot be assessed from the registry record alone. The primary result describes the one-year survival comparison, but it does not explain the clinical course or timing of events for individual participants.

7. Results Posted in the Registry

• N-acetylcysteine (NAC): 73.9% (68/92) versus 82.6% (76/92) on control; risk difference -8.7 percentage points (95% CI -20.5 to 3.2), risk ratio 0.89 (0.77–1.04); unadjusted two-proportion z-test p = 0.153.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Spontaneous Recovery

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • N-acetylcysteine (NAC): 35.9% (33/92) versus 53.3% (49/92) on control; risk difference -17.4 percentage points (95% CI -31.5 to -3.2), risk ratio 0.67 (0.48–0.94); unadjusted two-proportion z-test p = 0.018.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically lower for N-acetylcysteine (NAC) than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

Cumulative Percent Incidence of Transplantation by 1 Year

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • N-acetylcysteine (NAC): 44.6% (41/92) versus 34.8% (32/92) on control; risk difference 9.8 percentage points (95% CI -4.3 to 23.8), risk ratio 1.28 (0.89–1.84); unadjusted two-proportion z-test p = 0.175.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between N-acetylcysteine (NAC) and the control. The interval gives the range of effects that remain compatible with the data.

Infectious Complication

• Endpoint type: Binary: the number of participants with the event, compared as proportions.
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • N-acetylcysteine (NAC): 21.7% (20/92) versus 22.8% (21/92) on control; risk difference -1.1 percentage points (95% CI -13.1 to 10.9), risk ratio 0.95 (0.56–1.63); unadjusted two-proportion z-test p = 0.859.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between N-acetylcysteine (NAC) and the control. The interval gives the range of effects that remain compatible with the data.

The secondary outcomes address several parts of the clinical course beyond the primary survival endpoint. They include spontaneous recovery, transplantation, infection, and outcomes concerning hospital or ICU stay, organ-system failure, and hepatic encephalopathy. The detailed results available in the registry record cover spontaneous recovery, transplantation, and infectious complications. Results for the other named secondary outcomes are not reported in the registry record.

These outcomes can add context to the primary result because survival is a broad endpoint, while recovery without transplantation, transplantation, and infection describe different events or pathways. They are not interchangeable measures of one underlying result. The secondary findings do not replace the primary survival comparison, and an apparent pattern across outcomes cannot by itself establish an overall treatment effect.

Secondary comparisons generally carry less inferential weight when many outcomes are tested and the record does not report a multiplicity adjustment or a prespecified hierarchy. As a general statistical point, conducting multiple tests increases the chance that at least one result will appear unusual by chance, even when no true differences exist. A secondary p-value should therefore be interpreted in the context of the number of outcomes examined, their prespecification, and the analysis plan. The record does not report whether such adjustments or a formal hierarchy were used.

The secondary results also use different analysis methods, and not every named outcome has a detailed posted result. That mix limits the ability to draw a unified conclusion across all outcomes. The available secondary evidence can be viewed as descriptive and hypothesis-generating, while the primary endpoint remains the main basis for reading the trial's reported comparison. The registry record does not report enough information to characterize the full set of secondary analyses or their missing-data handling.

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

• Spontaneous Recovery
• Cumulative Percent Incidence of Transplantation by 1 Year
• Length of Hospital Stay
• Categorized Length of ICU Stay
• Number of Organ Systems Failing
• Highest Coma Grade of Hepatic Encephalopathy
• Infectious Complication

9. Statistical Interpretation

10. Statistical Methods Explained

For the primary outcome, the registry reports a log-rank test comparing the two randomized groups. As a general statistical explanation, the log-rank test compares the pattern of event timing between groups across follow-up. It is commonly used for time-to-event outcomes because it can account for when events occur, rather than reducing the entire follow-up to a single proportion. The posted registry result is p = 0.19. The record does not provide the test statistic, a hazard ratio, or further information about the underlying event-time data.

