Provided is a homogenous measurement method using insoluble carrier particles; in particular, an aggregation measurement method using insoluble carrier particles supporting antibodies, antigens, or the like. More specifically, an LTIA measurement method is provided that reduces matrix effects from the test specimen and also reduces differences in measurement precision among automated analysis devices with differing specifications. Also provided is a measuring reagent for use with an automated analysis device. Formulating said measuring reagent with the addition of a silicone antifoam reduces matrix effects from the test specimen and also, without changing the fundamental capabilities of the measuring reagent, reduces the range in measurement precision among automated analysis devices withdiffering specifications.