Background Haematological abnormalities are commonly seen in patients with systemic lupus erythematosus (SLE). Anaemia is frequently reported although there is little data in the literature regarding iron deficiency.
Purpose To identify the prevalence of anaemia and iron deficiency in a large cohort of patients with SLE.
Methods From February 2017, patients fulfilling revised ACR criteria of lupus were prospectively recruited from the Lupus Clinic at University College London Hospital, UK. Standard haematological measures including Haemoglobin (Hb), Red Blood Cell Distribution Width (RDW) and Mean Corpuscular Volume (MCV) were recorded. Anaemia was defined by World Health Organisation (WHO) criteria; Hb <120 g/L in women and <130 g/L in men. Iron status was assessed by serum Ferritin and Transferrin saturations.
Results A total of 284 patients were recruited. 93% (265/284) of patients were female with ages ranging between 16–82 years old (median 44; IQR 32–56). Hb ranged from 88–167 g/L (median 127; IQR 117–135). A third of patients (33%; 95/284) were found to be anaemic. Of those who were anaemic, 89 were female and 6 were male. A low MCV is suggestive of iron deficiency; 5.6% (16/284) of patients were microcytic while 19% (54/284) were macrocytic. In those who were anaemic, 13% were microcytic (12/95) and 18% were macrocytic (17/95). RDW was typically at the upper limit of the normal range (median 14.1%; NR 11.5%–14.5%). 38% (107/284) of patients had an elevated RDW (>14.5%). Ferritin levels were highly variable, ranging from 6–2536 ng/mL (median 62 ng/mL; IQR 38–123 ng/mL). Ferritin <20 ng/mL (suggestive of iron deficiency) was seen in 12% (35/284) of patients. Transferrin saturations<16% (suggestive of iron deficiency) were seen in 20% (57/284) of patients. These results are summarised in figure 1.
Conclusions Anaemia is a common feature of SLE (affecting one third of patients in this cohort). It is however difficult to verify how many cases are due to iron deficiency. Ferritin is a poor marker of total iron and is likely to be elevated in the context of inflammation. RDW (a marker of early iron deficiency) is however elevated in 38% of patients with SLE in this cohort.
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