This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Does Alkalinization Reduce Perceived Pain Levels During Sentinel Lymph Node Imaging? (NCT01660412), a randomized na study. The primary outcome is Perceived Pain Level.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01660412 |
| Phase | NA |
| Condition | Pain |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Quadruple |
| Enrollment | 60 |
| Arms in the primary outcome | 2 |
| Lead sponsor | University of Arkansas |
| Results posted | Yes |
2. Clinical Question
Population
The registry describes people undergoing non-breast sentinel lymphoscintigraphy. Enrollment was 60. Further participant characteristics, including age, sex, and the specific non-breast clinical settings, are not reported in the registry record.
Intervention
The intervention was a pH-altered injection of technetium-99m sulfur colloid. The trial summary describes using sodium bicarbonate to alkalinize the radiopharmaceutical; the registry does not give further detail about preparation or the achieved pH.
Comparator
The comparator was the standard-of-care injection. The registry describes treatment orders in which one group received standard of care first and the other received the pH-altered solution first, with remaining injections randomly assigned between the two solutions.
Primary question
Did perceived pain differ between pH-altered and standard-of-care injections during non-breast sentinel lymphoscintigraphy? Participants rated pain immediately after each injection on a validated scale from 0, no pain, through 10, severe disabling pain. Scores after each injection were averaged for each participant.
This is a question about reported pain scores under two injection conditions, not a question about diagnostic performance or other clinical outcomes. The primary endpoint was a continuous measure, summarized as a mean and standard deviation. The registry describes a paired t-test for testing whether the mean difference was different from 0, consistent with comparing conditions experienced by the same participant. The registry does not report participant characteristics or enough procedural detail to determine how broadly the results apply to particular non-breast settings.
3. Trial Design
This completed study was a randomized, quadruple-masked crossover trial sponsored by the University of Arkansas. The registry lists enrollment of 60. The study start date was 2012-08-01, and the primary completion date was 2016-12-30. The phase is listed as NA.
In a crossover design, participants receive more than one study condition, so comparisons can be made within the same participant. Here, the conditions were standard-of-care and pH-altered injections. The registry describes two starting orders: standard of care first or pH altered first. It also says remaining injections were randomly assigned as either standard of care or pH altered. This makes order relevant to interpreting the design; details about the randomization procedure, sequence allocation, or any period-by-period analysis are not reported in the registry record.
The primary pain rating was collected immediately after each injection, within less than 1 minute, over a timeframe of up to total 5 minutes. The registry says that pain ratings after each injection were averaged for each participant. Although enrollment was 60, the posted primary outcome has 57 participants in each condition. The reason for that difference, the number of participants with complete paired observations, and the analysis population definition are not reported in the registry record. The equal condition counts do not by themselves establish that every participant contributed a complete pair.
The registry gives no further account of masking implementation or whether participants, clinicians, or outcome assessors could infer the injection condition. The details of trial conduct beyond the listed design and injection order are not reported in the registry record. Those omissions limit assessment of how randomization, masking, and repeated measurements were handled in practice.
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: Each Participant received four injections. We tested four different injection sites. Each participant received all four injections at one site.
Overall Study
| Stage | pH Altered First | Standard of Care First |
|---|---|---|
| STARTED | 29 | 31 |
| Head | 1 | 4 |
| Thorax | 9 | 9 |
| Appendicular Structures | 17 | 11 |
| Other | 2 | 4 |
| Injection 1 | 29 | 31 |
| Injection 2 | 29 | 31 |
| Injection 3 | 29 | 31 |
| Injection 4 | 29 | 31 |
| COMPLETED | 29 | 28 |
| NOT COMPLETED | 0 | 3 |
Reasons for not completing this period:
| Reason | pH Altered First | Standard of Care First |
|---|---|---|
| Protocol Violation | 0 | 3 |
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.
| Characteristic | Unit | All Study Participants |
|---|---|---|
| Participants analysed | 57 | |
| Age, Continuous | years | 57 (SD 13.6) |
| Sex: Female, Male: Female | Participants | 26 |
| Sex: Female, Male: Male | Participants | 31 |
| Region of Enrollment: United States | Participants | 57 |
| Weight | lbs | 159.9 (SD 46.1) |
6. Primary Endpoint
The registry lists the primary outcome as Perceived Pain Level, measured over immediately after administration (<1 min) of each injection (up to total 5 minutes).
