Double trouble: Unmasking two hook effects on Siemens Atellica® - Total PSA and total hCG assays

• Published in: Practical laboratory medicine 2024-03, Vol.39, p.e00366, Article e00366
• Main Authors: Benamour, Meryem, Brouwers, Pauline, Nevraumont, Arnaud, Roy, Tatiana, Bayart, Jean-Louis
• Format: Article
• Language: English
• Subjects: Atellica; Case Report; Hook effect; Human health sciences; Immunoassay; Interferences; Laboratory medicine & medical technology; Médecine de laboratoire & technologie médicale; Sciences de la santé humaine; Total HCG; Total PSA
• ISSN: 2352-5517; 2352-5517
• DOI: 10.1016/j.plabm.2024.e00366

The “hook effect” or “prozone phenomenon” occurs when the concentration of a particular analyte saturates the antibodies used in the test, resulting in falsely low or negative results despite the presence of high analyte concentrations. We report two recent cases of hook effect encountered with a widely used immunoassay analyzer, the Siemens Atellica® IM1600. The first case involves a patient with advanced metastatic prostate cancer whose total PSA (tPSA) concentration dropped dramatically from his last biological control. The second case concerns a pregnant woman whose total HCG (ThCG) levels were also subject to the hook effect and who was found to have a molar pregnancy. In both cases, a dilution step enabled to overcome this analytical concern and to obtain a correct result. In addition, a comparison of the sensitivity of different immunoassay analyzers to this phenomenon was carried out. To avoid this analytical error, an additional dilution step should automatically be performed when there is a clinical suspicion of elevated levels of tumor or hormone markers. Finally, the most affected manufacturers should adapt their assays, accordingly. •Two cases of “hook effect” were encountered with the Siemens Atellica® analyzer, affecting total PSA and total hCG assays.•At high PSA or HCG levels, this can lead to inaccurately low results, leading to potential clinical consequences.•A dilution of the sample should be performed systematically when there is a suspicion of hook effect.