Comparison of the determination of superoxide dismutase and antioxidant capacity in neurological patients using two different procedures

As oxidative stress in relation with neurological diseases has become an important point in recent research, simple methods to be used in epidemiological studies and clinical practice are required. The hypothesis that the analytical methods used in research laboratories (RLM) can be used interchangeably with commercial kits (CKM) for SOD and TRAP is tested. Both methods were compared using linear transformations of the RLM measurements into the CKM scales. Data were obtained from Alzheimer's, Parkinson's, and vascular dementia patients and controls. The lack of fit and the run's test of residuals were not significant, but the same sign method detected significant nonlinearities (P<0.000001 for SOD, P<0.01 for TRAP). The intragroup CVs of both methods were comparable for TRAP, while in the RLM determinations of SOD resulted in <50% of those obtained with the CKM. The ANCOVA comparison of the regression parameters across the clinical groups resulted significant for SOD (P<0.0001) and not significant for TRAP. Both methods agree in describing the features of the clinical groups, but the degree of agreement at the individual concentration was poor and they could not be readily intercalibrated. Normal and pathological values should be obtained independently for the CKM to insure their applicability to large populations.