investigation and diagnosis

Last edited 12/2018 and last reviewed 09/2023

A full clinical history and physical examination should be undertaken.

• inquire about
• use of aspirin and other NSAID's
• family history of IDA - may indicate inherited disorders of iron absorption
• haematological disorders e.g. - thalassaemia
• telangiectasia and bleeding disorders
• family history of colorectal carcinoma (1,2)
  
  
• consider if patient meets either
  • criteria for urgent cancer referral or
  • use of faecal immunochemical test (FIT) in symptomatic patients outside urgent cancer referral guidance
  • see linked items

In patients with no obvious cause for iron deficiency anaemia (IDA), the following investigations could be carried out (2):

• coeliac serology (presence of anti-endomysial antibody or tissue transglutaminase antibody) - The British Society of Gastroenterology suggests that all patients with IDA should be screened for coeliac disease
  
  
• upper and lower GI investigations - in all postmenopausal female and all male patients in whom iron deficiency has been confirmed (except when there is a history of significant overt non GI blood loss)
  
  
• urine testing for blood - since around 1% of patients with IDA will have renal tract malignancy
  
  
• stool examination - if appropriate to detect parasites
  
  
• testing for Helicobacter pylori - H. pylori colonisation may impair iron uptake and increase iron loss
  
  
• faecal immunochemical test (FIT):
  • FIT in symptomatic patients outside urgenct cancer referral guidance (2 week wait criteria) (3)
    • NICE criteria for requesting test for occult blood in faeces (FIT)
      • should be offered to adults without rectal bleeding who:
        • are aged 50 or over with unexplained:
          • abdominal pain or weight loss or
        • are aged under 60 with:
          • changes in their bowel habit or iron-deficiency anaemia or
        • are aged 60 or over and have anaemia without iron deficiency
    • the the level of Hb used for an abnormal versus a normal result my vary with respect to implementation of this pathway
      • a level of greater than or equal to 10 µg Hb/g faeces for defining an "abnormal result" has been suggested by NICE
      • an "abnormal test" meets the criteria for urgent cancer referral (3)
        

Investigations in IDA include the following:

• full blood count and blood film examination

• recognise the indices of iron deficiency
• reduced haemoglobin - Men <13.5 g/dl, women < 11.5 g/dl
• reduced MCV - <76 fl (76–95 fl )
• reduced MCH - 29.5 ± 2.5 pg (27.0–32.0 pg)
• reduced MCHC - 32.5 ± 2.5 g/dl (32.0–36.0 g/dl) (1)
• blood film
• microcytic, hypochromic cells
• occasional target cells and pencil-shaped poikilocytes
• platelet count may be at or above the upper limit of normal if there is persistent bleeding

• haematinic assays:

• decreased serum ferritin - best biochemical marker (in the absence of inflammation)
• the cut off concentration that is diagnostic varies between 12 and 15 mg/l.
• but in the presence of an inflammatory disease a concentration of 50 mg/l or even more may still be consistent with iron deficiency
• vitamin B12, folate

• increased serum transferrin receptor (sTfR) assay - is a good indicator of iron deficiency in instances where ferritin estimation is likely to be misleading but its value in the clinical setting remains to be proven (1).
• serum iron and total iron binding capacity (TIBC)  

The best proof of iron deficiency anaemia is that the anaemia is cured by administration of iron.

Reference:

• (1) Provan D. (2010). Iron deficiency anaemia. ABC of clinical haematology  
• (2) Goddard AF et al. Guidelines for the management of iron deficiency anaemia. Gut. 2011;60(10):1309-16.
• (3) NICE (July 2017). Quantitative faecal immunochemical tests to guide referral for colorectal cancer in primary care