Urinary 8-oxo-7,8-dihydro-2 '-deoxyguanosine analysis by an improved ELISA: An inter-laboratory comparison study

WOS: 000376169800014PubMed ID: 27016072ELISA is commonly used for the detection of urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a marker of whole body oxidative stress. However, the method has been criticized for high inter-laboratory variability and poor agreement with chromatographic techniques. We performed an inter-laboratory comparison of 8-oxodG assessed in 30 urine samples and a urine spiked with four different concentrations of 8-oxodG by ELISA using standardized experimental conditions, including: sample pretreatment with solid-phase extraction (SPE), performing analysis using a commercial kit from a single manufacturer and strict temperature control during the assay. We further compared the ELISA results with high-performance liquid chromatography-tandem mass spectrometry (HPLC MS/MS) and performed tentative identification of compounds that may contribute to the discrepancy between both methods. For all but one participating laboratory (Data 1) we observed consistent ELISA results lying mostly within 1 SD of the mean 8-oxodG concentration. Mean 8-oxodG levels assessed by ELISA correlated with the data obtained by HPLC MS/MS (R=0.679, p < 0.001). The correlation improved when Data 1 were excluded from the analysis (R=0.749, p < 0.001). We identified three outlying urine samples; one with an ELISA 8-oxodG concentration lower, and two with 8-oxodG levels higher, than those measured by HPLC MS/MS. Omitting these samples further improved inter-methodology agreement (R=0.869, p