The posted counts also allow a simple unadjusted risk-difference calculation. This recalculated measure subtracts the proportion meeting the outcome in the placebo group from the proportion in the N-acetylcysteine group. Its estimate is -0.087, with the direction indicating a lower observed survival proportion in the N-acetylcysteine arm. This is a summary-statistic calculation, not a replacement for the registry's log-rank analysis. It does not use the timing of events and cannot reproduce all features of a time-to-event analysis.

A confidence interval accompanies an effect estimate to show a range of values compatible with the data and the calculation's assumptions. As a general concept, a wider interval indicates less precision, while an interval that includes no difference does not rule out that possibility. The primary recalculated interval includes no difference. The registry's posted log-rank result does not include a confidence interval for its test in the record.

The registry also reports secondary comparisons using different methods. Spontaneous recovery is assessed with a log-rank test. Transplantation is assessed using the Pepe and Mori test of cumulative incidence function difference. As a general explanation, cumulative incidence methods can account for competing events: the occurrence of one type of event can prevent another event from occurring or being observed in the same way. The record does not provide further explanation of the competing-event definitions or details of the implementation. Infectious complication is compared using a chi-squared test. As a general concept, a chi-squared test evaluates whether event counts differ across groups, without accounting for event timing.

These methods answer related but not identical questions. A log-rank test uses time-to-event information, a cumulative incidence comparison addresses event probability in the presence of competing events, and a chi-squared test compares categorical counts. Their p-values should not be treated as if they came from one common analysis or as if they all summarized the same outcome structure. The registry does not report a full statistical analysis plan, the exact analysis populations for every secondary endpoint, or details of any covariate adjustment.

The record describes allocation within age and hepatic encephalopathy strata. Stratification can, as a general design principle, help balance groups with respect to specified characteristics. The record does not say whether the posted analyses adjusted for those strata. The allocation description also uses the term adaptively allocated, but the precise algorithm and its operation are not reported in the registry record. No additional details about the randomization sequence or concealment are reported.

Secondary outcomes include counts, percentages, and measures such as length of stay and organ-system failure. General statistical practice requires the method to match the outcome's structure and distribution. The registry's detailed outcome descriptions and analysis results are incomplete for several named secondary outcomes, so the methods used for those outcomes are not reported in the registry record. No distributional assumptions or model diagnostics are posted.

Finally, the registry lists 8 outcome measures and 8 analyses, with a primary outcome and secondary outcomes. The record does not report whether the study used a prespecified hierarchy among secondary outcomes, adjusted for multiple comparisons, or treated the secondary tests as exploratory. That information matters because interpreting multiple tests together differs from interpreting one prespecified primary comparison. The absence of these details does not change the observed counts, but it limits the strength of inferences drawn from secondary p-values.

11. Confidence Intervals and Precision

The primary groups each contained 92 participants, and their posted survival counts were 68 in the N-acetylcysteine arm and 76 in the placebo arm. The recalculated risk difference was -0.087. Its confidence interval extends across the no-difference value, so the observed estimate does not pin down the direction of the underlying difference with high precision. The interval allows both a lower survival proportion with N-acetylcysteine and a higher one, based on the posted calculation.

As a general explanation, a confidence interval represents uncertainty in an estimate under the assumptions used to construct it. It is not a guarantee that the true value lies within the interval, nor is it a range of individual participant outcomes. A confidence interval that includes no difference indicates that the data do not exclude that value at the interval's confidence level. The registry does not give a confidence interval for its log-rank result, so the recalculated interval should not be attributed to that test.

Precision is constrained by the number of participants and the number of observed outcomes, as well as by the endpoint and analysis method. The total enrollment was 184, with equal posted group sizes. These counts support a comparison, but they do not make the estimate exact. The registry's p-value and the recalculated interval answer related questions in different ways: the p-value summarizes compatibility with a null model, while the interval shows uncertainty around an estimated risk difference.

