Povidone-Iodine Vs Essential Oil Vs Tap Water Gargling For COVID-19 Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Povidone-Iodine Vs Essential Oil Vs Tap Water Gargling For COVID-19 Patients (NCT04410159), a randomized phase 2 study. The primary outcome is Number of Participants With Early Viral Clearance.

2. Clinical Question

The study’s stated purpose was to assess whether regular gargling could eliminate SARS-CoV-2 in the throat and nasopharynx. The clinical question is therefore reflected in a laboratory-defined outcome rather than a direct measure of symptoms or recovery. The primary outcome counts participants who met the specified clearance definition by Day 6; it does not describe the timing of clearance within that period or the duration of any subsequent negative results.

The posted primary counts are 5 participants in the povidone-iodine arm, 4 in the essential-oils arm, 1 in the tap-water arm, and 0 in the control arm. Each arm records 5 participants. These are descriptive arm-level counts. The registry record does not report a two-arm statistical comparison for this binary endpoint, so the counts alone do not establish the size or precision of differences between regimens.

3. Trial Design

The registry identifies this as a Phase 2, randomized, open-label, parallel-group trial. It records an enrollment of 20 and four arms: povidone-iodine, essential oils, tap water, and control. The control received the standard treatment protocol without an additional intervention. The intervention descriptions specify the gargle volumes, a 30-second gargle, and a frequency of three times per day for 7 days.

The study is described as a pilot trial. Random assignment is a design feature intended to create comparable groups on average, but the small number of participants in each arm means that chance differences in participant characteristics can remain. The record does not report the randomization sequence method, allocation concealment, or whether any stratification was used. Masking is recorded as none, so the trial was open-label. The procedures used to reduce possible influence of that knowledge on outcome assessment are not reported in the registry record.

The study start date is 2020-06-22, and the primary completion date is 2020-06-29. Its status is completed. These dates and the recorded enrollment describe the registry entry; further details about recruitment, participant flow, withdrawals, or the number included in each outcome analysis are not reported in the registry record.

The four-arm structure permits descriptive comparisons across three gargling approaches and a no-additional-intervention control. However, a randomized design does not by itself supply an estimate of the effect of any one regimen. Such an estimate requires a defined comparison and an analysis that accounts for uncertainty. No comparative analysis for the primary binary outcome is reported in the registry record. Thus, the arm counts can be described, but they should not be treated as a tested ranking of the four approaches.

The trial’s pilot status and small enrolled sample are important context for interpreting its purpose and precision. Pilot studies can inform feasibility and generate preliminary observations, but the registry record does not state that this trial was designed to provide a definitive estimate of treatment effect. Its formal sample-size justification is not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: No significant event occurred after enrollment

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 Number of Participants With Early Viral Clearance, measured over Day 6.

The primary endpoint is the number of participants with early viral clearance at Day 6. The registry defines viral clearance as two negative RT-PCR results from swabs of the oropharynx and nasopharynx, with the results at least 24 hours apart. The reported measure is a count of participants meeting that definition in each arm.

This kind of endpoint is used to represent a specific laboratory outcome at a stated time. It gives a clear rule for classifying whether a participant met the endpoint, rather than relying on a subjective assessment. The requirement for two negative results separated in time makes the definition more specific than a single negative test. However, the count does not show the number of tests performed, the exact timing of each participant’s test results, or whether clearance persisted after the assessment period; those details are not reported in the registry record.

The primary outcome is not a direct measure of symptoms, disease severity, or transmission. The registry lists progression to more severe disease, abnormal radiological findings, and abnormal laboratory findings among secondary outcomes, along with negative RT-PCR results. Findings for those secondary outcomes are not reported in the registry record. The endpoint should therefore be interpreted narrowly: it records participants meeting the stated virological definition at Day 6, not a broader measure of clinical benefit.

Counts are useful for describing what was observed, especially when arm sizes are small. But counts alone do not express uncertainty around the difference between groups. A comparative estimate, such as a risk difference or ratio with an interval, would help show how compatible the results are with a range of possible underlying effects. Such comparative estimates are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry records a binary primary outcome in terms of participants with an event: early viral clearance by Day 6. For this type of outcome, each participant either meets the stated definition or does not. The arm-level count is the number who meet it, and the arm size gives the context for that count. Here, the posted counts are 5, 4, 1, and 0 across arms, with 5 participants in each arm. The count is descriptive; it is not itself a comparative effect estimate.

What does a comparison add?

General: A comparative analysis contrasts the outcome frequency between groups and estimates the size of the difference or relative contrast. An uncertainty interval communicates the range of effect values reasonably compatible with the data under the analysis assumptions. A p-value addresses how unusual data at least as incompatible with a stated null hypothesis would be if that null hypothesis and the model assumptions were true. These measures answer different questions: an estimate describes the direction and size of a contrast, an interval describes its precision, and a p-value is not a measure of clinical importance.

For this trial, no registry-reported two-arm estimate, confidence interval, or p-value is available for the primary binary endpoint. The record notes that values were missing or not estimable for a two-arm comparison. That absence means the reader can describe the arm counts but cannot rely on a registry-reported inferential comparison to assess the uncertainty of a contrast. It would be inappropriate to treat the count pattern as if it were a formal test.

