A School-Based Intervention to Reduce Lyme Disease: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A School-Based Intervention to Reduce Lyme Disease (NCT00594997), a randomized na study. The primary outcome is The Incidence of Lyme Disease Among Children and Families Living in an Endemic Area Using an Educational Intervention.

2. Clinical Question

The study also sought to evaluate children’s knowledge, attitudes, confidence, intentions, and prevention practices. These behavioral goals are relevant to the proposed pathway from education to preventive action, but they are not interchangeable with the primary disease-case outcome. The registry record does not report a complete sequence of measured steps connecting the educational session, behavior change, tick density, and incident disease.

Thus, the clinical question concerns both a disease outcome and a behavioral outcome, while the posted results support different levels of interpretation for each. A randomized design can support a comparison between assigned groups, but the registry record does not report enough information to assess the primary disease comparison statistically. The behavioral outcome has a posted group comparison, but its scale and analysis details require cautious interpretation.

3. Trial Design

The registry describes NCT00594997 as a randomized, parallel-group study with no masking. It lists Brigham and Women’s Hospital as sponsor and an enrollment of 3570. The study began in 2004-04, had primary completion in 2006-03, and is marked completed. The registry does not report the unit of randomization, the allocation procedure, or whether assignments were concealed.

Students in the education group received a 45 minute interactive presentation and a 30 minute health education entertainment session by a juggler. Control participants completed pre and post surveys and were scheduled to receive the intervention after the post-survey. That delayed offer makes the groups different in their access to the program during the outcome assessment period. The registry does not report whether the control group received other education or how intervention delivery and attendance were recorded.

The primary outcome description compares parent reports of new Lyme disease cases during the 12 months before baseline with reports a year later, after the educational intervention. The record says that new cases required confirmation by medical record review. Its timeframe is stated as baseline - 1 year. The record does not explain precisely how the before-and-after information was converted into the between-group primary comparison, or identify the statistical model used for it.

A secondary outcome concerns children’s self-confidence, intention, and actual practice of prevention behaviors. The posted measure is reported in units on a scale, with group means and standard deviations. A linear regression analysis is listed for the groups. The registry does not report the scale’s items, range, scoring rules, validation, or the analysis population.

Randomization can help reduce systematic differences between groups at the point of assignment, but it does not by itself clarify how outcomes were measured or analyzed. In particular, if assignment occurred at a school level, outcomes from students in the same school might be correlated. The randomization unit and any adjustment for such correlation 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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Number of Lyme cases reported in the intervention and control groups

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 The Incidence of Lyme Disease Among Children and Families Living in an Endemic Area Using an Educational Intervention, measured over baseline - 1 year.

The primary endpoint is the number of incident Lyme disease cases reported for children and families in the intervention and control groups. Parents were asked at baseline about new Lyme disease cases within the past 12 months, and the question was asked again a year later after the educational intervention. The description says that new cases had to be confirmed by medical record review.

Counting incident cases is intended to address whether disease occurred during the observation period, rather than only whether participants learned about prevention or intended to use it. It is therefore a more direct disease outcome than knowledge, confidence, or self-reported preventive behavior. Medical record confirmation is described as a condition for considering a reported new case, which may help distinguish confirmed cases from unverified reports. The registry does not explain how records were obtained, how cases were adjudicated, or whether confirmation was applied consistently across groups.

The posted primary endpoint information does not yield an estimable between-group comparison in the available record. The record does not report an analysis estimate, confidence interval, or p-value for this endpoint, and the result is marked as not estimable for a two-arm comparison. Consequently, the primary endpoint’s intended role is clear, but its comparative result and precision cannot be assessed from the registry record.

There is also no reported account of how missing parent responses, repeat reports, or differences in observation time were handled. These details matter because an incident-case count depends on ascertainment as well as disease occurrence. Without a reported comparison and its methods, the case-count endpoint cannot establish the direction or size of a group difference.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Randomization assigns participants or groups to study conditions by chance. In general, this can make the groups more comparable at the start of a study and reduce confounding by factors that influence both assignment and outcome. It does not guarantee that the groups are identical, and it does not remove bias caused by missing observations, outcome measurement, or deviations from the assigned intervention. This study is described as randomized, but the randomization unit and procedure are not reported in the registry record. If schools rather than students were assigned, students within a school could have related outcomes; whether analyses accounted for that possibility is not reported.

What does the secondary mean difference represent?

A mean is the arithmetic average of measured values in a group. The posted secondary outcome gives a mean and standard deviation for each group and a simple unadjusted recalculation of their mean difference. The recalculated mean difference of 1.02 describes the education-group mean relative to the control-group mean on the recorded scale. It is not an adjusted effect estimate from the listed regression model. Because the registry does not describe the scale’s range, items, or scoring direction, the clinical or behavioral meaning of a one-unit change cannot be established from the record alone.

A standard deviation describes how spread out individual measurements are around a group mean. It is not the same as the uncertainty in the mean difference. The group standard deviations are 1.31 and 1.3, while the recalculated comparison also reports an interval for the mean difference. Neither the standard deviations nor the interval describe every participant’s experience; they summarize different aspects of the data.

