Endocrine Abstracts (2002) 3 P63

A case of false immunoassay results due to assay interference

AJ Park1, C Goodlad1, O Chaudhri1, M Donaldson2, M Ghatei1 & K Meeran1

1Department of Metabolic Medicine, Imperial School of Medicine, Hammersmith Campus, London, UK; 2Clinical Chemistry, Hammersmith Hospital, London, UK.

WF a 52 year old female was referred to the Hammersmith Hospital in August 2001 for further investigation of her persistently elevated fasted gut hormones (GIH) [all previously assayed at the Hammersmith Hospital]. WF was initially diagnosed with irritable bowel syndrome 16 years ago. Following an exacerbation of her condition 9 years ago, fasting gut hormones were performed, which showed gross elevation of all peptides measured.The possibility of a neuroendocrine tumour was pursued. CT abdomen, MRI pancreas and an Octreotide scan performed at that time were all normal. The patient was monitored with bi-annual MRI scans (which were always normal) and annual fasting GIH, which remained both persistently and significantly elevated. Gastrin and neurotensin were the most affected peptides. The patient was not on any medication apart from oestrogen implants.

At the Hammersmith, the fasting GIH were again repeated and were elevated as before. Imaging of the abdomen and Octreotide scan were also normal. The patient was initially scheduled for pancreatic angiography with calcium stimulation. However, the possibility that heterophilic [interfering] antibodies were present in this patient was considered. The radioimmunoassays used for the GIH all employed rabbit antibodies. The patient and her husband had kept significant numbers of pet rabbits, with the patient having rabbit induced allergic rhinitis. The presence of heterophilic antibodies in the patient's serum was demonstrated, by the use of donkey anti-rabbit antibodies to eliminate the measured interference. The presence of heterophilic antibodies must be considered when results generated by immunoassays do not correspond to the rest of the clinical and diagnostic pictures.

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