Complex sentence: Electronic cross-matching can only be used if a patient has a negative antibody screen, which means that they do not have any active red blood cell atypical antibodies, or they are below the detectable level of current testing methods.
Split into simpler sentences: Electronic cross-matching can only be used if a patient has a negative antibody screen. This means that they do not have any active red blood cell atypical antibodies or they are below the detectable level of current testing methods.