Chlorhexidine Gluconate Oral Care for Adults Experiencing Trauma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Chlorhexidine Gluconate Oral Care for Adults Experiencing Trauma (NCT01382446), a randomized na study. The primary outcome is Effectiveness of Chlorhexidine Gluconate Oral Care for Trauma Patients.

2. Clinical Question

The registry record describes a study of adults experiencing trauma who were receiving ventilator support. The clinical question was whether adding chlorhexidine gluconate oral rinse to the existing oral-care protocol changed the number of participants who did not develop oral bacteria and ventilator-associated pneumonia (VAP). The primary outcome description specifies an intention-to-treat analysis and an 18 Months timeframe.

The comparison was between standard oral care and standard oral care with chlorhexidine gluconate 0.12% twice daily. Both groups’ care included the regularly scheduled oral-care protocol; the additional rinse distinguished the chlorhexidine regimen. The record describes the study objective as examining VAP incidence and oral bacterial load, while the primary endpoint is expressed as the number of participants meeting the stated no-bacteria-and-VAP criterion.

3. Trial Design

The registry record identifies this as a randomized, parallel-group study with no masking. It lists an enrollment of 66 and a completed status. The record gives the study start as 2010-07 and primary completion as 2012-04. The listed phase is NA.

The standard oral-care group received the existing protocol: 1.5% H2O2-coated swabs every four hours, toothbrushing with toothpaste every 12 hours, and a continuous subglottic suction apparatus. The chlorhexidine group received that regularly scheduled oral care plus chlorhexidine gluconate 0.12% twice daily. Thus, the registry’s intended comparison concerns the added rinse within the existing care regimen, rather than a comparison of oral care with no oral care.

The registry lists 33 participants in the standard-care group and 33 in the chlorhexidine group. The outcome record specifies an intention-to-treat analysis, but the record does not report details of how participants were handled if outcome data were unavailable or if assigned care was not followed. Allocation is described as randomized, but the randomization method, sequence generation, and allocation concealment are not reported in the registry record. Masking is explicitly listed as none.

The record identifies one outcome measure and no posted analysis records. It does not report the trial’s original sample-size calculation, its planned significance threshold, or a detailed statistical analysis plan. Those details should not be inferred from the planning illustrations associated with the observed result.

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: Patients were randomized into groups after enrollment.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Intention to Treat Analysis Used

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 Effectiveness of Chlorhexidine Gluconate Oral Care for Trauma Patients, measured over 18 Months.

The primary outcome is described as the number of participants who did not develop oral bacteria and VAP when chlorhexidine gluconate 0.12% was used as part of an oral-care protocol. Its unit is participants, and the registry identifies the population as an intention-to-treat analysis over 18 Months. The outcome is therefore presented as a count of participants meeting the stated criterion, with the comparison expressed as a proportion or risk in each group.

This kind of endpoint can summarize whether participants experienced a defined clinical and microbiological outcome during the stated period. Counting participants meeting a criterion makes the result interpretable as a group-level proportion, while a between-group risk difference expresses the contrast in percentage-point terms. The record’s description links oral bacteria and VAP, but it does not provide further operational definitions of either component, such as the criteria used to determine an infection or bacterial finding.

The endpoint should be read as the registry describes it, not as a measure of every aspect of oral health or respiratory infection. The record does not clarify whether “and” means participants had to meet both absence criteria, how missing assessments affected classification, or how outcome ascertainment was performed. Those details are not reported in the registry record.

7. Results Posted in the Registry

• Chlorhexidine Oral Care Regimen: 87.9% (29/33) versus 90.9% (30/33) on control; risk difference -3.0 percentage points (95% CI -17.9 to 11.8), risk ratio 0.97 (0.82–1.14); unadjusted two-proportion z-test p = 0.689.

8. Statistical Interpretation

9. Statistical Methods Explained

The registry presents a binary outcome: participants either meet the primary outcome description or do not. For this type of measure, a group’s risk or proportion is the number meeting the criterion relative to the number assessed in that group. The posted proportions are 0.909 for standard oral care and 0.879 for chlorhexidine oral care. The record also gives the underlying counts and group sizes, allowing the comparison to be read in both count and proportion terms.

What does the risk difference express?

The risk difference subtracts the standard-care proportion from the chlorhexidine proportion. Its reported estimate is -0.030. A risk difference is an absolute contrast: it describes the difference in proportions, rather than comparing one proportion as a multiple of the other. A value of zero represents no difference on this scale. The interval from -0.179 to 0.118 includes zero, so the data are compatible with no difference as well as with effects in either direction.

