Iron Deficiency Anaemia

Background

1. Iron deficiency anaemia (IDA) occurs in 2-5% of adult men and postmenopausal women in the developed world.
2. Gastrointestinal (GI) blood loss from colonic cancer or gastric cancer, and malabsorption in coeliac disease are the most important causes that need to be sought.

Definitions

1. Consider anaemic if Hb <120g/l in male, <110g/l in female.
2. Consider IDA if MCV <80, microcytosis and hypochromia on blood film, serum ferritin <50 with normal CRP or serum ferritin <100 with raised CRP.
3. Consider thalassaemia and request Hb electrophoresis when microcytosis and hypochromia present in patients of appropriate ethnic background to prevent unnecessary GI investigation.

History

1. Dietary history to identify poor iron intake as borderline iron deficient diets are common
2. Symptoms that suggest blood loss – dysphagia, dyspepsia, altered bowel habit and drugs incl aspirin, NSAIDs, warfarin.
3. Symptoms that suggest malabsorption – diarrhoea, weight loss
4. Family history – significant if one first degree realtive <50 years or two affected first degree relatives

Examination

1. May reveal an abdominal mass or cutaneous sign of rare cause of GI blood loss eg hereditary haemorrhagic telangiectasia
2. Rectal examination is seldom contributory, and, in the absence of symptoms such as rectal bleeding and tenesmus, may be postponed until colonoscopy.
3. Faecal occult blood testing is too insensitive and non specific to be of benefit in the investigation of IDA.
4. Urine testing for blood is important when investigating IDA as around 1% patients with IDA have renal tract malignancy.

Investigations

1. All patients should be screened for coeliac disease
2. Consider upper and lower GI investigations in all postmenopausal female and all male patients where IDA has been confirmed unless history of significant overt non-GI blood loss
3. If OGD is performed as the initial GI investigation, only the presence of advanced gastric cancer or coeliac disease should
4. deter lower GI investigation.
5. In patients aged >50 or with marked anaemia or a significant family history of colorectal carcinoma, lower GI investigation should still be considered even if coeliac disease is found.
6. Colonoscopy is the lower GI investigation of choice as will detect both tumours and angiodysplasia. CT colonography can be used for frail patients to exclude tumour but not angiodysplasia. Both colonoscopy and CT colonography are preferable to barium enema.
7. Clinicians who feel their patients with IDA smight need OGD/colonoscopy should refer to surgeons/gastroenterologists for further assessment first.

Further Evaluation

1. In patients with recurrent IDA, normal OGD and colonoscopy, check for Helicobacter pylori and eradicate if present.
2. Imaging of small bowel unnecessary unless there are symptoms suggestive of small bowel disease or an inadequate response to iron therapy, especially if patient becomes transfusion dependent
3. Video capsule endoscopy or enteroscopy may then be requested in hope of detecting angiodysplasia, Crohn’s disease or small bowel neoplasia.

Special Considerations

1. Premenopausal women with IDA – screen for coeliac disease but reserve other upper and lower GI investigation for those aged 50 years or older, those with symptoms suggesting gastrointestinal disease, and those with a strong family history of colorectal cancer.
2. Post gastrectomy – IDA is common with partial or total gastrectomy. There is also 2-3x increased risk of gastric cancer. Investigation of IDA in postgastrectomy patients is recommended in those over 50 years of age
3. Iron deficiency without anaemia – endoscopic investigation rarely detects malignancy. Such investigation should be considered in patients aged >50 after discussing the risk and potential benefits.
4. Frailty – consider severity and recurrent nature of anaemia, risk of bowel preparation and potential fitness of patient to withstand treatment on a case by case basis.
5. Warfarin and aspirin – may unmask occult cancer so do not attribute IDA to these drugs until GI investigations completed

Management

1. Treat all patients with oral iron and continue for 3 months after anaemia corrected so that iron stores replenished
2. Ferrous fumarate 305mg once daily is the preferred oral option. Consider reducing dose to once every other day if this is not tolerated.
3. Parenteral iron can be used when oral preparations are not tolerated – see below.
4. Blood transfusions should be reserved for patients with symptomatic anaemia despite iron therapy or at risk of cardiovascular instability due to the degree of their anaemia.

Parenteral Iron

1. Can be given as small boluses or as total dose infusion depending on preparation.
2. May become hypotensive if given too quickly
3. Risk of anaphylaxis is low but ensure Adrenaline IM and facilities for CPR are available
4. Renal patients – tend to use repeated small boluses of Iron Sucrose (Venofer) because cheaper and because patients usually seen very frequently – Rx 100mg IV over 10 minutes followed by 100-200mg IV at weekly intervals to total 1G. Thereafter Rx 100-200mg IV every 2-4 weeks as required.
5. Gastro patients – Iron Isomaltoside (Monofer) preferred as can be given by total dose infusion of 1G over 30 minutes.

Links

• BSG Guidelines for Management of Iron Deficiency Anaemia Gut 2011;60:1309-16 [pdf]
• Parenteral Iron Guideline

Content updated by Dr Mark Crowther