Soluble Transferrin Receptor –Ferritin Index in the Diagnosis of Anaemia of Chronic Disease in Patients with Rheumatoid Arthritis

INTRODUCTION: Anaemia is the most common cause of morbidity in Rheumatoid arthritis (RA)patients. It has been found that about 60% of Rheumatoid arthritis patients are anaemic. The causes of anaemia in RA may be due to anaemia of chronic disease (ACD), iron deficiency anaemia (IDA), anaemia due to vitamin B12 or folate deficiency. Serum ferritin reflects body iron stores and sTfR reflects cellular iron. Hence its ratio sTfR/log ferritin is used as an estimate of body iron stores. This ratio is used to differentiate anaemia of chronic disease from combined iron deficiency anaemia and ACD in RA patients. AIM OF THE STUDY: 1. To assess the anaemia in patients with Rheumatoid Arthritis. 2. To differentiate anaemia of chronic disease from iron deficiency anaemia using sTfR- ferritin index. MATERIALS AND METHODS: This study included three groups of 30 numbers each of anaemic RA patients, pure iron deficiency anaemia patients and age & sex matched controls. CBC, ESR, CRP, ferritin and sTfR were measured. The peripheral blood picture was also analysed. Ferritin and sTfR was measured by ELISA sandwich method. sTfR/log ferritin was calculated in all the study groups. RESULTS: Serum Ferritin was significantly raised in RA patients ( p< 0.001), serum soluble transferrin receptor was significantly raised in iron deficiency anaemia (p< 0.001) and sTfR-F index was raised in iron deficiency anaemia (p< 0.001) and decreased in anaemia of chronic disease (p< 0.001). CONCLUSION: Serum ferritin is affected by inflammation whereas serum soluble transferrin receptor is not affected by inflammation and increased in iron deficiency. Hence sTfr-F index is a better indicator of iron deficiency and is also useful to differentiate pure ACD from combined ACD with iron deficiency.