From a laboratory medicine perspective, the Association for Clinical Biochemistry and Laboratory Medicine (ACB) and the Royal College of Pathologists (RCPath) advise that: HbA1c may be unreliable in the presence of haemolytic anaemia, haemoglobinopathies, or nutritional deficiencies affecting red cell biology and the direction of distortion may be high or low Clinicians should document any known haematological conditions when requesting HbA1c, so laboratory staff can flag potential inaccuracies Serum B12 testing should be considered in patients on long-term metformin who are symptomatic or have risk factors for deficiency, in line with MHRA and NICE advice Alternative tests fasting plasma glucose, OGTT, or interim use of fructosamine/glycated albumin should be considered when HbA1c reliability is in doubt The NHS website (nhs.uk) provides patient-facing information on the HbA1c test and factors that can affect its accuracy, which patients may find a useful starting point
This remarkable selectivity stems from 5-amino-1MQs specific interaction with the nicotinamide-binding pocket of NNMT, rather than the SAM-binding site common to many methyltransferases
Peripherally, pancytopenia is most often observed, but only 12 of the major cell types (erythrocytes, leukocytes, platelets) may be depressed in some cases
Of 492 patients identified, 382 (78%) were receiving injections more frequently than the recommended three monthly dose of hydroxocobalamin
