In a study of 304 SLE patients, 285 patients with other rheumatic diseases and 205 healthy controls, Putterman and colleagues reported that CBCAPS on erythrocytes or B cells had higher sensitivity than standard complement levels (serum C3 and C4) and anti-dsDNA measurements when distinguishing between SLE and non-SLE, suggesting that CBCAPS could be more specific and sensitive biomarkers for diagnosis and prognosis of SLE (17). The gene discussed is C4A; the disease is systemic lupus erythematosus.