Beckman access immunoassay system

For the current study, serum PSA concentration, measured in ng/mL, was determined using the Hybritech Total PSA Assay in the Beckman Access Immunoassay System (Beckman Coulter, Fullerton, CA) [27 (link)]. All male participants above 40 years were eligible to have their PSA levels assessed, except those with recent rectal examination within the preceding week, cystoscopy or prostate biopsy within the past month, ongoing prostate gland inflammation or infection, and any history of PCa [28 ]. Dichotomous ( < = 4 ng/mL or > 4 ng/mL) PSA data were used as outcome variables in our analyses. where 4 ng/mL is the current clinical cut-point for a positive screen [29 (link)–31 (link)].

Serum levels of the sex hormones estradiol (E2) and follicle-stimulating hormone (FSH), as well as total cholesterol, triglycerides, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), fasting glucose, alanine aminotransaminase (GPT), and aspartate aminotransaminase (GOT), were measured using standard procedures at the Department of Laboratory Medicine, Changhua Christian Hospital. In brief, FSH and E2 levels in undiluted specimens were measured using the Access hFSH assay and the Access Estradiol assay on the Beckman Access Immunoassay system with a dynamic range of ≥3.5 log units (Beckman Coulter, Fullerton, CA, USA). The lower limits of detection for E2 and FSH were 20 pg/ml and 0.2 mIU/mL, respectively. All measured specimens were analyzed in duplicate and within the range of detection of the standard curve. The inter- and intra-assay laboratory CVs for E2 were <7.6% and 8.2%, respectively, and the corresponding CVs for FSH were <8.1% and 5.3%, respectively.

The concentrations of both estradiol and follicle-stimulating hormone (FSH) were measured using standard procedures at the Department of Laboratory Medicine, Changhua Christian Hospital. Briefly, the concentrations of estradiol and FSH were measured in plasma specimens using the Access Estradiol assay and the Access hFSH assay, respectively, on the Beckman Access Immunoassay system (Beckman Coulter, Fullerton, CA, USA). Values for estradiol were reported as pg/ml, and those for FSH were reported as mIU/mL. The interassay and intraassay laboratory coefficients of variation (CVs) for estradiol were < 8% and 8.3%, respectively, and for FSH were < 8% and 6.2%, respectively. In addition, total WBC number was counted by an automatic Lab instrument at the Department of Laboratory Medicine, Changhua Christian Hospital.

Blood samples were collected between 08:00 am and 10:00 am. All serum samples were measured in batches in the laboratory center of Wuhan Tongji Reproductive Medicine Hospital. Serum TT, sex hormone-binding globulin (SHBG) and luteinizing hormone (LH) were assayed by chemiluminescent immunoassays on a Beckman Access Immunoassay System (Beckman Coulter, USA). cFT was calculated from TT and SHBG using mass action equations as described by a previous study^{18 (link)}. Testosterone secreting Index (TSI) was calculated using the TT/LH equation and free testosterone index (FTI) was calculated using the TT/SHBG equation. Serum concentrations of fasting blood glucose (FBG), triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C) were measured directly with a Roche combas6000 System (Hoffmann-La Roche Ltd., Sweden).

TT, SHBG and luteinizing hormone (LH) were measured by chemiluminescent immunoassays on a Beckman Access Immunoassay system (Beckman Coulter, Inc., Brea, CA, USA). It is difficult and expensive to directly measure FT; however, calculated free testosterone (cFT) is highly correlated with FT and has been used in previous research studies [35 (link), 36 (link)]. cFT was quantified using Vermeulen’s formula [35 (link)]. Testosterone secreting index (TSI) was defined as TT (nmol/L) / LH (IU/L).

Height and weight were measured before the face-to-face interview, and BMI was calculated as mass (kg)/height (m)² [44 (link)]. A fasting venous blood sample was collected between 7:00 a.m. and 11:00 a.m., and serum was isolated, stored at -70° C, and assayed for TT, LH, and SHBG using standard chemiluminescent immunoassays (Beckman Coulter, USA) on a Beckman Access Immunoassay system (Beckman Coulter, USA). Between-day coefficients of variation for TT were 8.10% at 0.35 ng/mL and 6.26% at 12.88 ng/mL; SHBG, 5.4% at 6.3 nM and 5.2% at 171 nM; and LH, 6.4% at 4.01 IU/L and 5.4% at 55.04 IU/L. Serum calculated free testosterone (CFT) was calculated based on TT and SHBG as described [45 (link)].