Culture Media for Borrelia Burgdorferi Sensu Lato: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Culture Media for Borrelia Burgdorferi Sensu Lato (NCT02145754), a randomized na study. The primary outcome is Detection of Borrelia Burgdorferi Sensu Lato by Microscopy in Dark Field (Positive vs. Negative).

2. Clinical Question

The central question is about culture detection in skin specimens, not a clinical outcome measured in participants. A positive result is defined through microscopy of the culture; the listed endpoint is a count of positive skin samples. The record does not describe a separate question about symptom change, disease course, or treatment response.

The within-participant specimen description is important to the comparison: each participant contributed a sample to each medium. Results from samples belonging to the same participant may be statistically related. A comparison that accounts for this pairing can differ in interpretation from one that treats samples as independent. The registry record does not report the statistical method used to account for the paired specimens. Although the design field labels the model parallel, the specimen description should also be considered when interpreting the intended comparison.

The registry record reports randomized allocation and no masking, but does not specify what was randomized or how allocation was performed. It therefore does not establish from the available description whether the order, specimen halves, or another aspect of the procedure was randomized. The scientific question is clear at the level of comparing the two media, while the operational details of the allocation are not reported in the registry record.

3. Trial Design

The registry record describes a randomized, unmasked, parallel-model study with enrollment of 235. It lists erythema migrans as the condition and University Medical Centre Ljubljana as the sponsor. The phase field is recorded as NA. The study status is completed, with start listed as 2013-07 and primary completion as 2014-12.

The intervention descriptions are MKP media and BSK-H media. The record says that one half of a skin specimen obtained from a participant with erythema migrans was cultivated in MKP media and the other half in BSK-H media. The primary outcome description similarly states that each participant provided two skin samples, one for each medium. This indicates a within-participant specimen comparison in the description, although the model field is parallel. The registry record does not explain this apparent difference in design terminology.

Randomized allocation is recorded, but the randomization unit, sequence generation, allocation concealment, and the practical procedure for assigning specimens are not reported in the registry record. Masking is listed as none. The record does not specify whether microscopy readers or other personnel were aware of the culture medium during outcome assessment.

The primary endpoint is a count of skin samples in which Borrelia burgdorferi sensu lato was detected by dark-field microscopy. The timeframe is weekly examination during 9 weeks of cultivation for an individual specimen. The record does not provide additional operational details such as rules for a specimen with an incomplete examination schedule or how a positive result at any examination was summarized in the reported count.

There are no registered analyses for the primary outcome. The registry record does not report a statistical analysis plan, a sample-size justification for the trial, interim analyses, participant flow, or exclusions from analysis. Those absences limit assessment of how the study was planned and how the posted endpoint was intended to be compared.

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: Each participant provided two skin samples for analysis, one sample was cultivated in MKP, the other in BSK-H media.

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 Detection of Borrelia Burgdorferi Sensu Lato by Microscopy in Dark Field (Positive vs. Negative), measured over weekly examination during 9 weeks of cultivating for individual specimen.

The primary endpoint counts erythema migrans skin samples in which Borrelia burgdorferi sensu lato was detected by microscopy in dark field. Its unit is culture-positive skin samples, and the outcome is described as positive versus negative. The endpoint therefore records whether the organism was detected in a cultured specimen, rather than measuring a continuous quantity such as organism concentration or a clinical change in the participant.

The record states that each participant provided two skin samples, with one cultivated in MKP media and the other in BSK-H media. The endpoint makes it possible to describe detection in the specimens cultivated under each condition. The weekly examination timeframe during 9 weeks of cultivation indicates that microscopy was conducted repeatedly for an individual specimen. The record does not say whether the reported positive status meant detection at any examination, at a specified examination, or according to another summary rule.

As a general statistical consideration, a binary endpoint is useful when the outcome of interest is whether detection occurred, but it does not express how much organism was present or the timing of detection unless those features are separately defined and analyzed. Because each participant contributed specimens to both media, a comparison can also use the paired structure: outcomes from samples from the same person may be related. Appropriate interpretation depends on how such paired observations are handled.

The registry record lists the endpoint but does not report the number of positive or negative samples, a treatment contrast, or an uncertainty estimate. The endpoint definition alone therefore does not establish which medium had more detections or how precisely any difference was estimated.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Several statistical ideas help clarify what would be needed to interpret this comparison. They are general explanations, not a description of an analysis reported in the registry record: no analysis is listed for the primary outcome.

What does a positive-versus-negative endpoint capture?

A binary outcome assigns each specimen to one of two categories, here detection or no detection by dark-field microscopy. Counts in those categories can describe the observed frequency of culture-positive samples under each medium. A comparison can then be expressed as a difference in detection proportions, a relative measure, or another suitable effect estimate. Those forms answer related but not identical questions. The registry record does not report any such estimates, and no new estimate can be recovered from the endpoint description alone.

The endpoint is a count of positive skin samples, not a direct measure of the organism’s amount or the clinical condition of the participant. If microscopy was performed weekly during 9 weeks of cultivation, the rule used to convert repeated observations into a single specimen-level positive or negative outcome is important. For example, a method must define how a specimen with detection at one examination and no detection at another is classified. That rule is not reported in the registry record.

