Add the appropriate Level 1 or Level II CPT modifier to the five digit code or identify the modifier by use of a separate code by adding 099 before the 2 digit number e.g. 09950, 09951.
Level 1 Modifier Description
-59 Distinct Procedural Service The modifier –59 is appropriate to report multiple service submissions for the same patient on the same day. These situations usually involve microbiology where samples or cultures are taken from a patient from different anatomical sites or different wounds, use the same CPT code, and then are tested the same day.
-90 Reference (Outside) Laboratory When laboratory procedures are performed by a party other than the treating or reporting physician, the procedure may be identified by adding the modifier ‘-90’ to the usual procedure number or by use of the separate five digit modifier code 09990
-91 Repeat Clinical Diagnostic Laboratory Service The modifier –91 is used if an ordering physician requests a laboratory test that requires that several of the same services (CPT code) be performed for the same patient on the same day, modifier –91 should be used to indicate that multiple clinical diagnostic laboratory tests were done on the same day. (This modifier should not be used when multiple tests are described under a single code, e.g. glucose tolerance test.)