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 A Study of COVID-19 Patients Receiving Treatment With Nirmatrelvir; Ritonavir in the Kingdom of Saudi Arabia (NCT06016556), a registered phase not stated study. The primary outcome is Number of Participants Classified According to Education Level at Index Date.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT06016556 |
| Phase | Phase not stated |
| Condition | Covid-19 |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 250 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Pfizer |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns adults aged >=18 years with COVID-19 who were prescribed nirmatrelvir, ritonavir in the Kingdom of Saudi Arabia. The planned enrollment was 250. The analysis population is described as eligible participants whose data were included and observed; for the primary measure, participants needed non-missing, evaluable data. The registry record does not report the number evaluable for that measure.
Intervention
The treatment of interest was nirmatrelvir, ritonavir, also identified in the record as PAXLOVID. This is an observational description of people who received a prescription, not an assigned treatment in a randomized trial. The record does not report treatment adherence, dispensing, or whether participants completed a course.
Comparator
No comparator group is described. The record identifies a cohort receiving the treatment and does not provide a like-for-like control group. It therefore does not frame the study as a comparison of treatment with placebo, usual care, or another therapy.
Primary question
The primary measure counts participants by education level at the index date, defined as the date of the treatment prescription. Categories range from no formal education through primary and secondary school, undergraduate university, master's degree, and doctorate or PhD. The study also aims to describe baseline characteristics and healthcare resource use. Registry-listed resource-use outcomes include hospitalization, intensive care, oxygen, vasopressor use, and intubation during the 30-day post-index period. The record does not report outcome counts or estimates.
3. Trial Design
This is a retrospective observational, non-interventional study in Saudi Arabia. Its stated aim is to describe demographic and clinical characteristics and healthcare resource use among adults with COVID-19 prescribed nirmatrelvir, ritonavir. The registry lists a planned enrollment of 250 and a completed status. The study began on 2023-10-17, with primary completion on 2024-04-09.
The treatment prescription defines the index date. The eligible prescription date could fall between 1-Apr-2022 and 30-Jun-2023, a 15-month look-back period. The primary measure concerns education level at that index date. Resource-use outcomes focus on the 30-day period following the prescription. The record says retrospective data were evaluated during approximately 6 months of the study; it does not explain in greater detail how that evaluation period relates to the prescription look-back window.
Because treatment was not assigned by the study, the design describes people who received a prescription rather than estimating a randomized treatment contrast. No comparator group is described, and the registry record does not report a matching, weighting, or other comparative design. The allocation method is not stated. The record lists 40 outcome measures and zero analyses. Outcome results, participant flow, and the number evaluable for the primary measure are not reported in the registry record.
The listed secondary outcomes describe hospital admission, admission due to COVID-19, length of hospital stay, intensive care admission and stay, supplemental oxygen, vasopressor use, and intubation. These are framed around the 30-day post-index period. The record does not specify the detailed data sources or procedures used to ascertain these events.
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: Data was extracted from medical records of the participants and data was evaluated per objectives of this study in approximately 6 months of this study (study start date: 17-Oct-2023 to study completion date: 09-Apr-2024).
Overall Study
| Stage | All Participants |
|---|---|
| STARTED | 248 |
| COMPLETED | 248 |
| NOT COMPLETED | 0 |
Analysis population for the primary outcome, as defined in the registry: Analysis population included all eligible participants whose data were included and observed in this study. Here, "Overall Number of Participants Analyzed" signifies those number of participants who had non-missing values and were evaluable for this outcome measure.
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: Analysis population included all eligible participants whose data were included and observed in this study.
| Characteristic | Unit | All Participants |
|---|---|---|
| Participants analysed | 248 | |
| Age, Continuous | Years | 49.85 (SD 18.73) |
| Sex: Female, Male: Female | Participants | 148 |
| Sex: Female, Male: Male | Participants | 100 |
| Race/Ethnicity, Customized: Ethnicity – Arab | Participants | 247 |
| Race/Ethnicity, Customized: Ethnicity – Asian/Pacific Islander | Participants | 1 |
6. Primary Endpoint
The registry lists the primary outcome as Number of Participants Classified According to Education Level at Index Date, measured over At index date; retrospective data was evaluated during approximately 6 months of this study.
| Element | Registry entry |
|---|---|
| Result type | Count Of Participants |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary measure is the number of participants classified by education level at the index date. The index date is the date of the nirmatrelvir, ritonavir prescription. Education categories include no formal education, primary school, secondary school, undergraduate university degree, master's degree, and doctorate or PhD. The measure is a descriptive count, not a measure of treatment efficacy or a comparison between groups.
