Utility of reticulocyte haemoglobin content and percentage hypochromic red cells as markers of iron deficiency anaemia among black CKD patients in South Africa

INTRODUCTION: Iron deficiency anaemia (IDA) worsens the prognosis and outcomes of chronic kidney disease (CKD). However, while the haemoglobin level is unreliable for early detection of IDA, reticulocyte haemoglobin content (CHr) and hypochromic red cells (%HYPO) are early markers of IDA. METHODS: This was a cross sectional study of black adult participants (n = 258) with CKD and apparently healthy members of staff and patients’ relatives (n = 141) at the Charlotte Maxeke Johannesburg Academic Hospital, South Africa, between 1 June 2016 and 31 December 2016. Serum iron, serum ferritin and transferrin were measured using standard laboratory methods, while the haematology analyser was employed to measure CHr and %HYPO. The validity of CHr and %HYPO as markers of IDA were evaluated. Multivariable binary logistic regression was conducted to determine predictors of the relationship between IDA, CHr and %HYPO. The area under the receiver operator characteristics (ROC) curve (AUC) of the final models were utilised to evaluate the discriminatory value of CHr and %HYPO respectively. RESULTS: About one-quarter (26.1%) of the participants had IDA which was more than three times more frequent among CKD patients, compared to controls (35.3% vs 9.2%); 32.3% (95%CI: 27.90%– 37.10%) of the study population had iron deficiency without anaemia and the prevalence of iron deficiency without anaemia was lower in CKD patients compared to controls (29.5% vs 37.6%). The mean age of CKD patients was higher than in controls (52.7 ±14.3 vs 40.4 ±12.6 years, P-value<0.001). The sensitivity and specificity for diagnosing IDA among CKD participants was 62.6% and 80.2% respectively for CHr (at a cut-off value of <28pg) and 63.3% and 79.8% respectively for %HYPO. CKD participants with CHr levels >28pg were 82% less likely to be diagnosed as having IDA as compared to those with CHr levels ≤ 28pg) (adj odds ratio = 0.18, 95% CI: 0.09–0.37). The AUC of CHr (0.81, 95% CI: 0.76–0.87) was higher than the AUC of %HYPO (0.76, 95%CI: 0.70–0.82). CONCLUSION: The diagnostic usefulness of CHr and the screening performance of %HYPO in predicting IDA among CKD patients are high. Their lower cost compared to conventional markers of ID recommend their use in clinical practice. Further cost effectiveness studies of these parameters are warranted.