Targeting, monitoring and effect of oral iron therapy on haemoglobin levels in older patients discharged to primary care from inpatient rehabilitation:a cohort study using routinely collected data

Background: Oral iron is commonly prescribed to older patients with suspected or confirmed iron deficiency anaemia, however few studies have examined the effectiveness of oral iron therapy in the real world in this population. We therefore determined the prevalence of iron deficiency in older people prescribed oral iron, examined the response mounted to therapy and ascertained predictors of response to oral iron.Methods: We analysed a routinely collected, linked dataset from older patients who had undergone inpatient rehabilitation between 1999 and 2011. An initial analysis examined patients within this cohort who were prescribed iron after rehabilitation and derived three groups based upon their ferritin and transferrin indices; probably, possibly and not iron deficient. A second analysis compared pre- and post-treatment haemoglobin to determine the degree of response to iron therapy across each category of deficiency. Finally, patient demographics, linked biochemistry data and comorbid disease based on International Statistical Classification of Disease (ICD-10) codes from previous hospital admissions were used in regression modelling to evaluate factors affecting response to therapy.Results: 490 patients were prescribed oral iron within 90 days of rehabilitation discharge. 413/490 (84%) had iron indices performed; 94 (23%) were possibly deficient, 224 (54%) were probably deficient, and 95 (23%) were not deficient. 360/490 patients had both pre and post treatment haemoglobin data and iron indices; probably deficient patients mounted a slightly greater response to oral iron (17g/L vs 12g/L for not deficient; p<0.05). Only pre-treatment haemoglobin, mean cell volume (MCV) and lower gastrointestinal pathology were significant predictors of a response to oral iron therapy. Notably, acid-suppressant use was not a predictor of response.Conclusion: We conclude that many older patients are exposed to oral iron without good evidence of either iron deficiency or a significant response to therapy.