Not sure if this helps
I dont know if this would help but we use 87081 for our rapid strep test, and we dont have any problems.However we dont have Medi-care we are in Peds. but when billing the state insurance (Medi-cal) we add modifier ZS. This is some info I found for the description of the codes.
Code Description
87081
Culture, presumptive, pathogenic organisms, screening only;
Lay Description
This is a presumptive screening culture for one or more pathogenic organisms. The methodology is by culture and the culture should be identified by type (e.g., anaerobic, aerobic) and specimen source (e.g., pleural, peritoneal, bronchial aspirates). If a specific organism is suspected, the person ordering the test will typically use common names, such as strep screen, staph screen, etc., to specify the organism for screening. Presumptive identification includes gram staining as well as up to three tests, such as a catalase, oxidase, or urease test. Screenings included in this code are nonmotile, catalase-positive, gram-positive rod bacteria.
86403
Particle agglutination; screen, each antibody
Lay Description
These tests may be ordered as PA. The specimen is serum. There are several methods used in tandem with PA tests, such as fluorescence enzyme assay and scattered light flow cytometry. Particle agglutination (PA) tests may be performed to evaluate immune status to and diagnosis certain viruses (i.e., measles virus infection Use 86403 to report each separate antibody screen, and 86406 to report each antibody tested according to titer.