How should the confidence interval be read?

In general, a confidence interval expresses the precision of an estimate under the statistical model used to calculate it. The recalculated 95% confidence interval runs from 0.934 to 1.106 for the mean difference. A narrower interval indicates greater precision than a wider interval would, although precision does not establish that an outcome is important or that the analysis is free of bias. The interval is based on an unadjusted recalculation from the posted group summaries, not on the registry’s regression model. It should therefore be read as a separate summary-statistic analysis.

The registry lists a linear regression analysis and reports p < 0.001 for the secondary outcome. In general, a p-value describes how unusual data at least as incompatible with a null hypothesis would be under the assumptions of the specified model. It is not the probability that the null hypothesis is true, nor does it measure the size or practical importance of a result. The model details, including covariates and any adjustments for the study design, are not reported in the registry record. The recalculated unadjusted p-value is p <0.001; it should not replace or be conflated with the sponsor’s listed regression result.

Why might count outcomes need different methods?

The primary endpoint is a count of cases, not a continuous score. In general, methods for counts may need to account for the shape of the count distribution, differences in observation time, and variation beyond what a simple count model would expect. Over-dispersion means that observed counts vary more than a model’s basic assumptions allow; if present and ignored, uncertainty estimates may be inaccurate. The registry does not report a model for the primary count outcome, an assessment of over-dispersion, an exposure-time adjustment, or a primary comparison estimate. It is therefore not possible to determine which count-data method, if any, was used.

What do planning illustrations mean?

Sample-size illustrations based on an observed effect are planning calculations, not observed power and not a justification for the original study’s enrollment. The posted planning assumptions specify a two-sided significance level of 0.05, equal allocation, and a normal approximation, with planning based on stated fractions of the observed effect. In general, planning for a smaller effect requires more participants per arm to achieve a chosen power, under otherwise fixed assumptions. Such calculations depend on the effect used and the assumptions about variability and design. The registry does not report the trial’s own sample-size justification, target effect, or design-stage power calculation. The planning illustrations should therefore not be used to claim that the study was adequately powered for its primary disease endpoint.

In general, an analysis should also state which participants were included, how missing outcomes were addressed, and whether the analysis followed randomized assignment. Those choices affect interpretation and reproducibility. The registry record does not report these details for the primary outcome or the secondary regression analysis. The available numbers permit a limited description of the posted secondary summaries, but not a full reconstruction of either analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists a primary disease-case outcome and a secondary behavioral outcome. It does not report whether the outcomes were prespecified in a statistical analysis plan, whether there were additional analyses not posted, or whether any method was used to control the overall chance of false-positive findings across outcomes. The number of planned hypotheses and any testing hierarchy are not reported in the registry record.

In general, multiplicity arises when several outcomes, comparisons, time points, or analysis choices are examined. If each is tested without adjustment, the chance of at least one nominally significant result can increase. Adjustment methods or a prespecified hierarchy can help address that issue, but they may also affect the precision or interpretation of individual tests. The registry record does not establish whether the reported behavioral p-value was adjusted for other outcomes or analyses. It should therefore be read as a reported result without an assumed multiplicity correction.

Missing-data procedures are not reported for either the primary or secondary outcome. The record does not say how many participants had outcome data at each assessment, how parent nonresponse was handled, or whether any imputation or sensitivity analysis was performed. It also does not describe the analysis population, such as whether all randomized participants were analyzed according to assignment. These details are important because the people with observed follow-up data may differ from those without it.

The primary endpoint description relies on parent reports and medical record confirmation. The registry does not report the completeness of medical record review, how unconfirmed reports were treated, or whether outcome ascertainment was blinded to group assignment. The study itself is listed as unmasked. It is not possible to infer from that fact alone whether people confirming cases knew assignment, because the record does not identify who conducted confirmation or how it was done.

For the secondary outcome, the regression model’s covariates and handling of the design are not reported. The record also does not report whether the analysis accounted for possible clustering by school or another allocation unit. These gaps do not show that a particular method was or was not used; they mean the registry record does not provide enough information to evaluate it.

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 0% reporting threshold.

The registry’s serious adverse event fields report zero serious events and zero deaths in the education group and in the control group. The listed numbers at risk are 1562 for education and 2008 for control. The registry also reports zero other adverse events in each group. No serious adverse event terms are listed.

These figures describe what was recorded in the registry, not proof that no adverse experiences occurred. A zero count can reflect no events observed or reported within the registry’s collection and classification process; it does not establish that an event is impossible or that all events were captured. The record does not describe how adverse events were solicited, defined, monitored, or verified, or the period over which the event figures were collected.

The safety figures also do not answer the primary disease question. They concern adverse-event reporting, whereas the primary outcome concerns incident Lyme disease cases. The record does not report a safety comparison or uncertainty estimates. The appropriate reading is therefore limited: no serious or other adverse events are recorded for either group in these fields, and the available information does not permit broader conclusions about event ascertainment or risk.

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

The strongest conclusion supported by the registry record is limited. It describes a randomized, parallel-group school education study and a secondary behavioral measure with a posted between-group result. It does not provide an estimable comparison for the primary outcome of incident Lyme disease cases. As a result, the record does not establish whether the intervention was associated with more, fewer, or the same number of confirmed cases compared with control.

