When is a?a sleep study needed for a three year old?

?sleep study?: I worry about sleep apnea(sa) if a kid is snoring at three, having pauses over 10sec between breaths, or seems excessively tired compared to his/her playmates. Sometimes you can simply record the snoring behavior & take it in for review & many local ent's will remove tonsils/adenoids on that basis. Occasionally a sleep study may reveal asymptomatic sa.I have never actually found the need to do one.