Determination of biological variation of α-fetoprotein and choriogonadotropin (β chain) in disease-free patients with testicular cancer

Knowledge of biological variation (BV) is important for determining analytical goals and for establishing the magnitude of change between two consecutive measurements which indicate change in a patients' health status. The aim of this work is to determine the BV for total choriogonadotropin (β chain) (β-hCG) and α-fetoprotein (AFP) in patients diagnosed with testicular cancer but with no evidence of recurrence of disease.We estimated BV from a mean of five consecutive measurements in 28 patients diagnosed with testicular cancer, 3 months after tumor resection or 4 months after complete treatment with chemotherapy. The mean sampling interval was 3 months.The mean concentrations of α-fetoprotein and choriogonadotropin (β chain) were 3.9 μg/L and 0.79 IU/L, respectively. Between-run analytical variation was 7.1% at 4.1 μg/L for α-fetoprotein, and 19% at 0.65 IU/L for choriogonadotropin (β chain). BV obtained for α-fetoprotein and choriogonadotropin (β chain) was 12.4% and 16.7%, respectively, and the reference change value (RCV) for one-tail showed 38.2% and 60.7% for α-fetoprotein and choriogonadotropin (β chain), respectively.The estimation of BV allows us to calculate analytical goals and RCVs, necessary tools for the correct interpretation of serial measurements in the follow-up of patients.