Stylet Angle for McGrath Videolaryngoscopy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Stylet Angle for McGrath Videolaryngoscopy (NCT03000088), a registered phase not stated study. The primary outcome is Time to Intubation.

2. Clinical Question

The study’s stated aim is to determine an appropriate stylet angle for McGrath videolaryngoscopy by comparing time to intubation. Its brief summary explains the rationale: obtaining a laryngoscopic view may be possible while directing an endotracheal tube remains difficult, and stylet use is described as recommended. The comparison therefore concerns two device-and-technique configurations, not videolaryngoscopy versus another airway device or stylet use versus no stylet.

Because allocation is not stated and the record describes the comparison as nonrandomized, the groups should not be treated as necessarily exchangeable. Differences in participant characteristics, operator practice, or other factors could affect observed times, but the registry record does not provide information to assess these possibilities. The primary outcome values and an analysis comparing the groups are also not reported in the registry record. Consequently, the record establishes the question and the planned endpoint, but does not show which group had a shorter observed time or how uncertain any difference might be.

3. Trial Design

The registry identifies this as a completed study sponsored by Ajou University School of Medicine. It reports enrollment of 140 participants. The recorded study start is 2016-03 and primary completion is 2016-08. The condition listed is intubation. These details describe the study’s registration and timing, but do not establish how participants were recruited or how the procedures were organized.

The two arm descriptions specify use of a McGrath Videolaryngoscope with a 60° angled stylet or a 90° angled stylet. The registry labels the comparison as nonrandomized and says allocation was not stated. It also cautions that the arms are not a like-for-like control comparison. Thus, the available description does not support interpreting the groups as randomized or assuming that their baseline characteristics were balanced. The reason for assigning a particular angle, the method of allocation, and any steps to reduce operator or selection effects are not reported in the registry record.

The registry lists one outcome measure, time to intubation, with a mean and standard deviation as the stated summary. Its timeframe is described as 10 minutes around intubation. The record does not provide a more detailed operational definition of when timing starts and stops, nor does it report the outcome values by arm. Although enrollment is recorded, the number contributing data to the primary endpoint is not reported in the registry record.

The record lists no analyses. It therefore does not provide a statistical comparison, an estimate of the difference between groups, or an interval describing uncertainty. The registry also does not report a sample-size justification, detailed analysis plan, or whether outcome assessment was blinded. Study completion and enrollment alone do not fill those gaps: they indicate recorded status and recruitment size, not the strength or direction of an outcome finding.

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 Time to Intubation, measured over 10 minutes around intubation.

The primary endpoint is time to intubation, measured in seconds. It is described as a continuous measure summarized by its mean and standard deviation, with a timeframe of 10 minutes around intubation. The registry’s brief summary identifies comparison of this time as the study’s way of evaluating the two stylet angles. The endpoint is therefore intended to capture the duration of the intubation procedure under each described technique.

As a general statistical point, a continuous time measure retains information about the range of observed durations rather than reducing each procedure to a category such as success or failure. A mean describes the average observed time in a group; a standard deviation describes the spread of individual times around that group’s mean. Neither statistic alone describes the full distribution, and both depend on a clear, consistent timing definition. The registry does not report detailed start and stop rules, handling of unsuccessful or incomplete procedures, or the observed group summaries.

Time is used because the study’s stated objective is to compare how long intubation takes with the two stylet angles. It is not, by itself, a complete description of procedural performance or safety. The registry record does not report additional efficacy endpoints or a definition of what difference in time would be considered meaningful. Without the actual means, standard deviations, group comparison, and uncertainty estimate, the primary endpoint cannot be interpreted as showing one technique took less time than the other.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry specifies a continuous primary outcome, time to intubation in seconds, and identifies the mean and standard deviation as the summary measures. It does not report an analysis for that endpoint. The explanations below describe general statistical concepts relevant to a comparison of continuous outcomes; they should not be read as a description of analyses actually performed in this study.

What does a mean describe?

For a continuous outcome, the mean is the arithmetic average of the observed values in a group. In this setting, it would describe the average recorded time among the participants whose times were included in that group’s analysis. A comparison of group means can express the difference in average time between techniques, but a meaningful interpretation depends on how time was measured and which participants were included. The registry lists neither group mean nor a difference between means, so no value or direction can be interpreted.

The standard deviation describes how dispersed individual observations are around the mean. A small standard deviation indicates observations are more concentrated around the group average; a larger one indicates greater spread. It is not the same as the uncertainty in the estimated mean. The uncertainty in a group comparison also depends on the amount of outcome information and the variability of observations. Since the registry does not report group standard deviations or endpoint sample sizes, those features cannot be assessed for this comparison.

What would a confidence interval add?

As a general concept, a confidence interval gives a range of values compatible with an estimate under the assumptions of the statistical method. For a difference in mean time, it would help show both the estimated direction and the precision of the comparison. A narrow interval indicates greater precision than a wide interval, while an interval that includes values on either side of no difference may leave the direction uncertain. A confidence interval does not eliminate bias from nonrandom allocation or establish that a difference is important in practice. No confidence interval is reported in the registry record.

