Screening for Latent Tuberculosis Infection (LTBI) in US Army Recruits: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Screening for Latent Tuberculosis Infection (LTBI) in US Army Recruits (NCT00804713), a na na study. The primary outcome is TST Induration Will be Interpreted Relative to Risk, in Accordance With Published CDC Guidelines..

2. Clinical Question

The study’s overall objective was to assess the feasibility and potential impact of targeted testing for latent tuberculosis infection among military recruits. The registry describes universal Mantoux tuberculin skin testing as the existing policy and raises the concern that low-risk recruits may have TST reactions. Its central hypothesis was that questionnaire-based targeted testing could reduce unnecessary testing among low-risk recruits without affecting identification of higher-risk recruits.

A secondary hypothesis concerned discordant results between the TST and interferon-gamma release assays: the study proposed that some discordance might be explained by cross-reactivity to non-tuberculous mycobacteria with the TST. These are study questions and hypotheses, not findings. The registry record does not report results that establish whether either hypothesis was supported.

The recorded primary measure is a count of participants with positive TST results across risk-based interpretations. The endpoint description says risk factors were identified by questionnaire and that the approach followed the cited CDC guideline criteria; it does not give the resulting counts by risk category. Accordingly, the stated question is about how results are classified and counted, not a documented estimate of screening accuracy or a randomized comparison of strategies.

3. Trial Design

The registry record describes a completed, single-group study with double masking recorded. The allocation entry is NA, and the record does not describe a randomized allocation or a separate control arm. All study participants are described as receiving the TB skin test, Battey skin test, QFT-GIT, and T-Spot. The record does not explain the practical masking procedures or identify who was masked.

The study is listed under latent tuberculosis infection. Its overall objective was to assess the feasibility and potential impact of targeted testing based on questionnaire risk factors alongside two interferon-gamma release assays. The recorded primary endpoint applies risk-stratified interpretation to the TST. The outcome description states that this methodology was used because it is accepted for the TST and was prespecified for that test in the protocol. It was not applied to QFT, T-Spot, or BST in the reported primary endpoint.

The registry lists an enrollment of 2017. The endpoint description uses 1803 because valid results for all four tests were available for that number of participants. These counts refer to different aspects of the record and should not be treated as interchangeable denominators. The adverse-event record gives 1978 as the number at risk for serious and other adverse events. The registry does not explain how the analysis populations for these outcomes were selected or why their counts differ.

The record gives a start date of 2009-03, a primary completion date of 2009-06, and a status of COMPLETED. Phase and allocation are listed as NA. The sponsor is the Henry M. Jackson Foundation for the Advancement of Military Medicine. The registry record does not report a statistical analysis plan, sample-size justification, interim analyses, or details of the recruitment and follow-up procedures. The design therefore supports descriptive reading of the recorded tests and counts, but it does not provide a randomized between-group treatment-effect estimate.

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: 39 participants were enrolled but lost to follow-up before skin testing or blood draw were performed. This was due to the administrative requirements of the basic training setting, not because of the study itself.

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.

Population: recruits at Fort Jackson, SC in 2009 between April 1 and June 11

6. Primary Endpoint

The registry lists the primary outcome as TST Induration Will be Interpreted Relative to Risk, in Accordance With Published CDC Guidelines., measured over 48-72 hrs post administration.

The primary endpoint counts participants with positive tuberculin skin test results after interpreting induration in relation to risk. Risk was stratified using questionnaire-identified risk factors, and the registry specifies the 5, 10 and 15 mm criteria described in the cited CDC recommendations. The stated timeframe is 48-72 hrs post administration. The endpoint is expressed as a number of participants, rather than as a continuous measure of induration or a comparison of treatment effects.

Risk-based thresholds matter because interpretation of a skin-test reaction depends on the participant’s risk category under the stated guideline approach. In general, a threshold-based endpoint turns a measurement into a positive or negative classification, making it possible to count results under specified criteria. That classification does not, by itself, establish the presence or absence of infection in each individual or indicate the diagnostic performance of another test.

