Diagnostic performance of peripheral blood film and red blood cell indices as markers of iron deficiency among patients with chronic kidney disease in low resource settings

BACKGROUND: Iron deficiency anaemia (IDA) is a common finding among patients with chronic kidney disease (CKD) and a major contributor to the high morbidity, mortality and poor quality of life associated with the disease. Assessment of iron deficiency anaemia has become routine in the evaluation of patients with CKD and iron studies such as serum ferritin, total iron binding capacity and transferrin saturation are recommended as standard diagnostic work up. However, in Nigeria and other low and middle income countries (LMICs) where most patients pay out of pocket, only few patients could afford iron studies, in addition to other cost of care. It is therefore imperative to find and establish the utility of other relatively affordable markers of iron deficiency among patients in LMICs. In studies done within the general population, the percentage of hypochromic red blood cells (PHRC), RBC indices and reticulocyte haemoglobin concentration (CHr) have been shown to predict iron deficiency. However, the usefulness of these in CKD patients had not been established. Thus, we determined the utility of PHRC and RBC indices among patients with CKD. METHODS: this is a cross sectional survey of 157 participants with CKD and 157 apparently healthy controls. The patients with CKD were individuals receiving care at the renal unit of the University College Hospital, Ibadan. Clinical data were collected using standard care report forms and information obtained were demographic details, aetiologies of CKD, dialysis status, symptoms of iron deficiency anaemia, modalities of anaemia treatments and other medications. Blood samples were collected for iron studies, full blood count, red blood cell (RBC) indices, peripheral blood film for PHRC, plasma highly sensitive C- reactive protein, serum electrolytes, urea and creatinine. Data was analyzed using SPSS version 23. RESULTs: a total of 314 participants were enrolled in the study, half of them were patients with CKD while the remaining half were controls without CKD. The mean age for cases and controls were [45.5±14.4 vs 46.1±15.5 years respectively, p < 0.72] while females were 57% vs 60.1%, p < 0.06]. The prevalence of IDA using iron studies [67 (42.6%) vs 33 (21.0%), p < 0.01], RBC indices [46 (29.3%) vs 25 (15.9%), p < 0.002], and PHRC [48 (30.5%) vs 32 (20.4%), p < 0.038]. The sensitivity and specificity of RBC indices and PHRC as surrogate markers of iron deficiency anaemia were [73.8% ; 92.0%] and [80.0% ; 92.3%,] respectively. CONCLUSION: this study confirmed that the 3 methods of diagnosis of iron deficiency anaemia vis-a-vis iron studies (Serum ferritin and TSAT), RBC indices and percentage hypochromic RBC, all demonstrated high prevalence of iron deficiency anaemia among patients with CKD. While RBC indices and percentage hypochromic RBC are reliable and highly specific surrogate markers of iron deficiency anaemia among individuals with CKD.                                                                                                                                                                                                                                                          Â