A p-value, when reported, describes how compatible the data are with a specified null model under the assumptions of a test. It does not measure the probability that the null hypothesis is true, the size of an effect, or its practical importance. Interpretation should not rely on a p-value alone; an effect estimate and its uncertainty are also needed. The registry does not report a p-value or an outcome analysis, so statistical significance cannot be assessed.

Why does allocation matter?

In a randomized comparison, random assignment is intended to make treatment groups comparable on average with respect to both measured and unmeasured factors. This general property helps support causal interpretation, subject to other assumptions and study conduct. Here, the registry describes the comparison as nonrandomized and says allocation was not stated. It also warns that the arms are not a like-for-like control comparison. Thus, even if group times had been reported, a simple difference could reflect both stylet angle and other differences between groups. The record does not report baseline characteristics or an adjusted analysis that might help examine this concern.

Adjustment is a general statistical approach that accounts for measured variables associated with the outcome and possibly with group membership. It cannot automatically remove confounding from factors that were not measured, were measured poorly, or were not appropriately modeled. No adjusted or unadjusted analysis is listed in the registry, and the variables that might have been considered for adjustment are not reported.

What is over-dispersion?

Over-dispersion is a general concern for count outcomes when observed variability exceeds what a chosen model assumes. It is not the usual central issue for a continuous mean outcome analyzed with a standard model, though unequal variances, skewed distributions, outliers, or dependence among observations can still affect inference. A sound analysis would consider whether its assumptions fit the observed outcome and study structure. The registry does not report distributional checks, model details, or diagnostic results, so it is not possible to say how these issues were handled.

The study’s primary outcome is time, but the registry does not say whether all procedures produced a measurable time or how any missing or unusual observations were handled. In general, a mean comparison can be sensitive to extreme observations, while excluding observations may introduce bias if exclusion is related to the outcome or group. The timing definition, missing-data procedures, and analysis population are not reported in the registry record.

What do planning calculations mean?

As a general principle, sample-size planning uses assumptions about the effect to detect, variability, significance level, allocation, and analysis method. The planning assumptions associated with this record describe an illustration based on an observed effect, a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such calculations are planning illustrations, not observed power and not evidence that the study was designed with those assumptions. The registry record does not report the trial’s own sample-size justification. In the absence of reported endpoint results and analysis, a planning calculation cannot substitute for an estimate of what happened in the study.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("90°Angle Group", "60° Angle Group")
n   <- c(70, 70)
m   <- c(32.5, 29.3)
sp  <- c(9.4, 6.4)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  90°Angle Group  70  32.500  9.400  30.259  34.741
CARM  60° Angle Group  70  29.300  6.400  27.774  30.826

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and identifies time to intubation as primary. It records no analyses. It does not report a detailed statistical plan, the number of hypotheses tested, any prespecified hierarchy of outcomes, or whether interim analyses were performed. Therefore, the extent to which multiplicity was considered cannot be assessed. As a general matter, evaluating many outcomes, subgroups, or repeated looks at accumulating data can increase the chance of findings that appear notable by chance; planned methods can address that issue. No such methods are reported, and it would be inappropriate to assume either that multiplicity arose or that it was controlled.

The record gives an enrollment total but does not report how many participants contributed usable time-to-intubation data. It does not describe exclusions, withdrawals, protocol deviations, or missing outcome values. The analysis population is not reported in the registry record. It is therefore not possible to determine whether all enrolled participants were included, whether an intention-to-treat or other population was used, or how incomplete observations were handled. These distinctions matter because the participants with recorded outcomes may differ from those without them.

For a continuous endpoint, missing observations can affect both the group summaries and the estimated comparison. As a general concept, complete-case analysis may be biased when missingness relates to group assignment or to the unobserved outcome; other approaches also rely on assumptions. The registry does not report the amount or reasons for missing data or any method used to address them. Nor does it report sensitivity analyses that could show how conclusions might change under different assumptions.

Without the analysis plan, outcome results, and analysis-population details, neither multiplicity nor missing-data handling can be evaluated. These are limitations in what the registry record allows readers to assess, not proof that a particular problem occurred.

12. Safety Results

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

Other (non-serious) adverse events

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

The adverse-event entries record 70 participants at risk in the 60° Angle Group and 70 in the 90°Angle Group. For each group, the serious adverse event count is recorded as 0, and the count for other adverse events is also recorded as 0. The registry lists no serious adverse event terms. These figures mean that the record contains no reported events in those categories for the recorded groups; they should not be taken as proof that no events occurred outside the scope of recorded reporting.

The death entries are null. A null value is not a numeric zero: deaths are not reported in the registry record. The record also does not describe how adverse events were collected, the observation period for safety, definitions or thresholds, or whether reporting was complete. The primary outcome timeframe of 10 minutes around intubation is not enough to establish the adverse-event follow-up period.

These safety counts should be interpreted separately from the missing primary endpoint results. They do not provide information about the comparative time to intubation, and the registry does not report an analysis of differences in adverse events. With zero recorded event counts in both groups, the entries offer no observed contrast in those categories, but they do not establish equivalence or rule out events that were not recorded. The null death fields should remain described as not reported, rather than being recoded as zero.

