Letter to the Editor about the Beltrán-Corbellini et al. publication: 'Acute-onset smell and taste disorders in the context of Covid-19: a pilot multicenter PCR-based case-control study' (Eur J Neurol 2020. doi: 10.1111/ene.14273).,European Journal of Neurology

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Letter to the Editor about the Beltrán-Corbellini et al. publication: 'Acute-onset smell and taste disorders in the context of Covid-19: a pilot multicenter PCR-based case-control study' (Eur J Neurol 2020. doi: 10.1111/ene.14273).
European Journal of Neurology ( IF 4.5 ) Pub Date : 2020-05-22 , DOI: 10.1111/ene.14357
J R Lechien _{1,

2,

3,

4} , C Hopkins ₅ , S Saussez _{1,

2,

4}

Affiliation

Dear Editor,

We read, with interest, the paper entitled ‘Acute‐onset smell and taste disorders in the context of Covid‐19: a pilot multicenter PCR‐based case‐control study’ [1]. The authors observed that sudden loss of smell (LOS) was significantly more frequent in patients with Covid‐19 (39%) than those infected with influenza (12%). These data corroborated the results of Yan et al. [2] who reported that LOS affected 71% and 17% of positive and negative Covid‐19 patients with influenza‐like symptoms, respectively. The assessment of LOS was made through a patient questionnaire.

Their article raises several points. Firstly, the authors reported a prevalence of 5–48% for LOS in the current literature. However, recent European and American large case series reported that the LOS incidence would be higher than presumed by Beltrán‐Corbellini et al., reporting rates of 66% and 70% in mild cases of Covid‐19 infection [12, 3.

Second, the authors rejected the use of objective olfactory evaluations due to concerns about contamination and unnecessary burdens on both physician and patient. However, emerging evidence suggests that there may be a mismatch between the rate of self‐reported LOS of patients and the prevalence of anosmia and hyposmia according to psychophysical olfactory testing [4, 5]. Thus, in a cohort of 46 patients reporting LOS, objective olfactory testing found 52% and 24% of anosmic and hyposmic individuals, respectively, i.e. 24% of patients with LOS did not have olfactory dysfunctions [4]. In contrast, in a recent clinical series, Moein et al. [5] showed that 98% of patients with Covid‐19 presented an objective LOS, whereas only 38% self‐reported LOS. These studies highlight the importance of including objective testing in planning future studies. To reduce the risk of contamination or exposure for physicians, a system of mobile testing units with limited olfactory stick tests may help [4].

Third, many patients infected with influenza were contacted by telephone 2 months after discharge, which raises the possibility of underestimation of LOS in this group of patients due to recall bias.

Interestingly, the authors reported that only 13% of patients had nasal obstruction [1] whereas we observed up to 68% nasal obstruction in our series of 1420 patients with a mild form of Covid‐19 infection [3]. Despite the high frequency of nasal obstruction, there was no statistically significant correlation between anosmia and nasal obstruction, indirectly supporting the occurrence of damage to the olfactory neuroepithelium.

Finally, we fully share the conclusion of the authors suggesting the imperative to add LOS to the list of symptoms of Covid‐19 infection. We have previously stressed the need to consider initial and sudden LOS as a specific symptom of Covid‐19. France, Switzerland and the USA already adopted this point, but the World Health Organization has not yet updated their criteria. Use of self‐reported LOS and loss of taste as a marker of infection will be a very useful weapon in the Covid‐19 fight, especially in countries with emerging pandemics where access to testing will be greatly limited.

Disclosure of conflicts of interest

The authors declare no financial or other conflicts of interest.

References

中文翻译：

关于贝尔特兰-科尔贝里尼等人的致编辑的信。出版物：“Covid-19 环境下的急性嗅觉和味觉障碍：基于 PCR 的试点多中心病例对照研究”（Eur J Neurol 2020. doi: 10.1111/ene.14273）。

亲爱的编辑，

我们感兴趣地阅读了题为“Covid-19 环境下的急性嗅觉和味觉障碍：基于 PCR 的试点多中心病例对照研究”的论文 [ 1 ]。作者观察到，Covid-19 患者 (39%) 的突然嗅觉丧失 (LOS) 明显高于流感患者 (12%)。这些数据证实了 Yan等人的结果。[ 2 ] 报告说，LOS 分别影响了 71% 和 17% 的 Covid-19 阳性和阴性 Covid-19 患者的流感样症状。LOS的评估是通过患者问卷进行的。

他们的文章提出了几点。首先，作者报告了当前文献中 LOS 的患病率为 5-48%。然而，最近欧洲和美国的大型病例系列报道，LOS 发生率将高于 Beltrán-Corbellini等人的假设，在 Covid-19 感染的轻度病例中报告率为 66% 和 70% [ 1 2, 3。

其次，由于担心污染以及对医生和患者造成不必要的负担，作者拒绝使用客观的嗅觉评估。然而，新出现的证据表明，根据心理物理嗅觉测试，患者自我报告的 LOS 率与嗅觉丧失和嗅觉减退的患病率之间可能存在不匹配 [ 4, 5 ]。因此，在 46 名报告 LOS 的患者队列中，客观嗅觉测试分别发现 52% 和 24% 的嗅觉缺失和嗅觉减退个体，即 24% 的 LOS 患者没有嗅觉功能障碍 [ 4 ]。相比之下，在最近的临床系列中，Moein等人。[ 5] 显示，98% 的 Covid-19 患者呈现客观的 LOS，而只有 38% 的患者自我报告 LOS。这些研究强调了在规划未来研究中纳入客观测试的重要性。为了减少医生受到污染或接触的风险，带有有限嗅觉棒测试的移动测试单元系统可能会有所帮助 [ 4 ]。

第三，许多感染流感的患者在出院2个月后通过电话联系，这增加了该组患者由于回忆偏倚而低估LOS的可能性。

有趣的是，作者报告说只有 13% 的患者有鼻塞 [ 1 ]，而在我们的 1420 名轻度 Covid-19 感染患者系列中，我们观察到高达 68% 的鼻塞 [ 3 ]。尽管鼻塞的频率很高，但嗅觉丧失与鼻塞之间没有统计学上的显着相关性，间接支持了嗅觉神经上皮损伤的发生。

最后，我们完全同意作者的结论，即必须将 LOS 添加到 Covid-19 感染的症状列表中。我们之前曾强调需要将初始和突然的 LOS 视为 Covid-19 的特定症状。法国、瑞士和美国已经采用了这一点，但世界卫生组织尚未更新其标准。使用自我报告的 LOS 和味觉丧失作为感染标志物将是 Covid-19 战斗中非常有用的武器，尤其是在新出现大流行病的国家，这些国家的检测机会将受到极大限制。