The behavioral result concerns a scale measure that combines or relates to self-confidence, intention, and prevention practice. The registry does not explain the scale’s construction, range, or scoring, so the size of the mean difference cannot be translated into a clear practical interpretation. The listed regression p-value and the unadjusted recalculation indicate a statistical difference under their respective methods, but statistical evidence of a difference is not by itself evidence of a meaningful change in behavior or disease risk.

The result also does not show whether changes in knowledge or behavior persisted, whether tick density changed, or whether parental involvement contributed to any outcome. Although these topics appear in the study’s aims, corresponding estimates are not reported in the registry record. Nor can the behavioral result be taken as evidence that the primary disease endpoint changed.

In general, randomized assignment can support a causal comparison when the analysis preserves assignment, outcome ascertainment is sufficiently complete, and the statistical methods reflect the design. The registry record does not report enough detail to assess those conditions fully. It also does not describe missing-data handling, the analysis population, or the primary analysis method.

Accordingly, the posted record documents a behavioral group difference and records no adverse events in the event fields, while leaving the primary disease comparison unresolved. This is not evidence that the intervention did or did not reduce Lyme disease incidence. It is a statement about the limits of the results available in the registry record.

13. Why This Trial Matters Statistically

This trial illustrates why a study’s primary outcome matters when interpreting a collection of results. The stated primary question concerns incident Lyme disease cases, while the posted secondary result concerns a behavioral scale. These outcomes address different points in the pathway from education to disease. A result on behavior can be informative about an intervention’s immediate aims, but cannot stand in for a disease endpoint when the primary comparison is not estimable in the registry record.

It also demonstrates the difference between a statistically detectable group difference and an outcome’s practical meaning. The secondary measure has a posted mean difference and regression p-value, yet the scale’s range, scoring, and component structure are not reported. Without those details, readers cannot readily judge what a change of the reported size represents in everyday preventive behavior.

The record further highlights the importance of transparent analysis reporting. A count outcome needs a clearly described comparison and uncertainty estimate to answer a question about incident cases. The registry does not report those results or the model used. For the secondary outcome, it lists a linear regression analysis but not the model specification. Missing information about analysis populations, outcome ascertainment, and missing data also makes it harder to assess robustness.

Finally, the study is an example of why randomized design and complete reporting are complementary. Randomization is valuable, but it does not communicate how outcomes were measured or how the data were analyzed. A reader needs the result, its precision, and enough methods detail to judge whether the analysis matches the design and question. Here, the secondary result can be described, while the central disease question remains unanswered by the posted primary outcome information.

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 is that the registry does not report an estimable two-group comparison for the primary incident Lyme disease outcome. Although the outcome description specifies parent reporting and medical record confirmation, it provides no effect estimate, confidence interval, or p-value for the comparison. The primary question therefore cannot be answered from the posted results.

The primary outcome description also leaves important measurement details unclear. The record does not explain how baseline reports and reports a year later were used to define incident cases for each group, how duplicate reports were handled, or how the medical record review was conducted. It does not report whether the person confirming cases knew group assignment. The extent and completeness of record confirmation are not reported.

The secondary behavioral measure is not sufficiently described to interpret its scale units in practical terms. Its items, range, scoring rules, validation, and direction are not reported in the registry record. The listed linear regression result lacks model details, including covariates and any accounting for the randomization unit. The randomization unit itself is not reported, so possible clustering by school cannot be evaluated.

Missing-data methods and analysis populations are also not reported. The record does not say how many participants contributed data at each assessment, how absent responses were treated, or whether all randomized participants were included as assigned. There is no reported multiplicity procedure for the secondary finding. These omissions limit assessment of bias, precision, and the reliability of the behavioral result.

Finally, the record does not provide results for tick density, knowledge, or attitudes, despite their appearance in the study aims. The duration and completeness of adverse-event collection are not reported either. These limitations are specific to what can be evaluated from the registry record and should not be read as evidence that the unreported procedures or measurements were not conducted.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: A School-Based Intervention to Reduce Lyme Disease — NCT00594997.
• Registry record last updated 2025-10-03; status last verified 2025-09.
• Results first posted 2021-04-06.
• 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

NCT00594997, titled “A School-Based Intervention to Reduce Lyme Disease,” is listed as a completed randomized, parallel-group study with no masking. Brigham and Women’s Hospital is the sponsor. The registry lists enrollment of 3570, a start date of 2004-04, and primary completion in 2006-03.

The education group received a school presentation and health education entertainment session. The control group completed pre and post surveys and was scheduled to receive the intervention after the post-survey. The primary endpoint concerns incident Lyme disease cases, based on parental reports and medical record confirmation. No estimable primary comparison is reported in the registry record.

A secondary behavioral outcome has posted group summaries and a listed linear regression result. The scale and model details are not reported. The registry records zero serious adverse events, zero other adverse events, and zero deaths in both groups. Missing-data procedures, analysis populations, multiplicity handling, and a statistical plan are not reported in the registry record.