The Efficacy of Tamsulosin in the Treatment of Ureteral Stones in Emergency Department Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Efficacy of Tamsulosin in the Treatment of Ureteral Stones in Emergency Department Patients (NCT00448123), a randomized na study. The primary outcome is Stone Passage.

2. Clinical Question

3. Trial Design

The registry describes a randomized, triple-masked, parallel-group study comparing tamsulosin with placebo. The study is listed as completed, with an enrollment of 127. Its phase is recorded as NA. The registry lists kidney stones and ureteral stones as conditions. The listed start was 2007-02 and primary completion was 2011-09.

The primary endpoint results are reported as participant counts for the placebo and tamsulosin arms. The posted outcome data include 47 participants in the placebo arm and 53 in the tamsulosin arm. These are the arm counts associated with the primary result, not a restatement of total enrollment. The registry record does not explain the relation between total enrollment and the participants represented in this outcome, or give a reason for the arm counts shown.

The study objective described in the registry was to compare tamsulosin with placebo for time to stone passage or resolution of pain among emergency department patients with acute ureteral colic pain due to a ureteral stone. It also identified a secondary objective concerning whether response was related to stone size or ureteral position. The primary outcome actually posted is whether participants reported that their stone had passed within seven days. The record lists two secondary outcomes: amount of pain medication taken up to seven days after emergency department discharge, and high pain score by treatment group.

Further design details, including eligibility criteria, the allocation procedure, masking procedures, treatment duration, dose, and the trial's original sample-size justification, are not reported in the registry record. The registry does not identify a statistical analysis plan or analyses for the posted outcomes.

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

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: In the placebo group, of the 47 subjects 18 (46.2%) passed their stone by Day 7. In the Tamsulosin group, of the 53 subjects 21 (53.9%) passed their stone by Day 7.

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 Stone Passage, measured over 1-7 days.

The primary endpoint is stone passage, measured as whether a participant said during a follow-up phone call that the stone had passed within seven days of emergency department discharge. The outcome is binary: each participant is counted as having reported passage or not having reported passage within that period. The posted result gives the number and proportion of participants reporting passage in each treatment group.

Follow-up calls were conducted at days 1, 2, 3, 7, 10 and 30 after discharge. The primary result is based on information obtained up to the seventh day, not on later follow-up. The registry's outcome description does not specify a method for confirming passage independently of the participant's report.

A binary passage outcome offers a direct way to compare how many participants in each group reported the event by a defined time. It does not, by itself, measure the exact time of passage, the duration or severity of pain, or whether pain resolved before passage. Those are distinct outcomes, even though time to passage or pain resolution appears in the study objective. Results for time to passage, pain resolution, and the relationship between response and stone size or position are not reported in the registry record.

The endpoint narrative reports 18 of 47 participants in the placebo group and 21 of 53 in the tamsulosin group, while also giving the percentages 46.2% and 53.9%, respectively. Those percentages do not match the proportions implied by the accompanying counts. The unadjusted recalculation described in the statistical interpretation uses the posted counts.

7. Results Posted in the Registry

• Tamsulosin: 39.6% (21/53) versus 38.3% (18/47) on control; risk difference 1.3 percentage points (95% CI -17.8 to 20.5), risk ratio 1.03 (0.63–1.69); unadjusted two-proportion z-test p = 0.892.

8. Statistical Interpretation

9. Statistical Methods Explained

The posted primary outcome is binary: participants either reported stone passage by Day 7 or did not. A comparison of binary outcomes can be expressed as a risk difference, risk ratio, or odds ratio. Each summarizes the same broad between-group question on a different scale. The estimates in this analysis are recalculated without adjustment from the posted arm counts. The registry record does not report the sponsor's inferential analysis for this outcome.

What does the risk difference express?

The risk difference subtracts the event proportion in the control group from the event proportion in the intervention group. It is an absolute contrast, expressed on the probability scale. The recalculated risk difference is 0.013. A positive value corresponds to a higher observed event proportion in the tamsulosin group; a negative value would correspond to a lower observed event proportion. The confidence interval, from -0.178 to 0.205, includes both directions of possible difference.

