This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for COVID-19 Tests: Nasopharyngeal Swab vs Saliva Collected With Salivette® Cortisol for Viral RNA Sampling for RT-qPCR (NCT04599959), a non-randomized na study. The primary outcome is Number of Participants Testing Positive or Negative for SARS-CoV-2 Virus From Swab and Saliva Samples - Processed in Mexico.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04599959 |
| Phase | NA |
| Condition | Covid-19 |
| Allocation | Non-Randomized |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 151 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Boehringer Ingelheim |
| Results posted | Yes |
2. Clinical Question
Population
Eligible participants had a COVID-19 diagnosis confirmed by polymerase chain reaction (PCR) within the past 5 days before study entry. The primary outcome description further limits its population to participants whose samples were processed in Mexico. The registry lists 151 participants enrolled, but it does not report how many met the primary outcome population definition or contributed results to it.
Intervention
The saliva sampling method used Salivette® Cortisol. The study objective was to establish saliva collection with this device for viral RNA sampling and RT-qPCR. The registry does not report detailed collection instructions, whether collection was supervised, or whether samples were taken in a particular order.
Comparator
The other sampling method was a nasopharyngeal swab. The record describes a comparison of swab and saliva samples, not a randomized treatment comparison. It does not report enough detail to establish whether every participant contributed both types of sample or how the samples were paired for analysis.
Primary question
The primary outcome counts participants testing positive or negative for SARS-CoV-2 from swab and saliva samples processed in Mexico, at baseline on the test day, up to one day. The question is whether the recorded test classifications from the sampling methods provide a useful comparison. The registry does not report the positive and negative counts, agreement, diagnostic accuracy estimates, or an inferential comparison.
For a diagnostic sampling comparison, the interpretation depends on more than the names of the two collection methods. The participant population, reference for determining infection status, sample handling, and the relationship between each participant’s samples all affect what a comparison can establish. The registry identifies PCR-confirmed COVID-19 within the past 5 days as an eligibility condition, but does not describe a reference standard for evaluating the test results or specify the statistical estimand. It therefore does not establish whether the intended question concerned agreement, relative detection, or another performance measure.
3. Trial Design
NCT04599959 is a completed diagnostic-test study listed as phase NA. Its title describes a systematic comparison of viral RNA sampling for RT-qPCR using a nasopharyngeal swab or saliva collected with Salivette® Cortisol. The registry lists an enrollment of 151 and identifies COVID-19 as the condition. Boehringer Ingelheim is named as the sponsor.
The design is recorded as single-group, with non-randomized allocation and no masking. The arm description is “Overall (Swab/Saliva),” rather than separate randomized groups. The record specifically cautions that this is not a randomized comparison and that arms are not a like-for-like control comparison. Accordingly, the study should be read as an evaluation of sampling approaches, not as a trial assigning participants to competing treatments.
The recorded start date is 2020-10-26, the primary completion date is 2021-01-20, and the study status is completed. The primary outcome timeframe is at baseline on the test day, up to one day. The stated primary population consists of eligible participants with PCR-confirmed COVID-19 within the past 5 days before study entry whose samples were processed in Mexico.
Important operational details are not reported in the registry record. These include the order and timing of sample collection, whether both sampling methods were used for each participant, the handling of inadequate or invalid samples, and the laboratory procedures beyond the stated processing location and RT-qPCR context. The record also does not report a sample-size justification, protocol-level analysis plan, or interim-analysis plan. The design label and outcome description alone cannot resolve these omissions.
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: All subjects were screened for eligibility prior to participation in the trial. Subjects attended a specialist site which ensured that they (the subjects) strictly met all inclusion and none of the exclusion criteria.
Overall Study
| Stage | Overall |
|---|---|
| STARTED | 151 |
| COMPLETED | 151 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: All eligible participants in this study who had been diagnosed with COVID-19 confirmed by polymerase chain reaction (PCR) test within the past 5 days before study entry, and whose samples were processed in Mexico.
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: All eligible participants in this study who had been diagnosed with COVID-19 confirmed by polymerase chain reaction (PCR) test within the past 5 days before study entry.
| Characteristic | Unit | Overall |
|---|---|---|
| Participants analysed | 151 | |
| Age, Continuous | Years | 43.4 (SD 14.68) |
| Sex: Female, Male: Female | Participants | 80 |
| Sex: Female, Male: Male | Participants | 71 |
| Race and Ethnicity Not Collected | Participants | — |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants Testing Positive or Negative for SARS-CoV-2 Virus From Swab and Saliva Samples - Processed in Mexico, measured over At baseline (the test day), up to one day..
