Analytical performance and clinical classification value of a novel sandwich immunoassay for total testosterone measurement in low-concentration and hemodialysis populations

Abstract Objectives To evaluate the analytical performance and clinical classification value of a novel sandwich testosterone immunoassay, particularly for biochemical testosterone elevation in women and deficiency in male hemodialysis patients, using LC–MS/MS as the reference method. Methods A total of 387 residual clinical serum samples were compared using Mindray TESTO, Siemens TSTII, and liquid chromatography–tandem mass spectrometry (LC–MS/MS). Among these, 226 had testosterone concentrations <1.0 ng/mL, and 133 reproductive-age women were evaluated for biochemical hyperandrogenism classification. An additional 119 hemodialysis samples (94 men, 25 women) were assessed, with the 94 men evaluated for biochemical testosterone deficiency classification. Analyses included Passing–Bablok regression, Bland–Altman analysis, and independent imprecision, linearity, and interference studies. Results The Mindray TESTO assay showed total CVs of 1.68–2.71 % and good linearity (r=0.9997). Cross-reactivity was generally low, although phenylbutazone produced biases exceeding ±10 %. Both immunoassays correlated strongly with LC–MS/MS, with Mindray TESTO showing higher correlation and narrower limits of agreement in low-concentration samples (r=0.9603 vs. 0.8920). In women of reproductive age, Mindray TESTO demonstrated higher sensitivity (88.89 vs. 11.11 %) and κ agreement (0.784 vs. 0.189) for biochemical hyperandrogenism classification. In male hemodialysis patients, it achieved higher accuracy (94.68 vs. 88.30 %) and κ agreement (0.838 vs. 0.680) for biochemical testosterone deficiency classification. The ROC AUCs did not differ significantly (0.966 vs. 0.956; p=0.2776). Conclusions The novel sandwich immunoassay showed improved agreement with LC–MS/MS at low testosterone concentrations and favorable performance in classifying biochemical testosterone elevation and deficiency.