Absolute measures are often useful for clinical interpretation because they retain the scale of the event probability. In this case, the endpoint is framed as participants meeting the no-bacteria-and-VAP description. It is important not to silently reverse that endpoint into a different event definition, such as participants developing VAP. The registry does not provide separate counts for each element of the combined description.

How do relative measures differ?

The risk ratio compares the two group proportions as a ratio. The reported estimate is 0.967, with an interval from 0.819 to 1.142. A value of one represents equal proportions on the ratio scale. The odds ratio compares odds rather than probabilities; its estimate is 0.725, with an interval from 0.149 to 3.525. A value of one also represents no association on that scale. Odds and risks are different quantities, so the odds ratio should not be interpreted as a direct percentage-point difference. Both relative-measure intervals include their no-association value.

What does the p-value tell the reader?

The posted unadjusted p-value is 0.689. A p-value describes how unusual data at least as inconsistent with a specified null model would be if that model and the test assumptions held. It is not the probability that the null hypothesis is true, the probability that the finding occurred by chance, or a measure of the size or importance of the effect. It does not establish equivalence. The registry record does not report a multiplicity adjustment or a detailed test specification for this comparison.

In general, a confidence interval describes a range of effect values compatible with the data and the method’s assumptions. The interval conveys uncertainty in a way that a single estimate cannot. A broad interval means the estimate is not precise enough to rule out a range of effects. Here, the risk-difference interval crosses zero and includes appreciable values on either side. No confidence level is specified in the registry record, so the interval should not be assigned a confidence percentage based on assumption.

Why does randomization matter, and what remains unknown?

In general, random allocation aims to make comparison groups similar on average with respect to measured and unmeasured characteristics at assignment. It does not guarantee balance in a particular study, and it does not remove concerns about missing outcomes, departures from assigned care, or outcome measurement. The registry identifies the study as randomized but does not report the sequence-generation method, concealment procedure, or detailed implementation.

The primary outcome record says intention to treat. In general, intention-to-treat analysis seeks to compare participants according to their assigned group, regardless of whether they fully followed the assigned regimen. The registry does not explain how this principle was implemented, how missing endpoint information was handled, or whether any participants were excluded from the posted calculations. Those items are not reported in the registry record.

The result is a comparison of observed group summaries, not an adjusted estimate based on reported covariates. The record does not report an adjusted model, a prespecified primary statistical test, or analysis diagnostics. The posted estimate and interval therefore support a descriptive reading of the between-group contrast, with uncertainty, but not reconstruction of a more detailed analytical strategy.

10. Confidence Intervals and Precision

The risk-difference estimate is -0.030, and its interval extends from -0.179 to 0.118. This span crosses zero, the value corresponding to no difference on the risk-difference scale. It therefore leaves open both a lower endpoint proportion with chlorhexidine and a higher endpoint proportion with chlorhexidine. The estimate’s direction alone should not be treated as a definitive finding.

Precision concerns how narrowly the data locate the underlying effect. In general, an interval that covers a wide range of effects indicates limited precision. The posted interval includes values that could represent a meaningful difference in either direction, as well as no difference. Thus, the observed counts do not narrowly determine the size or direction of the contrast.

The risk-ratio interval, 0.819 to 1.142, includes one, the no-association value on that scale. The odds-ratio interval, 0.149 to 3.525, also includes one and is broad. These measures provide alternative scales for the comparison, but they do not eliminate the uncertainty visible in the absolute risk difference. Their interpretation also depends on the endpoint definition and the group risks.

The registry does not state the confidence level for these intervals. It also does not report a prespecified clinically important difference, so the interval cannot be judged against a recorded threshold for practical importance. The reported estimates should be read as uncertain, rather than as precise evidence for equivalence or for a particular size of effect.

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 planning illustrations give participants per arm, not total events. They use the observed effect as a starting point and show planning estimates for detecting 100% of that observed effect, 75% of the observed effect, and 50% of the observed effect. The planning assumptions listed are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The figures are computed from the observed effect; they are not the trial’s original design calculation. The trial’s own design assumptions are not reported in the registry record.