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary endpoint is a count of participants classified as testing positive or negative for SARS-CoV-2 from swab and saliva samples processed in Mexico. Its stated unit is participants, and its measurement timeframe is baseline on the test day, up to one day. The endpoint description places the result in the context of comparing a nasopharyngeal swab with saliva collected using Salivette® Cortisol.
As a general statistical explanation, a positive-or-negative endpoint is categorical: each recorded test result belongs to a defined classification rather than measuring a continuous quantity. Counts can show how many participants fall into each reported category, but counts alone do not establish how well a test identifies infection. Diagnostic measures such as sensitivity, specificity, or agreement require clearly defined comparison standards and adequate detail about which results are matched to which participants.
The registry record does not report the actual positive or negative counts, a reference standard for the comparison, or a derived diagnostic-performance measure. It also does not state whether the endpoint was analyzed as paired results from participants who provided both samples. Consequently, the endpoint’s intended subject is clear, but its observed distribution and the precise statistical contrast are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted registry information describes the study question and design, but does not provide the primary outcome results. Although the primary measure is defined as counts of participants testing positive or negative from swab and saliva samples processed in Mexico, no category counts or outcome estimates are reported in the record. The analysis count is 0. There is therefore no reported estimate of agreement or difference between sampling methods to interpret, and no reported uncertainty interval or hypothesis-test result for the primary outcome.
This distinction matters because a defined endpoint is not itself an observed result. The endpoint description indicates what the investigators intended to count and the period in which measurement was planned. It does not establish how many participants were positive or negative, whether the sampling methods yielded matching classifications, or whether either method had a particular level of diagnostic performance.
The design also limits what can be inferred from a comparison. This is a single-group, non-randomized diagnostic study with no masking. The record describes the sampling methods but does not provide enough detail to determine whether both were applied to each participant or how observations were paired. In general, when two measurements are made on the same person, their dependence should be reflected in the analysis; treating them as independent can misstate uncertainty. The appropriate analysis for this study cannot be identified from the registry information alone.
The registry’s stated population is restricted to eligible participants with a PCR-confirmed diagnosis within the past 5 days before entry, with the primary outcome further referring to samples processed in Mexico. Results from such a population would not automatically describe people outside those eligibility and processing conditions. However, because the primary results are not reported, even the result for this specified population cannot be characterized from the record.
The safety listing records 0 serious adverse events, 0 other adverse events, and 0 deaths among the overall group, with 151 listed at risk for each adverse-event category. These are registry counts, not evidence that an event could not occur. The record does not supply additional information about event collection, definitions, or reporting completeness.
Any sample-size planning calculations should be understood as planning illustrations, not observed power. The stated framework uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the target effect expressed as a fraction of the observed effect. The record does not report the primary outcome results needed to assess that observed effect in context. These assumptions do not replace the study’s own design rationale, which is not reported in the registry record.
9. Statistical Methods Explained
What does a count endpoint tell us?
The primary outcome is a count of participants classified as positive or negative. As a general statistical point, counts describe how many observations are recorded in categories. They are not by themselves a measure of diagnostic accuracy: that requires a defined basis for deciding which classifications are correct, along with enough information to connect each test result to that basis. The registry names PCR-confirmed COVID-19 as an eligibility requirement, but does not state how infection status was used as a reference for evaluating the swab and saliva results.
The record does not provide category counts or any analysis estimate for the primary outcome. It therefore does not support a recalculation from posted summary statistics. No comparison estimate, confidence interval, or p-value is reported in the registry record. In the absence of these results, statistical precision and compatibility with different possible effects cannot be assessed.
Why does pairing matter?
As a general statistical explanation, diagnostic sampling methods may be evaluated by comparing results from the same participants. When that is the design, the observations are paired: each participant can contribute a result from each method, and the two results may be related. An analysis that accounts for that relationship can differ from one that treats the results as independent groups. The registry describes swab and saliva samples but does not report whether every participant provided both, how any pairing was defined, or which analysis was used. It would therefore be inappropriate to assume a paired analysis or to select a particular test on that basis.
The record labels the study single-group and non-randomized, and its arm description is “Overall (Swab/Saliva).” These labels do not establish that the same participants contributed both samples. Nor do they identify a statistical model or a specific contrast. The registry’s caution that the arms are not a like-for-like control comparison reinforces that this should not be interpreted as a randomized comparison of treatment groups.
How should uncertainty be read?
As a general explanation, a confidence interval describes the range of effect estimates that are reasonably compatible with the data under the chosen statistical method. Its width reflects precision, which depends on factors including the amount and structure of the data and the variability in the observations. A p-value, when reported, addresses compatibility with a specified null model; it does not measure the size or practical importance of an effect. Neither can be interpreted without a stated analysis and an estimate from the observed data.