The record says the primary endpoint reports only a risk-stratified interpretation for the TST. It states that this approach is accepted for the TST and was prespecified for it in the protocol; the same risk-stratified method was not specified for QFT, T-Spot, or BST. The endpoint description notes that 1803 participants had valid results for all four tests. It does not provide the positive counts for the TST risk categories, so the magnitude or distribution of the primary endpoint cannot be described from the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The statistical information in the registry record is primarily descriptive. It identifies a count-based primary endpoint, a set of administered tests, and a study population, but it does not report the primary outcome counts or analyses. General statistical concepts can clarify what the endpoint and design could support; they cannot substitute for the unreported results.

What does the primary count represent?

The primary endpoint counts participants with positive TST results after risk-based interpretation. Questionnaire-identified risk factors determine the risk stratum, and the record names the 5, 10 and 15 mm criteria. In general, a count is a direct summary of how many observations meet a specified definition. To interpret such a count, readers need the denominator, the classification rule, and a clear account of which observations were available. The endpoint description gives 1803 as the number with valid results for all four tests, but it does not provide the positive counts by category.

A threshold-based outcome is not the same as a continuous measurement. General statistical explanation: when a measured value is classified using a threshold, the resulting count reflects both the observed values and the rule used to label them positive. The registry’s endpoint description explains the risk-based interpretation, but does not include the distribution of induration or a table of classifications. Therefore the endpoint’s definition is clear enough to describe, while its observed pattern is not reported in the registry record.

What does a single-group design allow?

The study is listed as SINGLE GROUP, and all participants are described as receiving the same set of tests. No randomized comparator is recorded. General statistical explanation: a single-group study can describe the results observed in its participants and can examine whether different tests produce matching or discordant classifications. It cannot, without a suitable comparison design and analysis, establish the causal effect of one screening strategy relative to another. The study’s stated objective includes assessing the potential impact of targeted testing, but the record does not report a direct randomized comparison of universal and targeted approaches.

The registry records double masking, but does not identify who was masked or how masking was implemented. Masking can reduce the influence of knowledge about other information on how outcomes are assessed, but the meaning of a masking label depends on the procedures. Those procedures are not reported in the registry record, so the practical protection against assessment bias cannot be evaluated from the label alone.

How should multiple tests be understood?

The study administered the TB skin test, Battey skin test, QFT-GIT, and T-Spot. The registry describes two interferon-gamma release assays and identifies Positive QFT-GIT Result as a secondary outcome. General statistical explanation: when multiple tests are performed in the same participants, their results may be compared within participants, but one test’s result does not automatically serve as a definitive reference standard for another. Assessment of agreement or diagnostic accuracy requires explicit definitions and suitable analyses. The registry record does not report the cross-tabulations, agreement measures, reference standard, or test-performance estimates needed to make those assessments.

The record’s secondary hypothesis proposes that some discordant TST and interferon-gamma release assay results might be explained by cross-reactivity to non-tuberculous mycobacteria. This is a proposed explanation, not an established mechanism in the reported results. No analysis of discordance or evidence attributing it to cross-reactivity is reported in the registry record.

What would uncertainty measures add?

General statistical explanation: a confidence interval describes a range of values compatible with the data and the chosen statistical method, while its width indicates precision. For a count or proportion, uncertainty depends on the data and analysis. The registry record does not report a confidence interval for the primary endpoint, and the underlying category counts are not reported. No numerical precision assessment can therefore be made from the registry record.

The record lists zero analyses. That entry does not provide a statistical analysis plan or explain how outcomes were analyzed. No inferential method, adjustment procedure, or treatment of clustering is reported. General statistical explanation: over-dispersion matters when observed variability exceeds what a chosen probability model assumes; using a model that fails to account for it can understate uncertainty. The record does not identify a model or provide data from which over-dispersion could be assessed, so that issue cannot be evaluated for these results.