The 80% power column means the planning estimate of participants per arm under which the specified effect would be detected in 80% of repeated studies if the assumptions and effect were correct. The 90% power column uses a higher target probability of detection and therefore gives a larger planning estimate for the same effect fraction. Power is a design concept describing performance across hypothetical repetitions, not a probability that the observed result is true.

The planning figures increase as the target effect becomes smaller: detecting 100% of the observed effect calls for fewer participants per arm than detecting 75% or 50% of it. In general, smaller effects are harder to distinguish from random variation and require more participants for the same power target. These estimates are illustrations, not observed power. They depend on the planning assumptions and observed effect used, and should not be read as evidence about the trial’s original planning or as a guarantee that a future study would achieve its target.

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, p₀ and p₁ are the control and treatment proportions, and p̄ is their average.

Worked calculation for this trial

1. Control proportion p₀ = 0.909; treatment proportion p₁ = 0.879; average p̄ = 0.894.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.4355 = 0.8535.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.4349 = 0.3660.
4. n = (0.8535 + 0.3660)² / (-0.0303)² = 1,619.6, rounded up to 1,620 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 <- 0.909090909090909                          # control proportion
p1 <- 0.878787878787879                          # 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(1382446)
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 = 1,620 (80% power), 2,168 (90% power)
 75% of observed effect: n per arm = 2,790 (80% power), 3,734 (90% power)
 50% of observed effect: n per arm = 6,070 (80% power), 8,126 (90% power)
power.prop.test: 1619.6 
Simulated power at n = 1,620 per arm: 0.805 (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.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and no posted secondary outcome results. It also records no analysis records. The primary outcome is described, but the statistical plan is not detailed enough to determine whether the reported comparison was the only analysis planned or whether other outcomes, time points, or subgroup comparisons were considered.

Multiplicity arises when several hypotheses or outcomes are tested. In general, testing many comparisons can increase the chance of at least one apparently unusual result. Whether an adjustment is needed depends on the prespecified analysis strategy and the inferential goals. The registry does not report a multiplicity strategy, so it is not possible to establish from the record whether adjustment was planned or appropriate. The posted p-value is described as unadjusted.

The primary outcome record names an intention-to-treat analysis population. That label indicates the intended population approach, but the record does not describe how assignment was retained in the analysis, whether all randomized participants contributed outcome data, or how deviations from assigned care were handled. Missing-data counts and methods are not reported in the registry record. The record also does not clarify whether participants without complete outcome assessment were classified as not meeting the endpoint, excluded, or handled through another procedure.

These omissions matter because missing outcome data can affect both the estimated proportions and the uncertainty around their comparison. In general, the implications depend on how much information is missing and whether missingness relates to group assignment or outcome status. Neither the extent nor the pattern of missingness is reported, so no missing-data analysis can be assessed.

The registry provides neither a detailed statistical analysis plan nor the protocol-specific rationale for outcome selection and analysis. The posted comparison can be described as reported, but multiplicity control, missing-data handling, and implementation of intention to treat cannot be independently evaluated from the registry record.

14. 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 5% reporting threshold.

The registry reports zero participants affected by serious adverse events in each group, with 33 at risk in each group. It also reports zero participants affected by other adverse events in each group, again with 33 at risk in each group. These are the posted affected-participant counts and should be read separately from the primary efficacy outcome.

A reported count of zero means no affected participants were recorded in that category in the registry result. It does not establish that no event could occur, nor does it by itself show that the groups have identical safety profiles. With a limited number of participants recorded at risk, uncommon events may not be observed. The registry does not provide event descriptions under serious adverse events, and the top serious-event terms list is empty.

Deaths are recorded as null for both groups. That is different from a reported count of zero: a null value means a death count is not reported in the registry record. The record does not give additional detail about adverse-event collection, follow-up completeness, severity definitions, or whether events were judged related to treatment. The safety figures therefore describe the registry entries, not a comprehensive assessment of all possible harms.

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

The posted results show similar observed counts meeting the primary outcome description: 30 in the standard oral-care group and 29 in the chlorhexidine group. The proportions are 0.909 and 0.879, with a risk-difference estimate of -0.030. The interval from -0.179 to 0.118 includes zero and spans estimates in either direction. The unadjusted p-value is 0.689.

These results do not establish that the two regimens are equivalent. Demonstrating equivalence requires an appropriate design and a prespecified equivalence margin; neither is reported in the registry record. The results also do not establish a clear difference between regimens. The interval and p-value indicate uncertainty, and the estimated effect should not be interpreted as a definitive measure of benefit or harm.

