The Usefulness of Testosterone in Saliva Tests to Detect Testosterone Deficiency in Men with Advanced Chronic Kidney Disease: A Single-Center Study

<b>Background:</b> Hypogonadism frequently occurs among men with chronic kidney disease (CKD) and is a highly unfavorable prognostic factor. Therefore, a simple and common screening for testosterone deficiency may be important. The measurement of testosterone in saliva appears to be an attractive alternative to serum testosterone. This study aimed to assess the usefulness of determining free testosterone concentration in saliva to detect testosterone deficiency in men with advanced CKD, including those on dialysis. <b>Methods:</b> A total of 77 adult, male patients (aged 41-89 years old)-30 with CKD stage G3-G4, 30 on hemodialysis (HD), and 17 on peritoneal dialysis (PD)-were evaluated. The concentration of free testosterone was determined in saliva (SalFT), while the concentration of total testosterone (TT) was determined in blood serum. Serum-free testosterone levels were calculated (cFT). <b>Results:</b> SalFT did not differ from cFT in the CKD (<i>p</i> = 0.547) and PD groups (<i>p</i> = 0.409). In the HD group, SalFT was higher than cFT (<i>p</i> = 0.009). SalFT was positively correlated with cFT (r = 0.435 in the CKD and r = 0.479 in the HD) and TT (r = 0.451 in CKD), but only in the group of patients with SalFT levels below 140 pg/mL and 120 pg/mL, respectively. A cut-off value of SalFT ≤ 60.6 pg/mL showed 73.9% sensitivity and 77.8% specificity for testosterone deficiency recognition. <b>Conclusions:</b> Our study supports the value of SalFT measurement as a non-invasive approach in the diagnosis of testosterone deficiency in men with advanced CKD, as well as patients on hemodialysis.