(Reuters) -Abbott missed analysts' estimates for third-quarter revenue on Wednesday, as weakness in its diagnostics and nutritional businesses failed to offset strong demand for its medical devices, sending its shares down 3% premarket. The company had flagged volatility in the businesses as it navigates a sharp decline in COVID-19 testing demand, new U.S. tariffs, and a freeze on foreign aid by President Donald Trump's administration. The decision to halt foreign aid has upended the supply chain for med ...