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