Diagnostic Accuracy of 2 cm Versus 4 cm Insertion Depth for Nasal Swabs for SARS-CoV-2 (COVID-19) Rapid Antigen Testing-A Randomized Controlled Trial

Diagnostic Accuracy of 2 cm Versus 4 cm Insertion Depth for Nasal Swabs for SARS-CoV-2 Rapid Antigen Testing-A Randomized Controlled Trial

Status

Completed

Phases

Unknown

Study type

Interventional

Source

ClinicalTrials.gov

Registry ID

NCT07597889

Enrollment

317

Registered

2026-05-19

Start date

2023-02-01

Completion date

2023-02-26

Last updated

2026-05-19

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

COVID -19

Keywords

covid-19

Brief summary

This study aims to compare the diagnostic accuracy of rapid antigen detection tests (RDTs) for SARS-CoV-2 using nasal swab insertion depths of 2 cm versus 4 cm. The study is an investigator-initiated, randomized clinical trial conducted at a public COVID-19 test center in Copenhagen, Denmark. Following enrollment, participants complete a questionnaire regarding symptoms and vaccination status. Participants are randomized in a 1:1 ratio to one of two sampling sequences: either a 2 cm swab in the left nostril and a 4 cm swab in the right nostril, or vice versa. All participants undergo a healthcare worker-collected throat swab for RT-PCR analysis, which serves as the reference standard for SARS-CoV-2 infection.

Interventions

DIAGNOSTIC_TEST4 cm nasal swab - left nostril

a 4 cm nasal swab insertion in the left nostril

DIAGNOSTIC_TEST2 cm nasal swab in the left nostril

a 2 cm nasal swab insertion in the left nostril

DIAGNOSTIC_TEST4 cm nasal swab - right nostril

a 4 cm nasal swab insertion in the right nostril

DIAGNOSTIC_TEST2 cm nasal swab - right nostril

a 2 cm nasal swab insertion in the right nostril

Study design

Allocation

RANDOMIZED

Intervention model

SINGLE_GROUP

Primary purpose

DIAGNOSTIC

Masking

NONE

Eligibility

Sex/Gender

ALL

Age

16 Years to No maximum

Healthy volunteers

Yes

Inclusion criteria

* Citizens, aged 16 years or older, showing up for a SARS-CoV-2 RT-PCR test at Testcenter Valby in Copenhagen, Denmark

Exclusion criteria

* non-fluent in Danish * citizens with nasopharyngeal or oropharyngeal anomalies (e.g. neck breathers with tracheostomy)

Design outcomes

Primary

Measure	Time frame
Diagnostic accuracy (sensitivity and specificity) of SARS-CoV-2 antigen rapid diagnostic tests (Ag-RDTs) using nasal swabs collected at 2 cm versus 4 cm insertion depth, with RT-PCR as the reference standard	Baseline (during the study visit at the time of sample collection). Ag-RDT results were available immediately, whereas RT-PCR results were reported the following days (1-3 days).

Secondary

Measure	Time frame	Description
Test discomfort on a 10-point VAS-scale	Baseline (during the study visit at the time of sample collection).	Test discomfort was evaluated using a 10-point visual analogue scale (VAS), ranging from 0 (no discomfort) to 10 (worst imaginable discomfort).
Self-reported symptoms of disease	Baseline (during the study visit at the time of sample collection). Self-reported symptoms of disease were collected immediately prior to testing, during the study visit.	Self-reported symptoms of SARS-CoV-2 infection collected via questionnaire at enrollment, including presence, type, and duration of symptoms (e.g., fever, cough, sore throat, nasal congestion, loss of taste or smell)

Countries

Denmark

Outcome results

None listed

Source: ClinicalTrials.gov · Data processed: May 20, 2026