Specificity Trial of the Recombinant Tuberculosis Allergen in BCG Vaccinated Healthy Volunteers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Specificity Trial of the Recombinant Tuberculosis Allergen in BCG Vaccinated Healthy Volunteers (NCT05203068), a na na study. The primary outcome is Number of the Volunteers With the True Negative RTA Result.

2. Clinical Question

In general, specificity describes how often a test is negative among people who do not have the condition the test is intended to detect. Interpreting a specificity estimate depends on how absence of the condition is established and which participants are included. The registry record does not report a reference standard, the detailed method for classifying volunteers as free of tuberculosis, or the analysis population used for the primary outcome. Those details are important to understanding what any estimate would represent, but they cannot be inferred from the stated study aim alone.

3. Trial Design

The registry record describes a completed, single-group diagnostic-test study sponsored by the National Medical Research Center of Phthisiopulmonology and Infectious Diseases. The listed enrollment is 150. The listed start date is 2021-11-24, and the primary completion date is 2022-01-18. The phase is recorded as NA. The intervention is recombinant tuberculosis allergen, also identified as RTA or CFP10-ESAT6, administered intradermally. The record specifies 0.2 µg/0.1 mL on the middle of the forearm.

There is no separate comparison arm described. Allocation is listed as NA, masking as NONE, and the model as SINGLE GROUP. Thus, this record describes assessment following administration of the diagnostic test, not a randomized trial comparing test results between intervention groups. A control-group result, a placebo result, and a between-group treatment effect are not reported in the registry record.

The primary outcome is the number of volunteers with a true negative RTA result. Its description refers to the absolute number and percentage with negative and positive test results, based on an infiltrate assessment at hour 72. Two secondary outcomes concern participants with local adverse reactions within 72 hours and participants with general and local adverse reactions within 28 days after administration. The registry lists three outcome measures in total, but does not provide the primary result or detailed results for those secondary outcomes beyond the adverse-event entries described in the safety reading.

The record marks the study as COMPLETED. Completion status indicates the registry status, not that results for each outcome are present in the record. A protocol, the sample-size justification, detailed eligibility criteria, the method of outcome assessment, and the statistical analysis plan are not reported in the registry record.

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.

RTA Result Assessment, 72 Hours

RTA Safety Assessment, 28 Days

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.

Population: 150 healthy adult subjects

6. Primary Endpoint

The registry lists the primary outcome as Number of the Volunteers With the True Negative RTA Result, measured over hour 72.

The primary endpoint is titled “Number of the Volunteers With the True Negative RTA Result.” It is a participant count, and the endpoint description also specifies reporting the absolute number and percentage of volunteers with negative and positive results. The assessment is based on the infiltrate 72 hours after the test application; the timeframe is listed as hour 72. The endpoint is intended to describe the test’s negative and positive results in the study population.

The choice of a true-negative endpoint aligns with the stated aim of evaluating specificity in BCG-vaccinated healthy adults at low risk of tuberculosis. In general, specificity concerns negative test results among people considered not to have the target condition. A count gives the number of participants classified in an outcome category, while a percentage expresses that count relative to a defined denominator. The denominator and handling of participants without an evaluable assessment are not reported in the registry record.

The label “true negative” requires a basis for determining that a participant does not have the condition. The registry description identifies the volunteers as healthy and at low risk, but the reference standard or classification procedure used to establish true-negative status is not reported in the registry record. The actual negative and positive counts, percentages, and any uncertainty estimates for this endpoint are also not reported. Accordingly, the endpoint definition and intended timing are available, but the posted record does not supply the result needed to quantify observed specificity.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The outcome is a participant count, with the endpoint description also calling for the percentage of volunteers with negative and positive RTA results. This is a binary-outcome framework: each assessed participant would be classified into an outcome category, such as negative or positive, according to the assessment rules. The registry record does not report those rules in detail or the observed counts. It also does not report how unevaluable assessments, withdrawals, or missing results were handled.

