Validation of a Diagnostic Test for Glucose-6-phosphate Dehydrogenase (G6PD) Deficiency in Anti-coagulated Blood: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Validation of a Diagnostic Test for Glucose-6-phosphate Dehydrogenase (G6PD) Deficiency in Anti-coagulated Blood (NCT04054661), a na na study. The primary outcome is Sensitivity of SD Biosensor STANDARD G6PD Test for Identifying G6PD Deficient Individuals.

2. Clinical Question

The central question is therefore about agreement with a defined reference classification: whether the test identifies participants whom the Pointe Scientific assay classifies as deficient. It does not ask whether a treatment changes a health outcome, and the diagnostic test itself is not a therapeutic intervention. Separate study aims addressed repeatability in capillary samples and accuracy of hemoglobin measurements, as well as sample stability during storage. Those aims add context about measurement performance but do not replace the primary sensitivity question.

3. Trial Design

This was a completed, single-group diagnostic validation study registered as NCT04054661. The registry lists an enrollment of 229. Its allocation is recorded as NA, and masking is recorded as none. These entries do not describe a randomized comparison or blinded assessment. The study started on 2019-08-12, and primary completion was recorded as 2020-01-31.

Participants provided whole blood and fingerstick capillary blood samples. At the clinic site lab, study staff conducted the SD Biosensor STANDARD point-of-care G6PD test and the point-of-care HemoCue hemoglobin test on both fingerstick blood and whole blood samples. The Pointe Scientific test kit served as the reference assay for the primary G6PD sensitivity question. The intervention list also names the HemoCue system, while secondary outcomes address the SD Biosensor hemoglobin measure against a reference hemoglobin test.

The primary outcome was sensitivity of the SD Biosensor STANDARD G6PD test for identifying G6PD-deficient individuals. It was defined as the percentage of participants positive on the reference test who were also positive on the test assay. The endpoint description says sensitivity was calculated from both venous and capillary blood samples, and that all samples were collected on study day 1. The record also lists secondary questions about accuracy, repeatability by operator and analyzer, and stability after room-temperature or refrigerated storage.

Because the design is single-group and diagnostic, the meaningful comparison is between test classifications and a reference assay, rather than between like-for-like treatment arms. The registry records the study as completed but does not report the primary estimate, its confidence interval, or results for the listed secondary outcomes. The study phase is recorded as NA.

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: Final analytic population with available data

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: Final analytic population includes all participants that were not previously enrolled, met eligibility criteria, and their STANDARD Test results were not affected by STANDARD Test Kit Recall.

6. Primary Endpoint

The registry lists the primary outcome as Sensitivity of SD Biosensor STANDARD G6PD Test for Identifying G6PD Deficient Individuals, measured over All samples were collected on study day 1.

The primary endpoint is the sensitivity of the SD Biosensor STANDARD G6PD test for identifying participants classified as G6PD deficient by the Pointe Scientific reference assay. Sensitivity is the proportion of reference-positive participants whom the test also classifies as positive. In this study, a true positive was defined using a reference result of ≤ 30% of normal G6PD activity in circulating venous blood. A reference-positive participant missed by the test is a false negative and contributes to the denominator without contributing to the numerator.

Sensitivity is useful because it focuses on how often a test detects people who meet the study’s reference definition of deficiency. It does not, by itself, describe how often a positive test is correct among everyone who tests positive. That complementary question concerns positive predictive value, which is not the primary endpoint described in the registry. Nor does sensitivity alone summarize overall agreement, specificity, or performance in every population or setting.

The endpoint description states that sensitivity was calculated using both venous and capillary blood samples, with all samples collected on study day 1. It specifies a 95% confidence interval as the measure of uncertainty. However, the registry record does not report the sensitivity estimate, the confidence interval, or the underlying classification counts. Thus the endpoint definition is available, but the observed diagnostic performance cannot be assessed from the reported primary result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does sensitivity measure?

Sensitivity is a conditional proportion. Its denominator consists of participants who meet the study’s reference definition of a positive case; its numerator consists of those same participants who also test positive on the diagnostic test being evaluated. In this study, a test-positive participant who is positive by the reference contributes to the numerator, while a reference-positive participant with a negative test is a false negative. A sensitivity estimate therefore addresses detection within the reference-positive group, not classification of all participants.

That distinction is important when interpreting diagnostic performance. Specificity instead considers reference-negative participants and asks how often the test is negative among them. Predictive values condition on the test result and ask how often a positive or negative result corresponds to the reference classification. These quantities answer different questions and cannot be substituted for one another. The registry describes sensitivity as the primary endpoint; the result needed to assess that measure is not reported in the registry record.

Why use a reference assay?