How do relative measures differ?

The risk ratio compares the event proportions by division, while the odds ratio compares the odds of the event. These relative measures are recalculated as 1.035 for the risk ratio and 1.057 for the odds ratio. A value of 1 represents no relative contrast. Their confidence intervals include 1: 0.632 to 1.692 for the risk ratio, and 0.472 to 2.366 for the odds ratio. Because the event proportions are based on modest arm counts, these relative estimates are also uncertain. The scales answer related but not identical interpretive questions, so their numerical values should not be compared as though they were the same quantity.

What does the p-value tell the reader?

The unadjusted p-value is 0.892. In general, a p-value describes how unusual data at least as discrepant as those observed would be under a specified null model. It is not the probability that the null hypothesis is true, nor a measure of the size or clinical importance of an effect. This recalculated value is based on the posted counts and does not indicate that the two groups are equivalent. A finding of no statistically compelling difference can coexist with a wide interval that includes meaningful effects in either direction.

Why use a confidence interval?

In general, a confidence interval presents a range of estimates compatible with the data under the method's assumptions. Its width conveys precision: narrower intervals indicate more precision, while wider intervals indicate greater uncertainty. The interval around the risk difference crosses zero and is wide relative to the point estimate. It therefore gives more information than the point estimate alone about how uncertain the comparison is. The registry record does not report whether the sponsor used a different confidence-interval method or an adjusted analysis.

What assumptions underlie a simple recalculation?

The recalculated comparison treats the posted counts as the basis for an unadjusted two-group analysis. It does not account for covariates, stratification, repeated measurements, or the timing of events. The outcome is reduced to passage reported by Day 7, rather than a time-to-event outcome. The registry record does not report an analysis plan explaining whether any of those methods were prespecified or used by the sponsor. Because the narrative percentages do not match the counts, the recalculated comparison should be understood specifically as a calculation from the posted counts, not as a resolution of that difference in the record.

General statistical interpretation also depends on how outcomes were observed and how incomplete follow-up was handled. The registry describes follow-up calls at days 1, 2, 3, 7, 10 and 30, and says the primary result uses information up to Day 7. It does not report the number of participants with missing follow-up, the rules for classifying incomplete reports, or a missing-data analysis. The effect of any incomplete outcome information therefore cannot be assessed from the registry record.

10. Confidence Intervals and Precision

The recalculated risk difference is 0.013, with a 95% confidence interval from -0.178 to 0.205. The interval crosses zero, the value corresponding to no absolute difference. It also extends below and above zero, so the posted counts are compatible with either direction of contrast under the recalculation method. The width of the interval indicates substantial uncertainty around the point estimate.

The relative measures are similarly imprecise. The risk ratio is 1.035, with a 95% confidence interval from 0.632 to 1.692; the odds ratio is 1.057, with a 95% confidence interval from 0.472 to 2.366. Each interval includes 1, the value corresponding to no relative contrast. The confidence intervals do not establish equivalence: they include a range of possible effects rather than demonstrating that effects are negligibly small.

In general, confidence intervals describe uncertainty in an estimate under the statistical method used. They do not guarantee that the true effect lies within the displayed limits, and they do not account for possible data-quality issues or unreported choices in analysis. Here, the recalculation uses the posted counts, and the registry narrative also gives percentages that do not match those counts. The record does not report a sponsor analysis or explain the percentage-count inconsistency. That limits how confidently the recalculated interval can be treated as a complete account of the registry's intended 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.

The planning figures are participants per arm, not total events. They are illustrations based on the observed effect, not the trial's original design calculation. The stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is set to the stated fraction of the observed effect. The registry record does not report the original sample-size assumptions or justification for the trial.

The 80% power column describes the planned number of participants per arm under which a study would have an 80% chance of detecting the assumed effect using those planning assumptions, if that effect and model were correct. The 90% power column uses a higher target chance of detecting the assumed effect and therefore gives larger participant requirements for the listed scenarios. These are planning calculations, not a description of what the completed trial achieved.