What does a count or percentage describe?

A count is the number of participants recorded in a particular category. A percentage relates that count to a denominator, such as participants assessed or participants enrolled. The choice of denominator matters: a percentage based on everyone enrolled can differ from one based only on participants with an interpretable test result. The registry endpoint description says that an absolute number and percentage are intended, but the denominator used for the percentage is not reported in the registry record. Neither the count nor the percentage for the primary outcome is posted.

In general, a point estimate is the value calculated from the observed participants. A confidence interval describes uncertainty around an estimate under the assumptions of the analysis; it is not a range that contains every individual participant’s result. Wider intervals generally indicate less precision, while narrower intervals indicate more precision, conditional on the analysis and its assumptions. No confidence interval or other uncertainty estimate for the primary endpoint is reported in the registry record, so its precision cannot be assessed from this entry.

How does specificity relate to this endpoint?

As a general statistical concept, specificity is the proportion of people without the target condition who have a negative test. Calling a result “true negative” therefore requires a way to establish that participants do not have the condition. The registry record describes the volunteers as healthy and at low risk of tuberculosis and states the aim of determining specificity. It does not describe a reference standard or the procedures used to classify disease status. The meaning of a calculated specificity estimate would depend on those procedures, as well as on the population studied.

The planned endpoint is an assessment of the infiltrate at hour 72 after the intradermal test. In general, an endpoint definition needs clear assessment criteria and consistent timing so that participants are classified in a comparable way. The registry describes the time and the general basis of assessment, but does not report the threshold or detailed criteria for classifying infiltrate results. It also does not say whether assessors were trained, whether assessments were independently checked, or whether any repeat readings were used. These methods are not reported in the registry record and should not be inferred.

What can a single-group design estimate?

The model is listed as SINGLE GROUP, with no separate comparator. In general, a single-group diagnostic study can describe the distribution of test results in the participants who receive the test. It does not, by itself, estimate a contrast between randomized groups. It also cannot establish comparative performance against another test unless such a comparison is separately designed and reported. In this record, no comparator test or control result is listed. Allocation is NA and masking is NONE. Further details about the conduct of assessment are not reported in the registry record.

The posted sample-size assumptions describe a planning illustration based on an observed effect, with two-sided significance level 0.05, equal allocation between two arms, and a normal approximation. The stated effect to detect is a fraction of the observed effect. These are planning assumptions, not a report of the trial’s own design justification. They also describe a hypothetical two-arm framework, whereas the registry record identifies this study as single-group. Any sample-size figures based on those assumptions are planning illustrations, not observed power and not evidence that the study had a particular probability of detecting an effect. The trial’s own sample-size justification is not reported in the registry record.

In general, power is a design quantity tied to a specified effect, variability, analysis, and significance level. It cannot be recovered as a meaningful measure of what happened merely by looking at the observed result. A planning calculation that uses an observed effect is especially not a substitute for a prespecified design calculation. No observed primary effect is posted in this record, and no trial-specific sample-size rationale or statistical analysis plan is reported. No new estimate can be inferred from the enrollment count alone.

What does over-dispersion mean for a count outcome?

In general, over-dispersion occurs when count variability is greater than a chosen statistical model expects. It can make standard errors too small if a model assumes less variability than the data contain. This issue is relevant to some count models, but the primary endpoint is described as a count of participants with a binary test classification, rather than a rate of repeated events. The registry record does not identify a count-regression model or report a model-based analysis. It would not be appropriate to claim that over-dispersion was assessed or that any particular model was used.

For a binary participant outcome, analysts often focus on a proportion and its uncertainty, while accounting for the denominator and the study design. General methods can differ in their assumptions, especially when event counts are sparse or when participants are clustered. The registry record does not report the method used for the primary endpoint, the standard error method, or whether any adjustment was planned. No analysis entries are listed. That absence means the registry does not document an analysis in the posted record; it does not establish that no analysis was conducted elsewhere.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists one primary outcome and two secondary outcomes. The primary outcome concerns negative and positive RTA results assessed at hour 72. The secondary outcomes concern local adverse reactions within 72 hours and general and local adverse reactions within 28 days. The registry record does not report a multiplicity plan, such as how interpretation would account for examining more than one outcome. It also does not report a hierarchy among secondary outcomes or whether any outcomes were exploratory.