Why does the sample size matter?

General: Estimates from small groups tend to be less precise because each participant represents a larger part of the observed group outcome. An interval, when estimated, would generally reflect this uncertainty. A small trial may also fail to detect a real difference, while an observed difference can be unstable. Neither a visually striking count pattern nor a non-significant test, if one were available, would by itself settle whether an underlying effect exists.

The record contains a description of a separate planning illustration based on a fraction of the observed effect, two-sided significance level 0.05, equal allocation, and a normal approximation. It explicitly describes this as planning rather than the trial’s own design. Such sample-size illustrations are not observed power and do not change the evidence represented by the enrolled participants. The registry record does not report the trial’s own sample-size justification.

How should randomization and masking be considered?

General: Randomization aims to balance prognostic factors across groups in expectation, reducing confounding by factors measured or unmeasured at baseline. It does not guarantee balance in a particular small sample. Details about the randomization method and allocation concealment are not reported in the registry record. The trial is recorded as open-label, with no masking. Knowledge of assignment can affect participant behavior, care, or outcome assessment in some settings. RT-PCR is a laboratory-defined outcome, but the record does not specify whether laboratory staff were masked to assignment or how samples were handled.

Why can over-dispersion matter?

General: Over-dispersion is a concern when observed variation is greater than a statistical model expects. It commonly arises in count models when outcomes are more variable than a Poisson model allows, and ignoring it can make uncertainty appear too small. This trial’s primary endpoint is recorded as a binary participant count, not a rate of events over person-time. Over-dispersion is therefore not the main interpretive issue for the posted primary result. The central limitations are the small arm sizes and the lack of a reported comparative analysis.

What do the analysis records tell us?

The registry records five outcome measures, including the primary endpoint and four secondary outcomes, and records zero analyses. The primary arm counts are posted, but no inferential analysis is listed. The secondary outcome names include negative RT-PCR results, progression to more severe disease, abnormal radiological findings, and abnormal laboratory findings. Results for those secondary outcomes are not reported in the registry record.

General: A prespecified analysis plan helps distinguish planned analyses from choices made after results are known. It can also specify the comparison of interest, covariate adjustment, missing-data handling, and how outcomes will be summarized. Those details are not reported in the registry record. The reader therefore cannot assess whether the posted outcome count corresponds to a prespecified analysis population or whether other analytical choices were planned.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Povidone-iodine", "Essential Oils", "Tap Water", "Control")
n      <- c(5, 5, 5, 5)
events <- c(5, 4, 1, 0)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Povidone-iodine  5  5  100.0  47.8  100.0  56.6  100.0  54.1  99.6
ARM  Essential Oils  5  4  80.0  28.4  99.5  37.6  96.4  35.9  95.7
ARM  Tap Water  5  1  20.0  0.5  71.6  3.6  62.4  4.3  64.1
ARM  Control  5  0  0.0  0.0  52.2  0.0  43.4  0.4  45.9

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures: the primary early viral-clearance endpoint and four secondary outcomes. Considering multiple outcomes can raise the possibility of chance findings when many statistical tests are performed. A multiplicity strategy might define one primary comparison, adjust inference across a family of tests, or treat secondary analyses as exploratory. The approach planned for this trial is not reported in the registry record. The registry records zero analyses, and it does not report inferential results for the secondary outcomes.

The primary endpoint has a clear operational definition, but the registry record does not state how missing or indeterminate RT-PCR results were handled. It also does not report whether every enrolled participant contributed to the Day 6 outcome count, how withdrawals were handled, or whether an intention-to-treat or other analysis population was used. The arm counts include 5 participants in each arm, but that alone does not establish how missing outcome data were treated or which population was analysed.

General: Missing data can affect interpretation when the chance of an unobserved outcome is related to a participant’s condition or assignment. Analyses may use different assumptions about such outcomes, and those assumptions can influence estimates. Without the number and reasons for missing assessments and a stated analysis approach, sensitivity to missing data cannot be evaluated.

Neither the multiplicity plan nor the missing-data strategy can be reconstructed from the posted counts. These are limitations on interpretation, rather than evidence that a particular procedure was or was not used.

12. 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 serious adverse events, other adverse events, and deaths by arm. For each of the four groups, 5 participants were listed as at risk for serious adverse events and 0 as affected. The corresponding figures for other adverse events are also 5 at risk and 0 affected in each group. Deaths are recorded as 0 in every group.

These are reported counts within a small trial. A zero count means that no events of the relevant category are recorded among the listed participants at risk; it does not establish that the true event risk is zero. With 5 participants per group, the data have limited ability to characterize uncommon or delayed events. The registry record does not list serious adverse-event terms, and it does not provide further details about event definitions, observation time for safety outcomes, severity grading, or attribution to an intervention.

Safety counts are descriptive and should be read separately from the viral-clearance endpoint. The absence of reported events in these groups does not establish comparative safety between regimens, particularly without a larger sample and a reported statistical comparison. It also does not support conclusions about risks outside the trial’s recorded follow-up.

