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Variable characteristics with insulin assays

Authors

  • S Kalathil MBBS, MRCP,

    Registrar in Diabetes & Endocrinology, Corresponding author
    1. Department of Endocrinology, Royal Victoria Infirmary, Newcastle upon Tyne, UK
    • Department of Endocrinology, Royal Victoria Infirmary, Newcastle Upon Tyne Hospitals NHS Foundation Trust, Queen Victoria Road, Newcastle upon Tyne NE1 4LP, UK
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  • C Napier MBBS, MRCP,

    Registrar in Diabetes & Endocrinology
    1. Department of Endocrinology, Royal Victoria Infirmary, Newcastle upon Tyne, UK
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  • SJ Pattman BSc, FRMS, MBChB, MRCP,

    Registrar in Chemical Pathology/Metabolic Medicine
    1. Department of Clinical Biochemistry, Royal Victoria Infirmary, Newcastle upon Tyne, UK
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  • G Wark BSc, MSc, PhD, FRCPath,

    Consultant Clinical Scientist
    1. SAS Peptide Section, Clinical Laboratory, Royal Surrey County Hospital, Guildford, UK
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  • K Abouglila MBBCh, MD, FRCP,

    Consultant in Diabetes & Endocrinology
    1. Department of Endocrinology, University Hospital of North Durham, UK
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  • RA James BSc, MD, FRCP

    Consultant Endocrinologist
    1. Department of Endocrinology, Royal Victoria Infirmary, Newcastle upon Tyne, UK
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Abstract

Factitious hypoglycaemia is a challenging diagnosis to confirm. Evaluation of surreptitious human insulin use can be distinguished from endogenous insulin excess by existing biochemical assays. However, the increasing use of insulin analogues poses a challenge because commercially available insulin assays detect these with varying accuracy and precision.

Insulin analogues are increasingly used in diabetes management and the case outlined here highlights the variations in assay. Initially, the local assay (ELISA kit – Dako, Copenhagen) failed to detect a significant concentration of insulin (<6pmol/L; range 9.6–65.4pmol/L) which an external reference laboratory subsequently detected using the Mercodia Iso-insulin two-site immunoassay (Uppsala, Sweden).

The key analytical point is the recognition that different immunoassays detect insulin analogues to varying degrees. Clinical teams need to consider this if such cases are to be recognised. Following recent media reports where surreptitious insulin administration may be implicated in inpatient mortality, this knowledge is crucial to empower us to accurately diagnose all cases of unexplained hypoglycaemia. Copyright © 2013 John Wiley & Sons. Practical Diabetes 2013; 30(3): 118–120

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