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | units on a scale |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was perceived pain level, recorded in units on a scale. Participants rated the pain of every injection using a validated scale ranging from 0, meaning no pain, to 10, meaning severe pain that is disabling. Ratings were collected immediately after administration, within less than 1 minute. The registry states that ratings across injections were averaged for each participant.
Pain is a subjective experience, so a participant-reported rating directly captures the experience the trial set out to compare. Treating the rating as a continuous measure allows the registry to report a mean and standard deviation for each injection condition and to estimate a mean difference. The mean gives the average score in the posted group of observations; the standard deviation describes how spread out individual scores were around that mean. Neither summary shows the full distribution of ratings or how many participants gave any particular score.
The endpoint focuses on pain during the injection procedure, rather than on longer-term outcomes. The registry's measurement window is immediate, and its summary is based on averaged ratings within participants. It does not report the name of the validated scale, the exact number of injections received by each participant, or additional endpoint validation details. The results therefore address the recorded pain ratings as defined in the registry, not every aspect of discomfort or the broader experience of the procedure.
7. Results Posted in the Registry
- PH Altered Injection: mean 4.39 versus 5.81 on control; difference -1.42 (95% CI -2.28 to -0.56), standardized effect d = -0.60; z-test p = 0.001.
Mean difference: PH Altered Injection
95% CI: -2.28 to -0.56
Recalculated from the posted summary statistics
8. Statistical Interpretation
The posted group means were 5.81 for standard of care and 4.39 for the pH-altered injection. The standard deviations were 2.24 and 2.45, respectively, with 57.0 participants in each condition. These summaries show lower average reported pain in the pH-altered condition in the posted results. A mean describes the center of the scores, while the standard deviations indicate that individual ratings varied within both conditions.
The recalculated mean difference is -1.42 when expressed as pH-altered minus standard of care. Its 95% confidence interval is -2.282 to -0.558, and the recalculated p-value is 0.001. The negative sign reflects that direction of subtraction; it does not mean the registry used that sign convention. The sponsor's reported mean difference is 1.42, with a 95% confidence interval from 0.85 to 2.00 and p < 0.001. The positive sponsor estimate is consistent with expressing the comparison in the opposite direction, as standard of care minus pH altered.
The registry describes a paired t-test, appropriate in concept for a within-participant comparison when the same people contribute ratings under both conditions. The recalculation uses posted condition-level summary statistics and is not a reconstruction of the participant-level paired analysis. The registry does not report the within-participant correlation or the individual paired differences, so that paired analysis cannot be independently reproduced from the group means and standard deviations alone. The recalculated and sponsor-reported inferential results are not identical; the registry does not explain the difference in their confidence intervals or p-values.
Both reported analyses point in the same direction: the pH-altered condition has a lower posted mean pain score than standard of care. The confidence intervals describe uncertainty in the estimated difference, rather than the range of scores for individual participants. The p-values address compatibility with a null hypothesis of no mean difference under the respective analyses; they do not quantify the probability that the null hypothesis is true or establish that the observed estimate will recur in another setting.
These results concern one primary endpoint in this trial and should be read in light of the crossover design, the limited information about missing observations and analysis populations, and the absence of participant-level data. Details about the population and non-breast procedures are sparse. The posted outcome is evidence about measured pain ratings in this trial, not a complete account of all relevant outcomes or a basis for claims beyond the recorded comparison.
9. Statistical Methods Explained
What does a mean difference represent? A mean difference subtracts one condition's average score from the other condition's average score. Its sign depends on the subtraction order. The group means were 5.81 for standard of care and 4.39 for the pH-altered injection. The recalculated estimate of -1.42 uses pH altered minus standard of care; the sponsor's estimate of 1.42 uses the opposite direction. Reading the direction is essential: a positive or negative sign alone does not identify which condition had the higher mean unless the order is stated.