How should planning illustrations be read?

The sample-size material is characterized as a planning illustration computed from an observed effect, not as the study’s own design calculation. It assumes a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a stated fraction of the observed effect. General statistical explanation: such calculations ask how many participants per arm might be needed under specified assumptions to detect a target effect with a chosen level of power. They do not show that those participants were enrolled in a randomized comparison, and they are not observed power. The registry record does not report the study’s own sample-size justification or provide the observed effect and planning results in the information available for this interpretation.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and zero analyses. It identifies Positive QFT-GIT Result as a secondary outcome, but the complete outcome results and analysis methods are not reported in the registry record. A listed outcome count does not reveal which comparisons were planned, which were tested, or how multiplicity was handled.

General statistical explanation: when several outcomes or comparisons are examined, the chance of at least one apparently notable result can increase unless the analysis plan accounts for the number and structure of tests. The registry record does not report a multiplicity procedure, a hierarchy among outcomes, or a plan for interpreting multiple comparisons. It is therefore not possible to determine how any statistical claims were intended to account for the multiple tests or outcomes.

The recorded populations differ by purpose: enrollment is 2017, the primary outcome description identifies 1803 with valid results for all four tests, and the adverse-event record lists 1978 at risk. The registry record does not explain these differences or specify a single analysis population applicable to every outcome. It also does not report a missing-data method, reasons for missing test results, or a comparison of participants with and without complete results. No attrition count should be inferred from these entries.

General statistical explanation: missing outcome data can affect interpretation when availability is related to participant characteristics or test results. Without details about missingness and the analysis population, readers cannot assess whether the participants with complete tests represent all enrolled participants. The registry record does not report an intention-to-treat analysis or another named population definition. The endpoint description’s complete-test count should therefore be read as the stated basis for that endpoint description, not as a fully documented missing-data strategy.

11. Safety Results

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

Other (non-serious) adverse events

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

The serious adverse-event record lists 1978 participants at risk and zero affected. The other adverse-event entry also lists 1978 at risk and zero affected. These are recorded counts for the registry’s all-participant group; they should not be combined into a new total.

A zero count means that no affected participants are recorded for those entries in the registry record. It does not establish that the underlying risk is exactly zero, and it does not show how events were sought, defined, attributed, or followed over time. General statistical explanation: a count alone does not describe the precision of an estimate; confidence intervals or other uncertainty measures would be needed to characterize how compatible the data are with a range of event risks. Such measures are not reported in the registry record.

The adverse-event denominator differs from the enrollment and primary endpoint counts. The record does not explain the reason for that difference or give an adverse-event observation period. Deaths are not reported in the registry record. The safety entries should therefore be read narrowly as recorded counts, not as a complete account of event ascertainment or a comparative safety analysis.

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

The record describes a study of latent tuberculosis infection screening in US Army recruits, with all participants administered four tests and the primary outcome defined as risk-stratified TST-positive counts. It establishes the study’s objectives, the tests used, and the criteria named for the primary endpoint. It does not report the category-specific primary counts, so the observed frequency of positive TST results cannot be described from the registry record.

The stated hypotheses concern whether targeted testing could reduce unnecessary testing among low-risk recruits without affecting identification of higher-risk recruits, and whether cross-reactivity to non-tuberculous mycobacteria might explain some discordant results. These statements explain the motivation for the study, but they are not results. The registry record does not report enough outcome data or analysis to determine whether either hypothesis was supported.

The single-group design and lack of a recorded randomized comparator limit causal interpretation. The study can be understood as examining screening tests in one participant group, but the registry record does not establish the effect of a targeted strategy compared with universal testing. Likewise, the fact that several tests were administered does not by itself establish diagnostic accuracy, agreement, or superiority of one test. Those conclusions require reported results and analyses that are not present in the registry record.

