I understand that to bill LT, among several other things, the regular physician is unavailable to provide the visit services, this LT cannot be billed for a continuous period over 60 days, charges must include Q6 modifier. Here is our potential scenario (I am researching just in case the docs really want to go this route): our anesthesia group is looking to use LT to cover call from 7 pm to 7 am and some weekends. I say it's not LT because this "LT" would not be taking the place of someone on vacation, sick, etc., but covering because the regular staff would prefer not being on call so often. One doc says he is "unavailable" and that meets the criteria. I think it means we need to hire someone else. This would not be a temporary situation. Also - if the LT works just Sundays, how does that apply to the continuous time? If I understand Chapter 12 of the Part B Manual, there are starting and ending times for the main physician's absence and that time period is the "continuous period" for the LT coverage. One last issue - what is the difference between Q5 and Q6?