Oral Zinc for the Treatment of Acute Diarrhea in US Children: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Oral Zinc for the Treatment of Acute Diarrhea in US Children (NCT01198587), a randomized na study. The primary outcome is Duration of Diarrhea in Acute Diarrheal Illnesses in a Developed Nation While Taking Zinc or Placebo..

2. Clinical Question

The clinical rationale in the registry focuses on whether findings from trials in developing-country populations apply to children treated in an industrialized setting. The stated aim was to assess a common pediatric illness in a setting where the record describes mortality as not a significant factor, but healthcare use and costs as relevant concerns. Those statements describe the rationale for conducting the trial; they are not results of the randomized comparison.

The posted outcome data separate participants by care setting and treatment arm. That distinction matters because the outpatient and inpatient groups are small, and the inpatient comparison includes 5 participants in each arm. The record explicitly notes that it did not enroll sufficient inpatients. The available comparisons therefore address different clinical settings with different amounts of information, rather than a single pooled estimate that can be assumed to represent each setting equally.

The primary question is about the time course of symptoms, not simply whether diarrhea occurred. The record gives arm-level means and standard deviations and also reports log-rank analyses for the outpatient and inpatient comparisons. These are different ways of describing or comparing duration data, so the interpretation should keep the posted summaries and the reported analyses distinct.

3. Trial Design

The registry describes a randomized, double-blind, placebo-controlled trial with quadruple masking and a parallel-group model. Its status is completed, and total enrollment is listed as 71. The sponsor is Boston Children's Hospital. The registry lists the study start as 2010-11 and primary completion as 2014-06. These are registry-record details, not evidence about the results or the adequacy of the design.

The interventions were zinc sulfate and a placebo oral capsule. Each intervention appears among both outpatients and inpatients, creating four reported groups: outpatient zinc sulfate, inpatient zinc sulfate, outpatient placebo, and inpatient placebo. The arm-level outcome summaries list 23 outpatient zinc participants, 5 inpatient zinc participants, 21 outpatient placebo participants, and 5 inpatient placebo participants. The record’s primary-outcome description says that patients were assessed separately by arm and then again together for overall severity, but the posted arm summaries and analyses do not give a complete account of every analysis population.

The study planned to examine duration of diarrhea over a 14-day timeframe. The registry says that the purpose was to distinguish the duration of symptoms before chronic diarrhea, defined in the record as lasting longer than 14 days. It also describes an interest in duration of hospitalization for inpatients. However, the record notes that it failed to enroll sufficient inpatients because hospitalization was uncommon in the stated population. The small inpatient groups make that part of the trial especially limited in the amount of information available.

The record lists two secondary outcomes: potential cost benefits related to daycare days missed and parents’ work days lost, and parent-report reliability compared with phone interview responses. Two analyses are posted, one for the inpatient zinc and placebo groups and one for the outpatient zinc and placebo groups. The registry does not report the original sample-size justification, allocation ratio, sequence-generation details, or a full statistical analysis plan. Randomization and masking are identified, but further operational details 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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The study failed to enroll sufficient inpatients due to the low hospitalization rate in the US for children who are otherwise healthy with diarrhea All patients were analyzed separately by arm and then again together for overall severity of diarrhea

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: Overall low number of inpatients with diarrhea meeting the study enrollment criteria of being otherwise healthy

6. Primary Endpoint

The registry lists the primary outcome as Duration of Diarrhea in Acute Diarrheal Illnesses in a Developed Nation While Taking Zinc or Placebo., measured over 14 days.

The primary endpoint is the duration of diarrhea in acute diarrheal illness, expressed in hours, with a 14-day timeframe. It is a continuous measure: each participant’s duration is recorded as a quantity of time, and the registry gives a mean and standard deviation for each arm. The record says symptoms would be assessed to identify duration before diarrhea became chronic, which it defines as lasting longer than 14 days.

Duration is relevant to the stated study question because the objective was to assess how long symptoms persisted, rather than only whether a child experienced an episode. In general, a continuous time measure can retain information about variation in duration across participants. Comparing group means is one way to summarize that information, while a time-to-event method can compare the timing of an event across groups without making the mean the sole focus.

The registry also describes a distinct inpatient objective concerning duration of hospitalization. The primary outcome title and the posted arm summaries, however, are framed as duration of diarrhea. The record does not clarify whether the posted means are calculated for all randomized participants, only participants with observed duration, or another analysis population. It also does not report a detailed operational definition for the event ending the diarrhea-duration measure or how participants whose symptoms continued beyond the timeframe were handled.

