Intravenous Ketorolac for Postoperative Pain in Percutaneous Nephrolithotomy: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Intravenous Ketorolac for Postoperative Pain in Percutaneous Nephrolithotomy (NCT00765128), a randomized phase 4 study. The primary outcome is Pain 'Right Now'.

2. Clinical Question

3. Trial Design

The registry identifies NCT00765128 as a completed Phase 4, randomized, parallel trial sponsored by Mayo Clinic. It describes the masking as quadruple and the design as double blinded in the official title. The record lists enrollment of 17. The study start is recorded as 2008-10, and primary completion as 2010-11.

Participants were assigned to ketorolac or placebo. Both arms received an intravenous infusion beginning 0.5 hours after surgery and lasting 18.5-23 hours at 40-120 mL/hr. The ketorolac arm received 90 mg in 1 L of normal saline; the placebo arm received 1 L of normal saline. These details describe the assigned regimens, not whether every participant completed the infusion as planned.

Randomization and masking can help reduce systematic differences in group assignment and influence on outcome measurement. Those design features do not by themselves establish that the groups were comparable in every respect, that masking was maintained, or that all randomized participants were included in the outcome analysis. Such details are not reported in the registry record.

The record reports arm-level mean pain scores and standard deviations at the stated time point. It does not report an analysis population, a method for handling missing observations, or an inferential comparison between arms. The registry also does not report the sequence-generation or allocation-concealment procedures, details of who was masked, or the protocol’s statistical analysis plan. The posted information therefore supports a description of the design and recorded outcome values, but not a full reconstruction of how the trial was conducted or analyzed.

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 Pain 'Right Now', measured over 24 hours after the end of surgery.

The primary endpoint is “Pain ‘Right Now’,” measured 24 hours after the end of surgery. The registry describes a visual analog scale with endpoints 0 = None and 10 = Worst. The reported summary is the mean score in each arm, accompanied by a standard deviation.

A pain scale captures a participant’s assessment at a specified time. A common scale and measurement time make it possible to describe the outcome in the two randomized groups. The mean summarizes the group’s average recorded score; the standard deviation describes how much individual scores varied around that mean. These summaries are descriptive, not a direct estimate of the uncertainty in the difference between groups.

The registry does not describe who recorded the score, how the scale was administered, whether scores were collected for all randomized participants, or how missing scores were handled. It also does not report a valid comparative analysis for this continuous endpoint. Consequently, the arm summaries alone cannot establish the size or precision of a treatment contrast. The clinical interpretation is further limited to the recorded time point: the registry’s primary outcome does not, by itself, describe pain at other times or other aspects of recovery.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies a continuous primary outcome summarized by a mean and standard deviation. It also states that values are missing or not estimable for a two-arm comparison of this endpoint. The distinction between descriptive summaries and comparative inference is central to reading the posted result.

What does a mean describe?

In general, a mean is an average of the observations included in a group summary. It gives a compact description of the group’s recorded scores, but it does not show every participant’s score or the distribution’s shape. Here, the registry reports means of 1.0 for ketorolac and 0.9 for placebo on the pain scale at 24 hours after the end of surgery. Those values describe the recorded arm summaries; they do not by themselves quantify a treatment contrast.

A comparison would normally express how the outcome differs between the assigned groups and would also describe uncertainty around that estimate. No such estimate is posted for this endpoint. The registry’s note that a comparison is missing or not estimable means the arm summaries should not be treated as though a formal test or adjusted analysis had been reported.

What does the standard deviation describe?

In general, a standard deviation describes the spread of individual observations around a group mean. The registry reports standard deviations of 1.2 for ketorolac and 1.5 for placebo. They indicate variability in recorded pain scores, not the precision of a comparison between arms. A standard deviation is not a confidence interval, and it does not tell the reader how uncertain the difference between group means would be.

A confidence interval, in general, gives a range of values compatible with an estimate under the assumptions of the analysis. Its width reflects statistical uncertainty as well as the analysis method and amount of information. No confidence interval for the between-arm outcome is reported in the registry record, so the precision of a comparative effect cannot be assessed from the posted result.

Why does the unavailable comparison matter?

Random assignment creates a basis for comparing groups, but a statistical analysis is still needed to estimate the contrast and quantify its uncertainty. The record lists 8 participants in the ketorolac outcome group and 9 in the placebo outcome group. It does not state how those participants were selected from the randomized enrollment, whether all randomized participants had usable scores, or how any missing observations were addressed. These omissions prevent a full appraisal of the analysis population and its assumptions.

