Comparison of HPLC method and commercial ELISA assay for asymmetric dimethylarginine (ADMA) determination in human serum

The performance of a new ELISA assay kit (DLD Diagnostika GmbH, Hamburg, Germany) for the determination of asymmetric dimethylarginine (ADMA) was evaluated against a reversed phase HPLC method. ADMA concentrations of 55 serum samples were measured with both methods. The intra-assay CV for ADMA-ELISA was 19% (n = 10). Inter-assay CVs for ADMA-ELISA were 9% for kit control 1 (0.410 ± 0.037 μM) and 14% for kit control 2 (1.174 ± 0.165 μM). The intra- and inter-assay CVs for HPLC assay for ADMA were 2.5% (0.586 ± 0.015 μM) and 4.2% (0.664 ± 0.028 μM), respectively. There was no correlation between these two methods (R2 = 0.0972). The effect of storage conditions of the samples on ADMA concentrations was investigated by HPLC. ADMA concentration was stable after four freezing and thawing cycles. Overall, the HPLC method offered better sensitivity, selectivity and, very importantly, simultaneous determination of ADMA, SDMA, l-homoarginine and l-arginine.