I2000

Detection of SARS-CoV-2 antibodies was performed by the Abbott Diagnostics SARS-CoV-2 IgG assay on an Abbott Architect i2000 according to the manufacturer’s instructions. This qualitative assay detects IgG binding to an undisclosed epitope of the SARS-CoV-2 nucleocapsid protein. The amount of IgG antibodies to SARS-CoV-2 in each sample is determined by comparing its chemiluminescent relative light unit (RLU) to the calibrator RLU (index S/C). Using an index S/C threshold of 1.4, the manufacturer reported a sensitivity of 86.4% 7 days after symptom onset and 100% after 14 days, and a specificity of 99.6%, using RT-PCR as the gold standard. These figures were corroborated by a validation study using a set of samples from patients who tested positive for SARS-CoV-2 by RT-PCR and in samples obtained in 2018–2019, thus before the epidemic (sensitivity of 100% 17 days after symptom onset and a specificity of 99.9%) (Bryan et al., 2020 (link)). A further verification study by the National Centre for Microbiology (Spain) used samples obtained before 8 December 2019 and showed a sensitivity of 89.7% in serum samples from RT-PCR-positive patients 14 days after symptom onset and a specificity of 100% (Pollán et al., 2020 (link)).

Blood samples were collected, and thyroid function was tested, by evaluating the levels of thyroid stimulating hormone (TSH), total triiodothyronine (TT3), serum total thyroxine (TT4), total triiodothyronine (TT3), free triiodothyronine (FT3) and free T4(FT4). Serum levels of TSH, TT3, TT4, FT3 and FT4 were determined by automated chemiluminescent immunoassays (Abbott i2000, Wiesbaden, Germany). Laboratory reference ranges were as follows: TSH, 0.56–5.91 μIU/ml; TT3, 1.01–2.48 nmol/l; TT4, 69.97–152.52 nmol/l; FT3, 3.28–6.47 pmol/l; FT4, 7.64–16.03 pmol/l. Thyroid dysfunction was defined as a decrease in TSH, FT3 or FT4.

A prospective single center study in 12 months period included 40 stabile a sample of 80 patients divided into two groups, test and control. In the study group is 40 stable patients with transplanted kidney of which 26 respondents forms a subgroup with duration of hemodialysis to 72 months and 14 patients forms a subgroup with duration of dialysis over 72 months before transplantation. In the control group are 40 patients with normal renal function.
Exclusion criteria were previous thyroid disorders, systemic illnesses, critically ill patients, acute inflammatory diseases.
The values of T3, T4, TSH were measured on the device Abbott Architect i2000. Reference values for TSH are 0.35 to 4.94 mIU/mL. Reference values for T4 are from 63.06 to 150.58 nmol/L, and for T3 are from 0.44 to 0.89 nmol/L. FT4 and FT3 were determined by radioimmunoassay RIA using commercial kits available. The reference values are: FT3 from 2.5 to 5.8 nmol/L, FT4 from 11.5 to 23 pmol/L. Subclinical hypothyroidism is defined by the finding of elevated TSH> 4.4 mmol/L and normal values of T3 and T4 (29 (link)). Clinical hypothyroidism is defined by the finding of TSH >10 mmol/L and a decreased level of T3 and T4 (29 (link)). Low T3 syndrome is defined by finding T3 <0.89 nmol/L, a low T4 syndrome by finding T4 <63.06 nmol/L and high T4 syndrome by findings T4 >150 nmol/L (30 (link)).