AKT-2919

A 65-year-old man with a history of ischaemic heart disease becomes more breathless and looks anaemic.
Test Result Normal Value
Haemoglobin (Hb) 95 g/l 130-170 g/l
Reticulocyte count 0.85% 0.5%-1.5%
Mean cell volume (MCV) 120.6 fl 82-102 fl
Vitamin B12 90.0 ng/l 130-700 ng/l
Intrinsic factor antibodies Positive
He is commenced on injections of hydroxocobalamin with blood tests to be repeated in seven days.
What is the most likely change at 1 week which would suggest that the patient is responding to treatment?