Does IV Acetaminophen Reduce Opioid Requirement in Pediatric Patients With Acute Sickle Cell Crises?: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Does IV Acetaminophen Reduce Opioid Requirement in Pediatric Patients With Acute Sickle Cell Crises? (NCT03541980), a randomized phase 4 study. The primary outcome is Cumulative Opioid Dosing.

2. Clinical Question

The clinical question concerns opioid use during acute pain management in the pediatric emergency department. The registry describes the primary outcome as the total opioid dose given after initial evaluation, expressed in mg/kg and assessed over 120 minutes. This makes the outcome a measure of cumulative medication use during a specified period, rather than a direct measure of pain relief or a measure of opioid use over the entire hospital stay.

The registry also lists pain scores, inpatient admission, adverse effects, and participant satisfaction as secondary outcomes. Those measures address aspects of the acute care experience beyond opioid dosing. Their inclusion does not make them interchangeable: opioid dose describes medication administered, pain scores describe reported pain, and admission captures a care disposition. The registry record does not report numerical results for every listed secondary measure.

The primary question is comparative: whether the assigned treatment groups differed in cumulative opioid dosing. A difference between group averages would be an estimate of the contrast, while its confidence interval would describe the precision of that estimate under the analysis method. The registry reports a mean and a 99% confidence interval for each arm, but the two-arm primary comparison is not estimable in the posted results. As a result, the arm summaries alone do not establish the size or precision of a treatment contrast.

3. Trial Design

The registry identifies this as a randomized, quadruple-masked, parallel-group Phase 4 trial. Participants were allocated to IV acetaminophen or IV normal saline placebo. The trial status is completed, and the registry reports enrollment of 71. The listed sponsor is Newark Beth Israel Medical Center. The recorded study start was 2018-02-20, and the primary completion date was 2020-02-20.

The parallel design assigns participants to one of the two groups and compares outcomes between them. Random allocation is intended to make treatment groups comparable on average, including with respect to characteristics that may not be measured. It does not ensure that the groups will be identical in a trial of this size. Masking is recorded as quadruple, but the registry record does not identify which roles were masked or describe procedures for maintaining masking.

The primary endpoint is cumulative opioid dosing during the 120 minutes after initial evaluation. The reported arm summaries include 35 participants in the intervention group and 36 in the placebo group. The primary measure is a mean in mg/kg, with a 99% confidence interval reported for each arm. The registry does not post an estimable two-arm comparison for this outcome, so the group summaries cannot be treated as a reported estimate of the treatment contrast.

The registry lists five outcome measures in total, comprising the primary endpoint and four secondary outcomes. Those secondary outcomes concern pain scores, inpatient admission, adverse effects, and participant satisfaction. Only the inpatient-admission outcome includes a posted two-group comparison in the available results. Details such as eligibility criteria, the planned target enrollment, the sample-size justification, and the analysis populations are not reported in the registry record. The trial’s actual enrollment should therefore not be interpreted as evidence about its original design target.

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

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 Cumulative Opioid Dosing, measured over 120 minutes.

Cumulative opioid dosing measures the total opioid dose given after the initial evaluation, expressed in mg/kg, over 120 minutes. The registry labels this endpoint as a mean. It is intended to capture how much opioid medication participants received during the defined acute-care interval. A cumulative measure can reflect repeated administrations during that window, rather than just the initial dose.

This endpoint addresses medication use, not pain itself. It can be considered alongside pain scores and other outcomes, but it does not directly establish how participants felt or whether their symptoms improved. Nor does the specified 120-minute period describe opioid use after that interval. The registry record does not provide further detail about which opioid medicines were counted or how dosing was handled in the analysis.