A diagnostic validation study needs an operational basis for determining which participants count as cases for comparison. Here, the Pointe Scientific test kit was the reference assay for the primary G6PD question. The record defines a true positive as a participant with ≤ 30% of normal G6PD activity in circulating venous blood as determined by that assay, and it states that an individual was considered G6PD deficient if they tested positive in the Pointe Scientific assay. The estimated sensitivity would therefore describe agreement with this reference definition. It should not be read as an assessment independent of the reference method or its stated classification rule.

Reference-based comparisons are informative, but interpretation depends on the reference procedure and the way the study applies it. The registry gives the assay name and the stated threshold, but it does not report the paired classification counts or the resulting sensitivity. It also does not provide results that would allow readers to assess other diagnostic measures such as specificity.

What does the confidence interval add?

A confidence interval communicates statistical uncertainty around an estimated quantity. General statistical interpretation is that a narrower interval indicates greater precision under the assumptions of the method used, while a wider interval indicates less precision. A confidence interval is not a guarantee that the true value lies inside that particular interval, and it does not by itself determine whether an estimate is useful for a particular purpose.

The primary endpoint lists a 95% confidence interval, but the actual interval is not reported in the registry record. Without both the estimate and its interval, it is not possible to assess either the observed sensitivity or the precision of that estimate. The registry also does not describe the interval calculation method.

How do repeatability and stability differ?

Repeatability concerns whether repeated measurements under the conditions being studied give similar results. The registry lists capillary G6PD and hemoglobin repeatability outcomes by operator and analyzer. That wording indicates that operator and analyzer are factors of interest; the record does not provide the repeatability estimates or enough detail to specify the exact statistical model.

Stability concerns whether measurements remain consistent after samples are stored over time. The listed stability outcomes distinguish room-temperature storage from refrigerated storage and address both G6PD and hemoglobin levels. These questions are related to measurement quality, but they are not the same as sensitivity against a reference assay. The registry record does not report the storage-time results or the analysis methods used for them.

What analysis plan is documented?

The registry states the primary endpoint, the reference definition, the available-data analysis population, and the confidence-interval level. It does not report a statistical analysis plan, the method used to construct the confidence interval, handling of missing observations, or any adjustment for multiple analyses. The record lists 12 outcome measures and 0 analyses. These registry entries do not establish whether analyses were performed outside the registry or what methods were used for them.

The record’s sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration is not the trial’s own design, and the registry’s study design is single-group rather than a randomized two-arm comparison. Such a planning illustration should not be interpreted as observed power or as evidence about the precision of this diagnostic estimate. Since the primary result is not reported, the observed effect underlying the illustration cannot be evaluated from the registry record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 12 outcome measures and 0 analyses. The named secondary outcome topics include accuracy comparisons for G6PD and hemoglobin, repeatability assessments, and sample stability assessments under room-temperature and refrigerated storage. The primary endpoint is sensitivity of the SD Biosensor STANDARD G6PD test against the Pointe Scientific reference assay. The registry record does not report results for these outcomes.

When a study examines multiple outcomes or analyses, the chance of finding an apparently notable result by chance can increase if each is assessed separately. Statistical approaches to address this include prespecifying a primary outcome, adjusting for multiple comparisons, or treating secondary analyses as exploratory. These are general considerations, not a description of what this study did. A multiplicity strategy or analysis hierarchy is not reported in the registry record, so it is not possible to determine whether or how multiplicity was handled.

The primary analysis population is described as the final analytic population with available data. This indicates that the endpoint concerns participants with available data, but the registry does not report how many had usable measurements for each sample type, how much data were missing, or why any measurements were unavailable. It does not describe imputation, exclusions, or sensitivity analyses for missing data. Enrollment should therefore not be assumed to equal the number included in every endpoint calculation.

The record also does not report the primary estimate, its 95% confidence interval, or the analysis method used to calculate it. These omissions limit assessment of both precision and robustness. No conclusion about the effects of missing data or multiple testing can be drawn from the registry record alone.

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 lists the G6PD Diagnostic Testing group with 229 participants at risk for serious adverse events and 0 affected, 229 at risk for other adverse events and 0 affected, and 0 deaths. No serious adverse event terms are listed. These are the safety figures recorded for this diagnostic-testing study.

Zero recorded events should be interpreted as a registry entry, not as proof that no events occurred under any circumstance. The record does not describe how adverse events were collected, the period or procedures used for safety surveillance, or whether all events were judged related to study procedures. It also does not provide detailed event narratives or additional context about reporting. The numbers do not support a comparison of safety between treatments: the study is single-group and does not have a like-for-like control arm.

These safety counts are separate from the diagnostic endpoint. They do not indicate how accurately the test classified G6PD status or how repeatable measurements were. The registry’s reported figures can be stated as recorded, but they do not substitute for the missing diagnostic results.

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

The registry record establishes what the study set out to evaluate: the SD Biosensor STANDARD G6PD test’s sensitivity relative to the Pointe Scientific assay, with sensitivity calculated from venous and capillary samples. It also records secondary measurement questions involving hemoglobin, repeatability, and sample stability. These design details help define the intended statistical interpretation.

