Pathology/Lab Coding Alert

Test your coding knowledge. Determine how you would code this situation before looking at the box below for the answer.
Question: We have a wound culture that we've identified as Staphylococcus aureus based on three tests: Gram stain, catalase and coagulase. In reading the preamble to CPT's microbiology section, a presumptive culture identification uses up to three tests. Adefinitive identification requires additional tests beyond the three (for example, biochemical panels) and results in identification to the species level. Because we did only three tests but identified the organism to the species level, is this considered a presumptive or definitive identification? Iowa Subscriber

Answer: CPT defines presumptive and definitive identification based on the tests performed to identify the organism, not based on whether you can name the genus, species or subspecies. The introduction to the microbiology section states, "Presumptive identification of microorganisms is defined as identification by colony morphology, growth on selective media, Gram stains, or up to three tests (e.g., catalase, oxidase, indole, urease)."

Based on this definition, you have performed a presumptive identification because you carried out only three tests. You should report this service as CPT 87070 (Culture, bacterial; any other source except urine, blood or stool, with isolation and presumptive identification of isolates). You did not meet the CPT definition of definitive identification, which "requires additional tests (e.g., biochemical panels, slide cultures)."

"These are billing definitions and are very confusing and frustrating to microbiologists," says Jodi Garrett, MT (ASCP) (SM), manager of the microbiology-virology division of Nebraska Health Systems laboratory in Omaha. "This organism is definitively identified as S. aureus in a taxonomic sense, but is 'presumptive'in a billing sense."

If the coagulase is determined by a rapid particle agglutination method, however, you can also bill 87147 (Culture typing; immunologic method, other than immunofluorescence [e.g., agglutination grouping], per antiserum), Garrett says.