Multiple Sleep Latency Test, or MSLT, is a daytime examination done following a comprehensive diagnostic With the help of the NPSG, it is possible to assess a patient’s level of sleepiness following a night of rest. The MSLT is a set of five timed tests spaced two hours apart that measure a patient’s ability to fall asleep, how quickly they do so, and the stage of sleep they reach. Most frequently, narcolepsy or some other form of excessive daytime sleepiness is diagnosed with the MSLT.