What does the standard deviation describe? The standard deviation summarizes the spread of individual observed scores around a group mean. The posted values are 2.24 for standard of care and 2.45 for pH altered. These values describe variation among ratings, not uncertainty in the mean difference. They also do not reveal the distribution's shape, whether scores cluster at particular scale values, or the relationship between a participant's ratings under the two conditions.
Why does the crossover design matter? General statistical explanation: a crossover comparison uses repeated observations within participants. If the same person receives both conditions, their paired difference can account for stable differences between people. The uncertainty of that paired difference depends on how strongly a person's ratings in the two conditions are related. A paired t-test analyzes the participant-level differences; it is not equivalent in general to treating condition groups as independent. The registry description says a paired t-test was used, but participant-level differences and their variability are not reported.
The recalculated results use posted condition-level summary statistics, with an estimate of -1.42, a 95% confidence interval from -2.282 to -0.558, and p = 0.001. Those are simple unadjusted recalculations, not a reanalysis of the paired observations. The registry's sponsor analysis reports a two-sided t-test and gives a mean difference of 1.42, a 95% confidence interval from 0.85 to 2.00, and p < 0.001. The registry separately describes the treatment effect as the difference between buffered and standard-of-care mean scores and says a paired t-test was used. The analysis entry does not provide participant-level data or enough detail to reproduce that test independently.
What does a confidence interval convey? General statistical explanation: a confidence interval gives a range of estimates compatible with the data and the method used, reflecting sampling uncertainty. It is not a range that contains a specified proportion of individual participant scores. A narrower interval indicates greater precision under that method; a wider interval indicates more uncertainty. The recalculated and sponsor-reported intervals use opposite directions for the difference. Their endpoints are not the same, and the registry record does not state why the estimates of uncertainty differ.
What does a p-value convey? General statistical explanation: a p-value measures how unusual data at least as inconsistent with a specified null hypothesis would be, if that null hypothesis and the test assumptions were true. It is not the probability that the null is true, and it does not measure the size or practical importance of a difference. The recalculated p-value is 0.001, while the sponsor reports p < 0.001. Their inferential procedures should not be treated as interchangeable merely because they point in the same direction.
Why can over-dispersion matter? General statistical explanation: over-dispersion occurs when observed variability is greater than a statistical model assumes. If a method underestimates variability, its standard errors and confidence intervals can be too small and its p-values can give an overly strong impression of precision. The registry does not report an over-dispersion assessment or a model-based analysis, and the continuous endpoint is summarized with means and standard deviations. Over-dispersion therefore cannot be assessed from the registry's summaries alone.
What do the masking and randomization labels establish? The registry labels allocation as randomized and masking as quadruple. These labels describe the recorded design, but do not by themselves explain sequence generation, concealment, who was masked, or whether masking was maintained. Those operational details are not reported in the registry record. For a crossover study, order and possible carryover are also relevant to analysis; whether these were evaluated or adjusted for is not reported in the registry record.
The record reports one primary outcome measure and one analysis, with no secondary outcomes posted. It does not report a multiplicity adjustment, missing-data method, participant-level analysis set, or original statistical analysis plan. These omissions do not establish that the procedures were absent; they mean that their use cannot be determined from the registry record.
10. Confidence Intervals and Precision
The recalculated mean difference is -1.42 for pH altered minus standard of care, with a 95% confidence interval from -2.282 to -0.558. This interval does not include 0 under the recalculation's method. The sponsor reports the opposite direction of comparison: a mean difference of 1.42, with a 95% confidence interval from 0.85 to 2.00. Both intervals place the estimated average difference in a direction corresponding to lower mean scores for the pH-altered condition.
A confidence interval communicates uncertainty about the estimated mean difference, conditional on the analysis method and its assumptions. It does not describe the spread of pain scores among participants; the standard deviations of 2.24 and 2.45 describe that spread. Nor does the interval mean that individual participants' scores fall within its endpoints. The point estimate is the center of the reported contrast, while the interval indicates how precisely that contrast is estimated by each analysis.
