Question: Our lab performs a chromosome analysis of amniotic fluid that involves performing a tissue culture and supplying two karyotype analyses. How should we code the service? Iowa Subscriber Answer: You should use the cytogenetic studies codes, reporting a separate CPT code to describe each step that the lab performs: - For the tissue culture, report 88235 (Tissue culture for non-neoplastic disorders; amniotic fluid or chorionic villus cells). - List the chromosome analysis (first karyotype) on the tissue culture as 88269 (Chromosome analysis, in situ for amniotic fluid cells, count cells from 6-12 colonies, 1 karyotype, with banding). - Report the additional karyotype as 88280 (Chromosome analysis; additional karyotypes, each study). - When appropriate, don't forget to bill for the professional interpretation of the entire amniotic fluid chromosome analysis using 88291 (Cytogenetics and molecular cytogenetics, interpretation and report). Hidden trap: You can only bill Medicare for 88291 when a pathologist -- not a PhD -- performs the service. That's because Medicare pays 88291 on the Physician Fee Schedule as a professional-only code, not billable with modifiers TC (Technical component) or 26 (Professional component). Also, Medicare does not list 88291 on the Clinical Laboratory Fee Schedule or as an APC on the Outpatient Prospective Payment Fee Schedule.