The registry reports arm means of 0.2 mg/kg in both groups. Each arm has a reported 99% confidence interval from 0.1 to 0.2 mg/kg. These are rounded summaries. The registry does not report an estimable two-arm comparison for the primary endpoint, so the arm-level intervals should not be read as a confidence interval for the difference between groups. Without that contrast, the posted primary summaries do not quantify how precisely any between-group effect was estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry presents a randomized parallel-group comparison of IV acetaminophen with IV normal saline placebo. Randomization assigns participants to groups by chance, helping reduce systematic differences in measured and unmeasured characteristics at the time of allocation. It does not guarantee balance in every characteristic, particularly when enrollment is limited. Quadruple masking means the registry records masking at four levels, but the identities of those roles and the masking procedures are not reported in the registry record.

What does a confidence interval describe?

In general, a confidence interval expresses the statistical uncertainty around an estimate under a particular analysis method. A narrower interval indicates greater precision for that estimate, while a wider interval indicates less precision. An interval for one group’s mean answers a different question from an interval for a difference between groups. For a treatment comparison, the interval around the contrast is especially important because it shows which between-group effects remain compatible with the data and analysis.

The primary outcome is a mean, and the registry reports a 99% confidence interval for each group. The group means are both 0.2 mg/kg, with reported intervals from 0.1 to 0.2 mg/kg. The registry does not report an estimable interval for the two-arm contrast. The method used to construct the arm-level intervals, and the reason the comparison could not be estimated, are not reported in the registry record. The equal rounded arm means and overlapping arm intervals cannot be used to reconstruct a valid comparison interval.

How should the secondary comparison be read?

In general, a risk difference compares the proportion with an outcome in one group with the proportion in another, expressed as an absolute difference. For inpatient admission, the posted comparison gives a risk difference of 0.131. Its interval extends from -0.089 to 0.351, which includes zero. The unadjusted p-value is 0.248. The registry also reports relative-risk and odds-ratio summaries for this outcome; these express the comparison on relative rather than absolute scales. Relative measures can appear different in magnitude from an absolute difference because they use different scales.

The inpatient comparison is labeled as recalculated and unadjusted. In general, a recalculation from group counts does not incorporate covariate adjustment or other elements of a trial’s planned analysis. The registry record does not report a sponsor analysis for this outcome. The p-value is unadjusted, and the record does not specify whether or how any secondary-outcome testing was adjusted for multiple comparisons. These registry entries make the comparison useful as a descriptive statistical summary, but they limit its role as confirmatory evidence.

What do the planning illustrations mean?

The registry includes sample-size planning illustrations based on fractions of the observed inpatient-admission effect. They assume a two-sided significance level of 0.05, equal allocation between groups, and a normal approximation. They report participants per arm for 80% and 90% power under each stated planning scenario. The illustrations are hypothetical design calculations, not the number enrolled and not a calculation of the trial’s observed power.

For planning for 100% of the observed effect, the illustration gives 208 participants per arm for 80% power and 278 participants per arm for 90% power. For planning for 75% of the observed effect, it gives 378 participants per arm for 80% power and 505 participants per arm for 90% power. For planning for 50% of the observed effect, it gives 865 participants per arm for 80% power and 1,158 participants per arm for 90% power. These values depend on the stated assumptions and on using an effect derived from the observed result. They are not evidence that the trial was designed with these targets; the trial’s own sample-size justification is not reported in the registry record.

In general, power is a design quantity: it is the chance that a specified analysis will reject a null hypothesis under a particular assumed effect and set of assumptions. It is not a measure of whether a completed study’s result is trustworthy, and observed power should not be inferred from a p-value. When the observed effect is used as the planning basis, the illustration is sensitive to sampling variation in that estimate. Smaller assumed effects generally require larger planned samples to reach the same target power, as reflected by the registry’s scenarios.

Why can variability matter?

General statistical methods distinguish between the average outcome and the variability of outcomes around that average. Greater variability can make a group comparison less precise because the data provide less information about the difference in means. For count outcomes, extra variability beyond a simple model’s assumptions is often called over-dispersion; it can also reduce precision if not handled appropriately. The registry does not report a dispersion estimate for the primary outcome, and it does not describe an over-dispersion assessment or adjustment. The posted primary comparison is not estimable, so no claim about a specific variance model can be made from the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures: one primary outcome and four secondary outcomes. Testing or estimating several outcomes raises a multiplicity concern. In general, when many comparisons are considered, the chance of at least one apparently notable result can increase unless the analysis plan accounts for the number and structure of comparisons. The registry record does not report a multiplicity adjustment, a hierarchy for testing outcomes, or another strategy for controlling that concern.

