[SARS-CoV-2 seroprevalence study in patients undergoing addiction treatment in Madrid.]

Patients with addiction are a vulnerable group in which there is little data on the infection and severity of COVID-19. The objective of this study was to analyze the seroprevalence against SARS-CoV-2 in users in treatment for addictions in Madrid and to describe the factors related to the infection in this group.

Cross-sectional descriptive study (June-October 2020), in a non-probabilistic sample of 473 patients with Substance Use Disorder, from the 8 Addiction Care Centers (CAD) of the Madrid City Council. Their demographic, habits and health characteristics, IgM and IgG for SARS-CoV-2, previous PCR, presence of symptoms, contact with COVID-19 cases were described, and multivariate analysis was performed using binary logistic regression.

5.1% of the users had positive serology for SARS-CoV-2 (5.8% in men and 2.7% in women). The patients with the highest percentage of seropositivity were between 50-59 years old (8.3%), being the most prevalent main substance consumed alcohol (7.4%). Having a previous positive CRP showed a significant odds ratio (OR) regarding being seropositive in the frequentist analysis.

The highest seroprevalence rate occurred among men, epidemiologically known factors being the ones that showed the greatest strength of association. The CAD seropositive user profile was a man at the age of 50, an alcohol user and without comorbidities. No characteristic related to substance use was found to justify the difference in risk of infection with the general population.