2022 Volume 49 Issue 6 Pages 615-617
[Objectives] The test was conducted by assessing antibody titer after vaccination for two purposes. One was to provide information to patients and health checkup participants. The other was epidemiological evaluation. The number of clinical case reports of prozone phenomenon is very limited, and it is worthwhile to alert the public to this phenomenon in antibody assays.
[Subjects] Two cases of false low values due to the prozone phenomenon on examination during a health checkup visit.
[Method] The research protocol was approved by the Ethics Committee of Kohsei Chuo General Hospital (approval number: 2022-01). Antibody titers were measured by measuring device cobas8000 (Roche Diagnostics K.K.) and measuring reagent ElecsysAnti-SARS-CoV-2S (300) RUO.
[Results] In case 1, the range was 1x (157), but at 10x and 100x, it was over the range and the prozone phenomenon was observed. Case 2 was 1x (212), but the same phenomenon was observed at 10x, 100x, and 200x.
[Conclusions] In case of low antibody titer, close examination by retesting seemed to be important.
