Specificity and sensitivity of commercially available assays for glucagon-like peptide-1 (GLP-1): Implications for GLP-1 measurements in clinical studies
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AIMS: To evaluate performances of commercially available glucagon-like peptide-1 (GLP-1) assays and implications for clinical studies.
MATERIALS AND METHODS: Known concentrations (5-300 pmol/l) of synthetic GLP-1 isoforms (GLP-1 1-36NH2 , 7-36NH2 , 9-36NH2 , 1-37, 7-37 and 9-37) were added to the matrix (assay buffer) supplied with ten different kits and to human plasma, and recoveries determined. Assays giving meaningful results were analysed for precision and sensitivity by repeated analysis and ability to discriminate low concentrations. Endogenous GLP-1 levels in clinical samples were assessed with 3 commercial kits.
RESULTS: The USCN LIFE assay detected none of the GLP-1 isoforms. The active GLP-1 ELISAs from Millipore and DRG seemed identical and were specific for intact GLP-1 in buffer and plasma. The Meso Scale Discovery Total GLP-1 kit detected all six GLP-1 isoforms, although recovery of non-active forms was incomplete, especially in plasma. Millipore Total GLP-1 ELISA kit detected all isoforms in buffer, but mainly amidated forms in plasma. The Alpco, Phoenix and Bio-Rad kits detected only amidated GLP-1,but the Alpco kit had a limited measurement range (30 pmol/l), the Phoenix kit had incomplete recovery in plasma and the Bio-Rad kit was insensitive (detection limit in plasma 40 pmol/l). The pattern of postprandial GLP-1 responses in clinical samples was similar between the kits tested, but the absolute concentrations measured varied.
CONCLUSIONS: The specificity and sensitivity of commercially available kits for analysis of GLP-1 levels varies considerably. This should be taken into account when selecting which assay to use and when comparing data from different studies.
|Diabetes, Obesity and Metabolism
|Number of pages
|Published - 2014