Detection of K-RAS61 mutations using ACB-PCR. (A) Sensitivity of ACB-PCR when analyzing FACS-sorted PCs. FACS sorting of 1, 2, or 10 MM PCs from a patient with a K-RAS61 mutation to PCR tubes containing 100 FACS-sorted CD19⁺ B cells from a healthy donor. In 4 of 5 PCR tubes with a single FACS-sorted K-RAS61⁺ MM PC among 100 normal B cells, a K-RAS61⁺ MM PC was detected. (B) From all patients with an N-RAS61 mutation, 100 PCs were analyzed. (C) Patients that did not have any RAS mutations detectable by direct sequencing were analyzed (10 cases shown) and a single patient was identified as positive. All MGUS patients were analyzed and all were found to be negative for K-RAS61 mutations (10 cases shown). P indicates positive control, 100 FACS-sorted PCs from a patient with a K-RAS61 mutation. N indicates negative control, 100 FACS-sorted CD19⁺ B cells from a healthy donor.