No confidence interval, p-value, or model result for the primary endpoint is reported in the registry record. Thus there is no basis for judging statistical precision or evidence against a null hypothesis from the primary endpoint. The absence of an analysis entry should not be read as a result showing equality or no difference.
What do the planning assumptions mean?
The stated sample-size framework is a planning illustration based on an observed effect, not the trial’s own design. It uses a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The target is defined as a stated fraction of the observed effect. These are assumptions used for planning calculations; they do not describe a randomized allocation in this study, whose design is recorded as single-group and non-randomized.
As a general statistical point, planning calculations estimate the amount of information that might be needed to detect a target effect under specified assumptions. They do not tell readers the probability that the completed study found a true effect, and they are not observed power. The target effect, variance assumptions, and analysis model all matter. The primary outcome counts and effect estimate are not reported in the registry record, so the planning illustration cannot be evaluated against those results. The record also does not report a sample-size justification from the study’s own design.
Can the stated endpoint support diagnostic claims?
As a general explanation, diagnostic accuracy measures require a reference classification and a clear accounting of test results relative to it. Agreement between methods is a different question from correctness against a reference. Two methods could agree with each other without either being evaluated against a suitable standard. The registry describes a PCR-confirmed population and a positive-or-negative outcome, but does not report a reference-standard analysis, sensitivity, specificity, predictive values, or agreement estimates. Those measures should not be inferred from the endpoint title alone.
Overall, the statistical information in the registry is enough to identify the intended endpoint type and broad design, but not to reproduce or interpret an outcome analysis. The test classifications, analysis population actually used, handling of missing or invalid results, statistical methods, and uncertainty estimates are not reported in the registry record.
10. Multiplicity, Missing Data and Analysis Populations
The registry identifies a primary outcome and lists 2 outcome measures, but it does not report the statistical analysis entries for those measures; the analysis count is 0. The record does not describe a testing hierarchy, a multiplicity adjustment, or how any secondary outcomes relate to the primary question. Without an analysis plan and reported tests, it is not possible to assess whether multiplicity was considered or whether any inferential result was selected from multiple analyses.
Missing-data procedures are not reported in the registry record. In particular, the record does not explain how missing samples, invalid results, inconclusive results, or participants without results from one of the sampling methods were handled. It also does not report the number of participants contributing to the primary endpoint. Enrollment is listed as 151, but that figure alone does not establish the analysis denominator for the Mexico-processed samples or for any outcome category.
The stated primary population is all eligible participants diagnosed by PCR within the past 5 days before study entry whose samples were processed in Mexico. The registry does not report a separate analysis-population definition, deviations from eligibility, or how participants were selected for the reported analyses. Because the outcome analysis is not reported, the relationship between enrollment and the population used for analysis cannot be assessed.
These omissions affect interpretation, not merely presentation. Missingness can change the group of observations represented by the results, and choices about multiple outcomes or analyses can affect the interpretation of inferential findings. Since neither those choices nor primary outcome findings are reported, conclusions about their impact are not available from the registry record.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Overall | 0 | 151 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Overall | 0 of 151 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Overall | 0 of 151 |
The registry lists the overall group as having 151 participants at risk for serious adverse events and 0 serious adverse events. It also lists 151 at risk for other adverse events and 0 other adverse events. The recorded death count is 0. No serious-event terms are listed.
These figures are counts in the registry record. They do not establish that no adverse event occurred outside the record’s collection or reporting process, and they do not provide detail about how events were defined, monitored, or attributed. The record does not report the safety observation period separately from the primary outcome timeframe, nor does it describe the method used to collect adverse-event information. The at-risk figures should therefore be read as the registry’s stated denominators, not as evidence about reporting completeness.
Because the study evaluates diagnostic sampling methods, the safety counts do not answer the primary sampling-comparison question. They are a separate registry outcome. No event rates or comparisons should be inferred from the counts beyond the recorded values.
12. What the Result Does, and Does Not, Mean
The record identifies a diagnostic sampling study comparing nasopharyngeal swab collection with saliva collected using Salivette® Cortisol for SARS-CoV-2 RNA testing by RT-qPCR. It also specifies a primary outcome based on positive or negative participant classifications, measured at baseline on the test day, up to one day. These details describe the intended question and measurement, not the observed answer.
The primary outcome counts and statistical analyses are not reported in the registry record. Consequently, the posted information does not establish whether the sampling methods produced similar or different classifications, how precisely any comparison was estimated, or how either method performed against a reference standard. It does not support a conclusion that either approach is more accurate, less accurate, or equivalent.