In general, multiplicity arises when several hypotheses or outcomes are considered. If each is tested separately, the chance of at least one apparently unusual result can increase, depending on the analyses and their relationship. A prespecified approach can clarify which outcome is primary and how other findings should be interpreted. Here, the primary and secondary outcome descriptions are listed, but the statistical plan for handling multiple outcomes is not reported in the registry record. No p-values or outcome analyses are reported in the posted results, so there is no multiplicity-adjusted result to interpret.

Missing-data methods are also not reported in the registry record. The enrollment is 150, but the record does not state how many participants completed the hour 72 assessment, whether any test results were unevaluable, or how missing assessments were handled in the primary analysis. It does not specify whether participants were analyzed according to a defined analysis population or whether exclusions were made. The analysis population field is blank.

These omissions matter because a count or percentage depends on who is included in its denominator. In general, excluding participants with missing assessments can affect an estimate if the missingness is related to test results or participant characteristics. The registry record does not provide enough information to assess whether missing data occurred or what assumptions would be appropriate. No analysis entries are listed, which describes the record’s reporting status rather than proving that no analyses were performed.

11. Safety Results

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

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 1% reporting threshold.

Most frequent non-serious adverse event terms

The registry’s safety fields list 150 at risk in the serious adverse-event category and 0 affected. In the other adverse-event category, 150 are listed at risk and 1 is listed as affected. Deaths are recorded as 0. These figures are counts in the registry record; they should not be read as a detailed account of the type, severity, timing, or cause of an event.

The listed secondary outcomes refer to local adverse reactions within 72 hours and general and local adverse reactions within 28 days after RTA administration. The safety entries do not identify which outcome period the other-category affected participant belongs to, describe the event, or state whether it was local or general. The registry record also does not provide a narrative of serious events, because the serious affected count is 0, or detail how events were collected and classified. These details are not reported in the registry record.

In general, “at risk” identifies the number of participants included as a denominator for the corresponding safety category, while “affected” is a count of participants recorded with an event in that category. The posted figures are descriptive and do not provide a comparison with an untreated group. Because this is a single-group record, the safety counts alone cannot establish whether an event was caused by the test. They also do not replace the missing primary diagnostic outcome.

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

The registry record documents a completed, single-group study of intradermal RTA in BCG-vaccinated healthy adults described as having low risk of tuberculosis. It specifies the intended primary assessment: the count and percentage of volunteers with negative and positive test results based on an infiltrate assessment at hour 72. It also records an enrollment of 150 and gives selected safety counts. These details clarify the study question and setting.

The record does not report the primary negative or positive counts, the percentage of true-negative results, or an uncertainty interval. It therefore does not show a numerical estimate of specificity in the posted results. The stated aim is not evidence that a particular degree of specificity was observed. The record also does not provide the reference standard or other procedures used to confirm that participants were free of the target condition, which would be important for interpreting a true-negative classification.

Because no separate comparator group is listed, the study does not provide a randomized comparison with another diagnostic test or a control group. Its design, as recorded, is suited to describing outcomes in the enrolled group, not to attributing differences between groups. The posted safety data list 0 affected in the serious category, 1 in the other category, and 0 deaths, but the event detail is not reported in the registry record.

In general, a registry entry is most informative when its outcome definitions, analysis populations, missing-data handling, and statistical methods accompany the numerical results. Those details are not reported. The record therefore supports a description of the trial’s intended question, intervention, design, timing, and limited safety counts. It does not support a conclusion about the magnitude or precision of the primary diagnostic result, comparative test performance, or how broadly any unreported result would apply.

