Real time observation and automated measurement of red blood cells agglutination inside a passive microfluidic biochip containing embedded reagents

Anti-A or anti-B typing reagents were dried inside the microchannel of a passive microfluidic chip designed to enhance capillary flow. A blood drop deposit at the tip of the biochip established a simple biological protocol. In situ agglutination of autologous RBCs was achieved by means of embedded reagents and real time agglutination process was monitored by video recording. Using a training set of 24 experiments, two real-time indicators based on correlation and variance of gray levels were optimized and then further confirmed on a validation set. 100% correct discrimination between positive and negative agglutinations was performed within less than 2 min by measuring real-time evolution of both correlation and variance indicators.