The two confidence intervals differ in width and endpoint values. The registry does not explain the difference between the recalculated interval and the sponsor's interval. Because the trial is a crossover study and the registry describes a paired t-test, the relationship between each participant's ratings matters for the paired standard error. The participant-level paired differences and their standard deviation are not reported, so the paired uncertainty cannot be checked from the posted condition-level summaries alone.
The posted mean scores and standard deviations provide useful descriptive context, but they do not resolve this precision issue. The number with complete paired endpoint data and the handling of missing observations are also not reported in the registry record. The confidence intervals should therefore be interpreted as results of their respective reported or recalculated methods, rather than as interchangeable estimates from one fully reproducible analysis.
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.
| Effect to detect | Participants per arm, 80% power | Participants per arm, 90% power |
|---|---|---|
| 100% of the observed effect | 43 | 58 |
| 75% of the observed effect | 77 | 103 |
| 50% of the observed effect | 172 | 230 |
The sample-size figures are planning illustrations based on the observed effect, not the trial's original design justification. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect. These figures are participants per arm, not total event counts.
For planning to detect 100% of the observed effect, the figures are 43 participants per arm for 80% power and 58 participants per arm for 90% power. For planning to detect 75% of the observed effect, the figures are 77 participants per arm for 80% power and 103 participants per arm for 90% power. For planning to detect 50% of the observed effect, the figures are 172 participants per arm for 80% power and 230 participants per arm for 90% power.
In general, power is the probability that a study will reject a specified null hypothesis under a particular assumed effect and analysis plan. The 80% and 90% columns give the planned number of participants per arm under the stated assumptions to reach those respective power targets. Smaller effects require more participants to detect with the same power target, as illustrated by the increasing figures when the assumed effect fraction is reduced.
These are not observed power estimates. They do not establish what power the completed trial had for its actual analysis. The trial's own original sample-size assumptions and justification are not reported in the registry record. The planning calculation is also described as an equal-allocation, two-arm illustration, while the trial itself is a crossover design; it should not be read as a reconstruction of the trial's original design calculation.
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 z1−α/2 = 1.960) and the desired power (z1−β = 0.842 for 80% and 1.282 for 90%).
Formula
n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.
Worked calculation for this trial
- Observed difference Δ = -1.420; pooled standard deviation σ = 2.347.
- n = 2 × (1.96 + 0.842)2 × 2.3472 / -1.4202 = 42.9, rounded up to 43 participants per arm for 80% power.
The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).
R code
alpha <- 0.05
z_a <- qnorm(1 - alpha / 2) # two-sided
delta <- -1.42 # observed difference in means
sigma <- 2.34734956919501 # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))
# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")
# Simulation: exact two-sample t-test using simulated means and variances
set.seed(1660412)
n <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n)) # difference in sample means
s2 <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1)) # pooled sample variance
tstat <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))
Output from running the code
100% of observed effect: n per arm = 43 (80% power), 58 (90% power)
75% of observed effect: n per arm = 77 (80% power), 103 (90% power)
50% of observed effect: n per arm = 172 (80% power), 230 (90% power)
power.t.test: 43.9
Simulated power at n = 43 per arm: 0.790 (20000 replicates)The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.
13. Analyses Reported by the Sponsor
| Method | Estimate | 95% CI | P-value |
|---|---|---|---|
| t-test, 2 sided | Mean Difference (Final Values) 1.42 | 0.85 to 2.00 | < 0.001 |
The sponsor's reported analysis gives a mean difference of 1.42, a 95% confidence interval from 0.85 to 2.00, and p < 0.001. The registry lists the groups in the order standard of care and pH altered; the positive estimate is consistent with expressing the difference as standard of care minus pH altered. In that direction, a positive value corresponds to a higher mean pain score in the standard-of-care condition.
The recalculated estimate is -1.42, with a 95% confidence interval from -2.282 to -0.558 and p = 0.001, when the contrast is expressed as pH altered minus standard of care. The opposite sign reflects the reversed subtraction order. However, the confidence interval endpoints and p-values also differ. The registry does not explain the difference between these inferential results, so the reason should not be inferred from the posted summaries.
The registry describes a paired t-test, while the analysis entry labels the sponsor method as a two-sided t-test. The participant-level paired data needed to reproduce the paired test are not reported. The recalculation is an unadjusted calculation from posted summary statistics, not a substitute for the sponsor's participant-level analysis. Both estimates indicate a lower mean pain score in the pH-altered condition, but their uncertainty measures should be read with their respective methods in mind.
14. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome measure and one analysis. It lists no secondary outcomes. This reduces the number of posted outcome analyses that can be considered from the record, but it does not establish what analyses may have been planned or conducted outside the registry entry. Whether the trial specified a multiplicity strategy, such as adjusting for multiple outcomes or repeated tests, is not reported in the registry record.
The primary outcome description says ratings after each injection were averaged for each participant. It also describes a paired t-test to test whether the mean difference differed from 0. The analysis entry reports a two-sided t-test, but does not give detail sufficient to establish precisely how repeated observations, order, or periods entered the analysis. The protocol and full statistical analysis plan are not reported in the registry record.
Enrollment was 60, while 57.0 participants are listed for each condition in the primary outcome. The record does not explain the difference, state how many participants contributed complete pairs, or identify an analysis population such as intention-to-treat or per-protocol. The method for handling missing ratings, withdrawals, or incomplete sequences is not reported. Equal participant counts in each condition cannot establish how missing observations were handled or whether those participants were the same people in both conditions.
General statistical explanation: multiplicity can arise when many outcomes, time points, subgroup comparisons, or repeated tests are evaluated. More testing can increase the chance of finding a nominally unusual result by chance if the tests are treated as independent discoveries. The registry's single posted primary outcome does not reveal whether additional exploratory analyses were performed, and the record does not report an adjustment plan. These missing details limit assessment of the analysis framework, but do not show that a particular adjustment or population definition was or was not used.
15. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Standard of Care Injection | 0 | 60 | 0.0% |
| PH Altered Injection | 0 | 60 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Standard of Care Injection | 0 of 60 |
| PH Altered Injection | 0 of 60 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Standard of Care Injection | 11 of 60 |
| PH Altered Injection | 0 of 60 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Standard of Care Injection | PH Altered Injection |
|---|---|---|---|
| Injection Site Pain | General disorders | 11 of 60 | 0 of 60 |
The serious adverse event figures are 0 of 60 for standard-of-care injections and 0 of 60 for pH-altered injections. No deaths are listed in either condition. The registry also lists other adverse events in 11 of 60 for standard of care and 0 of 60 for the pH-altered condition. The record gives no serious adverse event terms.
These counts describe events recorded in the registry; they do not establish that an injection caused or prevented an event. A count of zero means no event of that category was recorded in the listed group, not that the possibility of such an event is ruled out. The record does not provide event descriptions for the other adverse events, their severity, timing, relationship to injection, or the rules used to collect and classify them.
The safety counts should be read separately from the pain outcome. They do not provide a comparison adjusted for the crossover design, and the registry does not explain how adverse events were attributed when participants received both conditions. Further details about safety monitoring and event ascertainment are not reported in the registry record.
16. What the Result Does, and Does Not, Mean
The posted results show a lower mean pain rating for the pH-altered injection than for standard of care: 4.39 compared with 5.81. The recalculated mean difference is -1.42 for pH altered minus standard of care. The sponsor's reported difference is 1.42 in the opposite direction. The reported confidence intervals and p-values are consistent with a difference in average scores under their respective methods, but they are not identical and the registry does not explain why.
This comparison is limited to immediate perceived pain ratings during non-breast sentinel lymphoscintigraphy, as described in the registry. The outcome was averaged across injections for each participant. The result does not establish how individual participants experienced every injection, since group means and standard deviations do not show individual trajectories or paired differences.
The registry record does not report enough participant or procedural detail to determine which non-breast settings are represented or how well the results apply to other settings. It also does not report the participant-level paired data, missing-data approach, or full analysis plan. These limitations matter because the design is crossover and the precision of a paired comparison depends on the within-participant data.
