A rapid smartphone-based lactate dehydrogenase test for neonatal diagnostics at the point of care

There is a growing recognition of the importance of point-of-care tests (POCTs) for detecting critical neonatal illnesses to reduce the mortality rate in newborns, especially in low-income countries, which account for 98 percent of reported neonatal deaths. Lactate dehydrogenase (LDH) is a marker of cellular damage as a result of hypoxia-ischemia in affected organs. Here, we describe and test a POC LDH test direct from whole blood to provide early indication of serious illness in the neonate. The sample-inresult- out POC platform is specifically designed to meet the needs at resource-limited settings. Plasma is separated from whole blood on filter paper with dried-down reagents for colorimetric reaction, combined with software for analysis using a smartphone. The method was clinically tested in newborns in two different settings. In a clinical cohort of newborns of Stockholm (n = 62) and Hanoi (n = 26), the value of R using Pearson's correlation test was 0.91 (p < 0.01) and the R-2 = 0.83 between the two methods. The mean LDH (+/- SD) for the reference method vs. the POC-LDH was 551 (+/- 280) U/L and 552 (+/- 249) U/L respectively, indicating the clinical value of LDH values measured in minutes with the POC was comparable with standardized laboratory analyses.