TABLE 1.

Serum samples and controls used to evaluate specificity parameters.

Positive control (HP-HS)	Human serum COVID-19 IgG/IgM BIOIVT cod. 368424-SR1
Negative control (NS-HS)	Negative human serum, Minus IgA/IgM/IgG
Pool of heterologous sera (HP-HET)	BIOIVT cod. 406910-SR1; Pertussis Antiserum (human) 1st IS-WHO international Standard; Influenza antibody (human) to A/California/7/2009 “like” (H1N1v) virus (2nd International Standard); Diphtheria antitoxin human IgG (1st International Standard).
Pos-Het (HP-HS/HP-HET)	Positive antibody response for homologous virus mixed with heterologous serum (ratio 1:1)
Pos-Neg (HP-HS/NS-HS)	Positive antibody response for homologous virus mixed with negative serum sample (ratio 1:1)
Negative human serum sample	Negative human serum sample provided by the University of Milan (UNICORN study) (Milani et al., 2020)