Association between elevated serum cobalamin concentrations and malignancy: a retrospective cohort study from the western Cape, South Africa

Introduction Serum cobalamin (vitamin B12) is routinely measured to diagnose deficiency, while elevated concentrations have been associated with malignancy, renal and liver impairment. Limited data on these associations exists in South African populations. This study aimed to characterise laboratory utilisation of serum cobalamin testing and assess the association between elevated serum cobalamin concentrations and malignancy in a South African population.Materials and methods A retrospective analysis of serum cobalamin tests performed over five years was undertaken to describe laboratory utilisation. A retrospective cohort study of tests performed over three years was conducted to investigate associations between elevated serum cobalamin concentrations and pathological comorbidities, including histologically or cytologically confirmed malignancy diagnosed within three years of measurement. Patients with serum cobalamin concentrations of 145-569 pmol/L were defined as the unexposed group, while those with concentrations >569 pmol/L were defined as the exposed group.Results A total of 1561 tests from patients admitted to Tygerberg Hospital between 2017 and 2019 were included, comprising an unexposed group (n = 791) and an exposed group (n = 770). Higher serum cobalamin concentrations were observed in males and individuals with renal or liver impairment (p Conclusion In South African individuals without cobalamin supplementation, elevated serum cobalamin concentrations were independently associated with malignancy. Elevated concentrations should therefore increase the clinical index of suspicion for underlying malignancy, particularly solid tumours.