Clinical application of free/total PSA ratio in the diagnosis of prostate cancer in men over 50 years of age with total PSA levels of 2.0-25.0 ng ml-1 in Western China

The goal of this study was to investigate the clinical application of free/total prostate-specific antigen (F/T PSA) ratio, considering the new broad serum total PSA (T-PSA) “gray zone” of 2.0–25.0 ng ml⁻¹ in differential diagnosis of prostate cancer (PCa) and benign prostate diseases (BPD) in men over 50 years in Western China. A total of 1655 patients were included, 528 with PCa and 1127 with BPD. Serum T-PSA, free PSA (F-PSA), and F/T PSA ratio were analyzed. Receiver operating characteristic curves were used to assess the efficiency of PSA and F/T PSA ratio. There were 47.4% of cancer patients with T-PSA of 2.0–25.0 ng ml⁻¹. When T-PSA was 2.0–4.0 ng ml⁻¹, 4.0–10.0 ng ml⁻¹, and 10.0–25.0 ng ml⁻¹, the area under the curve (AUC) of F/T PSA ratio was 0.749, 0.769, and 0.761, respectively. The best AUC of F/T PSA ratio was 0.811 when T-PSA was 2.0–25.0 ng ml⁻¹, with a specificity of 0.732, a sensitivity of 0.788, and an optimal cutoff value of 15.5%. The AUC of F/T PSA ratio in different age groups (50–59 years, 60–69 years, 70–79 years, and ≥80 years) was 0.767, 0.806, 0.815, and 0.833, respectively, and the best sensitivity (0.857) and specificity (0.802) were observed in patients over 80 years. The T-PSA trend was in accordance with the Gleason score, tumor node metastasis (TNM) stage, and American Joint Committee on Cancer prognosis group. Therefore, the F/T PSA ratio can facilitate the differential diagnosis of PCa and BPD in the broad T-PSA “gray zone”. Serum T-PSA can be a Gleason score and prognostic indicator.

[Interference of Exogenous Insulin on Insulin Detection Test by Electrochemiluminescence Immunoassay]

OBJECTIVE

To explore the interference of exogenous insulin therapy on insulin detection test by electrochemical luminescence immunoassay (ECLIA).

METHODS

Insulin level was determined by ECLIA. According to the requirements of EP7-A2 of American Society for Clinical Laboratory Standards Institute Standards, paired difference experiment was conducted to evaluate the interference of 8 kinds of exogenous insulin on insulin detection, dose effect experiment was conducted to determine the relationship between exogenous insulin concentration and interference degree.

RESULTS

When the interfering substance concentrations were ≤250 μU/mL, Gansulin N^Ⓡ, Gansulin R^Ⓡ, Humulin R^Ⓡ,Novolin R^Ⓡ and Lantus^Ⓡ all showed linear positive interference, while Levemir^Ⓡ showed a linear negative interference in high concentrations insulin and non-interfering in low concentrations insulin, Humalog^Ⓡ and Novo Rapid^Ⓡ showed non-interference in insulin detection.

CONCLUSIONS

The use of different exogenous insulin may have different interference on insulin measurement, which need laboratorians and physicians notice to avoid misdiagnosis.