For the secondary outcomes, the posted recalculated intervals also reflect uncertainty, and some include no difference. Their interpretation additionally depends on the outcome definition and analysis method. The registry does not report confidence intervals for the sponsor's posted tests, and the confidence intervals from simple recalculations should be understood as unadjusted. The record does not report an adjustment for the number of outcomes considered.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are illustrations based on the observed effect, not the trial's original design assumptions. The original sample-size justification is not reported in the registry record. The planning calculation assumes a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. It considers effects equal to 100%, 75%, and 50% of the observed effect.

For these binary outcomes, the figures are participants per arm. In general, the 80% power column describes the number of participants per arm that the planning calculation estimates would be needed to have an 80% chance of detecting the specified effect under its assumptions. The 90% power column describes the corresponding estimate for a 90% chance. A higher target probability of detecting the effect generally requires more participants. Smaller effects also require more participants, which is why the planning values rise as the assumed fraction of the observed effect becomes smaller.

These are not observed power. They are prospective planning illustrations recalculated from the observed group results, not evidence that the completed trial had a particular probability of finding a result. They should not be read as proof that an effect exists or as a substitute for the uncertainty intervals. The effect used in the calculation is itself an estimate from the trial and may not represent the effect in another study.

For time-to-event planning calculations, the stated convention is to report total events rather than participants per arm. The displayed primary outcome is categorized as binary, so its planning figures are participants per arm. Differences in outcome type and planning assumptions mean figures for one outcome should not be transferred to another without care. The registry does not report the assumptions used for the trial's original design, so these illustrations cannot establish whether the planned enrollment was adequate for that original design.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.826; treatment proportion p₁ = 0.739; average p̄ = 0.783.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.5833 = 1.1433.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.5801 = 0.4882.
4. n = (1.1433 + 0.4882)² / (-0.0870)² = 352.0, rounded up to 353 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
p0 <- 0.826086956521739                          # control proportion
p1 <- 0.739130434782609                          # treatment proportion
n_per_arm <- function(power, frac = 1) {
  q1 <- p0 + (p1 - p0) * frac               # smaller effect = fraction of the observed difference
  pbar <- (p0 + q1) / 2
  z_b <- qnorm(power)
  ceiling(round((z_a * sqrt(2 * pbar * (1 - pbar)) + z_b * sqrt(p0 * (1 - p0) + q1 * (1 - q1)))^2 / (q1 - p0)^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 (unrounded n per arm)
cat("power.prop.test:", round(power.prop.test(p1 = p0, p2 = p1, power = 0.80)$n, 1), "\n")

# Simulation: how often does the z-test reject at the 80%-power sample size?
set.seed(248625)
n    <- n_per_arm(0.80)
reps <- 20000
x0 <- rbinom(reps, n, p0); x1 <- rbinom(reps, n, p1)
ph <- (x0 + x1) / (2 * n)
z  <- ((x1 - x0) / n) / sqrt(ph * (1 - ph) * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(z) > z_a, na.rm = TRUE), reps))

Output from running the code

100% of observed effect: n per arm = 353 (80% power), 471 (90% power)
 75% of observed effect: n per arm = 604 (80% power), 808 (90% power)
 50% of observed effect: n per arm = 1,306 (80% power), 1,748 (90% power)
power.prop.test: 352 
Simulated power at n = 353 per arm: 0.803 (20000 replicates)

The simulation draws many pairs of event counts at the planned sample size and counts how often the two-proportion z-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Analyses Reported by the Sponsor

The registry reports the trial's primary comparison using a log-rank test, with p = 0.19. A recalculated, unadjusted risk-difference analysis based on the posted group counts gives an estimate of -0.087 and p = 0.153. The recalculation is a simple comparison of outcome proportions; the log-rank test uses event timing. The two p-values therefore come from different methods and need not match.

The registry record does not provide enough detail about event times, censoring, or the full analysis procedure to reproduce the log-rank result from the posted summary counts. The record marks no discrepancy between the reported analysis and the recalculation. The recalculated risk difference is best treated as a descriptive check on the posted counts, not as a correction to the trial's reported test.

The sponsor's reported analysis remains the direct record of the trial's own inferential comparison. The simple recalculation complements it by expressing the observed difference in group proportions, but does not have the same analytic basis. Neither p-value alone establishes equivalence, proves a difference, or measures clinical importance. Details such as the prespecified analysis plan and any adjustment beyond the posted method are not reported in the registry record.