The rows use 100%, 75% and 50% of the observed effect. Smaller assumed effects are harder to distinguish from random variation, so they require more participants per arm to reach the same target power. The displayed figures are extremely large because the observed effect used for the illustration is small. The curve conveys the same general relationship: planning requirements rise as the target effect becomes smaller. These figures are not observed power.

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 = 0.383; treatment proportion p₁ = 0.396; average p̄ = 0.390.
2. First term: z_1−α/2 × √[2p̄(1−p̄)] = 1.96 × 0.6897 = 1.3517.
3. Second term: z_1−β × √[p₀(1−p₀) + p₁(1−p₁)] = 0.842 × 0.6896 = 0.5804.
4. n = (1.3517 + 0.5804)² / (0.0132)² = 21,270.0, rounded up to 21,271 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 <- 0.382978723404255                          # control proportion
p1 <- 0.39622641509434                          # 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(448123)
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 = 21,271 (80% power), 28,475 (90% power)
 75% of observed effect: n per arm = 37,756 (80% power), 50,544 (90% power)
 50% of observed effect: n per arm = 84,819 (80% power), 113,547 (90% power)
power.prop.test: 21270 
Simulated power at n = 21,271 per arm: 0.801 (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 three outcome measures, including the primary stone-passage outcome and two secondary outcomes: amount of pain medication taken up to seven days after emergency department discharge, and high pain score by treatment group. It reports zero analyses and gives no statistical analysis plan. The plan for defining a primary analysis, prioritizing secondary outcomes, or controlling the chance of false-positive findings across multiple comparisons is not reported in the registry record.

In general, multiplicity arises when several outcomes, time points, or subgroup comparisons are tested. The more comparisons made, the greater the opportunity for a chance finding unless the analysis plan addresses that issue. The registry describes follow-up calls on days 1, 2, 3, 7, 10 and 30, while the primary outcome is based on information up to Day 7. It does not report whether additional time points or subgroup comparisons were analyzed, or whether any multiplicity adjustment was used. The stated secondary objective concerning stone size and ureteral position has no results reported in the registry record.

The outcome description does not report the number of participants with missing or incomplete follow-up, how such outcomes were classified, or whether any imputation or sensitivity analysis was used. The analysis population is not described: the registry record does not say whether the reported outcome counts follow an intention-to-treat, per-protocol, or other population definition. It also does not explain why the outcome counts represent fewer participants than the total enrollment of 127. These omissions make it difficult to assess how the primary comparison relates to all enrolled participants.

In general, missing outcome data can affect a group comparison if the chance of an outcome being unobserved is related to treatment assignment or the outcome itself. The registry record does not provide enough information to assess whether missingness could have influenced this result. No conclusion about the direction or size of any such influence can be drawn from the posted information.

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.

Most frequent non-serious adverse event terms

The registry lists zero serious adverse events among 47 participants at risk in the placebo group and zero among 53 participants at risk in the tamsulosin group. These are the serious adverse event figures recorded for the two groups. The registry does not provide serious adverse event terms because none are listed, and death counts are not reported in the registry record.

The record also lists other, non-serious adverse events for 5 participants in the placebo group and 4 in the tamsulosin group, with 47 and 53 participants at risk, respectively. These counts should be kept distinct from the serious adverse event figures; they are not estimates of event severity or comparative risk after adjustment.

In general, zero recorded events in a group do not establish that an event is impossible or that no risk exists. The registry entry does not describe adverse-event collection procedures, definitions, duration of safety follow-up, or a comparative safety analysis. These figures therefore describe only what is recorded in the registry and do not support broader claims about safety.

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

The posted primary outcome describes stone passage reported within seven days of emergency department discharge. The counts are 18 of 47 in the placebo group and 21 of 53 in the tamsulosin group. A recalculation from those counts gives a risk difference of 0.013, with a 95% confidence interval from -0.178 to 0.205 and an unadjusted p-value of 0.892. The estimate is close to zero, but the interval is wide and includes differences in either direction.

This result does not establish that the treatments are equivalent. An absence of strong statistical evidence for a difference is not the same as evidence that any difference is absent or unimportant. The confidence interval indicates uncertainty, and the registry record does not report an analysis designed to demonstrate equivalence or noninferiority.

