The differentiation of anaemia in rheumatoid arthritis: parameters of iron-deficiency in an Indian rheumatoid arthritis population

Serum or plasma ferritin concentration as an index of iron deficiency and overload

BACKGROUND

Reference standard indices of iron deficiency and iron overload are generally invasive, expensive, and can be unpleasant or occasionally risky. Ferritin is an iron storage protein and its concentration in the plasma or serum reflects iron stores; low ferritin indicates iron deficiency, while elevated ferritin reflects risk of iron overload. However, ferritin is also an acute-phase protein and its levels are elevated in inflammation and infection. The use of ferritin as a diagnostic test of iron deficiency and overload is a common clinical practice.

OBJECTIVES

To determine the diagnostic accuracy of ferritin concentrations (serum or plasma) for detecting iron deficiency and risk of iron overload in primary and secondary iron-loading syndromes.

SEARCH METHODS

We searched the following databases (10 June 2020): DARE (Cochrane Library) Issue 2 of 4 2015, HTA (Cochrane Library) Issue 4 of 4 2016, CENTRAL (Cochrane Library) Issue 6 of 12 2020, MEDLINE (OVID) 1946 to 9 June 2020, Embase (OVID) 1947 to week 23 2020, CINAHL (Ebsco) 1982 to June 2020, Web of Science (ISI) SCI, SSCI, CPCI-exp & CPCI-SSH to June 2020, POPLINE 16/8/18, Open Grey (10/6/20), TRoPHI (10/6/20), Bibliomap (10/6/20), IBECS (10/6/20), SCIELO (10/6/20), Global Index Medicus (10/6/20) AIM, IMSEAR, WPRIM, IMEMR, LILACS (10/6/20), PAHO (10/6/20), WHOLIS 10/6/20, IndMED (16/8/18) and Native Health Research Database (10/6/20). We also searched two trials registers and contacted relevant organisations for unpublished studies.

SELECTION CRITERIA

We included all study designs seeking to evaluate serum or plasma ferritin concentrations measured by any current or previously available quantitative assay as an index of iron status in individuals of any age, sex, clinical and physiological status from any country.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods. We designed the data extraction form to record results for ferritin concentration as the index test, and bone marrow iron content for iron deficiency and liver iron content for iron overload as the reference standards. Two other authors further extracted and validated the number of true positive, true negative, false positive, false negative cases, and extracted or derived the sensitivity, specificity, positive and negative predictive values for each threshold presented for iron deficiency and iron overload in included studies. We assessed risk of bias and applicability using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS)-2 tool. We used GRADE assessment to enable the quality of evidence and hence strength of evidence for our conclusions.

MAIN RESULTS

Our search was conducted initially in 2014 and updated in 2017, 2018 and 2020 (10 June). We identified 21,217 records and screened 14,244 records after duplicates were removed. We assessed 316 records in full text. We excluded 190 studies (193 records) with reasons and included 108 studies (111 records) in the qualitative and quantitative analysis. There were 11 studies (12 records) that we screened from the last search update and appeared eligible for a future analysis. We decided to enter these as awaiting classification. We stratified the analysis first by participant clinical status: apparently healthy and non-healthy populations. We then stratified by age and pregnancy status as: infants and children, adolescents, pregnant women, and adults. Iron deficiency We included 72 studies (75 records) involving 6059 participants. Apparently healthy populations Five studies screened for iron deficiency in people without apparent illness. In the general adult population, three studies reported sensitivities of 63% to 100% at the optimum cutoff for ferritin, with corresponding specificities of 92% to 98%, but the ferritin cutoffs varied between studies. One study in healthy children reported a sensitivity of 74% and a specificity of 77%. One study in pregnant women reported a sensitivity of 88% and a specificity of 100%. Overall confidence in these estimates was very low because of potential bias, indirectness, and sparse and heterogenous evidence. No studies screened for iron overload in apparently healthy people. People presenting for medical care There were 63 studies among adults presenting for medical care (5042 participants). For a sample of 1000 subjects with a 35% prevalence of iron deficiency (of the included studies in this category) and supposing a 85% specificity, there would be 315 iron-deficient subjects correctly classified as having iron deficiency and 35 iron-deficient subjects incorrectly classified as not having iron deficiency, leading to a 90% sensitivity. Thresholds proposed by the authors of the included studies ranged between 12 to 200 µg/L. The estimated diagnostic odds ratio was 50. Among non-healthy adults using a fixed threshold of 30 μg/L (nine studies, 512 participants, low-certainty evidence), the pooled estimate for sensitivity was 79% with a 95% confidence interval of (58%, 91%) and specificity of 98%, with a 95% confidence interval of (91%, 100%). The estimated diagnostic odds ratio was 140, a relatively highly informative test. Iron overload We included 36 studies (36 records) involving 1927 participants. All studies concerned non-healthy populations. There were no studies targeting either infants, children, or pregnant women. Among all populations (one threshold for males and females; 36 studies, 1927 participants, very low-certainty evidence): for a sample of 1000 subjects with a 42% prevalence of iron overload (of the included studies in this category) and supposing a 65% specificity, there would be 332 iron-overloaded subjects correctly classified as having iron overload and 85 iron-overloaded subjects incorrectly classified as not having iron overload, leading to a 80% sensitivity. The estimated diagnostic odds ratio was 8.

