Journal Information
Journal ID (publisher-id): BM
Journal ID (nlm-ta): Biochem Med
Title: Biochemia Medica
Abbreviated Title: Biochem. Med.
ISSN (print): 1330-0962
ISSN (electronic): 1846-7482
Publisher: Croatian Society of Medical Biochemistry and Laboratory Medicine
Article Information
Copyright: 2016, Croatian Society of Medical Biochemistry
Date received: 03 February 2016
Date accepted: 08 August 2016
Publication date (print and electronic): 15 October 2016
Volume: 26
Issue: 3
Pages: 436-443
Publisher ID: bm-26-436
DOI: 10.11613/BM.2016.046
Misleading FT4 measurement: Assay-dependent antibody interference
Lianne SM Boesten[2]
Jan Linthorst[3]
Elif Yildiz[4]
Johannes W Janssen[1]
Yolanda B de Rijke[5]
[1] Department of Clinical Chemistry and Hematology, Franciscus Gasthuis, Rotterdam, The Netherlands
[2] General Clinical Laboratory, IJsselland Hospital, Capelle a/d IJssel, The Netherlands
[3] General practitioner’s office Linthorst, Berkel en Rodenrijs, The Netherlands
[4] General practitioner’s office J.A. de Schepper and E. Yildiz, Rotterdam, The Netherlands
[5] Departments of Clinical Chemistry and Internal Medicine, Erasmus MC University Medical Center, Rotterdam, The Netherlands
[6] Department of Clinical Chemistry and Laboratory Medicine, Leiden University Medical Center, Leiden, The Netherlands
Author notes:
Corresponding author: a.albersen@lumc.nl
Introduction
Commonly used free thyroxine (FT4) immunoassays can be falsely elevated due to interference causing misinterpreted thyroid function. We present two cases with high FT4 concentrations due to antibody interference. This study’s aim was to investigate the source of the FT4 immunoassay interference and possibility of its removal by two different techniques in order to correct the discrepancy between obtained FT4 values and the patient’s clinical status.
Materials and methods
Two patients presented at their general practitioners’ with elevated FT4 concentrations in combination with a normal and increased thyroid stimulating hormone (TSH) concentrations. Clinical symptoms differed between patients but did not correspond with the hyperthyroid status suggested by the laboratory results. FT4 concentrations from both patients were measured on four common commercial immunoassays and the dialysis method before and after treatment with heterophilic blocking tubes and protein A/G.
Conclusion
This report illustrates falsely elevated FT4 concentrations due to assay interference on the Immulite immunoassay analyser caused by heterophilic antibodies, which were eliminated by protein A/G treatment. We point out the importance of a close collaboration between doctors and the laboratory to avoid unnecessary clinical intervention.
Keywords: FT4; thyroid function test; diagnostic errors; interference; immunoassay
