Ready-to-use format 1X medium is a frozen, ready to use upon thawing. No supplementation is required. Thawed medium can be stored at 2° to 8°C for up to 14 days. Quality and performance testing Every lot of is performance tested by a certified US reference cytogenetics laboratory to ensure consistently superior performance. Peripheral blood lymphocytes from a normal adult donor are cultured for 72 hours in Gibco PB-MAX Karyotyping Medium before measuring the mitotic index and chromosome banding resolution. In addition, each lot is tested for sterility, pH, osmolality, and mycoplasma. Classic formulation Gibco PB-MAX Karyotyping Medium is an optimized RPMI 1640 medium, supplemented with Fetal Bovine Serum (FBS), L-glutamine, and phytohemagglutinin (PHA). Gibco PB-MAX Karyotyping Medium is based on formulations referenced in the Association for Cytogenetic Technologists Laboratory Manual for the culture of peripheral blood lymphocytes for cytogenetic analysis.