Nickan Research Institute Journal of Parathyroid Disease 2345-6558 10 1 2022 01 01 Interference caused by anti-streptavidin antibodies in a parathyroid hormone assay; a case report e6134 e6134 10.34172/jpd.2022.6134 EN Benjamin Siegfried Trautz https://orcid.org/0000-0001-5330-5957 Thomas Negele Journal Article 10.34172/jpd.2022.6134 2021 07 02 2021 07 31 Endogenous antibodies can lead to test interference in streptavidin-biotin based laboratory assays, such as thyroid function tests or parathyroid hormone (PTH) levels. We report about a patient, who presented for thyroid surgery, showing undetectable PTH levels despite normocalcaemia in internally assessed preoperative laboratory work. Previously, anti-streptavidin antibodies were detected in the patient’s blood and normal PTH levels could be measured in a streptavidin-free assay. To our knowledge this is the first reported case of a clinically relevant PTH test interference due to endogenous anti-streptavidin antibodies, thus complicating the evaluation of postoperative hypoparathyroidism.