The Washington Post writes the latest effort by the federal government in measuring medical quality in hospitals – the combining of dozens of metrics into one patient-friendly quality indicator – is proving the most contentious. Hospital leaders who previewed the preliminary rating system say the formula is skewed against institutions that treat the poorest or toughest patients, meaning those with complex illnesses. The number of stars would be based on 64 different measures, which CMS has posted on Medicare’s Hospital Compare website. The metrics on mortality, readmission, patient experience and patient safety are the most influential, each representing 22 percent of a facility’s rating. Consumer advocates defend the rating system, saying that while not perfect, it correctly reflects higher rates of problems in some big institutions despite their lofty reputations.