Counts by category can characterize who was represented in the observed cohort and can help describe its baseline profile. Such information may be useful when interpreting healthcare resource-use descriptions, because the people included in an observational cohort have particular characteristics and may not represent every person with COVID-19. The primary measure alone does not establish whether education is associated with resource use, nor does it show that education affects treatment outcomes.
The registry defines the analysis population for this outcome as eligible participants whose data were included and observed. It further defines the overall number analyzed as participants with non-missing values who were evaluable for the measure. The actual category counts and evaluable denominator are not reported in the registry record. The record also does not specify how missing or ambiguous education classifications were handled beyond requiring non-missing values for evaluation.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The record describes a cohort of adults with COVID-19 who were prescribed nirmatrelvir, ritonavir, with planned enrollment of 250. Its stated purpose is descriptive: to characterize participants and report healthcare resource use. It is not a randomized comparison, and no comparator group is described. Consequently, the design as recorded does not support a treatment-versus-control estimate.
The primary outcome is a count of participants across education categories at the prescription date. The record gives the category definitions but does not report counts, proportions, or an evaluable denominator. It therefore does not establish which education categories were most common or how complete the education data were. Although the study lists healthcare resource-use outcomes, no estimates for hospitalization, intensive care, oxygen, vasopressor use, or intubation are reported in the registry record.
The registry lists 40 outcome measures and zero analyses. This distinction matters: an outcome's appearance in a registry is not itself evidence that its results were reported. Without the outcome values, there is no basis to describe the observed frequency of resource use or the precision of any estimate. There are no confidence intervals or other uncertainty measures in the record.
More generally, a confidence interval expresses the range of values compatible with an estimate under the statistical model and its assumptions. A narrow interval indicates greater precision than a wide one, but neither guarantees that the study is free from bias. No such interval is reported for the outcomes in this record.
The design also limits causal interpretation. In a retrospective observational cohort, treatment receipt is not randomized, and there is no specified comparison group. Characteristics that influence treatment prescription or the chance of healthcare use could also be related to the outcomes. The registry record does not report an adjustment strategy or analysis results that would address such factors. Therefore, the record supports describing the study's objectives and design, but not drawing conclusions about treatment effects or the frequency of its listed outcomes.
9. Statistical Methods Explained
The registry describes a retrospective, observational, non-interventional study. In general, an observational study records exposures and outcomes as they occurred in routine settings rather than assigning participants to treatment groups. Retrospective studies use information collected about an earlier period. These features can make a study useful for describing care and participant characteristics, while also limiting the strength of causal conclusions. The registry record does not report a detailed statistical analysis plan.
What does a descriptive count tell us?
The primary measure is a count of participants classified by education level. A count indicates how many observed participants fall into a category, while a proportion would express that count relative to a defined denominator. The registry describes the categories and says that participants with non-missing values were evaluable. It does not report the category counts, proportions, or denominator. No additional calculation can be inferred from the category definitions alone.
Counts are appropriate descriptive summaries for categorical outcomes such as education classification or whether an event occurred. Interpretation depends on knowing the denominator and how records with missing values were handled. The registry states an evaluability rule for the primary outcome, but the number excluded for missing data and the number analyzed are not reported in the registry record.
How should the resource-use outcomes be understood?
The listed secondary outcomes include event counts and measures of duration, such as hospitalization or intensive care stay. In general, event counts describe how often an event was observed in a defined population and time window. Duration outcomes describe time spent in a state, but interpretation depends on how the duration is defined and whether people without the event are included. The registry identifies a 30-day post-index period for these outcomes, but detailed operational definitions and analysis methods are not reported in the registry record.
For binary event outcomes, a count of participants with an event is not the same as an event rate per unit of follow-up time. If follow-up differs among participants, time at risk can matter. The record does not report participant-level follow-up completeness or the methods used to address incomplete observation. These general considerations cannot establish how the study handled them.
Over-dispersion is a general issue for count data: it occurs when observed variability is greater than a simple model assumes. A model that does not account for such variability can produce uncertainty estimates that are too small. The record does not report whether count models were used, whether over-dispersion was assessed, or whether any model-based estimates were calculated. Given the absence of reported analyses, no particular method should be attributed to this study.
