[Value of the serum free testosterone level in detecting erectile dysfunction].

Objective: To investigate the values of serum calculated free testosterone (cFT), testosterone secretion index (TSI), and free testosterone index (FTI) in the diagnosis of ED with androgen deficiency by observing their changes in the patient.

Methods: We conducted this study among 185 men complaining of ED and 35 20－40 years old healthy males presenting at the clinic for premarital medical checkup. We asked them about their medical history, to fill in the International Index of Erectile Function (IIEF-5) Questionnaire, and to complete the nocturnal penile tumescence (NPT) test. According to the data obtained, 150 of the complainants were diagnosed as ED patients and 25 of the healthy examinees were included in the control group. We determined the levels of total serum testosterone (TT), luteinizing hormone (LH), sex hormone-binding globulin (SHBG), serum albumin (ALB), cFT, bio-available testosterone (bio-T), TSI, and FTI in the two groups of subjects. Using cFT ≤0.3 nmol/L, TSI ≤2.8, and FTI ≤0.4 as the critical values and TT ≤11.5 nmol/L as the gold standard for androgen deficiency, we calculated cFT-, TSI-, and FTI-related rates of missed diagnosis, misdiagnosis, and diagnostic coincidence.

Results: With TT ≤11.5 nmol/L as the criterion, the cFT-, TSI-, and FTI-related rates of coincidence in the diagnosis of androgen deficiency in the ED patients were 90.8%, 85.8%, and 80.8%, those of missed diagnosis were 4.0%, 33.3%, and 44.0%, and those of misdiagnosis were 10.5%, 19.4%, and 12.6%, with the Kappa of values 0.755, 0.564, and 0.427, respectively (P <0.05). The levels of serum TT, cFT, Bio-T, TSI, and FTI were decreased with increased age of the 20－40 years old ED patients, with statistically significant differences among different age groups except the serum TT level. However, no statistically significant differences were found in the levels of TT, cFT, Bio-T, TSI, and FTI among the patients with different IIEF-5 scores.

Conclusions: The level of cFT has a higher value than those of TT, TSI, and TSI in the diagnosis of ED with androgen deficiency in 20－40 years old men.