Those omissions matter when interpreting a time endpoint: its meaning depends on how symptom onset and resolution are defined, how follow-up is conducted, and what happens when the event is not observed within the stated timeframe. Such details are not reported in the registry record.

7. Results Posted in the Registry

• Outpatient Zinc Sulfate: mean 73.00 versus 48.00 on control; difference 25.00 (95% CI -13.95 to 63.95), standardized effect d = 0.37; z-test p = 0.208.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry includes arm-level means and standard deviations for a continuous duration outcome, as well as log-rank tests for the outpatient and inpatient comparisons. A recalculated unadjusted comparison is available for the outpatient means. These analyses answer related but not identical questions, so it is useful to distinguish the summary measures, the test, and the uncertainty around an estimated difference.

What does a mean summarize?

In general, the arithmetic mean is the total of observed values divided by the number of values included. It gives a central summary on the original measurement scale: in this trial, hours. The posted outpatient means are 73.0 hours for zinc and 48.0 hours for placebo; the inpatient means are 72.0 and 76.8 hours, respectively. A mean is easy to interpret in the units of the endpoint, but it can be influenced by unusually long or short observations. The registry record does not provide participant-level durations or distribution plots from which to judge the shape of the data.

The standard deviation describes how spread out individual observations are around the mean. It is not the uncertainty of the mean itself. The posted outpatient standard deviations are 77.8 hours and 52.6 hours; the inpatient values are 78.7 hours and 81.2 hours. In general, when measurements vary substantially within arms, the estimated group means and their contrast may be less precise, especially when the groups are small.

What does a mean difference express?

A mean difference subtracts one arm’s mean from the other arm’s mean and retains the endpoint’s units. The recalculated outpatient difference is 25.0 hours, expressed as zinc minus placebo. Because the calculation uses the posted arm summaries without adjustment, it is an unadjusted re-calculation, not the registry’s reported analysis. The confidence interval for this estimate ranges from -13.95 to 63.95 hours. Its inclusion of zero means that the interval is compatible with no mean difference as well as with differences in either direction, under the calculation’s assumptions.

This summary does not show how individual durations were distributed, and it should not be read as a prediction for every participant. It is a group-level estimate. The registry does not report covariate-adjusted estimates, details of any transformations, or the exact data-handling rules used for this endpoint.

What does the log-rank test compare?

In general, a log-rank test compares the timing of an event between groups over follow-up. For a duration outcome, it can use information about when the event occurs, including the ordering of event times, rather than reducing the comparison to a difference between arithmetic means. The registry reports log-rank p-values of 0.19 for outpatients and 0.88 for inpatients. It does not post a corresponding effect estimate or confidence interval for either test.

A log-rank p-value is not an estimate of hours gained or lost, and it does not by itself describe how large a difference might be. Its interpretation also depends on features of the time-to-event data and the analysis. The registry does not report the event and censoring definitions, a model-based estimate, or enough methodological detail to reconstruct the reported tests. It is therefore appropriate to quote the registry’s test results while avoiding claims about unreported details of their implementation.

Why can analyses of the same endpoint differ?

The outpatient recalculation compares means from posted summaries, while the registry’s log-rank analysis compares event timing. The methods use different aspects of the data and may have different assumptions. The outpatient mean-difference p-value is 0.208, while the registry reports 0.19 for the log-rank test. The difference in these values does not by itself demonstrate a contradiction: they do not represent duplicate calculations of the same statistic. The record marks no discrepancy between the posted analysis and recalculation.

In general, the analysis method should match the endpoint’s measurement and the scientific question. A mean difference is directly interpretable in hours but may not capture the full timing pattern. A time-to-event method may be useful when event timing is the focus, but its result should ideally be accompanied by an effect estimate and uncertainty interval. Those details are not reported for the log-rank analyses in the registry.

What does a p-value tell the reader?

In general, a p-value describes how unusual data at least as incompatible with a specified null hypothesis would be if that null model and the test assumptions were true. It is not the chance that the treatment has no effect, not the chance that the result occurred “by chance,” and not a measure of clinical importance. It should be considered together with the estimated effect, its precision, the design, and the quality and completeness of the data.

For the outpatient comparison, the recalculated confidence interval communicates a broad range of plausible mean differences under the calculation. The inpatient p-value is accompanied by no posted interval, and the inpatient group sizes are small. Neither p-value removes the need to consider uncertainty. The registry does not state a threshold for interpreting these tests, nor does it report a multiplicity adjustment for the posted analyses.