What can a confidence interval add?
In general, a confidence interval communicates statistical uncertainty around an estimated quantity under the model used. It does not account automatically for systematic problems such as incomplete records, selection into the cohort, or incorrect outcome classification. The registry record does not report confidence intervals for the listed outcomes, so their precision cannot be assessed from the record.
The record's planning assumptions describe an illustration based on a stated fraction of an observed effect, a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. For time-to-event illustrations, the stated quantity is total events; other illustrations are expressed as participants per arm. These are planning conventions, not observed study findings or observed power. They do not change the recorded design: the registry describes a single treated cohort and no comparator group. The registry record does not report the study's own sample-size justification, a planned treatment comparison, or a detailed protocol for applying those illustrative assumptions.
What is not available for evaluation?
The registry lists 40 outcome measures and zero analyses. It does not report a statistical model, covariate adjustment, hypothesis-testing procedure, or estimates for the primary and secondary outcomes. These omissions prevent assessment of how the investigators summarized outcomes or quantified uncertainty. They also mean that statistical methods used in the study should not be guessed from the outcome titles or from general practice.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 40 outcome measures, including a primary measure and multiple secondary healthcare resource-use outcomes. Considering many outcomes can raise a multiplicity issue: if several statistical hypotheses are tested, the chance of at least one apparently unusual result can increase. In general, a prespecified hierarchy or adjustment method may help address that concern. The registry record does not report a multiplicity strategy, and it lists zero analyses, so it is not possible to determine whether formal hypothesis tests were conducted or adjusted.
Missing data are also relevant because the primary outcome's analysis population is defined by having non-missing, evaluable values. The number of participants with missing education data, the reasons for missingness, and any imputation or sensitivity analyses are not reported in the registry record. A complete-case description can be affected if participants with recorded values differ from those without them; this is a general concern, not a finding established for this cohort.
The registry describes the overall analysis population as eligible participants whose data were included and observed. It does not report participant flow from planned enrollment to inclusion in each outcome analysis, or whether the same participants contributed to all outcomes. Although planned enrollment is 250, the evaluable denominator for the primary measure is not reported in the registry record.
The sample-size assumptions describe a planning illustration with two-arm allocation, while the study design is recorded as observational and no comparator is specified. The illustration should therefore be read as a hypothetical planning framework rather than as evidence of the study's actual design, achieved power, or analysis population. The registry record does not report its own sample-size justification or a prespecified analysis plan that reconciles these assumptions with the cohort design.
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 |
|---|---|---|---|
| All Participants | 2 | 248 | 0.8% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| All Participants | 0 of 248 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| All Participants | 0 of 248 |
Most frequent serious adverse event terms
| Event term | Organ system | All Participants |
|---|---|---|
| Drug-Drug Interaction | General disorders | 2 of 248 |
Serious events with the highest arm-level rate: drug-drug interaction (0.8%).
The registry's safety information is listed for the group titled All Participants. It reports 248 participants at risk for serious adverse events and 2 affected, alongside 248 at risk for other adverse events and 0 affected. Deaths are listed as 0. The record also lists Drug-Drug Interaction at 0.8% among the top serious terms.
These figures should be read as the safety information recorded for the stated group, not as a comparison between treatment groups. The study is not described as randomized and no control group is listed. The registry record does not explain the detailed event-collection process, the time window for the safety summary, or whether the adverse-event fields refer to participants, event episodes, or another unit beyond the labels in the record. It does not report a breakdown of event severity beyond the serious-event classification or explain how the listed term was coded.
The safety counts do not establish that an event was caused by treatment. In general, observational safety summaries record events occurring in the population studied; attribution requires additional information and methods. No causal assessment is reported in the registry record. The listed 0.8% should not be treated as a comparative risk or used to infer the chance of an event in a different population.
12. What the Result Does, and Does Not, Mean
The record establishes that a completed retrospective observational study was registered to describe participant characteristics and healthcare resource use among adults with COVID-19 prescribed nirmatrelvir, ritonavir in Saudi Arabia. Its primary measure concerns education level at the prescription date, and its listed secondary outcomes concern healthcare use during the 30-day post-index period. The record includes safety counts for the group titled All Participants.
It does not report the outcome analyses. Although the registry lists 40 outcome measures, it lists zero analyses, and the education-category counts, healthcare resource-use estimates, and uncertainty measures are not reported in the registry record. As a result, the record does not show how many participants experienced the listed outcomes, how precise any estimate was, or how complete follow-up was for each outcome.
