Immulite 1000 immunoassay system

All study participants underwent the following hormonal work-up: 8 a.m. serum/plasma cortisol, ACTH, Ald, DRC, dehydroepiandrosterone sulfate (DHEA-S), natrium (na), potassium (K), 8 p.m. cortisol, 8 a.m. post 1 mg DST cortisol, 24 h urinary excretion of: free cortisol (UFC), aldosterone, natrium (UNaE), potassium, as well as meta- and normetanephrines, and 3-metoxy-thyramine. Morning baseline blood samples were drawn after a night’s rest and two hours of upright posture (seated position 5–15 min before venipuncture). The following were also examined: high-sensitivity CRP, TSH, lipid profile, and 24 h albumin excretion. Laboratory examinations were performed in the Central Diagnostic Laboratory of the same hospital using a Siemens IMMULITE 1000 Immunoassay System (most biochemical tests) and Abbott Architect analyzer (spectrophotometric method). Ald and DRC were determined by immunochemiluminescence using DiaSorin assays. Reference ranges recommended by manufacturers were adopted as normal. Due to a lack of local ADRR thresholds, in accordance with a recent consensus statement, a permissive cutoff of 1.2 ng/mL/mIU/L was adopted (ADRR is further given without units) [11 (link)]. Ald of at least 4 ng/dL was considered unsuppressed.

Blood was drawn from an upper extremity vein between 8 and 10 a.m., centrifuged for 10 minutes at 12000 rpms, after which serum and plasma were extracted and kept at -20 degrees C. Dry ice was used to transport frozen samples to the Central Diagnostic Laboratory of the same hospital, where concentrations of PTH, Ca, phosphate (P), aldosterone (Ald), B-type natriuretic peptide (BNP) and plasma renin activity (PRA) were determined. A Siemens IMMULITE 1000 Immunoassay System was used to measure serum PTH concentrations; Ca, P and BNP concentrations were measured with an Abbott Architect analyzer (spectrophotometric method). Ald concentrations and PRA were determined by immunochemiluminescence using DiaSorin assays. Reference ranges recommended by manufacturers were adopted as normal. Ald-to-PRA ratio (ARR) below 30 ng/dL: ng/mL/h was considered normal.