General statistical practice distinguishes a difference in observed group summaries from evidence about a population-level effect. The observed summaries can vary because of chance, particularly when the amount of information is limited. A comparison estimate with an uncertainty interval would help show what effect sizes are compatible with the data. Because those results are not posted, no claim about the statistical significance or precision of a contrast can be supported from this record.

How should planning calculations be read?

The registry’s planning description says that any sample-size illustrations use the observed effect, a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation; the effect to detect is expressed as a stated fraction of the observed effect. These are planning assumptions, not a report of the trial’s original design justification. The registry does not report the original sample-size rationale or a planned target in the available record.

In general, a sample-size calculation estimates how many participants a future study might need under specified assumptions. Such an illustration is not observed power and does not indicate that the completed trial had a particular probability of detecting an effect. Its interpretation depends on the assumptions and on the effect used for planning. The registry’s description alone does not establish that these planning illustrations were part of the trial protocol.

Over-dispersion is a general concern when the variability in observed data is greater than a model assumes. If a model understates variability, its uncertainty estimates can be too narrow. The registry does not report a model-based analysis for this continuous outcome, so there is no basis to say that over-dispersion affected the trial result. More generally, analysis choices should match the outcome and its observed distribution, but the analysis specification is not reported.

What can be concluded from the method record?

The record supports identification of the endpoint, its scale, its measurement time, and the descriptive summaries. It also identifies the randomized, parallel, quadruple-masked design. It does not report the statistical analysis plan, the method for a between-arm comparison, an inferential result, or the handling of missing endpoint data. These gaps mean that a reader cannot verify whether the analysis followed a prespecified plan or evaluate the assumptions behind a comparative estimate. The most defensible statistical reading is descriptive, with the absence of an estimable posted comparison made explicit.

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("Ketorolac", "Placebo")
n   <- c(8, 9)
m   <- c(1, 0.9)
sp  <- c(1.2, 1.5)
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  Ketorolac  8  1.000  1.200  -0.003  2.003
CARM  Placebo  9  0.900  1.500  -0.253  2.053

11. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures, but the record does not report posted secondary outcomes: the count of posted secondary outcomes is zero. The primary outcome described is “Pain ‘Right Now’” at 24 hours after the end of surgery. Details of any other outcome measures, their timing, or their results are not reported in the registry record.

Multiplicity arises in general when several outcomes, time points, or statistical tests are examined. If many tests are conducted, the chance of at least one apparently notable result can increase unless the analysis plan accounts for that. The registry does not report a multiplicity strategy or enough posted analyses to determine what testing was undertaken. No multiplicity adjustment should be inferred from the record.

The analysis population for the primary outcome is not reported in the registry record. Although arm-level outcome group sizes are listed, the record does not explain whether these reflect all randomized participants, participants with available scores, or another analysis set. It does not describe missing-data amounts by reason, the method used to handle missing scores, or any sensitivity analysis. The note that a two-arm continuous comparison is missing or not estimable reinforces that the posted arm summaries are not accompanied by a complete inferential analysis.

In general, missing outcome data can affect both the amount of information and the validity of a comparison, depending on why values are absent and how they are handled. Without the missing-data methods and analysis populations, the registry does not permit an assessment of those issues. The protocol’s planned approach to multiplicity and missing data is not reported in the registry record.

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.

Most frequent non-serious adverse event terms

The registry reports no serious adverse events in either arm: 0 among the 8 participants at risk in the ketorolac group and 0 among the 9 at risk in the placebo group. These are observed counts in the posted safety groups. They do not establish that serious adverse events could not occur, and they do not show that the two regimens have identical safety profiles. The record lists no top serious adverse-event terms.

For other, non-serious adverse events, the record reports 8 affected participants among 8 at risk in the ketorolac group and 8 among 9 at risk in the placebo group. These counts describe the registry’s recorded event category; specific event terms are not included in the information. The figures should not be read as proof that every participant experienced the same event, or that an event was caused by the assigned infusion.

In general, adverse-event counts depend on how events are defined, collected, coded, and attributed. The registry does not report further detail on those procedures in the available record. Death counts are not reported in the registry record. The safety figures are descriptive and should be interpreted alongside the limited group sizes and the absence of additional detail, rather than as definitive comparative evidence.

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

The posted results establish that the registry records mean pain scores of 1.0 for ketorolac and 0.9 for placebo at 24 hours after the end of surgery, with standard deviations of 1.2 and 1.5, respectively. The scale runs from 0 = None to 10 = Worst. These summaries describe the participants included in the reported outcome groups. They do not constitute a complete statistical comparison.

