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Psoriasis or eczema? One‐year results from the DGUV research project FB323 with application of the Molecular Classifier in occupational dermatoses

hand eczema is a complex and multifactorial skin disease, for which treatment remains challenging [1]. The most important differential diagnosis is psoriasis. An exact diagnosis is often not possible, due to a similar clinical picture. Moreover, dermatopathohistological analysis often cannot distinguish between the two diseases [2]. This is of great importance, however, especially because of differences in systemic therapeutic treatment. A few years ago, the development of the Molecular Classifier signified an important step towards an accurate diagnostic tool able to distinguish psoriasis from eczema with high probability [3]. The disease-specific expression of the genes NOS2 and CCL27 is used for this purpose. With such expression data it was possible to train a classifier that achieved an average accuracy of about 97 % in test cohorts [4]. In occupational dermatology practice, individual cases have shown how molecular diagnostics can positively influence the course of treatment and lead to improvement or healing of the clinical picture [5]. Since November 2020, a patient cohort (N ≥ 282) is being established in the Division of Occupational Dermatology at Heidelberg University Hospital. The aim is to verify whether a diagnosis made with the Molecular Classifier shortens the course of the disease, reduces therapy costs, reduces sick days, reduces the individual burden of disease, improves health-related quality of life, and enables continued occupational activity in the long term (described in more detail in [6]). For this purpose, participants will be followed up at 6, 12, 24, and 36 months after study inclusion using standardized survey instruments. Primary endpoints of the study are the number of days of incapacity to work during the one-year follow-up and the number of patients who have had to give up their occupation due to the skin disease. These will then be compared with reference values already available from another cohort (control group). Here, data from a total of 224 patients with the suspected diagnosis “psoriasis palmo-plantaris” and the differential diagnosis “palmoplantar eczema” over a 3-year follow-up period are available. Initial results will be presented after completion of the first project year. By November 2021, 154 participants from 49 centers across Germany were included (85 men, 69 women, median: 53 years, range: 20–67 years, standard deviation [SD]: 12.1). The mean number of sick days was 20.6 (min: 0, max: 304), but with considerable dispersion (SD: 49.77, interquartile range [IQR]: 14.2). The therapies performed so far and changes after six months are shown in Table 1. Study participants were mainly employed in the metal/electrical (17.5 %, 27) and nursing/health (16.9 %, 26) sectors. In 105 (68.2 %), treatment was covered by an employers’ liability insurance association (Berufsgenossenschaft, BG) mainly (BG Holz Metall: 16.2%, BG Gesundheitsdienst und Wohlfahrtspflege: 15.6 %, BG Rohstoffe und chemische Industrie: 7.8 %). A skin disease had persisted in median for three years (min: < 1 year, max: 47 years, SD: 8.59). Hands were affected in 76.0 % of cases, mainly palms (67.5 %), interdigital spaces (38.3 %), and the backs of hands (26.0 %), as well as feet (48.1 %), legs (27.8 %), and arms (18.8 %). Using the Physician Global Assessment (PGA), the severity of skin disease on the hands was rated as “moderate” by the treating dermatologist in 48.1 % (65) of study participants. “Severe” and “very severe” dermatosis of the hands was present in 28.1 % (38) and 3.7 % (5) of study participants, respectively, and “mild” instances in 20.0 % (27) (n = 135). In 31.2 % of cases, no specific clinical diagnosis could be made by the dermatologist. Using the Molecular Classifier, these physicians obtained a diagnosis in over 99 % of cases (Table 1). The suspected diagnosis of “psoriasis” was made in 23.6 % of cases. However, the Molecular Classifier deClinical Letter