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

The record establishes that a completed study enrolled 140 participants and compared two described McGrath Videolaryngoscope techniques: a 60° angled stylet and a 90° angled stylet. It identifies time to intubation in seconds as the primary endpoint and states that the study aimed to determine an appropriate stylet angle by comparing this measure. These registry entries define the research question, but they do not answer it.

The primary outcome results are not reported in the registry record. There are no group means or standard deviations, no estimated difference, and no reported uncertainty interval or test. As a result, the posted information does not indicate whether one group had a shorter observed time, how large any difference was, or how precise an estimate might be. A completed status and an enrollment count cannot be used as substitutes for those results.

The design description also limits what a group comparison could establish. The registry calls the comparison nonrandomized, says allocation was not stated, and notes that the arms are not a like-for-like control comparison. In general, nonrandomized groups can differ in ways that influence outcomes. Without allocation details, group characteristics, and a reported analysis, any causal interpretation would be unsupported.

The safety record reports zero serious and zero other adverse events among 70 participants at risk in each arm. Deaths are not reported. Those entries describe recorded counts, not a complete evaluation of safety, because collection methods and follow-up details are not reported. They also do not address the primary timing question.

In short, the registry record describes what the investigators set out to compare and some study and safety details, but does not report the outcome findings needed to judge the observed comparison. It neither demonstrates a difference nor demonstrates that the techniques have the same results. The absence of a reported analysis should not be interpreted as evidence for either conclusion.

14. Why This Trial Matters Statistically

This study presents a clear example of the distinction between a research question and an answer supported by reported results. The registry states the comparison, identifies a continuous primary endpoint, and gives the summary form intended for that endpoint. Yet it does not report the endpoint values or an analysis. A well-defined outcome is essential for interpretation, but it cannot establish the direction, size, or precision of a finding without results.

The nonrandomized design makes transparent reporting especially important. When allocation is not stated, readers cannot assess how the groups were formed or whether characteristics related to timing might have differed. The registry’s own warning that the arms are not a like-for-like control comparison directs attention to this issue. If outcome estimates were available, readers would still need design and analysis details to judge whether the observed contrast could plausibly be attributed to stylet angle.

The case also illustrates why the type of summary matters. A mean and standard deviation describe different features of a continuous outcome: the average and the spread. A comparison would be more informative with an effect estimate and a measure of its uncertainty, alongside clear endpoint definitions and analysis-population information. None of those outcome results is reported in the registry record. The recorded sample size and completion status cannot replace them.

Finally, safety counts need careful reading. Zero reported events are not equivalent to proof of no risk, and a null death field is not the same as a recorded zero. Distinguishing those entries helps prevent stronger claims than the record supports. Statistically, the main lesson is that registration details, outcome reporting, design information, and analysis results each answer different questions; conclusions depend on having enough of each.

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.

The registry record does not report the primary outcome results, despite identifying time to intubation as the primary endpoint. It provides no mean, standard deviation, between-group estimate, confidence interval, or p-value. The number of analyses is recorded as 0. Consequently, the intended comparison cannot be evaluated from the posted results.

The design information is limited. The registry describes the comparison as nonrandomized, says allocation was not stated, and cautions that the arms are not a like-for-like control comparison. It does not report how participants entered either group, whether operators or outcome assessors were blinded, or what participant and procedural characteristics were present in each arm. These omissions prevent assessment of comparability and potential confounding.

Although enrollment is reported as 140, the number included in the primary endpoint analysis is not reported. The record does not describe missing observations, exclusions, withdrawals, or analysis populations. It also lacks a detailed definition of timing start and stop points and a description of how incomplete or unsuccessful procedures would be treated. These details can affect how time measurements are interpreted and compared.

The registry does not report a sample-size justification or a detailed statistical plan. The planning assumptions describe an illustration, not the trial’s own design rationale or an observed power calculation. Information about interim analyses, multiplicity, distributional assumptions, and sensitivity analyses is not reported in the registry record. For safety, adverse-event collection and follow-up methods are also absent, and deaths are not reported. Together, these gaps limit assessment of both the primary comparison and the completeness of safety reporting.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Stylet Angle for McGrath Videolaryngoscopy — NCT03000088.
• Registry record last updated 2017-04-13; status last verified 2017-03.
• Results first posted 2017-04-13.
• 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 record describes a completed study sponsored by Ajou University School of Medicine, with enrollment of 140 participants and a condition of intubation. The recorded study start is 2016-03; primary completion is 2016-08. The comparison is between McGrath Videolaryngoscopy using a 60° angled stylet and using a 90° angled stylet. Allocation is not stated, and the registry describes the comparison as nonrandomized and not like-for-like.

Time to intubation, measured in seconds and summarized as a mean and standard deviation, is the sole listed primary outcome. Its timeframe is 10 minutes around intubation. The registry does not report outcome values or an analysis. Serious and other adverse event counts are recorded as 0 among 70 participants at risk in each group; deaths are not reported. The record does not provide enough outcome information to assess the comparative timing result.