The adverse-event entries report zero affected participants among 1978 at risk for both serious and other adverse events. These counts are informative as registry entries, but without event-collection methods, follow-up details, or precision estimates they do not establish an absence of risk. Enrollment, complete-test availability, and adverse-event counts refer to distinct record entries, and the registry does not explain their relationship.

Overall, the record supports a description of the study question and endpoint definition, not a conclusion about the performance or impact of the screening approach. The absence of reported primary results and statistical analyses is a key boundary on what can be inferred.

13. Why This Trial Matters Statistically

This study illustrates a common statistical distinction between a research question and an analyzed result. The registry presents a clear objective—assessing targeted testing and the use of multiple tests—but the primary endpoint description alone is not enough to answer whether the approach changed screening outcomes. Counts by risk category and an analysis relating those counts to the stated objective would be needed to assess the question.

It also highlights why denominators need explicit context. The record gives 2017 enrolled participants, 1803 with valid results for all four tests for the primary endpoint description, and 1978 at risk in the adverse-event entries. Each value serves a different role in the record, and the relationship among them is not explained. Treating them as interchangeable would obscure which participants contribute to each result.

Risk-based interpretation is another statistical point of interest. A TST result is interpreted according to both induration and the participant’s risk classification under the stated criteria. That makes the questionnaire-based risk assessment part of the endpoint definition rather than a separate descriptive detail. The registry does not provide results by risk category, so the rationale can be understood without assuming the proposed targeting approach achieved its objective.

Finally, the record distinguishes planning calculations from the study’s own design and results. A planning illustration based on an observed effect is not evidence of an observed comparison, and it is not observed power. These distinctions matter when readers encounter sample-size material alongside a single-group registry record. The design, endpoint, denominators, and reporting gaps all need to be considered together before drawing statistical conclusions.

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 primary limitation for interpreting this trial is that the registry record defines the primary endpoint but does not report its observed counts. Without the TST-positive results by risk category, the primary outcome’s size and distribution cannot be assessed. The record also does not report a confidence interval or a p-value for that endpoint.

The design is recorded as single-group, with no separate comparator or randomized allocation. Therefore, the record does not support a randomized estimate of the effect of targeted testing versus universal testing. Although the study administered four tests, the registry does not report the cross-tabulations or agreement analyses needed to evaluate concordance, discordance, or diagnostic performance.

The primary endpoint description uses 1803 participants with valid results for all four tests, while enrollment is listed as 2017 and the safety entries list 1978 at risk. The registry does not explain how these populations relate, why results were unavailable for some participants, or whether missingness could affect interpretation. It also does not describe the analysis population or a missing-data method.

Other limitations include the lack of a reported statistical analysis plan, sample-size justification, interim-analysis information, or details of how double masking was implemented. The record lists five outcome measures and zero analyses, but does not explain multiplicity handling or provide the results needed to assess secondary outcomes. The safety record gives counts without a stated observation period or event-collection methods. These omissions limit conclusions about both the screening objectives and the completeness and precision of the reported safety information.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Screening for Latent Tuberculosis Infection (LTBI) in US Army Recruits — NCT00804713.
• Registry record last updated 2023-03-29; status last verified 2023-03.
• Results first posted 2014-10-15.
• 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

The registry record for NCT00804713 describes the completed study “Screening for Latent Tuberculosis Infection (LTBI) in US Army Recruits,” sponsored by the Henry M. Jackson Foundation for the Advancement of Military Medicine. It lists latent tuberculosis infection as the condition, SINGLE GROUP as the model, and DOUBLE as the masking designation. Phase and allocation are recorded as NA.

The record lists enrollment of 2017, a start date of 2009-03, and a primary completion date of 2009-06. All study participants are described as receiving the TB skin test, Battey skin test, QFT-GIT, and T-Spot. The primary endpoint is a risk-stratified count of positive TST results, assessed 48-72 hrs post administration. The endpoint description identifies 1803 participants with valid results for all four tests. Primary outcome counts and statistical analyses are not reported in the registry record.