Triturus system

suPAR was measured using the BioVendor Human suPAR ELISA on the automated analyzer Triturus System (GRIFOLS, Vicopisano, Italy). The intra- and inter-assay coefficients of variation were ˂5%. IL-6 determination was performed by Chemiluminescent Immunoassay (CLIA) by Immulite 2000 (Siemens Healthcare Diagnostics, Milan, Italy). The analysis of C3, C4 and C1inh was performed through nephelometric detection by BN ProSpec System (Siemens Healthcare Diagnostics, Italy). The intra- and inter-assay coefficients of variation were ˂5%.
C-reactive protein (CRP) was determined on serum samples using an immunoturbidimetric method by Architect ci8200 (Abbott Laboratories, Illinois, USA). The reference range for CRP has been measured within the 0.5 to 1 mg/dL.
Procalcitonin was detected using chemiluminescence immunoassay on the bioMérieux VIDAS analyzer. The reference value of procalcitonin in adults is 0.15 ng/mL or less.

Apolipoprotein AI (apoAI) concentration in the HDL subfractions (HDL₂ and HDL₃) was determined using single radial immunodiffusion as previously described (24 (link)). SAA, in serum and associated with HDL₂ and HDL₃, was analyzed by an ELISA (Invitrogen UK, KHA0011), as per the manufacturer's instructions. Analysis was performed using a Grifols TRITURUS system (Italy). Interleukin-6 (IL-6) was determined by ELISA (R&D Systems). High-sensitivity C-reactive protein (hsCRP) was measured at the Department of Clinical Biochemistry at Aberdeen Royal Infirmary using a standardized automated procedure (Behring nephelometry system).

A chemiluminescent Immunoassay (CLIA) was performed for IL-6 serum determination by IMMULITE 2000 (SIEMENS Healthcare Diagnostics, Milan, Italy). Serum levels of sIL-6R and sgp130 were determined using an automated enzyme-linked immunosorbent assay (ELISA) by Triturus System (GRIFOLS, Naples, Italy). R&D Quantikine ELISA Kits (R&D Systems, Minneapolis, MN, USA—DIACHEM s.r.l., Naples, Italy) were employed for all determinations. The intra-assay and inter-assay variation coefficients were ˂5% for IL-6 and sgp130 serum levels, and ˂10% for sIL-6R, respectively.
Healthy control subjects (N = 98) without a family history of COVID-19 and with a mean age of 62.13 ± 9.28, recruited from employees of the Azienda Ospedaliera Universitaria “Federico II”, Naples, were enrolled for reference values evaluations and patient comparisons. Patient blood samples were taken at 3 intervals every 48 h to determine levels of IL-6, sIL-6R, and sgp130. Intra-assay and inter-assay variation coefficients were ˂5% for IL-6 and sgp130 serum levels and ˂10% for sIL-6R, with detection limits of: IL-6 (0.01 ÷ 350.24 pg/mL), sIL-6R (3.01 ÷ 232.82 ng/mL), and sgp130 (0.01 ÷ 2.40 ng/mL).