CPT code 0606U is a Proprietary Laboratory Analyses (PLA) code for Osmotic Gradient Ektacytometry performed by Cincinnati Children's Clinical Laboratories and RR Mechatronics; the test quantitatively measures red blood cell deformability across an osmotic gradient to identify red cell membrane disorders, reported as a specialized laboratory diagnostic service typically performed in a clinical laboratory setting and sent from inpatient or outpatient hospital labs or reference laboratory collection sites.