15. Multiplicity, Missing Data and Analysis Populations

The registry lists 8 outcome measures and 8 analyses, including the primary outcome and secondary outcomes. Considering several outcomes creates a multiplicity issue: as a general statistical matter, repeated testing can make chance findings more likely across a collection of results. The registry record does not report whether the investigators adjusted secondary p-values, set a hierarchy among outcomes, or designated particular secondary comparisons as confirmatory or exploratory. The secondary findings should therefore not be interpreted as though each were an isolated, prespecified primary test.

The primary outcome description says that all participants enrolled in the study were included in the survival analysis. That is the only explicit analysis-population statement in the posted endpoint descriptions. The analysis populations used for the secondary endpoints are not reported in the registry record. The record also does not describe how missing outcome data, loss to follow-up, or incomplete assessments were handled. It does not report imputation, sensitivity analyses, or exclusions for the secondary outcomes.

The registry identifies the study as randomized and describes allocation within age and hepatic encephalopathy strata. It reports a log-rank test for the primary comparison but does not provide the full statistical analysis plan or say whether the primary analysis was adjusted for the allocation strata. Interim analyses and any stopping rules are not reported in the registry record. These omissions do not change the posted counts, but they prevent a complete audit of the analysis decisions and the role of interim monitoring.

As a general principle, randomization supports a comparison of assigned groups, while missing outcome data and multiple testing can affect how confidently results are interpreted. Here, the explicit statement that all enrolled participants were included applies to the survival analysis; it should not be extended automatically to every secondary outcome. Without further details, the extent and handling of missing data across the broader outcome set remain uncertain.

16. 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 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: respiratory distress (1.1%), bacteremia (1.1%), bradycardiac episode (1.1%), hypoglycemia (1.1%), aplastic anemia (1.1%).

The registry lists serious adverse events affecting 5 of 92 participants in the N-acetylcysteine group and 4 of 92 in the placebo group. It also lists other adverse events affecting 19 of 92 and 16 of 92 participants, respectively. These are counts of participants with reported events, not estimates of causal effect. The record does not provide additional detail on how events were attributed or on the event-level analysis.

Among the serious-event terms listed, respiratory distress, bacteremia, bradycardiac episode, hypoglycemia, aplastic anemia, and Epstein-Barr virus are each shown with 1.1%. The record does not establish from these term listings whether the same participant could have contributed to more than one term. The adverse-event section does not report death counts for these groups.

As a general statistical point, relatively small event counts can yield imprecise comparisons, and differences in counts do not by themselves establish that an intervention caused an event. The posted serious and other adverse-event counts should be read descriptively alongside the registry's limited detail. The safety information in the registry record does not provide a complete account of event timing, severity beyond the serious classification, or causal assessment.

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

The posted primary counts show fewer participants meeting the one-year survival outcome in the N-acetylcysteine group than in the placebo group. The recalculated risk difference is negative for N-acetylcysteine relative to placebo, and its confidence interval includes no difference. The registry-reported log-rank p-value is 0.19. Together, these results describe the observed comparison and its uncertainty; they do not establish that the groups were equivalent or that a difference is certain.

The result applies to the endpoint as defined: survival one year after randomization, including survival after transplantation. It does not answer whether spontaneous recovery differed in the same way, whether transplantation explains the survival pattern, or how other outcomes changed. Those are separate questions. A result from this population also does not automatically apply to other causes of acute liver failure or to populations not represented in the trial.

As a general statistical principle, a non-small p-value is not evidence that an effect is exactly absent. Likewise, an observed difference is not, by itself, evidence that an intervention caused the difference. Interpretation depends on the design, endpoint, uncertainty, analysis, and completeness of reporting. The randomized comparison provides a structured basis for comparing assigned groups, but the registry record does not provide every detail needed to assess the full analysis or potential limitations.

