Modifier 91
Repeat Clinical Diagnostic Laboratory Test
Modifier 91 is used to report repeat laboratory tests or studies performed on the same day on the same patient.
CPT codes for use with modifier 91 are in the laboratory code range 80047-89398.
Appropriate Usage:
In the course of treatment of the patient, it may be necessary to repeat the same laboratory test on the same day to obtain subsequent test results. Under these circumstances, the laboratory test performed can be identified by its usual procedure number and the addition of modifier 91.
In this case, you should report the appropriate lab test code such as 82947, Glucose; quantitative, blood [except reagent strip], followed by a second line item of 82947 with modifier 91.
But you might also use modifier 91 when a single code describes the same test for different analytes or organisms. In this case, codes 87804 and 87400 can describe an influenza A or influenza B test.
If your payer recommends using modifier 91 to indicate that you performed the test twice, once for type A and once for type B, you may do so.
Note:
Do not use 91 if the lab runs the test again for the following reasons,
• To confirm initial results
• Because of testing problems related to specimens or equipment
• For any other reason when a normal, one-time reportable result is all that the physician needs for appropriate patient treatment.
Difference between 59 and 91 modifier.
If the same test was performed on different sites, use modifier 59 instead of 91.
For example, if two wound cultures were taken from two different wound sites, modifier 59 would be appended to the second wound culture code. However, if a second culture was taken of the same wound site, then it would be appropriate to append modifier 91 to the second wound culture code.
