TUBB and amyotrophic lateral sclerosis: Our result on the variability of ACTB are in agreement with the latest studies of Zhang et al. [19] who classified them as unstable in PBMC of patients with chronic hepatitis B. According to Zhang, the best pair of ICGs for their studies were GAPDH and beta-tubulin, however in our ranking the GAPDH was localized on the sixth position in both ALS and control PBMCs.