Novel Colorimetric and Light Scatter Methods to Identify and Manage Peritoneal Dialysis-Associated Peritonitis at the Point-of-Care

IntroductionPeritoneal dialysis-related peritonitis is a common cause of transfer to haemodialysis, patient morbidity and is a risk factor for mortality. Associated patient anxiety can deter selection of PD for renal replacement therapy. Diagnosis relies on hospital laboratory tests, however this might be achieved earlier if such information was available at the point-of-care, thereby significantly improving outcomes. The presence of culturable microbes and the concentration of leukocytes in effluent both aid peritonitis diagnosis, as specified in the International Society for Peritoneal Dialysis diagnostic guidelines. Here we report the development of two new methods providing such information in simple point-of-care tests.MethodsOne approach uses a tetrazolium-based chemical reporting system, primarily focused on detecting bacterial contamination and associated vancomycin-sensitivity. The second approach uses a novel forward light-scatter device (QuickCheck) to provide an instant quantitative cell count directly from PD patient effluent.ResultsThe tetrazolium approach detected and correctly distinguished lab isolates, taking 10h to provide non-quantitative results. We compared the technical performance of the light scatter leukocyte counting approach with spectrophotometry, haemocytometer counting and flow cytometry (Sysmex) using patient effluent samples. QuickCheck had high accuracy (94%) and was the most precise (coefficient of variation <4%), showing minimal bias, overall performing similarly to flow cytometry.ConclusionsThese complementary new approaches provide a simple means to obtain information to assist diagnosis at the point-of-care. The first provides antibiotic sensitivity following ten hours incubation, whereas the second optical approach (QuickCheck), provides instant accurate total leukocyte count.