10. Confidence Intervals and Precision

The outpatient recalculated mean difference is 25.0 hours, with a 95% confidence interval from -13.95 to 63.95 hours. In general, a confidence interval gives a range of values compatible with the data and the method used, subject to the assumptions behind that method. It is not a guarantee that the true value lies within the specific interval, and it is not a range containing a stated proportion of individual participants’ durations.

The outpatient interval includes zero, so the posted estimate does not pin down the direction of the mean difference. It also extends across a broad range of hours, indicating that the estimate is not precise. The point estimate alone should not be treated as a settled measure of the difference. The interval reflects the uncertainty of the recalculated unadjusted comparison; it does not incorporate unreported adjustments or other sources of uncertainty that cannot be evaluated from the registry record.

The arm-level standard deviations are 77.8 hours for outpatient zinc and 52.6 hours for outpatient placebo. In general, variability within arms contributes to uncertainty in a difference between means. The relatively small outpatient groups also limit the information available for estimating the contrast. These are features of the posted data that help explain why a single point estimate should be read cautiously.

No confidence interval is posted for either registry log-rank analysis. The inpatient log-rank p-value is 0.88, but without an effect estimate and interval, the size and precision of the inpatient contrast cannot be read from that p-value alone. The inpatient arms each include 5 participants, and the record explicitly notes inadequate inpatient enrollment. The available evidence for the inpatient question is therefore particularly limited.

In general, greater precision requires more information, and precision is distinct from whether an estimate is statistically significant. The record’s planning illustration gives hypothetical future sample sizes, not additional evidence about the precision achieved in this completed trial.

11. 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 sample-size figures are planning illustrations based on the observed outpatient effect, not the original design calculation. The displayed figures are participants per arm, not total events. The assumptions listed for the illustration are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The target effect is set to a stated fraction of the observed effect.

The rows describe planning for 100%, 75%, and 50% of the observed effect. For planning at 100% of the observed effect, the illustration lists 113 participants per arm for 80% power and 151 participants per arm for 90% power. For planning at 75% of the observed effect, it lists 201 participants per arm for 80% power and 269 participants per arm for 90% power. For planning at 50% of the observed effect, it lists 451 participants per arm for 80% power and 604 participants per arm for 90% power.

In plain language, the 80% power column gives the illustrative number of participants per arm for a design with an 80% chance of detecting the specified effect under the stated assumptions. The 90% power column gives the corresponding number for a higher chance of detecting that effect, again under those assumptions. Smaller effects require more participants because they are harder to distinguish from random variation. That pattern is reflected in the planning figures.

These are not observed power calculations and do not describe what power the completed trial achieved. They are hypothetical planning values based on the observed effect, which itself is uncertain. The original sample-size justification and the trial’s own design assumptions are not reported in the registry record. The time-to-event convention of total events applies to time-to-event planning displays; the figures are participants per arm.

12. 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, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 25.000; pooled standard deviation σ = 66.993.
2. n = 2 × (1.96 + 0.842)² × 66.993² / 25.000² = 112.7, rounded up to 113 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
delta <- 25                      # observed difference in means
sigma <- 66.9928354378287                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^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 (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1198587)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 113 (80% power), 151 (90% power)
 75% of observed effect: n per arm = 201 (80% power), 269 (90% power)
 50% of observed effect: n per arm = 451 (80% power), 604 (90% power)
power.t.test: 113.7 
Simulated power at n = 113 per arm: 0.796 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-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.

13. Analyses Reported by the Sponsor

The registry’s own reported comparisons use the log-rank method. For the outpatient zinc and placebo groups, the reported p-value is 0.19; for the inpatient groups, it is 0.88. The registry does not post effect estimates or confidence intervals alongside those tests.

The outpatient recalculation is a separate, unadjusted comparison of the posted means. It gives a mean difference of 25.0 hours, a 95% confidence interval from -13.95 to 63.95 hours, and an unadjusted p-value of 0.208. It is not a replacement for the registry’s analysis: it uses a different summary and method, and the two p-values should not be interpreted as if they were estimates from the same test. The record marks no discrepancy, so there is no stated conflict requiring one result to displace the other.

The registry reports no effect estimate or confidence interval for the inpatient log-rank analysis, and the inpatient groups are small. The re-calculation is available for the outpatient means only; it does not recreate the reported log-rank analyses. The registry’s reported results should therefore be described as log-rank findings, while the mean-difference calculation should be labeled as an unadjusted re-calculation from the posted summary statistics.

