Can somebody shed some light on my 12 week bloods?

HIV, hepatitis etc came back negative, but next to the sickle cell / thalassaemia box there is a small downwards arrow then MCH next to it. Im assuming it says low MCH but what is this?? the midwife said she would call me if there was a problem and post the results otherwise. I havent had a call so im assuming its not serious ?