13. Why This Trial Matters Statistically

This trial is statistically interesting because its stated objective is diagnostic specificity in a population defined by prior BCG vaccination and low tuberculosis risk. That context makes the definition of a true negative central to interpretation. A test result alone does not establish that a participant is truly negative; the classification depends on how disease absence is determined. The registry record gives the study aim and population description but does not report the reference standard or detailed classification procedure.

The single-group structure also shapes what can be learned. It permits a descriptive assessment of test outcomes among the volunteers who received RTA, but it does not supply a randomized control comparison. There is no comparator arm listed against which to quantify relative diagnostic performance. Clear distinction between a within-group description and a comparative effect is important when reading studies that use the language of evaluation or specificity.

The record also illustrates why outcome reporting and design details are both needed. It identifies the primary endpoint and its timing, but does not report the observed result, the analysis population, missing-data handling, or statistical analysis plan. Without those elements, readers cannot assess the estimate’s precision or determine how it was calculated. The enrollment of 150 does not on its own establish how many participants contributed to an endpoint analysis.

Finally, planning illustrations should not be confused with evidence from the completed study. The stated sample-size assumptions describe a hypothetical equal-allocation, two-arm calculation, whereas this trial is recorded as single-group. Such illustrations are not observed power and do not substitute for a trial-specific sample-size justification. The registry record’s value lies in making the intended diagnostic question and design visible, while its missing outcome and analysis details limit statistical interpretation.

14. 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 most consequential limitation for statistical interpretation is that the primary outcome result is not reported in the registry record. The record describes the intended count and percentage of negative and positive RTA results at hour 72, but does not give the counts, percentages, or uncertainty. The posted information therefore cannot quantify the observed specificity or its precision.

The population is described as healthy, previously BCG-vaccinated adults at low risk of tuberculosis, but detailed eligibility criteria and recruitment methods are not reported in the registry record. Nor is the method for establishing the absence of tuberculosis described. Without a reported reference standard or classification procedure, the basis for calling an outcome a true negative remains unclear. The detailed threshold used to interpret the infiltrate is also not reported.

The design is single-group, with no separate comparator and masking listed as NONE. The record does not describe who assessed the infiltrate, whether assessors knew participant characteristics, or whether assessment procedures were standardized. It does not report a statistical analysis plan, the primary analysis population, missing-data handling, or a sample-size justification. The analysis population field is blank, and no analysis entries are listed. These record omissions prevent assessment of how the planned endpoint was analyzed; they do not establish that the procedures were absent from the study itself.

Safety reporting is limited to counts: 0 affected in the serious category, 1 in the other category, and 0 deaths. The event description, timing, and relationship to the listed adverse-reaction outcomes are not reported in the registry record. The registry status is COMPLETED, but completion status does not resolve these reporting limitations.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Specificity Trial of the Recombinant Tuberculosis Allergen in BCG Vaccinated Healthy Volunteers — NCT05203068.
• Registry record last updated 2023-08-25; status last verified 2022-10.
• Results first posted 2023-08-25.
• 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.

18. Record Summary

NCT05203068 is a completed, single-group diagnostic-test study titled “Specificity Trial of the Recombinant Tuberculosis Allergen in BCG Vaccinated Healthy Volunteers.” The registry lists 150 enrolled, a start date of 2021-11-24, and a primary completion date of 2022-01-18. The intervention is intradermal RTA, identified as CFP10-ESAT6, at 0.2 µg/0.1 mL on the middle of the forearm. The population is described as healthy, previously BCG-vaccinated adults at low risk of tuberculosis.

The primary endpoint is the number of volunteers with a true-negative RTA result, with negative and positive results assessed from the infiltrate at hour 72. Two listed secondary outcomes concern local adverse reactions within 72 hours and general and local adverse reactions within 28 days. The primary outcome result and detailed analysis methods are not reported in the registry record. Safety fields list 0 affected in the serious category, 1 in the other category, and 0 deaths. No separate comparator group is listed.