Medtronic (MDT) this morning announced it received a new arm indication for its Guardian Sensor 3 which improves the accuracy of the sensor to an 8.7% MARD, likely leading to a non-adjunctive claim for standalone, Piper Jaffray analyst JP McKim tells investors in a research note. The news is an incremental negative for Dexcom (DXCM) shares as a path to non-adjunctive claim for Medtronic has become much clearer, McKim contends. He expects a stand-alone launch of Guardian Sensor 3 sometime in 2018. The analyst believes Dexcom carries more negative headline risk in the near term, but he expects the company to remain the market leader in continuous glucose monitors. As such, McKim thinks longer term investors should be buying the stock. He keeps an Overweight rating on Dexcom with a $60 price target. The stock in morning trading is down 12c to $56.24.

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Pre-earnings options volume in DexCom is 11.4x normal with calls leading puts 11:2. Implied volatility suggests the market is anticipating a move near 5.8%, or $8.05, after results are released. Median move over the past eight quarters is 5.4%.