GP Connect is an initiative to facilitate a broader understanding of laboratory testing by focusing on common enquires between General Practitioners and Pathologists at Australian Clinical Laboratories. In this edition, Clinical Labs haematologist/pathologist Associate Professor Chris Barnes responds to questions asked by general practitioner Dr Jon Barrell about the topic of iron deficiency and fatigue in patients.
A/Prof Chris Barnes
(Pathologist)
MBBS, FRACP, FRCPA
A/Prof Chris Barnes is a clinical and laboratory trained haematologist and the National Director of Haematology at Australian Clinical Labs. He also works as director of the Haemophilia Treatment Centre at the Royal Children’s Hospital, Melbourne. A/Prof Barnes has an active clinical research interest and is also director of Melbourne Haematology (Clinical) and Melbourne Paediatric Specialists.
Dr Jon Barrell
(General Practitioner)
MBBS, DRACOG, FRACGP
Dr Jon Barrell is founding principal of Springs Medical and works full-time between the Daylesford and Trentham clinics. He is also Conjoint Senior Clinical Lecturer in the School of Medicine, Faculty of Health at Deakin University. Dr Barrell enjoys teaching medical students and GP Registrars, and has been a FRACGP Examiner and Vice Chairman of the Ballarat and District Division of General Practice.
In the 2014 ABS Census, over 20% of randomly selected Australian adults had iron deficiency, usually undiagnosed. Diving deeper into the statistics, 34% of Australian women of child bearing age have iron deficiency, and 70% of pregnant women in their third trimester were affected. Determining a patient’s iron levels is essential for prompt diagnosis of iron deficiency or overloading, with an undiagnosed condition being a high risk to patient safety, potentially leading to more serious conditions, including colorectal cancer.
Dr Jon Barrell (General Practitioner)
One of my female patients in her late 30s presents with being tired. What tests should I order to see if she is iron deficient?
A/Prof Chris Barnes (Pathologist)
Iron deficiency is a common cause for fatigue and up to 1 in 6 females in the reproductive age range has iron deficiency and this may be even higher in certain ethnic groups. A complete assessment of iron studies is recommended, by a number of groups, as an important first step in the investigation of patients with lethargy.
Dr Jon Barrell (General Practitioner)
Should I order iron studies or just ferritin?
A/Prof Chris Barnes (Pathologist)
This is somewhat controversial. A serum ferritin is adequate if the patient is otherwise well, however it’s known to be an acute phase reactant, and may be artificially increased in both acute and chronic inflammation. Serum ferritin may be increased in fatty liver, raised BMI or in the setting of OCP use. A number of authorities suggest that additional laboratory markers may be helpful in the assessment of patients for iron deficiency. Iron studies can certainly offer more information regarding iron deficiency with a low transferrin saturation (<20%) supporting the diagnosis of iron deficiency in patients with concomitant inflammation or systemic illnesses (even in the presence of a normal serum ferritin). You may avoid the need for the patient to have another test done, if you order iron studies instead of just serum ferritin.
Dr Jon Barrell (General Practitioner)
I find interpreting complete iron studies results confusing - can you please break it down for me?
A/Prof Chris Barnes (Pathologist)
Trying to keep it simple, I first look at the serum ferritin and the transferrin saturation. If both are low, the patient is iron deficient. If the serum ferritin is normal (or low normal) and the transferrin saturation is also low, then I would be suspicious that the patient is also low in iron and act accordingly (e.g. consider excluding sources of blood loss, review dietary history, consider a trial of iron supplementation with close review).
Dr Jon Barrell (General Practitioner)
Are there other tests that help?
A/Prof Chris Barnes (Pathologist)
An assessment of inflammatory markers can be helpful if you are concerned the patient has inflammation present. CRP / ESR can be helpful in this scenario, but needs to be guided by the clinical situation. More sophisticated tests, like soluble transferrin receptor can be done, but are a non medicare rebatable item and the patient may incur out-of-pocket fees.
Dr Jon Barrell (General Practitioner)
There seems to be some variability in normal ranges for ferritin & age & gender. And some Cardiologists (heart failure) & surgeons / anaesthetists (Pre-op) advocate ferritin > 100. What are your views on this? Should one consider ferritin < 100 as suboptimal in some circumstances and consider possible underlying causes and interventions in some cases?
A/Prof Chris Barnes (Pathologist)
Reference ranges for laboratory tests are most commonly established using large numbers of samples (e.g. 10,000) from a “normal” population. We need to show our accrediting bodies that our reference ranges are established using robust science. From a practical point of view, particularly when dealing with complex patients that may have more than one pathological process, a general rule-of-thumb is that if the patient has a serum ferritin above 100ng/ml, they are generally not likely to have any significant iron deficit. I think surgeons are quite keen on this to ensure that there is adequate iron in the setting of potential blood loss. I am not sure I would intervene and expose the patient to potential side effects of iron supplementation if they have very “normal” iron stores as assessed by iron studies, but I would be reaching out to the patient / surgeon in order to discuss relevant risks and benefits.
Dr Jon Barrell (General Practitioner)
When considering oral iron supplement, is there evidence to advocate one preparation over another?
A/Prof Chris Barnes (Pathologist)
Oral iron therapy is typically associated with a high incidence of gastrointestinal side effects such as nausea and constipation. This may occur in up to 40% of patients treated with therapeutic iron supplementation. Many of the manafacturers claim their preparation is associated with a low incidence of side effects, but in my experience these claims cannot be substantiated. If a iron preparation is not causing any side effects, it is often because there is very little iron. Iron in supplements is measured as equivalent to elemental iron. Recommended supplements to treat iron deficiency and improve iron stores contain 75 – 100mg per day of elemental iron. Some medications proposing to provide iron supplements
contain as little 5mg per day of elemental iron and will therefore, be an inadequate supplement.