The endpoint also has a limited scope. It records whether passage was reported by Day 7, not the exact time at which passage occurred, whether pain resolved, or how much pain medication was used. Although the study objective included time to passage or pain resolution and a possible relationship between response and stone size or ureteral position, those results are not reported in the registry record. Results for the listed secondary outcomes are also not reported.

The narrative percentages of 46.2% and 53.9% do not match the accompanying counts. The comparison is a recalculation from the counts and should be interpreted with that inconsistency in mind. The record does not explain the mismatch or provide a sponsor-reported analysis that could clarify it. Missing-data handling and the analysis population are not reported, which further limits interpretation of the counts as a complete account of all enrolled participants.

16. Why This Trial Matters Statistically

This trial illustrates why an effect estimate should be considered alongside its uncertainty. The recalculated risk difference is 0.013, but its 95% confidence interval ranges from -0.178 to 0.205. The estimate alone is close to zero; the interval shows that the posted data do not pin down the direction or size of the contrast precisely. Reading only the point estimate or only the unadjusted p-value would leave out important information.

The example also shows why outcome definitions matter. A report of stone passage by Day 7 is not interchangeable with time to passage, pain resolution, or pain-medication use. The study objective refers to broader questions than the primary result posted in the registry. When those outcomes are not reported, the primary endpoint cannot answer them by proxy.

Finally, interpretation depends on the quality and completeness of the record. The narrative percentages differ from the posted counts, and the registry does not report missing-data handling, analysis populations, or a statistical analysis plan. Those issues do not change the arithmetic of a recalculation from the counts, but they do limit what can be concluded about the analysis as a whole. The trial is therefore a useful example of separating what a specific posted outcome suggests from what remains unresolved by the registry record.

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.

Several trial-specific limitations constrain interpretation of the posted result. The endpoint narrative's percentages, 46.2% for placebo and 53.9% for tamsulosin, do not match the accompanying counts of 18 of 47 and 21 of 53. The recalculated comparison uses the counts; the registry record does not explain the inconsistency. This makes it important not to treat the narrative percentages and the count-based estimates as interchangeable.

The registry reports total enrollment as 127, while the primary outcome is presented for 47 participants in the placebo group and 53 in the tamsulosin group. It does not explain why the outcome counts account for fewer participants than the enrollment figure, or state whether the figures reflect exclusions, incomplete follow-up, or another reason. Missing outcome data and the analysis population are not described.

The study objective concerns time to passage or resolution of pain, but the primary result posted is a binary report of passage by Day 7. Although follow-up calls occurred at several time points through day 30, results for time to passage are not reported in the registry record. Pain resolution, the listed secondary outcomes, and the stated objective about stone size or ureteral position also have no results reported.

Further limitations include the absence of a reported statistical analysis plan, sponsor-reported comparison, and original sample-size justification. Details of eligibility, treatment dose, treatment duration, outcome confirmation, and missing-data methods are not reported in the registry record. The recalculated estimates are therefore limited to an unadjusted comparison of the posted counts and cannot address these unreported design and analysis details.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: The Efficacy of Tamsulosin in the Treatment of Ureteral Stones in Emergency Department Patients — NCT00448123.
• Registry record last updated 2016-10-12; status last verified 2016-10.
• Results first posted 2016-10-12.
• 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 lists a completed, randomized, triple-masked, parallel-group study comparing tamsulosin with placebo in emergency department patients with ureteral stones. Total enrollment is 127. The primary outcome is participant-reported stone passage by Day 7 after emergency department discharge.

The outcome counts are 18 of 47 participants for placebo and 21 of 53 for tamsulosin. A recalculated unadjusted comparison gives a risk difference of 0.013, with a 95% confidence interval from -0.178 to 0.205 and p = 0.892. The narrative percentages do not match the counts, and the registry record does not explain this inconsistency.

The record also lists two secondary outcomes, but their results are not reported. Missing-data handling, analysis populations, the trial's statistical analysis plan, and its original sample-size justification are not reported in the registry record.