Architect i2000 platform

Standard biochemical parameters were assessed in the laboratory at the Faculty Hospital in Pilsen. The estimated glomerular filtration rate (eGFR) was calculated using the Modification of Diet in Renal Disease (MDRD) formula. Albuminuria is expressed as a urinary albumin-to-creatinine ratio (ACR). High-sensitivity cardiac troponin I (hsTnI) was measured using the Architect i2000 platform with STAT High Sensitive Troponin-I assay (Abbott Diagnostics, USA) (limit of quantification 4–10 ng/l, 10 % coefficient of variation 4.7 ng/l, 99th percentile 26.2 ng/l, percentage of measurable values in healthy population >80 %). Plasma levels of osteoprotegerin were measured using multiplex immunoanalyses based on xMAP® technology, commercially available kits MILLIPLEX MAP Human Bone Panel 1A magnetic (Merck-Millipore Corporation, USA) and the MAGPIX instrument (Luminex Corporation, USA). xMAP® technology and the MAGPIX system uses color-coded magnetic microspheres coated by antibodies to perform quantitative sandwich immunoanalysis of proteins in a variety of sample matrices.

Serum testing was conducted by the Regional Clinical laboratory using the quantitative SARS-CoV-2 S1/S2 IgG LIAISON® test (DiaSorin, Vercelli, Italy) on the LIAISON XL platform, following the manufacturer’s instructions. This test discriminates among negative (<12AU/mL; with 3.8 as the limit of IgG detection), equivocal (12.0–15.0 AU/mL) and positive (> 15.0 AU/mL) subjects.
In those cases in which a) IgG anti S1/S2 quantification was higher than the limit of detection (i.e. >3.8 AU/mL) but did not reach the limit of discrimination (i.e. <15 AU/mL) and/or b) when the healthcare workers answered the questionnaire saying that he or she had been diagnosed of COVID-19 but IgG anti S1/S2 where lower than 15 AU/ml, additional serological study was performed using a different antigen (N) as a target. In this case, a SARS-CoV-2 IgG test (Abbott Diagnostics, Sligo, Ireland) was run on an Architect i2000 platform (Fig 1). This test discriminates among negative (<1.4 Index (S/C)) and positive (≥1.4 Index (S/C) subjects.
Positive and equivocal results were accompanied by a statement that the results did not indicate immunity to COVID-19 and healthcare workers should continue to wear full personal protective equipment. Participants with equivocal results were offered to be retested 4 weeks after the initial sample extraction.

All serologic testing was performed using the Chemiluminescent Microparticle ImmunoAssay (CMIA) technique on the Architect i2000 platform (Abbott Diagnostics, Wiesbaden, Germany). The system provides standardized quantitative results for HBsAg and anti HBsAg, expressed as International Units and milliInternational Units (IU/mL and mIU/mL), respectively (samples exceeding the linear range were quantified after automatic dilution using the instrument for both assays). HBV DNA load was measured using the COBAS TaqMan HBV test (Roche, Pleasnton, CA, USA).