The statistical plan and details needed to independently reproduce the sponsor’s tests are not reported in the registry record. Consequently, the relationship between the log-rank results and the arm-level means cannot be examined beyond noting that they summarize the duration outcome using different approaches.

14. Multiplicity, Missing Data and Analysis Populations

The record lists a primary outcome and two secondary outcomes. The secondary outcomes concern potential cost benefits related to daycare days missed and parents’ work days lost, and the reliability of parent reporting compared with phone interview responses. Three outcome measures and two analyses are listed in the registry information. The reported analyses are the inpatient and outpatient log-rank comparisons.

When multiple outcomes or comparisons are examined, general statistical practice recognizes that the chance of at least one apparently unusual result can increase if each test is considered independently. Whether and how to account for multiplicity depends on the planned analysis and the purpose of the comparisons. The registry record does not report a multiplicity strategy, a hierarchy among outcomes, or whether any adjustment was applied. It is therefore not possible to determine from the record whether the posted p-values were intended as confirmatory tests or how they fit into a broader testing plan.

The primary outcome description states that patients were analyzed separately by arm and then again together for overall severity of diarrhea. However, the record does not clarify the exact analysis populations, how the overall analysis was constructed, or whether all randomized participants were included in each analysis. It does not report whether the analyses followed an intention-to-treat principle, how protocol deviations were handled, or whether participants were excluded after randomization.

The registry does not report the amount or pattern of missing outcome data, reasons for missingness, imputation methods, or sensitivity analyses. For a duration endpoint, missing follow-up or an unobserved event can affect the analysis, but the record does not state how such cases were treated. The time-to-event analyses’ definitions of event and censoring are also not reported. These gaps limit assessment of whether the reported comparisons reflect all randomized participants and how robust they are to missing data.

The record’s statement that insufficient inpatients were enrolled is important to interpretation, but it does not explain whether recruitment targets were revised or how this affected the analysis plan. The original sample-size justification, interim analyses, and a complete statistical analysis plan are not reported in the registry record. No conclusion about those procedures can be drawn from the posted results.

15. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hospitalization after starting the study protocol within 14 days (4.3%), surgical abdomen (0.0%).

The registry lists serious adverse events by arm. Among outpatients, 1 of 23 participants in the zinc group had a serious adverse event, while 0 of 21 participants in the placebo group did. Among inpatients, 0 of 5 participants in each group had a serious adverse event. Deaths are listed as 0 in all four groups.

The adverse-event summary also lists “Hospitalization after starting the study protocol within 14 days” at 4.3% and “Surgical abdomen” at 0.0%. The record does not specify an arm allocation for these term-level percentages in that summary, so they should not be assigned to a treatment group based on the percentage alone.

These figures are counts recorded during the trial, not estimates of comparative risk. The numbers of participants in the groups are small, especially among inpatients, and a small count cannot establish that an event is more or less likely under one intervention. The registry does not provide a statistical comparison or confidence intervals for adverse events. It also does not provide further detail in the listed summary about event timing, severity grades beyond the serious classification, or causal attribution. The safety figures therefore describe what was recorded, without supporting a broader conclusion about comparative safety.

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

The posted results describe a small randomized trial in children with acute diarrhea in a developed-country setting, with outpatient and inpatient groups analyzed separately. For outpatients, the observed mean duration was 73.0 hours in the zinc group and 48.0 hours in the placebo group. The unadjusted recalculated mean difference is 25.0 hours, with a wide confidence interval that includes zero. The registry’s log-rank test for the outpatient comparison has p = 0.19. Together, these results show an uncertain outpatient estimate rather than a precisely established difference.

For inpatients, the reported means were 72.0 hours in the zinc group and 76.8 hours in the placebo group, and the registry reports a log-rank p-value of 0.88. The inpatient comparison is based on 5 participants per arm, and the registry explicitly notes that it failed to enroll sufficient inpatients. The available data therefore provide limited information about the inpatient question.

These results do not establish that zinc shortened or lengthened diarrhea, and they do not establish equivalence between zinc and placebo. A non-small p-value is not proof that there is no difference; it can also arise when data are too limited or variable to distinguish a difference clearly. Likewise, an observed difference in means is not by itself proof of an effect. The outpatient interval’s breadth and the absence of intervals for the registry’s log-rank analyses are central to interpreting uncertainty.