Why does pairing matter?

The record describes two samples from each participant, with one cultivated in each medium. This creates paired observations: each result in one medium has a natural counterpart from the same participant. As a general statistical principle, outcomes within a pair may be correlated because they share participant-level features and collection circumstances. A paired comparison uses information about whether the two results agree or differ within each participant. An analysis that instead treats all samples as independent may use the data structure incorrectly and can give a different measure of uncertainty.

For a binary paired outcome, the pattern of pairs matters, not just the separate totals of positive specimens in each medium. Pairs positive in both media and pairs negative in both media do not contribute to the direction of a within-pair contrast in the same way as pairs with discordant results. The registry record does not give these pair-level counts or state how pairing was handled. It also labels the model parallel; the specimen description and this model label should be read together rather than assuming that the analysis treated observations as independent.

What does a confidence interval communicate?

In general, a confidence interval describes the uncertainty around an estimated effect under the assumptions of the statistical method. Its width reflects both the amount of information and variability in the observations, as well as the method used. An interval that is narrow indicates greater precision than a wide interval, but it does not by itself establish that an effect is important or free of bias. A confidence interval for this comparison is not reported in the registry record.

A p-value, when reported, addresses how compatible the observed data are with a specified null hypothesis under a statistical model. It is not the probability that the null hypothesis is true, nor a measure of the size or practical importance of an effect. The registry record reports no p-value for the primary outcome. Statistical significance should not be inferred from the existence of a randomized design or from the number enrolled.

How should planning illustrations be read?

The registry record describes planning illustrations based on a fraction of the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. These are planning assumptions, not a report of the trial’s original design rationale. The record does not report the trial’s sample-size justification or say that these assumptions governed the study.

A sample-size calculation asks what sample size may be needed to detect a specified effect under assumed conditions. Such planning values are not observed power and do not show that a completed study had adequate power for its actual result. The illustrations are also dependent on the effect chosen for planning; if that is based on an observed effect, it should not be treated as a known or stable quantity. Because no primary outcome estimate is reported in the registry record, the posted information does not allow a reader to judge the empirical effect or its precision from the registered outcome.

What does absence of an analysis mean?

The registry record lists zero analyses. This means the available entry does not provide a statistical comparison to interpret; it does not show that no analyses were performed outside the registry. Without a registered analysis result, readers cannot inspect model choices, handling of paired specimens, uncertainty estimates, or any adjustment for multiple testing. The sponsor’s own analysis cannot be compared with a recalculation because no posted outcome summary statistics or sponsor analysis are included in the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists one primary outcome measure and zero analyses. It does not report a plan for multiple comparisons, a testing hierarchy, or adjustment for multiplicity. The available information therefore does not establish whether other outcomes or subgroup comparisons were planned, conducted, or considered alongside the primary endpoint. No correction or unadjusted significance result is available to interpret.

Missing-data handling is also not reported in the registry record. The outcome timeframe involves weekly examination during 9 weeks of cultivation for an individual specimen, but the entry does not say whether all scheduled examinations were completed for every specimen, how an incomplete examination sequence was handled, or what counted as an evaluable sample. It does not report missing or excluded specimen counts.

The record describes two skin samples per participant, one for each medium, but does not state whether any participant lacked a usable sample in one medium, whether paired records were retained together, or how incomplete pairs would be analyzed. As a general statistical principle, missingness can affect both the number of observations contributing to a comparison and the interpretation of the result, particularly when a paired analysis requires information from both conditions.

The analysis population is not reported in the registry record. There is no stated intention-to-treat, per-protocol, or other analysis population, and no description of exclusions after enrollment. Consequently, the enrollment figure should not be assumed to equal the number of participants or specimens contributing to the primary endpoint. These gaps prevent evaluation of whether the analysis followed a prespecified plan and how omissions might have influenced the estimated comparison.

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 adverse-event entry uses a group labeled MKP Media Versus BSK-h Media. It reports 235 participants at risk for serious events and 0 affected, and 235 at risk for other events and 0 affected. These are the figures recorded for the combined comparison label; the entry does not provide separate adverse-event counts by medium.

The death field is null. A null value is not a reported count of zero, so deaths are not reported in the registry record. The entry also lists no serious-event terms. The zero affected counts describe the registry’s recorded figures for the categories shown; they should not be interpreted as proof that no events occurred outside the record or that safety was comprehensively assessed.

These safety figures are distinct from the primary outcome, which concerns microscopy detection in cultured skin samples. They do not indicate how often either medium produced a positive culture, and they do not provide a comparative estimate of adverse-event risk. The registry record does not report the event definitions, collection procedures, duration of safety observation, or separate exposure information for each medium.

As a general statistical point, a zero count can be compatible with uncertainty about the underlying event frequency, especially when information about event ascertainment and follow-up is limited. The displayed figures should therefore be read as registry-recorded adverse-event counts rather than as a complete measure of comparative safety.