The inpatient-admission comparison is unadjusted. The registry lists no reported analyses for the primary outcome, and it does not report a sponsor analysis for the secondary result. Consequently, the posted statistical summaries do not establish which outcomes, if any, were designated for formal confirmatory testing or how the study’s conclusions were meant to depend on them. The statistical analysis plan is not reported in the registry record.

Information about missing data is also limited. The primary two-arm comparison is marked as not estimable because values were missing or not estimable for that comparison, but the registry does not state the number of missing observations, their reasons, or how any missing values were handled. It does not report whether the analysis used all randomized participants, a subset defined by treatment received, or another analysis population. The group denominators in the posted results should not be taken as proof that every randomized participant contributed to every outcome.

The record also does not report the trial’s sample-size justification, interim analyses, or detailed statistical plan. Their absence from the registry record does not show that such procedures were or were not used; it means they cannot be assessed from the posted information. These omissions matter because the choice of analysis population, treatment of missing data, multiplicity strategy, and any planned interim decisions can affect both estimates and uncertainty. The posted results should therefore be interpreted as limited registry summaries rather than a complete account of the trial’s analysis.

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.

The registry reports zero serious adverse events among 35 participants in the intervention group and zero among 36 participants in the placebo group. It also reports zero other adverse events in each group and zero deaths in each group. These are counts of observed events in the recorded groups.

Zero recorded events means that no events of those categories were reported for the participants counted in the registry results. It does not establish that the risk of an adverse event is zero, or that the treatments have identical safety profiles. With a finite number of participants, uncommon events may not occur during observation even when they remain possible. The registry record does not provide a comparative safety estimate or confidence interval, nor does it report further detail about adverse-event collection or the relevant observation period.

Serious adverse events, other adverse events, and deaths are distinct categories in the registry results. The absence of reported events in these categories should be read as a descriptive finding for this trial, not as a general guarantee about safety. It also does not address events that may not have been captured or reported in the registry record.

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

The results establish that the registry reports the same rounded primary mean, 0.2 mg/kg, for each treatment group, with a 99% confidence interval from 0.1 to 0.2 mg/kg for each. They do not establish that the groups had exactly the same underlying mean. The figures are rounded arm summaries, and the registry does not provide an estimable between-group primary comparison. As a result, the posted primary data do not quantify the treatment contrast or its precision.

The inpatient-admission comparison is a secondary, unadjusted result. Its estimate and interval describe uncertainty in that comparison under the recalculated method, but they do not replace the missing primary contrast. It is not appropriate to use this result alone to make a conclusion about cumulative opioid dosing, pain, or the overall clinical effect of assignment to IV acetaminophen rather than placebo.

More generally, a trial result is not a simple yes-or-no verdict. An estimate indicates the direction and size of a contrast, while its uncertainty indicates how much the data constrain plausible values. Here, the primary contrast is not posted as estimable, and secondary results are incomplete or unadjusted. The data therefore do not support a precise comparative conclusion about the primary question from the registry record alone.

The record also does not report enough information to assess the original sample-size rationale, handling of missing observations, analysis population, or multiplicity strategy. Those details can change how confidently an estimate is interpreted. The planning illustrations based on the inpatient-admission result are hypothetical calculations and should not be mistaken for evidence about the trial’s original design or its chance of detecting an effect after completion.

These limits do not erase the descriptive information that is posted. They define its scope: arm-level primary summaries, a secondary admission comparison, and adverse-event counts. They do not establish that IV acetaminophen does or does not reduce opioid use, and they do not establish equivalence between the groups. The central limitation is the absence of an estimable primary comparison in the registry results.