The primary endpoint is described as participants who did not develop oral bacteria and VAP. Because the record does not give detailed definitions or separate results for those components, the posted comparison cannot determine which component contributes to the combined result. Nor does it answer broader questions about all forms of infection, oral health, duration of ventilation, or outcomes beyond the stated endpoint and timeframe.

The study was randomized, but the registry record does not provide the randomization procedure, detailed analysis plan, missing-data handling, or endpoint ascertainment methods. The posted safety counts record zero affected participants for serious and other adverse events in both groups, while deaths are not reported. Those entries should not be taken as proof that no safety events were possible or that the regimens have the same safety profile.

The appropriate interpretation is limited to the observed comparison and its uncertainty in this registry record. The result is not a treatment recommendation and cannot support conclusions beyond the population, regimen, endpoint, and timeframe described.

16. Why This Trial Matters Statistically

This trial illustrates why a point estimate and its uncertainty need to be considered together. The risk-difference estimate is -0.030, but its interval ranges from -0.179 to 0.118. The point estimate gives one best estimate under the analysis, while the interval conveys that the data remain compatible with a range of contrasts, including no difference and effects in either direction.

It also shows why a non-significant p-value is not proof of equivalence. The unadjusted p-value is 0.689, but equivalence is a separate question that requires a prespecified margin and a design suited to that objective. The registry does not report such a margin. A reader should not convert a failure to show a difference into evidence that the regimens perform identically.

The outcome definition is central to interpretation. The registry frames the primary measure as the number of participants who do not develop oral bacteria and VAP, but does not report separate component results or detailed definitions. A combined endpoint may be concise, yet without component-level reporting it can be difficult to tell what aspect of the clinical question is reflected in the estimate.

Finally, the planning illustrations make clear that sample-size requirements depend on the effect a study aims to detect. Smaller effects require more participants under the stated planning assumptions. Those illustrations do not substitute for the original trial design, which is not reported. Together, these features underscore the importance of prespecified methods, clear endpoints, and sufficiently precise estimates when evaluating a randomized comparison.

17. 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 outcome description leaves important operational details unspecified. The registry does not define how oral bacteria or VAP were assessed, how the combined criterion was applied, or whether assessors were blinded. Masking is listed as none, but the record does not describe whether outcome assessment involved any safeguards against bias. These gaps limit assessment of how consistently the endpoint may have been measured.

Randomization is reported, but sequence generation and allocation concealment are not. The registry does not report baseline characteristics, so the extent of group comparability cannot be assessed from this record. Although the primary outcome identifies an intention-to-treat analysis, the handling of nonadherence, withdrawals, and missing assessments is not reported.

The record contains one outcome measure and no posted secondary results or analysis records. It does not provide a detailed statistical analysis plan, a sample-size justification, or information about interim analyses. Consequently, it is not possible to assess prespecification, analysis selection, or whether the reported comparison follows a complete planned analysis.

The interval around the risk difference is broad and includes zero. The record does not state a clinically important threshold against which the estimate could be judged. It also does not report separate outcome counts for oral bacteria and VAP, limiting interpretation of the combined endpoint.

Safety reporting is also limited. Zero affected participants are recorded for serious and other adverse events in both groups, but deaths are not reported and details of adverse-event ascertainment are absent. These limitations apply to interpretation of the registry record and do not establish that unreported procedures or analyses did not occur.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Chlorhexidine Gluconate Oral Care for Adults Experiencing Trauma — NCT01382446.
• Registry record last updated 2017-02-06; status last verified 2016-12.
• Results first posted 2013-11-28.
• 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.

21. Record Summary

The registry record describes a completed randomized, parallel-group study without masking, comparing standard oral care with standard oral care plus chlorhexidine gluconate 0.12% twice daily in adults experiencing trauma on ventilator support. The listed enrollment is 66, with 33 participants in each group. The primary outcome is the number meeting the description of not developing oral bacteria and VAP over 18 Months, using an intention-to-treat population.

The posted counts are 30 for standard oral care and 29 for chlorhexidine oral care. The risk-difference estimate is -0.030, with an interval from -0.179 to 0.118 and an unadjusted p-value of 0.689. Serious and other adverse-event counts are recorded as zero in both groups; deaths are not reported. The registry does not report detailed endpoint methods, missing-data handling, a statistical analysis plan, or the original sample-size assumptions.