In the Background section of “Establishment of Human PD-1/PD-L1 Blockade Assay Based on Surface Plasmon Resonance (SPR) Biosensor" (https://bio-protocol.org/e4765), “Alsaab et al., 2018” is incorrectly referenced. The correct citation is “Alsaab et al., 2017”. The sentence should read as follows: “Clinical data have demonstrated that the blockade of PD-1 or PD-L1 can boost T cell–mediated antitumor responses, generates durable clinical responses, and prolongs patient survival time (Ohaegbulam et al., 2015; Alsaab et al., 2017).”