The record does not report an estimable two-arm comparison for the continuous primary endpoint. It therefore does not give a comparative effect estimate, confidence interval, or inferential test. Without these, the size and precision of a between-arm difference cannot be determined from the registry results. The arm means alone should not be treated as evidence that the regimens are equivalent, nor as proof of a difference.

The trial’s randomized, quadruple-masked, parallel design provides important context for the intended comparison. Nevertheless, the registry does not report enough analysis detail to determine which participants contributed to each summary, how missing scores were handled, or whether the analysis followed a prespecified statistical plan. The posted record also does not give results for secondary outcomes.

The safety results report no serious adverse events in either group and describe other adverse events as recorded for the two arms. These observations should not be generalized beyond the trial record or taken as a complete characterization of safety. The registry does not report death counts or detailed adverse-event terms.

Overall, the record documents the trial design, regimens, primary measurement, and descriptive outcomes. It does not provide the comparative statistical result needed to judge the estimated effect and its uncertainty. This distinction is important: a missing or non-estimable comparison is not a finding of no effect. The information in the registry supports a cautious description of what was recorded, not a definitive conclusion about the relative outcomes.

14. Why This Trial Matters Statistically

This trial is statistically informative as an example of the difference between a randomized design and a reported comparative result. Randomization and masking describe safeguards intended to support a fair comparison. Readers still need an outcome estimate and an account of its uncertainty to assess what the trial data say about the contrast.

The registry posts group means and standard deviations for a continuous pain outcome, but it flags the two-arm comparison as missing or not estimable. This leaves the reader with descriptive information without the inferential result needed to judge precision. It demonstrates why arm summaries should not be mistaken for a treatment-effect estimate, and why absence of a reported test cannot be interpreted as evidence that there was no difference.

The record also makes clear how outcome timing and measurement definition frame interpretation. The reported endpoint concerns pain “Right Now” at 24 hours after surgery on a stated visual analog scale. It does not summarize pain across the recovery period or other outcomes. In general, a sharply defined endpoint can make a result easier to interpret, while still leaving questions about its relevance beyond the measured time and scale.

Finally, the registry provides safety counts but little contextual detail about event definitions or analysis populations. For statistical readers, that makes it important to distinguish counts from comparative safety estimates and to note what the record does not report. The trial matters as a case in reading design features, endpoint summaries, missing analyses, and safety counts without overstating what the posted evidence can establish.

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 principal limitation in the registry record is the absence of an estimable comparison for the continuous primary outcome. Means and standard deviations are posted for each arm, but no between-arm estimate, confidence interval, or inferential test is reported. The data therefore do not allow the precision of a comparative result to be evaluated.

The registry does not describe the analysis population or explain how the outcome group sizes relate to randomized enrollment. It does not report the amount or pattern of missing pain scores, reasons for missingness, or methods used to address missing data. The statistical analysis plan, including any prespecified model or handling of potential covariates, is not reported in the registry record.

Further details of the trial conduct are also unavailable in the record, including eligibility criteria beyond the stated condition, allocation procedures, who was masked, and whether masking was maintained. The registry does not report participant characteristics that could help readers assess the groups’ clinical context. It lists two outcome measures but reports no posted secondary outcomes, limiting assessment of outcomes beyond the primary measure.

The safety reporting is limited to the posted counts. Serious adverse-event terms are not listed, other adverse events are not described by specific event, and death counts are not reported in the registry record. The small outcome groups also mean the descriptive summaries represent limited information; no additional precision estimate is available to quantify that limitation. These gaps do not establish that the trial was improperly conducted, but they restrict what can be independently interpreted from the registry results.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Intravenous Ketorolac for Postoperative Pain in Percutaneous Nephrolithotomy — NCT00765128.
• Registry record last updated 2012-01-27; status last verified 2011-12.
• Results first posted 2012-01-27.
• 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

NCT00765128 is a completed randomized, parallel, quadruple-masked Phase 4 trial sponsored by Mayo Clinic. It compared continuous intravenous ketorolac with saline placebo after percutaneous nephrolithotomy for kidney stone disease. The registry records enrollment of 17 and gives the study start as 2008-10 and primary completion as 2010-11.

The primary outcome was “Pain ‘Right Now’” at 24 hours after the end of surgery, measured on a visual analog scale from 0 = None to 10 = Worst. The registry reports arm-level means and standard deviations, but states that a two-arm comparison for this continuous endpoint is missing or not estimable. No comparative estimate or inferential analysis is posted. Safety results include no reported serious adverse events in either arm and counts for other adverse events; death counts are not reported in the registry record.