AUTHORS' CONCLUSIONS

At a threshold of 30 micrograms/L, there is low-certainty evidence that blood ferritin concentration is reasonably sensitive and a very specific test for iron deficiency in people presenting for medical care. There is very low certainty that high concentrations of ferritin provide a sensitive test for iron overload in people where this condition is suspected. There is insufficient evidence to know whether ferritin concentration performs similarly when screening asymptomatic people for iron deficiency or overload.

Pathobiochemical Mechanisms Relating Iron Homeostasis with Parameters of Inflammatory Activity and Autoimmune Disorders in Rheumatoid Arthritis

Aim: To find the correlations between the parameters of iron homeostasis, inflammatory activity and autoimmune disorders in rheumatoid arthritis (RA).

Materials and methods: The present study included 114 patients with RA and 42 healthy controls. We determined the parameters of iron homeostasis: serum iron, total iron binding capacity (TIBC), ferritin and soluble transferrin receptor (sTfR), the parameters of inflammatory activity: C-reactive protein (CRP), interleukin-6 (IL-6) and prohepcidin, and the parameters of autoimmune disorders: rheumatoid factor (RF), anti-cyclic citrullinated peptide (antiCCP) antibodies and DAS 28.

Results: The levels of sTfR, CRP, IL-6 and prohepcidin were significantly higher in RA patients than those in the controls and the level of serum iron was significantly lower in RA than that in the control group. Unlike the controls, in RA, there was a significant positive correlation of sTfR with the parameters of inflammatory activity (IL-6, prohepcidin, ESR) and with the parameters of autoimmune disorders (DAS 28, RF, antiCCP). A negative correlation of serum iron with sTfR was found only in RA patients. Prohepcidin positively correlated with the parameters of inflammation (CRP, ESR) and with the parameters for evaluation of autoimmune disorders (DAS 28 and RF) in the RA group.

Conclusion: Our study shows that the simultaneous determination of the two parameters sTfR and prohepcidin is most informative for evaluation of the changes in iron homeostasis in RA. The increase of both parameters provides information for tissue iron deficiency (assessed by the level of sTfR), caused by the inflammation when prohepcidin is expressed.

Pathobiochemical Mechanisms Relating Iron Homeostasis to Parameters of Inflammatory Activity and Autoimmune Disorders in Rheumatoid Arthritis

Aim: To find the correlations between the parameters of iron homeostasis, inflammatory activity and autoimmune disorders in rheumatoid arthritis (RA).

Materials and methods: The present study included 114 patients with RA and 42 healthy controls. We determined the parameters of iron homeostasis: serum iron, total iron binding capacity (TIBC), ferritin and soluble transferrin receptor (sTfR), the parameters of inflammatory activity: C-reactive protein (CRP), interleukin-6 (IL-6) and prohepcidin, and the parameters of autoimmune disorders: rheumatoid factor (RF), anti-cyclic citrullinated peptide (antiCCP) antibodies, and DAS 28.

Results: The levels of sTfR, CRP, IL-6 and prohepcidin were significantly higher in RA patients than those in the controls and the level of serum iron was significantly lower in RA than that in the control group. Unlike the controls, in RA, there was a significant positive correlation of sTfR with the parameters of inflammatory activity (IL-6, prohepcidin, ESR) and with the parameters of autoimmune disorders (DAS 28, RF, antiCCP). A negative correlation of serum iron with sTfR was found only in RA patients. Prohepcidin positively correlated with the parameters of inflammation (CRP, ESR) and with the parameters for evaluation of autoimmune disorders (DAS 28 and RF) in the RA group.

Conclusion: Our study shows that the simultaneous determination of the two parameters sTfR and prohepcidin is most informative in evaluating the changes in iron homeostasis in RA. The increase of both parameters provides information for tissue iron deficiency (assessed by the level of sTfR), caused by the inflammation when prohepcidin is expressed.

