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Modifier 59 vs Modifier 91 for Laboratory


Palo Alto Chapter
Best answers
I would like to clarify on how and when to use these two modifiers, modifier 59 & modifier 91.

Can someone please advise if mod -59 or -91 should be use on CPT 82784 - Gammaglobulin (immunoglobulin); if we have results for IgA, IgG & IgM, is this to bill with modifier 59 or 91? Does this CPT calls for "Distinct Procedural Service?"

How about CPT 83883 x2 - Nephelometry, each analyte, does this call for mod -59 or -91?

88271 x2 - Molecular cytogenetics; DNA probe, each; Mod -59 or -91?

How about for allergy testing, 86003 (Allergen specific IgE)
86003 - Egg
86003 - Milk
86003 - Nut
Is this mod -59 or 91? The results gives a description or different results.

How about if a lab panel is performed and one of the test within the panel is repeated, is this a modifier -91? If done on the same day? How about if a different physician order the test but the same facility and on the same day?
80048 - Basic Metabolic Panel
82565 - Creatinine

Please advise.
Last edited:


Upper Saddle River, NJ
Best answers
I am hoping to bump this question up in the forum.
I have similar questions. We have been advised to use Modifier -91 for different anylates of the same test but this is being denied.

Since it is not a repeat of a previous test, but in fact a new test, is Mod-59 more appropriate?

Thank you