13. Why This Trial Matters Statistically

This trial illustrates why a registry entry can contain arm-level outcome summaries without supplying the comparison needed to answer a randomized-trial question. The primary issue is not simply whether the two rounded means look alike. A comparative analysis must estimate the difference between groups and quantify uncertainty for that difference. The registry marks that primary comparison as not estimable, so a reader cannot recover the primary contrast from the posted summaries.

It also demonstrates the distinction between an outcome’s clinical meaning and its statistical role. Cumulative opioid dose, pain scores, admission, adverse effects, and satisfaction can each describe different aspects of care. A secondary result may offer context, but it cannot automatically stand in for the primary outcome. An unadjusted comparison among several outcomes also deserves more caution than a prespecified primary analysis with a reported estimation method.

The planning illustrations provide another useful statistical distinction. Sample sizes calculated from an observed effect are planning scenarios, not a retrospective measure of whether the completed trial was adequately powered. The illustrations depend on their assumptions and on an effect estimate that may be uncertain. The registry does not report the trial’s own sample-size justification, so the hypothetical planning values cannot establish what the study originally intended to detect.

Finally, the sparse information about missing data, analysis populations, and multiplicity shows why registry summaries are not always a complete statistical account. Such details help readers understand which participants contributed to each result and how selective uncertainty or multiple outcomes were handled. The trial record is informative about the design and posted findings, while leaving important aspects of the analysis unclear.

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 direct limitation is that the primary outcome has no estimable two-arm comparison in the registry results. Both groups have rounded arm means and arm-level intervals, but neither supplies the contrast or its uncertainty. The reason given is that values were missing or not estimable for a two-arm comparison; further explanation is not reported in the registry record.

The posted primary values are rounded to one decimal place. That precision may obscure smaller distinctions between the underlying summaries. The record does not report additional digits or a primary effect estimate that would clarify the comparison. The confidence intervals are also arm-specific, not a reported interval for the treatment difference.

Other limitations concern the scope and reporting of secondary outcomes. The inpatient-admission comparison is unadjusted, while numerical results for pain scores and satisfaction are not reported in the registry record. The safety counts report no events in the posted categories, but do not provide a comparative safety estimate or further information about event collection. The registry does not report a multiplicity strategy, so the inferential weight of secondary comparisons is difficult to assess.

The record does not describe missing-data handling, analysis populations, the primary statistical method, interim analyses, or the sample-size justification. It also does not provide further detail about the roles masked or the procedures used to maintain masking. These reporting gaps do not demonstrate a flaw in how the trial was conducted, but they prevent a reader from evaluating those aspects from the registry record.

Finally, the endpoint’s 120-minute timeframe limits what can be inferred about opioid dosing beyond that interval. The registry does not report additional detail about the opioid medicines counted or how dosing was summarized. The posted results therefore address a defined, short-term medication-use measure rather than every dimension or duration of care.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Does IV Acetaminophen Reduce Opioid Requirement in Pediatric Patients With Acute Sickle Cell Crises? — NCT03541980.
• Registry record last updated 2021-04-02; status last verified 2021-03.
• Results first posted 2021-04-02.
• 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

NCT03541980 is a completed randomized, quadruple-masked, parallel-group Phase 4 trial sponsored by Newark Beth Israel Medical Center. The registry reports enrollment of 71 and compares IV acetaminophen with IV normal saline placebo in pediatric emergency-department patients with acute sickle cell crises.

The primary outcome is mean cumulative opioid dosing after initial evaluation over 120 minutes, measured in mg/kg. The registry reports a mean of 0.2 mg/kg in each group and a 99% confidence interval from 0.1 to 0.2 mg/kg for each, but no estimable two-arm comparison. A secondary inpatient-admission comparison is posted as an unadjusted recalculation. The registry also reports zero serious adverse events, other adverse events, and deaths in both groups.

Details on the primary analysis, missing data, analysis populations, multiplicity, and the trial’s sample-size justification are not reported in the registry record. The posted results therefore offer limited comparative evidence for the primary question.