I am in the process of re-writing our SOP for out-of-specification testing. Just had a thought, if your ABO controls failed on the forward group you would have to retest ALL samples from neonates up to the last 'passed' control, as you would not have a reverse group as a 'check'. Also, this gets worse......if your corrective action showed that you needed to replace your LISS, capture indicator cells or other diluent , as this was found to be the cause of the OOS result (sorry Jules!!!!!!!), then all the screens up to the last 'passed' control would need re-testing. The more I think about this , the more complex it becomes am I going over the top with this?....aaargh!!!!