#1797 Evaluation of clinical sensitivity and limit of detection for neutrophils of the homodimer neutrophil gelatinase-associated lipocalin (H-NGAL) rapid test in patients with peritoneal dialysis-related peritonitis (PDRP)

Abstract Background and Aims Peritonitis is a common cause of morbidity and mortality in patients undergoing peritoneal dialysis (PD). Early diagnosis of PDRP can reduce mortality and improve PD outcomes. H-NGAL, produced by activated neutrophils, is present in the peritoneal dialysis effluent (PDE) of PDRP patients and may serve as a reliable marker for peritonitis. This study aims to determine the lowest neutrophil count detectable by the H-NGAL point-of-care test (POCT) and to evaluate the influence of time, temperature, and other factors on its performance. Method Eighteen patients diagnosed with PDRP (according to the International Society for Peritoneal Dialysis [ISPD] guidelines) were enrolled in the study. Age, sex, diabetes status, peritoneal dialysis (PD) modality, symptoms-to-hospital arrival time (SH), symptoms-to-laboratory arrival time (SL), and symptoms-to-treatment time (ST) were recorded. Peritoneal dialysis effluent (PDE) samples were analyzed for white cell count (WCC), differentiation, and culture. The H-NGAL point-of-care test (POCT) was performed on PDE samples collected from home and hospital settings upon patient arrival. Hospital-collected PDE samples were serially diluted to approximate WCC concentrations of 200, 100, 50, 25, 12, 6, and 3 cells/μL and tested using the H-NGAL POCT at baseline (Time 0, T0) under room temperature (RT, 22.0–24.9°C) conditions. The last two positive tubes and the first two negative tubes were incubated at RT, 35°C, 40°C, and 45°C for 1 hour (T1), 2 hours (T2), and 12 hours (T12). The minimum white cell and neutrophil counts required to yield a positive H-NGAL POCT result (MWCP and MNCP, respectively) at T0 under RT conditions were set as reference values. The correlation and differences between MNCPs at different time points and temperatures and the above clinical factors were analyzed and compared to the MNCP at T0 under RT conditions. Results The median (Q25, Q75) white cell count and percentage of neutrophils in the PDE samples were 1,269 (592, 4,604) cells/μL and 90% (91%, 97%), respectively. All undiluted PDE samples (from home and hospital settings) tested positive using the H-NGAL POCT. The median (Q25, Q75, range) MWCP, consisting of 100% neutrophils and representing the MNCP, was 9 (5, 19; 3–22) cells/μL at T0 under RT conditions. The MNCP decreased after 12 hours, with a statistically significant reduction (P = 0.021 and P = 0.028, respectively) at T2 and T12 when incubated at 45°C, compared to the MNCP at T0 under RT conditions (Table 1). No statistically significant associations were found between MNCP and age, diabetes status, WCC, bacterial type causing peritonitis, ST, SH, SL time, or PD modality. Conclusion The H-NGAL POCT is a highly sensitive diagnostic tool capable of detecting PDRP at very low neutrophil counts. Its sensitivity is influenced by incubation time and temperature.