The results do not establish effects on outcomes other than the measured pain ratings, and the registry does not provide evidence about longer-term outcomes. They also do not establish that any observed difference is important to every participant or that it will be reproduced in another study. Interpretation should remain tied to the recorded endpoint, the posted analysis, and the limitations of the registry information. No treatment recommendation follows from these statistics alone.
17. Why This Trial Matters Statistically
This trial is statistically notable for combining a subjective continuous outcome with a randomized crossover design. Pain ratings directly address the experience under study, while the crossover structure can support within-participant comparisons. That design also makes the paired data important: the association between a participant's ratings under the two conditions influences the uncertainty of the comparison.
The registry explicitly describes a paired t-test, but the posted group means and standard deviations do not provide the participant-level differences needed to reproduce it. The recalculated estimate and interval are useful as an unadjusted reading of the summary statistics, yet they are not the same as an independently verified paired analysis. The differing confidence intervals and p-values make this distinction particularly relevant. Understanding which contrast direction is used also prevents a sign change from being mistaken for a disagreement about which condition had the higher mean.
The record illustrates why a p-value alone is an incomplete description. The mean difference conveys the estimated direction and size on the pain scale, and the confidence interval conveys precision under the particular method. The standard deviations describe variation in observed ratings, a different feature of the data. Together, these statistics provide more context than a significance statement alone, while still leaving important uncertainty about paired observations and missing data.
Finally, planning illustrations based on the observed effect are not evidence of the trial's original sample-size rationale or its achieved power. Keeping those planning quantities separate from the completed study's observed results is important for responsible interpretation. The registry provides a focused comparison, but its reporting gaps define how far statistical conclusions can be taken.
18. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
Several limitations are specific to the information recorded for this trial. The registry describes non-breast sentinel lymphoscintigraphy but does not identify the particular anatomical sites or provide participant characteristics. This makes it difficult to assess whether the enrolled population and procedures match a reader's setting. The name of the validated pain scale is also not reported.
The crossover design raises questions about order, period effects, and possible carryover between injections. The registry describes differing starting orders and random assignment of remaining injections, but does not report whether order effects or carryover were assessed. The full randomization and masking procedures are not described. The exact injection sequence and number of ratings contributed by each participant are not reported beyond the stated timing and averaging approach.
There is a gap between enrollment of 60 and 57.0 participants listed for each condition in the primary outcome. Reasons for this difference, completion of paired observations, withdrawals, and the handling of missing data are not reported. The analysis population is also unspecified. Without participant-level paired observations, the paired analysis and its uncertainty cannot be reproduced from the condition-level summaries.
The recalculated results do not exactly match the sponsor-reported confidence interval and p-value. The registry does not explain the difference, and the summaries do not permit a definitive account of its source. The sample-size illustrations use the observed effect and stated planning assumptions; the trial's original sample-size justification is not reported. Finally, only one primary outcome and no secondary outcomes are posted, while multiplicity procedures and a full statistical analysis plan are not reported in the registry record.
19. Related Tutorials
20. Related Statistical Calculators
21. Sources
- ClinicalTrials.gov: Does Alkalinization Reduce Perceived Pain Levels During Sentinel Lymph Node Imaging? — NCT01660412.
- Registry record last updated 2017-11-20; status last verified 2017-11.
- Results first posted 2017-11-20.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
22. Record Summary
NCT01660412 is a completed randomized, quadruple-masked crossover trial sponsored by the University of Arkansas. It enrolled 60 participants and compared standard-of-care with pH-altered injections during non-breast sentinel lymphoscintigraphy. The primary endpoint was participant-rated pain immediately after each injection, averaged across injections for each participant.
The posted mean scores were 5.81 for standard of care and 4.39 for pH altered, with 57.0 participants listed in each condition. The recalculated contrast was -1.42 for pH altered minus standard of care; the sponsor reported 1.42 in the opposite direction. Their confidence intervals and p-values differ, and the registry does not explain why. Participant-level paired data, missing-data methods, and the original sample-size justification are not reported in the registry record.