Changes to USP <1788>: Determination of Subvisible Particle Matter from the HIAC and Coulter Counters<p>A revised version of the USP chapter on Subvisible Particulate Matter USP<1788> became official on 1st May 2021. USP<1788> is meant to expand on the information given in the chapters <787>, <788> and <789> to include for the first time the use of Flow Imaging techniques to provide orthogonal complimentary information to the HIAC high accuracy particle counter used in the compendial Light Obscuration Limit Test.</p>