Analytical and clinical performance of an automated chemiluminescent immunoassay for direct renin measurement: comparison with PRA and aldosterone assays

The analytical performance of a fully automated chemiluminescentimmunoassay (CLIA) by Nichols Institute Diagnostic for direct renin, was evaluated. Within-assay imprecision (CV) resulted 5.6% at 4.7 μU/ml; 1.9% at 33.7 μU/ml and 2.3% at 194.9 μU/ml; between-assay imprecision 12.4% at 5.3 μU/ml; 8.7% at 32.4 μU/ml, 8.2%at 90.2 μU/ml, 5.5% at 196.5 μU/ml. Direct renin CLIA showed good linear relationship with direct renin IRMA and with plasma renin activity (PRA). The clinical performance of direct renin CLIA, PRA and aldosterone assays was tested by ROC analysis in patients with heart failure (HF). For mild HF, areas under the curve were: PRA = 0.733, direct renin = 0.671, aldosterone = 0.789; for severe HF: PRA = 0.855, direct renin = 0.792, aldosterone = 0.801. In conclusion, direct renin CLIA measurement showed good analytical performance (shorter turn around time, better precision and practicability than IRMA and PRA) and good clinical performance in HF patients with different severity of disease similar to that of aldosterone and PRA measurement.