What the record does not establish is the observed sensitivity, its 95% confidence interval, or the results of the secondary outcomes. Without these results, readers cannot judge how often the test identified reference-positive participants, how uncertain the estimate was, or whether performance differed across the sample types and repeatability conditions that the study considered. The missing result is not evidence for a particular level of performance in either direction.

Even a reported sensitivity estimate would answer a limited question: how often the test was positive among participants classified as deficient by the study’s reference assay and definition. It would not alone provide specificity, predictive values, overall agreement, or performance in populations beyond the study’s analytic population. Those quantities require their own data and interpretation. Nor would a diagnostic validation result by itself establish clinical outcomes or the consequences of using the test in practice.

The study is recorded as completed, with enrollment of 229, but the primary analysis population is described as participants with available data. The registry does not report the endpoint-specific number of available observations or the missing-data approach. As a result, enrollment cannot be used as a substitute for the denominator in the sensitivity calculation.

The appropriate conclusion is narrow: the registry describes a diagnostic validation design and specifies its primary endpoint, but it does not report the primary result needed to assess that endpoint. No claim that the test does or does not perform well follows from the information recorded.

13. Why This Trial Matters Statistically

This study is statistically useful as an example of how a diagnostic question differs from a treatment comparison. The central comparison is between an index test and a reference assay, not between randomized clinical groups. Sensitivity is defined relative to the reference-positive classification, which makes clear both the target population for the calculation and the limits of what the measure answers.

The registry also distinguishes several measurement questions that can otherwise be conflated. Accuracy against a reference assay asks about classification agreement. Repeatability asks whether repeated measurements are consistent across operator and analyzer conditions. Stability asks whether values change after storage. These properties may all matter in evaluating a diagnostic method, but evidence for one does not automatically establish the others.

Statistical interpretation depends on more than an endpoint definition. An estimate and its confidence interval are needed to understand the observed sensitivity and its precision. The record gives a 95% confidence interval as the dispersion measure but does not report the estimate or interval. It also records an available-data analysis population without detailing endpoint-specific missingness. Those gaps show why registry status and a clearly defined endpoint are not equivalent to a complete statistical results record.

The single-group design is appropriate to describe as a diagnostic validation comparison, but it should not be mistaken for a randomized evaluation of clinical benefit or for a treatment safety comparison. The record identifies the reference assay and the classification threshold, allowing readers to understand the basis of the intended sensitivity calculation. Without reported outcome results, however, the registry cannot support a quantitative conclusion about diagnostic performance.

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 main trial-specific limitation in the registry record is the absence of the primary sensitivity estimate and its 95% confidence interval. Although the endpoint definition and reference classification are described, the record does not give the underlying counts of true positives and false negatives. The sensitivity calculation therefore cannot be checked or interpreted for magnitude and precision.

The primary endpoint combines results from venous and capillary blood samples, but separate sensitivity estimates by sample type are not reported. The official title emphasizes capillary samples, and repeatability outcomes are listed for capillary G6PD and hemoglobin measurements; however, the registry does not provide those results. The listed secondary accuracy and stability outcomes are also not accompanied by reported estimates.

The primary analysis population is stated to be the final analytic population with available data. The registry does not give endpoint-specific denominators, missingness counts, reasons for missing measurements, or a missing-data method. It is consequently not possible to assess whether available observations differ systematically from those not included in an analysis.

The record does not report the statistical analysis plan, confidence-interval method, or multiplicity approach. It records 12 outcome measures and 0 analyses, but those entries do not explain what analyses may have been carried out or how results were selected for registry reporting. The study’s single-group design also means it is not a randomized comparison of diagnostic testing arms. These limitations concern what can be concluded from the registry record; they do not establish that the study’s unreported results had any particular direction.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Validation of a Diagnostic Test for Glucose-6-phosphate Dehydrogenase (G6PD) Deficiency in Anti-coagulated Blood — NCT04054661.
• Registry record last updated 2021-11-09; status last verified 2021-08.
• Results first posted 2021-10-05.
• 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

NCT04054661 is a completed, single-group diagnostic validation study sponsored by PATH. The registry records enrollment of 229, allocation as NA, and no masking. The study evaluated the SD Biosensor STANDARD G6PD test against the Pointe Scientific reference assay and included venous and fingerstick capillary blood samples. HemoCue hemoglobin testing and the Pointe Scientific test kit are also listed among the interventions.

The primary outcome was sensitivity for identifying reference-defined G6PD deficiency, with a 95% confidence interval specified. Secondary outcome topics included diagnostic accuracy, repeatability, and sample stability. The primary result, confidence interval, secondary results, analysis methods, and endpoint-specific missing-data details are not reported in the registry record. Safety entries list 0 serious adverse events, 0 other adverse events, and 0 deaths.