of topical lignocaine to decrease the gag reflex while sampling for Covid-19:
Does it affect the yield of the specimen?
Covid-19 Real Time- Polymerase Chain Reaction (RT-PCR)
testing hinges on the undertaking of nasal/
nasopharyngeal and oropharyngeal swabs.1,2,3 One of the major challenges while doing this
sampling is the gag and cough reflex that may lead to aerosol generation.4
The gag leads to additional risk to
health care personnel. It is also possible that the consequent inadequate or
“defensive” sampling may lead to false negative tests.
Otolaryngologists have been using lignocaine
lozenges to minimise the gag reflex while performing the pharyngeal and
laryngeal procedures. However, before we advocate widespread use of these
lozenges for oropharyngeal sampling, we need to know whether these sprays
affect the quality of the specimen obtained, causing false negatives or
positives. Through this prospective study we wish to assess the effect of
topical lignocaine on the quality of the specimen obtained.
objective - To ascertain if a pre-swab lignocaine lozenge affects the quality
of the nasal and pharyngeal swab taken to conduct of the RT-PCR Covid-19 test.
Adult patients testing positive on the
RT-PCR Covid-19 test undertaken as per standard practice (no topical lignocaine)
at AIIMS, New Delhi will be included after a written informed consent.
criteria- Minors, pregnant ladies, patients refusing to participate in the
study, patients with history of hypersensitivity to lignocaine and patients on ventilator
support will be excluded.
Sample size (N) = 30
The pharyngeal swab shall be repeated
within 72 hours of the first swab tested as positive. Unlike the first swab
(Gold Standard) the second swab would be taken after xylocaine anaesthesia.
xylocaine anaesthesia would be administered by the patient sucking a lignocaine
lozenge (200 mg) to achieve local pharyngeal anaesthesia. The repeat swab shall
be taken after 3-5 minutes of the local anaesthetic application.
The repeat throat and nasal swab shall be tested as per usual procedure by qualitative
reverse transcription real-time Polymerase Chain Reaction (RT-PCR) for
detection of SARS Coronavirus-2 RNA.
The sensitivity of the second “swab with anaesthesia” shall be compared with
the Gold Standard initial swab without anaesthesia
1. Wang W,
Xu Y, Gao R, et al. Detection of SARS-CoV-2 in Different Types of Clinical
Specimens. JAMA. March 2020. doi:10.1001/jama.2020.3786
2. Zou L, Ruan F,
Huang M, et al. SARS-CoV-2 Viral Load in Upper Respiratory Specimens of
Infected Patients. N Engl J Med. 2020;382(12):1177-1179.
3. Kim C, Ahmed
JA, Eidex RB, et al. Comparison of nasopharyngeal and oropharyngeal swabs for
the diagnosis of eight respiratory viruses by real-time reverse
transcription-PCR assays. PLoS One. 2011;6(6):e21610-e21610.
4. van Doremalen
N, Bushmaker T, Morris DH, et al. Aerosol and Surface Stability of SARS-CoV-2
as Compared with SARS-CoV-1. N Engl J Med. March 2020.