Low-shear viscometry is one of the methods commonly used to estimate t
he degree of red blood cell (RBC) aggregation in various bloods and RB
C suspensions, However, it has been previously shown that alterations
in RBC morphology and mechanical behavior can affect the low-shear app
arent viscosity of RBC suspensions; RBC aggregation is also sensitive
to these cellular factors, This study used heat treatment (48 degrees
C, 5 min), glutaraldehyde (0.005-0.02%) and hydrogen peroxide (1 mM) t
o modify cell geometry and deformability, Red blood cell aggregation w
as assessed via a Myrenne Aggregometer (''M'' and ''M1'' indexes), RBC
suspension viscosity was measured using a Contraves LS-30 viscometer,
and RBC shape response to fluid shear stresses (i.e., deformability)
was determined by ektacytometry (LORCA system), Our results indicate t
hat low-shear apparent viscosity and related indexes may not always re
flect changes of RBC aggregation if cellular properties are altered: f
or situations where RBC aggregation has been only moderately affected,
cellular mechanical factors may be the major determinant of low-shear
viscosity, These findings thus imply that in situations which may be a
ssociated alterations of RBC geometry and/or deformability, low-shear
viscometry should not be the sole measurement technique used to assess
RBC aggregation. (C) 1997 Elsevier Science Ltd.