The test device comprises a substantially opaque light reflecting matrix having {TAIL ~ a refractive index} significantly different from {HEAD ~ the refractive index} of blood 
The test device comprises a substantially opaque light reflecting matrix having { TAIL ~ a refractive index } significantly different from { HEAD ~ the refractive index } of blood
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH