How can a person know if they have sleep apnea without a sleep test?

Typical symptoms: Symptoms of obstructive sleep apnea (osa) include snoring, witnessed pauses in breathing, snort arousals, feeling unrefreshed upon awakening, morning dry mouth, daytime sleepiness, tiredness, memory/concentration difficulties among others. Physical features such as being overweight, set-back chin (retrognathia), large neck are also suggestive. You would need a sleep study to confirm.

They can't: There are symptoms, there are signs, there are scales. They all suggest sleep apnea, but the only way to prove it is an objective test, a sleep study.