To evaluate the role of real-time reverse transcription-polymerase chain reaction (RT-PCR) in the diagnosis of measles cases, 46,363 suspected measles cases with rash and 395 suspected measles cases without rash were analyzed in this study; the cases were obtained from the Chinese measles surveillance system (MSS) during 2014–2017 and simultaneously detected by measles-specific IgM enzyme-linked immunosorbent assay (ELISA) and real-time RT-PCR. The gene discussed is CD40LG; the disease is measles.