Portable, on-site blood typing methods will help provide life-saving blood 
transfusions to patients during an emergency or natural calamity, such as 
significant earthquakes. We have previously developed waveguide-mode (WM) 
sensors for forward ABO and Rh(D) blood typing and detection of antibodies 
against hepatitis B virus and hepatitis C virus. In this study, we evaluated a 
WM-sensor for reverse ABO blood typing. Since reverse ABO blood typing is a 
method for detection of antibodies against type A and type B oligosaccharide 
antigens on the surface of red blood cells (RBCs), we fixed a synthetic type A 
or type B trisaccharide antigen on the sensor chip of the WM sensor. We obtained 
significant changes in the reflectance spectra from a WM sensor on type A 
antigen with type B plasma and type O plasma and on type B antigen with type A 
plasma and type O plasma, and no spectrum changes on type A antigen or type B 
antigen with type AB plasma. Signal enhancement with the addition of a 
peroxidase reaction failed to increase the sensitivity for detection on 
oligosaccharide chips. By utilizing hemagglutination detection using regent type 
A and type B RBCs, we successfully determined reverse ABO blood groups with 
higher sensitivity compared to a method using oligosaccharide antigens. Thus, 
functionality of a portable device utilizing a WM sensor can be expanded to 
include reverse ABO blood typing and, in combination with forward ABO typing and 
antivirus antibody detection, may be useful for on-site blood testing in 
emergency settings.