The design is recorded as single-group, non-randomized, and unmasked. It is not a randomized treatment comparison. The record also does not explain whether samples from the two methods were paired within participants, how the comparison was analyzed, or how invalid and missing samples were handled. These details matter for evaluating the strength and meaning of any diagnostic comparison.
The listed population had PCR-confirmed COVID-19 within the past 5 days before study entry, and the primary outcome description refers to samples processed in Mexico. Even if primary results were available, their scope would need to be interpreted in relation to that defined population and processing context. The registry information does not justify extending findings to other populations, settings, or collection procedures.
The safety listing records 0 serious adverse events, 0 other adverse events, and 0 deaths. Those counts describe what the registry reports; they do not establish the completeness of event ascertainment. In sum, the record is informative about the study’s intended sampling comparison, but it does not report the primary findings needed to judge the result.
13. Why This Trial Matters Statistically
This study raises a practical statistical question: how to compare results from different specimen-collection methods when the outcome is a positive-or-negative test classification. The answer depends on the study’s data structure. If the methods were used on the same participants, their results are related and the analysis should account for that relationship. If the methods were applied to different groups, other assumptions would be relevant. The registry record does not report which structure was used for the primary analysis.
The distinction between counting classifications and evaluating diagnostic performance is also important. Positive and negative counts describe the recorded results, but accuracy requires a reference standard and a clearly defined comparison. Agreement between methods and correctness against a reference answer different questions. The registry states the eligibility diagnosis and outcome categories, while leaving the reference-standard approach and derived performance measures unreported.
The record also illustrates why an endpoint definition should not be mistaken for a result. A defined measure makes the intended outcome understandable, but it cannot show the observed classification pattern or the uncertainty around a comparison. Here, the primary outcome counts and analysis estimates are not reported. Statistical conclusions about similarity, difference, or precision therefore cannot be drawn from the registry information.
Finally, the design labels place appropriate boundaries on interpretation. A single-group, non-randomized diagnostic study is not a randomized treatment trial, and the registry explicitly warns that the arms are not a like-for-like control comparison. Together, the design and reporting gaps make it especially important to separate the study’s stated objective from evidence about test performance. That distinction is useful in reading diagnostic studies generally, even when the outcome results are unavailable.
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 interpretation is that the registry record does not report the positive and negative outcome counts or any primary analysis. There is no reported estimate of agreement, diagnostic accuracy, or comparative performance, and no uncertainty measure with which to judge precision. The study’s endpoint and objective are described, but the results needed to answer the stated question are absent from the record.
The design and sample relationship are not fully described. Although the study is labeled single-group and non-randomized and its arm description refers to swab and saliva, the registry does not state whether each participant contributed both sample types, how samples were paired, or the sequence and timing of collection. The absence of masking is recorded, but the record does not explain laboratory blinding or other procedures that could affect classification.
The primary population is limited to eligible participants with PCR-confirmed COVID-19 within the past 5 days before study entry whose samples were processed in Mexico. Enrollment is listed as 151, but the number contributing to the primary outcome is not reported. Sample-processing details, invalid or missing result handling, reference-standard procedures, and the actual analysis population are also not reported in the registry record.
The registry does not report a protocol-level statistical plan, sample-size justification, multiplicity procedures, or interim-analysis plan. Its stated planning framework is an illustration rather than the study’s own design, and no primary outcome results are available for assessing that framework. These limitations prevent independent evaluation of the study’s statistical precision and the extent to which any findings apply beyond the specified population and processing context.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: COVID-19 Tests: Nasopharyngeal Swab vs Saliva Collected With Salivette® Cortisol for Viral RNA Sampling for RT-qPCR — NCT04599959.
- Registry record last updated 2021-07-26; status last verified 2021-07.
- Results first posted 2021-07-26.
- 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.
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18. Record Summary
NCT04599959 is a completed, phase NA, single-group, non-randomized, unmasked diagnostic-test study sponsored by Boehringer Ingelheim. It compares nasopharyngeal swab sampling with saliva collected using Salivette® Cortisol for SARS-CoV-2 viral RNA sampling for RT-qPCR. Enrollment is listed as 151; the recorded start date is 2020-10-26 and primary completion date is 2021-01-20.
The primary outcome counts participants testing positive or negative from swab and saliva samples processed in Mexico, at baseline on the test day, up to one day. Its stated population had PCR-confirmed COVID-19 within the past 5 days before study entry. The registry record does not report primary outcome counts or statistical analyses. It lists 0 serious adverse events, 0 other adverse events, and 0 deaths in the overall group.