The record’s rationale discusses prior evidence from developing-country settings and the question of whether findings apply in an industrialized setting. The results posted for this trial do not resolve that broader question for all populations or care settings. The trial record contains specific outpatient and inpatient summaries, but the inpatient enrollment limitation and the lack of a posted overall treatment-effect estimate restrict broader conclusions.

The results also do not provide a complete account of economic outcomes or parent-report reliability. Those appear as secondary objectives, but their results are not included in the posted outcome information described in the registry record. The findings should therefore be understood as the available duration and adverse-event summaries, with substantial uncertainty and important reporting gaps.

17. Why This Trial Matters Statistically

This trial raises a statistical question about transporting evidence between settings: whether results from trials conducted in developing-country populations would also apply to children treated in an industrialized setting. Its randomized, masked, placebo-controlled design is relevant to that question, while the posted results show why design alone does not guarantee precise answers. The amount of information available within each clinical setting also matters.

The distinction between outpatient and inpatient participants is especially important. The inpatient groups contain only 5 participants per arm, and the registry states that sufficient inpatients were not enrolled. A combined summary could obscure how little information is available for that subgroup, while separate estimates remain uncertain because of the small groups. Reporting setting-specific results makes this limitation visible.

The trial also illustrates why an estimate, its uncertainty, and a test result should be read together. The outpatient mean difference is expressed in hours and is accompanied by a confidence interval, while the registry’s log-rank analyses are reported only with p-values. Those outputs answer related but different statistical questions. A p-value alone cannot convey the magnitude or precision of a difference, and the recalculated mean difference cannot stand in for the registry’s time-to-event analysis.

Finally, the planning illustration shows how assumptions about the target effect shape sample-size requirements. Smaller effects require more participants under the stated planning assumptions, while the trial’s original design assumptions are not reported. The case therefore illustrates the difference between retrospective planning based on an observed estimate and the prospective justification that would have informed the trial’s original enrollment target.

18. 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 primary limitation evident in the registry is limited enrollment, especially among inpatients. The study enrolled 71 participants overall, but the posted inpatient groups each contain 5 participants. The record directly states that it failed to enroll sufficient inpatients because hospitalization was uncommon in the stated population. Estimates for that subgroup are consequently based on very little information.

The outpatient groups are also modest in size, with 23 participants assigned to zinc and 21 to placebo in the posted outcome summaries. The observed standard deviations are substantial, and the outpatient confidence interval for the recalculated mean difference is broad. These features limit precision. The registry does not post confidence intervals for its log-rank comparisons, so the uncertainty around those reported analyses cannot be assessed directly from the record.

The outcome reporting leaves methodological details unclear. The registry does not report a detailed definition of the event ending diarrhea duration, how durations beyond the 14-day timeframe were handled, or how missing observations and censoring were addressed. It also does not clarify the analysis populations or provide a complete account of the stated overall severity analysis. The original sample-size justification, full statistical analysis plan, and multiplicity strategy are not reported.

The posted duration summaries and log-rank analyses use different approaches, but the record does not provide enough detail to reconstruct the latter. The registry also does not post results for the listed secondary outcomes concerning daycare and work days or parent-report reliability. These reporting gaps restrict interpretation of the full set of intended outcomes.

Finally, the record’s stated context is children with acute diarrhea in a developed-country setting, with outpatient and inpatient groups considered. The registry information alone does not establish how applicable these results are to other populations or care settings. No additional population characteristics or subgroup results are reported in the information summarized for this trial.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Oral Zinc for the Treatment of Acute Diarrhea in US Children — NCT01198587.
• Registry record last updated 2018-08-22; status last verified 2018-08.
• Results first posted 2018-08-22.
• 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.

22. Record Summary

NCT01198587 is a completed randomized, double-blind, placebo-controlled, quadruple-masked, parallel trial sponsored by Boston Children's Hospital. It enrolled 71 participants and compared oral zinc sulfate with a placebo oral capsule among children with acute diarrhea, with outpatient and inpatient groups reported separately.

The primary outcome is duration of diarrhea in hours over a 14-day timeframe. The outpatient recalculated unadjusted mean difference is 25.0 hours, with a 95% confidence interval from -13.95 to 63.95 hours and an unadjusted p-value of 0.208. The registry reports log-rank p-values of 0.19 for outpatients and 0.88 for inpatients, without effect estimates or confidence intervals for those tests.

Inpatient enrollment was insufficient according to the record, and the posted inpatient groups each include 5 participants. The registry does not report the original sample-size justification, full statistical analysis plan, missing-data procedures, or multiplicity strategy. The results should be read with these reporting and precision limitations in mind.