Ms Lamont was referring to a report by Audit Scotland which tracked relatively extensive past use of "social unavailability" codes to exclude patients from waiting time guarantees.
The Scottish Parliament's public audit committee suggested samples of patient records were tested to make sure the use of social unavailability codes on the NHS computer system was "appropriate".
The investigation came after NHS Lothian was found to be manipulating waiting time codes in 2011, although ministers said the practice was not widespread and that concerns raised in the Audit Scotland report were "historical".