Evaluation of symmetric dimethylarginine in cats using a point-of-care analyzer and commercial laboratory assay: limitations in chronic kidney disease staging

Objective To evaluate the precision of a point-of-care (VCheck V200) and commercial laboratory (Eurolyser commercial laboratory) assay and assess their agreement with a reference method (IDEXX commercial laboratory) for symmetric dimethylarginine (SDMA) measurement in cats. We hypothesize that the VCheck and Eurolyser assays would demonstrate acceptable precision and agreement with the reference method. Methods This prospective study was conducted from May 2019 to May 2023 and utilized 39 residual feline serum samples for VCheck and Eurolyser SDMA analytical precision assessment. Sixty-one feline serum samples were assessed for the agreement of SDMA results from each analyzer with the IDEXX method. Results Acceptable within- and between-run azotemic and nonazotemic Eurolyser assay and VCheck nonazotemic between-run precision was achieved. Method comparisons (58 samples) demonstrated that Eurolyser and VCheck results were not comparable to IDEXX SDMA results. Agreement with IDEXX results was moderate and substantial for VCheck and Eurolyser, respectively, when applied to feline chronic kidney disease (CKD) International Renal Interest Society staging guidelines. Conclusions A strong positive correlation was found between VCheck, Eurolyser, and IDEXX assays. The SDMA results were not comparable between assays. Wide dispersion of a single SDMA result prohibits its use for the International Renal Interest Society CKD staging. Clinical Relevance VCheck and Eurolyser use for SDMA measurement in feline CKD is supported. Establishment of method-specific/analyzer-specific reference intervals and serial SDMA monitoring using the same analyzer is recommended. International Renal Interest Society CKD staging based on a single SDMA result should be avoided.