Palmetto granted final coverage of Natera's (NTRA) cell-free DNA transplant assay Prospera, Piper Jaffray analyst William Quirk tells investors in a research note. The analyst continues to believe CareDx (CDNA) has a "strong competitive moat" in transplant, and that AlloSure is used in centers that represent 65% of transplant volume. Investors were waiting on this negative headline risk for CareDx, says the analyst, who recommends buying the stock today on weakness. Quirk believes investors have been treating the Palmetto decision as a "clearing event" for CareDx shares. He maintains an Overweight rating on the name with a $63 price target.