Iron deficiency anaemia

Anaemia affects roughly a third of the world's population; half the cases are due to iron deficiency. It is a major and global public health problem that affects maternal and child mortality, physical performance, and referral to health-care professionals. Children aged 0-5 years, women of childbearing age, and pregnant women are particularly at risk. Several chronic diseases are frequently associated with iron deficiency anaemia--notably chronic kidney disease, chronic heart failure, cancer, and inflammatory bowel disease. Measurement of serum ferritin, transferrin saturation, serum soluble transferrin receptors, and the serum soluble transferrin receptors-ferritin index are more accurate than classic red cell indices in the diagnosis of iron deficiency anaemia. In addition to the search for and treatment of the cause of iron deficiency, treatment strategies encompass prevention, including food fortification and iron supplementation. Oral iron is usually recommended as first-line therapy, but the most recent intravenous iron formulations, which have been available for nearly a decade, seem to replenish iron stores safely and effectively. Hepcidin has a key role in iron homoeostasis and could be a future diagnostic and therapeutic target. In this Seminar, we discuss the clinical presentation, epidemiology, pathophysiology, diagnosis, and acute management of iron deficiency anaemia, and outstanding research questions for treatment.

Pure red cell aplasia in systemic onset juvenile idiopathic arthritis

Common causes of anemia in juvenile idiopathic arthritis are anemia of chronic disease and iron deficiency. We report a 4 year old boy with biopsy proven systemic onset juvenile idiopathic arthritis and severe anemia. Bone marrow aspiration revealed pure red cell aplasia without evidence of hemophagocytosis. This rare, unexplained but well known entity responded to corticosteroids.

Diagnosing anemia in inflammatory bowel disease: beyond the established markers

The main types of anemia in inflammatory bowel disease (IBD) are iron deficiency anemia (IDA) and anemia of inflammatory etiology, or anemia of chronic disease (ACD). In the management of IBD patients with anemia it is essential for the physician to diagnose the type of anemia in order to decide in an evidence-based manner for the appropriate treatment. However, the assessment of iron status in IBD in many cases is rather difficult due to coexistent inflammation. For this assessment several indices and markers have been suggested. Ferritin, seems to play a central role in the definition and diagnosis of anemia in IBD and transferrin, transferrin saturation (Tsat), and soluble transferrin receptors are also valuable markers. All these biochemical markers have several limitations because they are not consistently reliable indices, since they are influenced by factors other than changes in iron balance. In this review, in addition to them, we discuss the newer alternative markers for iron status that may be useful when serum ferritin and Tsat are not sufficient. The iron metabolism regulators, hepcidin and prohepcidin, are still under investigation in IBD. Erythrocytes parameters like the red cell distribution width (RDW) and the percentage of hypochromic red cells as well as reticulocyte parameters such as hemoglobin concentration of reticulocytes, red blood cell size factor and reticulocyte distribution width could be useful markers for the evaluation of anemia in IBD.

Iron homoeostasis in rheumatic disease

Iron is critical in nearly all cell functions and the ability of a cell, tissue and organism to procure this metal is obligatory for survival. Iron is necessary for normal immune function, and relative iron deficiency is associated with mild immunosuppression. Concentrations of this metal in excess of those required for function can present both an oxidative stress and elevate risks for infection. As a result, the human has evolved to have a complex mechanism of regulating iron and limiting its availability. This homoeostasis can be disrupted. Autoimmune diseases and gout often present with abnormal iron homoeostasis, thus supporting a participation of the metal in these injuries. We review the role of iron in normal immune function and discuss both clinical evidence of altered iron homoeostasis in autoimmune diseases and gout as well as possible implications of both depletion and supplementation of this metal in this patient population. We conclude that altered iron homoeostasis may represent a purposeful response to inflammation that could have theoretical anti-inflammatory benefits. We encourage physicians to avoid routine iron supplementation in those without depleted iron stores.

Iron deficiency anemia: diagnosis and management

PURPOSE OF REVIEW

Iron deficiency anemia (IDA) still remains universally problematic worldwide. The primary focus of this review is to critique articles published over the past 18 months that describe strategies for the diagnosis and management of this prevalent condition.

RECENT FINDINGS

The medical community continues to lack consensus when identifying the optimal approach for the diagnosis and management of IDA. Current diagnostic recommendations revolve around the validity and practicality of current biomarkers such as soluble transferrin-receptor concentrations and others, and cause-based diagnostics that potentially include endoscopy. Management of IDA is based on supplementation combined with effective etiological treatment. Advances in oral and parenteral low-molecular-weight iron preparations has expanded and improved treatment modalities for IDA. Since the introduction of low versus high-molecular-weight intravenous iron administration, there have been fewer serious adverse events associated with parenteral iron preparations.

SUMMARY

Best practice guidelines for diagnosing and managing IDA should include the design of an algorithm that is inclusive of multiple biomarkers and cause-based diagnostics, which will provide direction in managing IDA, and distinguish between IDA from the anemia of chronic disease.