Diagnostic testing and information services company to the healthcare industry, Quest Diagnostics (NYSE:DGX) fell sharply Thursday after lowering guidance. At one point, DGX lost 9.32 percent to trade at $87.87 a share. The stock is breaking down from a bearish daily chart base, which indicates lower prices ahead. The next key support level that should be watched closely is around $80. That's where the stock broke out of a monthly chart bullish base in 2017. Often, when a stock retests prior break-out levels it finds defense from the institutional money crowd.