Iron deficiency anaemia (IDA) in adults is common, and a major cause of morbidity worldwide.

Serum ferritin is the single most useful marker of IDA. A good response to iron therapy (Hb rise ≥10g/L within a 2-week timeframe) in anaemic patients is highly suggestive of absolute iron deficiency, even if the results of iron studies are equivocal.

Initial clinical assessment

• Take a detailed history, as it may provide important clues as to the cause(s) of IDA in the individual case.
• Initial investigation of confirmed IDA should include urinalysis or urine microscopy, screening for coeliac disease (CD) and in appropriate cases, endoscopic examination of the upper and lower GI tract.
• CD is found in 3%–5% of cases of IDA, and it should be routinely screened for serologically, or on small bowel biopsy at the time of gastroscopy.
• Age, sex, Hb concentration and mean cell volume are all independent predictors of risk of GI cancer in IDA, and need to be considered as part of a holistic risk assessment. It follows that the cancer risk in iron deficiency without anaemia is low.
• There are insufficient grounds at present to recommend faecal immunochemical testing for risk stratification in patients with IDA.
• In men and postmenopausal women with newly diagnosed IDA, gastroscopy and colonoscopy should generally be the first-line GI investigations. In those not suitable for colonoscopy, CT colonography is a reasonable alternative.

Hb levels normalise with iron replacement therapy (IRT) in most cases of IDA, but IDA recurs in a minority of these on long-term follow-up. In those with negative bidirectional endoscopy of acceptable quality and either an inadequate response to IRT or recurrent IDA, do further investigation of the small bowel and renal tract to exclude other causes.

Treatment of IDA

IRT should not be deferred while awaiting investigations for IDA unless colonoscopy is imminent. The initial treatment of IDA should be with one tablet per day of ferrous sulphate, fumarate or gluconate. If not tolerated, a reduced dose of one tablet every other day, alternative oral preparations or parenteral iron should be considered.

Limited transfusion of packed red cells may on occasion be required to treat symptomatic IDA, in which case IRT is still necessary post-transfusion. Patients should be monitored in the first four weeks for an Hb response to oral iron, and treatment should be continued for a period of around three months after normalisation of the Hb level, to ensure adequate repletion of the marrow iron stores.

Parenteral iron should be considered when oral iron is contraindicated, ineffective or not tolerated. This consideration should be at any early stage if oral IRT is judged unlikely to be effective, and/or the correction of IDA is particularly urgent.

After the restoration of Hb and iron stores with IRT, the blood count should be monitored periodically (perhaps every six months initially) to detect recurrent IDA. 

Reference

Snook J, Bhala N, Beales ILP, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut 2021;70:2030-2051.