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

The registry record establishes that the study was intended to compare MKP and BSK-H media for cultivation of Borrelia burgdorferi sensu lato from skin specimens obtained from participants with erythema migrans. It identifies a microscopy-based positive-versus-negative endpoint and says that each participant provided a sample for each medium. The outcome timeframe is weekly examination during 9 weeks of cultivation for an individual specimen.

Those details explain the scientific question and the type of observation collected, but they do not supply the answer to the comparison. No outcome counts, analysis, effect estimate, confidence interval, or p-value are reported in the registry record. Thus, the posted information does not show whether one medium had more detected cultures, whether results were similar, or how uncertain a difference might be.

The result does not establish that either medium is superior or inferior. It also does not show that the two media are equivalent: equivalence requires a suitable design and analysis with a prespecified margin, which are not reported in the registry record. A lack of a posted result is not evidence of no difference.

The record’s randomized allocation label does not, on its own, resolve how specimens were assigned or whether the paired structure was incorporated in the analysis. The sample-level description suggests a paired comparison, while the model field says parallel. The allocation procedure and statistical approach are not reported, so the design labels cannot be used to reconstruct an analysis.

The adverse-event figures are limited to the recorded group and categories, with zero affected reported for serious and other events and the death field not reported. They do not answer the primary culture question or establish comparative safety. Overall, the registry record documents a completed study and its intended measurement, but the posted information is insufficient to draw a statistical conclusion about the relative culture detection observed in the two media.

13. Why This Trial Matters Statistically

This study illustrates why a clear endpoint description is not the same as a report of a result. The registry record specifies the organism, culture media, specimen source, microscopy method, and examination timeframe. Those details make the intended measurement understandable. Yet without positive and negative counts or an analysis, the comparative question remains unanswered in the posted record.

It also highlights the importance of matching analysis to the unit of observation. Participants contributed specimens to both media, so their results are paired in the described procedure. Statistical methods that preserve the pairing can use within-participant information, whereas treating the observations as unrelated may not represent the study structure. The registry record does not say how this issue was handled, and no analysis is listed.

Another statistical lesson is the distinction between planning and evidence. Planning illustrations can show how assumptions about effect size, significance level, allocation, and model affect a required sample size. They do not replace an observed treatment contrast, and they should not be described as observed power. The registry record gives assumptions for such illustrations but does not provide the trial’s own sample-size justification or a primary outcome estimate.

Finally, registry entries have limits as sources for evaluating a completed study. This record conveys design labels and an endpoint, but key details about randomization, masking of assessment, missing specimens, analysis populations, multiplicity, and statistical methods are not reported. These omissions matter because they determine how observations are converted into an estimate and how much confidence to place in it. Statistical interpretation requires both a well-defined question and transparent results with their uncertainty.

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 central limitation of the registry record for evaluating this trial is that it contains no primary outcome results or analyses. Although it specifies culture detection by dark-field microscopy, it does not report positive or negative sample counts for either medium. A comparative effect and its precision therefore cannot be assessed.

The design description also leaves unresolved details. Randomized allocation is recorded, but the object and procedure of randomization are not reported in the registry record. Masking is listed as none, while masking of microscopy assessment is not separately described. The model is labeled parallel even though each participant is described as providing one sample for each medium. The record does not explain this terminology or state how paired observations were treated.

Outcome ascertainment is described as weekly examination during 9 weeks of cultivation, but the rule for creating the specimen-level positive-or-negative result is not reported. The record does not say how incomplete examinations, contaminated or unusable specimens, or other indeterminate outcomes were handled. Missing-data methods, analysis populations, participant flow, and exclusions are not reported in the registry record.

The entry includes no statistical analysis plan, multiplicity approach, interim-analysis information, or trial-specific sample-size justification. These absences make it difficult to assess whether the endpoint analysis was prespecified or whether the enrollment was selected to address a stated precision or power target. The planning assumptions recorded separately are not evidence of the trial’s original design rationale.

Safety information is also limited: the adverse-event figures are attached to a combined media-comparison label rather than reported separately by medium, and the death value is null. Definitions and ascertainment procedures are not reported. These limitations concern what can be concluded from the registry record; they do not establish what methods or results may exist elsewhere.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Culture Media for Borrelia Burgdorferi Sensu Lato — NCT02145754.
• Registry record last updated 2015-06-30; status last verified 2015-06.
• Results first posted 2015-06-30.
• 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 describes a completed randomized comparison of MKP and BSK-H media for cultivation of Borrelia burgdorferi sensu lato from skin specimens from participants with erythema migrans. Enrollment is recorded as 235. The record lists University Medical Centre Ljubljana as sponsor, phase as NA, masking as none, and a parallel model. It gives study start as 2013-07 and primary completion as 2014-12.

The primary outcome is the number of skin samples with detection by dark-field microscopy, assessed weekly during 9 weeks of cultivation for an individual specimen. Each participant is described as providing two samples, one for each medium. The registry record lists one outcome measure and zero analyses, and does not report primary outcome counts or a comparison.

The adverse-event entry reports 0 affected for serious and other events in the combined comparison group; the death field is null. The record does not provide separate adverse-event counts by medium. Details of randomization, missing-data handling, analysis populations, and statistical methods are not reported in the registry record.