I agree with Lisa~
Excerpt from CPT Assistant...(5-09)
Whether to report one or two units of code 87804, Infectious agent antigen detection by immunoassay with direct optical observation; influenza, varies according to the type of rapid testing method used distinguishing influenza A from influenza B. The rapid detection of influenza virus types A and B may be part of two entirely separate procedures or may be included within the same test device. If the assays provide two separate results (ie, a result for influenza virus A and a result for influenza virus B), it would be appropriate to report two units of code 87804. When two units of code 87804 are submitted, modifier 59, Distinct Procedural Service, may be used to indicate that the two results represent separate services (codes 87804 and 87804-59).
Modifier 59 Versus Modifier 91
For laboratory reporting purposes, modifier 59 is used, for example, to report procedures that are distinct or independent, such as performing the same procedure (that uses the same procedure code) for testing of a different specimen or different strain. Use modifier 59 when separate results are reported for different species or strains that are described by the same CPT code. This advice should serve to clarify the use of the modifier in these instances.
As a matter of differentiation, modifier 91, Repeat Clinical Diagnostic Laboratory Test, is used when, in the course of treating a patient, it is necessary to repeat the same laboratory test on the same day to obtain subsequent test results. An example is repeated blood testing for the same patient, using the same CPT code, performed at different intervals during the same day (eg, initial and three subsequent blood potassium levels).