Hook effect although rare, still exists
The hook effect occurs when extremely high concentrations of an analyte in the sample, saturate the antibodies used in the method, leading to falsely low results. We describe a case observed with the Atellica IM 1600 (Siemens) analyzer for the measurement of human chorionic gonadotropin (β-HCG) in serum of a pregnant woman at the thirteenth week of pregnancy. The β-HCG result was inconsistent with the gestational age and helped us to highlight the hook effect and supported the clinical diagnosis of vesicular mole in the patient. The same sample was also analyzed using the Alinity-i Total β-hCG kit (Abbott), and the authors highlight how differences between diagnostic kits can significantly affect the analytical result. In cases of discrepancies between laboratory data and clinical findings, it is essential to consult with laboratory specialists to rule out analytical interferences. To minimize the risk of the hook effect, we modified the analytical procedure and submitted a report to Siemens European Support.