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NCT Number: NCT07597889

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

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.

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Key information

Conditions

COVID -19 COVID-19 Coronaviridae Infections Coronavirus Infections Infections Lung Diseases Nidovirales Infections Pneumonia Pneumonia, Viral RNA Virus Infections Respiratory Tract Diseases Respiratory Tract Infections Virus Diseases

Age range

16 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Rigshospitalet

Copenhagen, Denmark

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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)

Treatment and study plan

4 cm nasal swab - left nostril

Diagnostic Test

a 4 cm nasal swab insertion in the left nostril

2 cm nasal swab in the left nostril

Diagnostic Test

a 2 cm nasal swab insertion in the left nostril

4 cm nasal swab - right nostril

Diagnostic Test

a 4 cm nasal swab insertion in the right nostril

2 cm nasal swab - right nostril

Diagnostic Test

a 2 cm nasal swab insertion in the right nostril

Primary outcomes

  1. 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

    Time frame: 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 outcomes

  1. Test discomfort on a 10-point VAS-scale

    Time frame: 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).

  2. Self-reported symptoms of disease

    Time frame: 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)

Sponsors and collaborators

Lead sponsor

Rigshospitalet, Denmark

Other

Registry information

Official study title

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

Important dates

Study start
2023
Primary completion
2023
Study completion
2023
First posted
May 19, 2026
Registry last updated
May 19, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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