An olfactory perceptual fingerprint in people with olfactory dysfunction due to COVID-19.

The sense of smell is based on sensory detection of the molecule(s), which is then further perceptually interpreted. A possible measure of olfactory perception is an odor-independent olfactory perceptual fingerprint (OPF) defined by Snitz et al. We aimed to investigate whether OPF can distinguish patients with olfactory dysfunction (OD) due to coronavirus disease (COVID-19) from controls and which perceptual descriptors are important for that separation. Our study included 99 healthy controls and 41 patients. They rated 10 odors using 8 descriptors such as "pleasant," "intense," "familiar," "warm," "cold," "irritating," "edible," and "disgusting." An unsupervised machine learning method, hierarchical cluster analysis, showed that OPF can distinguish patients from controls with an accuracy of 83%, a sensitivity of 51%, and a specificity of 96%. Furthermore, a supervised machine learning method, random forest classifier, showed that OPF can distinguish patients and controls in the testing dataset with an accuracy of 86%, a sensitivity of 64%, and a specificity of 96%. Principal component analysis and random forest classifier showed that familiarity and intensity were the key qualities to explain the variance of the data. In conclusion, people with COVID-19-related OD have a fundamentally different olfactory perception.

Diagnosis and management of non-clonal erythrocytosis remains challenging: a single centre clinical experience.

Erythrocytosis has a diverse background. While polycythaemia vera has well defined criteria, the diagnostic approach and management of other types of erythrocytosis are more challenging. The aim of study was to retrospectively analyse the aetiology and management of non-clonal erythrocytosis patients referred to a haematology outpatient clinic in an 8-year period using a 3-step algorithm. The first step was inclusion of patients with Hb > 185 g/L and/or Hct > 0.52 in men and Hb > 165 g/L and/or Hct > 0.48 in women on two visits ≥ two months apart, thus confirming true erythrocytosis. Secondly, polycythaemia vera was excluded and secondary causes of erythrocytosis (SE) identified. Thirdly, idiopathic erythrocytosis patients (IE) were referred to next-generation sequencing for possible genetic background evaluation. Of the 116 patients, 75 (65%) are men and 41 (35%) women, with non-clonal erythrocytosis 34/116 (29%) had SE, 15/116 (13%) IE and 67/116 (58%) stayed incompletely characterized (ICE). Patients with SE were significantly older and had significantly higher Hb and Hct compared to patients with IE. Most frequently, SE was attributed to obstructive sleep apnoea and smoking. Phlebotomies were performed in 56, 53 and 40% of patients in the SE, IE, and ICE group, respectively. Approx. 70% of patients in each group received aspirin. Thrombotic events were registered in 12, 20 and 15% of SE, IE and ICE patients, respectively. Congenital erythrocytosis type 4 (ECYT4) was diagnosed in one patient. The study demonstrates real-life management of non-clonal erythrocytosis which could be optimized using a 3-step diagnostic algorithm.