Viral load and chemosensitive disorders in COVID-19 patients: a
correlation that need accurate investigation.
Dear editor,
We read with interest the article by Balajelini et al. [1].
The authors analysed correlations between viral load (VL) and the
presence and duration of chemosensory disorders (CD) in a series of
coronavirus disease 2019 (COVID-19) patients. Authors reported
significant inverse correlation between these two variables. Other
researchers did not find such significant correlations [2,3]. This
topic is interesting from a pathogenetic rather than a prognostic point
of view as most authors agree that VL does not represent a reliable
prognostic index. We congratulate authors for the research. However, we
would like to point out some critical issues that may have influenced
their results in order to present some reflection points for further
studies.
First, the assessment of the chemosensitive functions was not based on
psychophysical tests. The use of psychophysical assessment is important
because it has been shown that the self-reported olfactory and gustatory
loss may significantly underestimate the real prevalence and recovery of
CD in COVID-19 patients [4]. Second, the VL is indirectly
determined, through the cycle threshold (CT) which is inversely
proportional to the amount of viral nucleic acid in the sample. Although
it is widely used due to its ease of execution and low cost, a growing
number of authors are reporting that CT is an unreliable index to
estimate the VL and, therefore, considering its use with great caution
in clinical studies [5]. The CT value is largely influenced by the
possible bias introduced by an incorrect sampling correlated to an
operator-dependent procedure such as the naso-pharyngeal swab. On the
contrary, direct quantitative tests allow to normalize the VL on the
basis of the swab’s concentration of human endogenous targets, normally
present in the nasopharyngeal mucosa, eliminating the bias of any
incorrect sampling [3,5]. Using a direct method of viral
quantification and psychophysical tests, we did not find any correlation
with either the severity or the persistence of CD at 60 days [3],
supporting that chemosensitive dysfunctions in COVID-19 are independent
from viral load and activity and rather related to individual factors.
A solid and accurate methodology is needed to explore such delicate
topics, which can feed wrong attitudes in the lay public in the belief
that the presence of a chemosensitive disorder can be an indication of a
lower VL and therefore of a lower contagiousness or a better prognosis.
REFERENCES
- Taziki Balajelini MH, Rajabi A, Mohammadi M, Nikoo HR, Tabarraei A,
Mansouri M et al. Virus load and incidence of olfactory, gustatory,
respiratory, gastrointestinal disorders in COVID-19 patients: a
retrospective cohort study. Clin Otolaryngol. 2021.
Doi:10.1111/COA.13844.
- Cho RHW, To ZWH, Yeung ZWC, Tso EYK, Chau SKY, Leung EYL et al.
COVID-19 viral load in the severity and recovery from olfactory and
gustatory function. Laryngoscope. 2020;130:2680-2685.
- Vaira LA, Deiana G, Lechien JR, De Vito A, Cossu A, Dettori M et al.
Correlations between olfactory pshychophysical scores and SARS-CoV-2
viral load in COVID-19 patients. Laryngoscope. 2021. Doi:
10.1002/lary.29777.
- Vaira LA, Lechien JR, De Riu G, Saussez S. Chemosensory dysfunction in
COVID-19: is there really a correlation with viral load? Am J
Otolaryngol. 2021;42:103037.
- Rhoads D, Peaper DR, She RC, Nolte FS, Wojewoda CM, Anderson NW et al.
College of American Pathologists (CAP) Microbiology Committee
Perspective : caution must be used in interpreting the cycle threshold
(Ct) value. Clin Infect Dis. 2021;72:e685-e686.