More nursing homes are waiting longer for covid-19 test results for residents and staffers, according to federal data, making the fight against record numbers of omicron cases even harder. The double whammy of slower turnaround times for lab-based PCR tests and a shortage of rapid antigen tests has strained facilities where quickly identifying infections is crucial for keeping a highly vulnerable population safe. A KHN analysis of data from the Centers for Medicare & Medicaid Services finds that 25% of nursing homes that sent tests to a lab waited an average of three or more days for results a…