No medical recommendation follows from these statistics. The record describes a completed trial and posts outcome counts and analyses, but its results should not be converted into advice for an individual child. It also does not establish effects on outcomes for which detailed results are not reported. The appropriate statistical conclusion is limited to what the primary and posted secondary results measure, with uncertainty retained rather than replaced by a categorical claim.

18. Why This Trial Matters Statistically

This trial illustrates why endpoint definitions matter in clinical research. Survival includes both spontaneous survival without transplantation and survival following transplantation, whereas spontaneous recovery is a separate, narrower outcome. Those endpoints describe distinct aspects of the clinical course. A clear distinction helps prevent readers from treating survival, transplant incidence, and recovery as if they were the same measure.

It also shows how the analysis method can shape the reported comparison. The registry's primary log-rank test uses event timing, while the simple recalculation compares proportions from the posted counts. Their p-values differ, but that does not imply an error: they summarize the data differently. Comparing the method and the effect measure is essential when interpreting a reported result alongside a recalculation.

The trial's equal group sizes and randomized design support a direct comparison of assigned groups, while the modest enrollment and uncertainty in the primary estimate limit precision. The record also demonstrates the importance of transparent reporting. Details on the original sample-size justification, analysis plan, missing data, multiplicity, and interim analyses are not reported in the registry record. These omissions constrain interpretation even when the main endpoint and counts are available.

Finally, the secondary outcomes span different event types and use different tests. Their interpretation requires attention to the question each outcome addresses, as well as the possibility of multiplicity. Statistical significance alone cannot substitute for effect size, precision, and endpoint meaning. This trial is a useful example of reading all those elements together rather than relying on one p-value.

19. 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 original sample-size justification or the assumptions used to plan enrollment. The planning illustrations based on observed effects are not a substitute for that design information. The full statistical analysis plan is also not reported, including whether the primary analysis incorporated the age and hepatic encephalopathy strata used in allocation.

The primary endpoint combines spontaneous survival without transplantation with survival following transplantation. That broad definition is clinically interpretable as one-year survival, but it cannot show from the primary result alone how outcomes differed across those pathways. Transplantation is reported separately as a secondary outcome, but the registry's posted results do not explain the relationship between individual transplant timing and survival.

The detailed secondary results available are incomplete relative to the named outcomes. The registry does not report detailed results for hospital stay, ICU stay, organ systems failing, or highest coma grade in the record. The analysis populations and missing-data handling for secondary outcomes are not reported. It is also not reported whether the investigators adjusted for multiple comparisons or used interim analyses.

The primary groups each had 92 participants, and the recalculated interval includes no difference. This leaves uncertainty around the size and direction of the underlying group difference. The registry-reported log-rank analysis lacks a posted effect estimate and confidence interval, while the recalculation from summary counts does not use event timing. Those differences limit direct comparison of the two analyses.

Finally, the trial concerns children with acute liver failure not caused by acetaminophen who were enrolled through the Pediatric Acute Liver Failure Study Registry. The findings should not be generalized automatically to other populations or causes. The record gives a completed status and primary completion date, but further detail on follow-up completeness, protocol changes, and deviations is not reported in the registry record.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: N-acetylcysteine in Non-Acetaminophen Pediatric Acute Liver Failure — NCT00248625.
• Registry record last updated 2016-07-28; status last verified 2016-06.
• Results first posted 2016-07-28.
• 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.

23. Record Summary

The registry describes a completed, Phase 3, randomized, parallel-group trial of intravenous N-acetylcysteine versus placebo for pediatric acute liver failure not caused by acetaminophen. Enrollment was 184, with 92 participants in each arm. The primary outcome was survival one year after randomization, counting survival without transplantation and survival following transplantation.

The posted survival counts were 68 in the N-acetylcysteine arm and 76 in the placebo arm. The registry reports a log-rank p-value of 0.19; a simple unadjusted recalculation from the counts gives a risk difference of -0.087, with a confidence interval that includes no difference. The record names multiple secondary outcomes, but detailed results are available for only some of them. The original sample-size rationale, missing-data procedures, multiplicity approach, and broader analysis plan are not reported in the registry record.