The study's observational design and absence of a specified comparator also matter. Descriptive findings from a treated cohort, even when reported, would not by themselves establish what would have happened to similar people without the treatment or with another treatment. The record does not report an adjusted comparative analysis or a strategy for addressing differences that may influence prescription and healthcare use.
General statistical interpretation requires both an estimate and context: the population, outcome definition, denominator, observation window, and uncertainty. Several of these design elements are described, but the estimates and analysis details needed to assess results are not reported in the registry record. No conclusion about treatment benefit, lack of benefit, or comparative safety follows from the information available in the registry entry.
13. Why This Trial Matters Statistically
This study is statistically notable as a real-world descriptive cohort rather than a randomized treatment comparison. Such studies can address questions about who received a prescription and what healthcare resources were recorded afterward. Those questions are distinct from whether a treatment caused a particular outcome. Keeping that distinction clear is important when interpreting registry entries for non-interventional research.
The primary outcome is educational classification, while the broader study aim includes demographic and clinical characteristics and healthcare resource use. This combination makes the intended descriptive scope clear, but the registry record does not report the actual counts or analyses. The difference between a registered outcome and a posted result is important: outcome definitions alone do not reveal what was observed.
The time windows also shape interpretation. The prescription date is the index date, eligible dates span 1-Apr-2022 to 30-Jun-2023, and listed resource-use outcomes concern the 30-day post-index period. A reader needs to distinguish the prescription look-back period from the period used to assess subsequent resource use. The registry gives those broad windows but does not report detailed follow-up or ascertainment procedures.
Finally, the record lists planning assumptions based on a two-arm framework, while the study design does not describe a comparator arm. This illustrates why sample-size planning assumptions should not be confused with the actual design or with observed statistical power. In general, planning calculations depend on assumptions about the comparison, effect, and allocation; they do not substitute for reported results. The registry record does not report its own sample-size justification or analyses that would connect the planning framework to the descriptive cohort.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The most consequential limitation for interpreting the registry entry is that outcome analyses are not reported. The record lists 40 outcome measures and zero analyses, leaving no posted estimates for the primary education measure or the secondary healthcare resource-use outcomes. The number evaluable for the primary measure is also not reported in the registry record.
The study is retrospective and observational, and no comparator group is described. This design can describe the cohort and its recorded resource use, but it cannot by itself separate treatment effects from other influences on prescription, patient characteristics, or healthcare use. The registry record does not report an adjustment approach or a comparative analysis.
Important operational details are not reported in the registry record, including the data sources, outcome ascertainment procedures, completeness of follow-up, and handling of missing data beyond the stated evaluability rule for the primary measure. The record does not explain how participants were identified or how eligibility was applied in practice. The number of people with missing primary-outcome data and the denominator for each secondary outcome are not reported.
The record also does not report a detailed statistical analysis plan, a multiplicity approach, interim analyses, or the study's own sample-size justification. The planning assumptions mention equal allocation between two arms, which is not a description of the recorded single-cohort design. These gaps prevent appraisal of analytic choices and precision. The listed safety figures are not accompanied by a detailed collection window or an explanation of event attribution. These limitations concern what the registry record reports; they do not establish that the underlying study lacked procedures or data that were not entered in the record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: A Study of COVID-19 Patients Receiving Treatment With Nirmatrelvir; Ritonavir in the Kingdom of Saudi Arabia — NCT06016556.
- Registry record last updated 2025-06-05; status last verified 2025-05.
- Results first posted 2025-04-29.
- 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
NCT06016556 is a completed retrospective observational, non-interventional study sponsored by Pfizer. It concerns adults with COVID-19 prescribed nirmatrelvir, ritonavir in Saudi Arabia, with planned enrollment of 250. The study began on 2023-10-17 and had primary completion on 2024-04-09.
The primary measure counts participants by education level at the prescription date. Listed secondary outcomes cover healthcare resource use during the 30-day post-index period, including hospitalization, intensive care, oxygen, vasopressor use, and intubation. The registry lists 40 outcome measures and zero analyses; outcome estimates are not reported in the registry record.
The safety entry lists 248 participants at risk for serious adverse events, 2 affected, 0 affected by other adverse events, and 0 deaths. Drug-Drug Interaction is listed at 0.8% among the top serious terms. These safety figures are descriptive and are not a comparison between treatment groups.