vabbca

I was having weird problems recently with weakly reactive positive controls and patient tests with anti-D. The buttons were small and loose like the image you attached - the positive controls were reading 1-2+ instead of 3-4+. It started out as an intermittent problem, just some of the patients. They would usually repeat with weak reactions. A couple of days later the controls started getting a bit weaker. The next day, most of the patients were weak, so we took it out of service. Did as much troubleshooting as we could think of and called service. Everything checked out when service came...centrifuge speed, volumes dispensed, shake, etc. My service engineer finally thought of changing the pinch valve associated with the probe. Normally when this valve fails fluid drips from the probe, but he thought maybe the valve was not opening fully, dispensing less reagent as it went through it's dispense cycle. That did the trick. All my positives were back to normal, nice and strong with good buttons.