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

The registry result establishes a narrow observation: by Day 6, the posted numbers meeting the defined early viral-clearance criterion were 5 in the povidone-iodine arm, 4 in the essential-oils arm, 1 in the tap-water arm, and 0 in the control arm. There were 5 participants in each arm. This pattern is the descriptive result for the participants and endpoint recorded.

It does not establish that gargling caused the difference in counts. Randomization is a useful design feature, but the sample is small and the registry does not report a comparative estimate with its uncertainty. The counts cannot show how much of the pattern might reflect chance variation, nor do they quantify a treatment effect with precision. They also do not establish that the pattern would be repeated in another group of patients.

The result is specific to the registry’s definition of early viral clearance at Day 6. It does not directly answer questions about symptom improvement, disease severity, duration of viral detection, later test results, transmission, or long-term outcomes. Although the registry lists several secondary outcomes, results for those outcomes are not reported in the registry record.

The zero recorded serious and other adverse events and deaths should also be interpreted in context: each group had 5 participants at risk. Those observations do not rule out events that were not captured or events that may occur in a larger or longer study. Further details on safety follow-up are not reported in the registry record.

Overall, these data are preliminary and descriptive. They document outcomes in a small randomized pilot trial, but they do not supply a precise inferential comparison or a basis for broad conclusions. The registry record does not report the sample-size justification, detailed analysis plan, missing-data approach, or participant flow needed to resolve several questions about design and analysis.

14. Why This Trial Matters Statistically

This trial illustrates why the number of participants and the form of the reported result both matter. A randomized, four-arm structure may appear to invite direct comparisons, but the observed counts are based on 5 participants per arm. Each count therefore represents a small set of observations and carries substantial uncertainty when used to infer what might happen beyond the trial participants.

The endpoint also highlights the distinction between a clearly defined outcome and a precise treatment-effect estimate. The registry gives a specific definition of early viral clearance: two negative RT-PCR results from oropharynx and nasopharynx swabs at least 24 hours apart, assessed at Day 6. This clarity supports consistent classification. It does not, by itself, provide an estimate of the difference between randomized groups or a measure of how precisely that difference is known.

Another statistical lesson is that a registry can contain outcome counts without reporting a comparative analysis. The arm counts are available, while a two-arm estimate, confidence interval, and p-value are not reported for the primary binary endpoint. Readers must distinguish those descriptive findings from inferential evidence rather than assuming that randomization automatically makes the counts conclusive.

The record also lists secondary outcomes and safety counts, but no analyses are recorded and secondary results are not reported. This makes transparency about analysis plans, missing outcomes, and multiplicity especially relevant. The trial matters statistically as a compact example of the difference between observing a pattern and estimating an effect with useful precision.

15. 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.

Several details needed to evaluate the trial’s conduct and analysis are not reported in the registry record. These include eligibility criteria beyond the Stage 1 COVID-19 description, baseline characteristics, participant flow, reasons for withdrawal, the randomization procedure, and allocation concealment. Without baseline information, it is not possible to assess whether the small groups differed in characteristics relevant to the outcome.

The trial is open-label, and the record does not describe whether outcome assessors or laboratory staff were masked. It also does not provide details on RT-PCR testing schedules, handling of indeterminate or missing results, or the timing of outcome assessments beyond the Day 6 endpoint definition. Such details would help establish how consistently the outcome was measured across arms.

Only arm-level counts are reported for the primary endpoint. A comparative estimate and its uncertainty are not reported in the registry record, and the record states that values were missing or not estimable for a two-arm comparison. The four secondary outcomes are listed without results. The analysis plan, multiplicity approach, and analysis population are not reported in the registry record.

The small number of participants per arm limits precision and the ability to assess uncommon outcomes. Safety event definitions and follow-up details are also not reported. The registry describes the study as a pilot, but the trial’s own sample-size justification is not reported in the registry record. These limitations constrain interpretation of both efficacy-related and safety observations.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Povidone-Iodine Vs Essential Oil Vs Tap Water Gargling For COVID-19 Patients — NCT04410159.
• Registry record last updated 2020-07-21; status last verified 2020-07.
• Results first posted 2020-07-21.
• 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.

19. Record Summary

The registry describes NCT04410159 as a completed Phase 2, randomized, open-label, parallel-group pilot trial sponsored by Universiti Sains Islam Malaysia. It records 20 participants and four arms: povidone-iodine gargling, essential-oils gargling, tap-water gargling, and standard treatment without an additional intervention. The study start date is 2020-06-22, and the primary completion date is 2020-06-29.

The primary outcome is the number of participants meeting the early viral-clearance definition at Day 6: two negative RT-PCR results from oropharynx and nasopharynx swabs at least 24 hours apart. The posted counts are 5 for povidone-iodine, 4 for essential oils, 1 for tap water, and 0 for control, with 5 participants in each arm. The registry records zero analyses and does not report a two-arm comparison for this binary endpoint. Four secondary outcomes are listed, but their results are not reported in the registry record.