CAN WE IMPROVE ACCURACY OF DIAGNOSING IRON DEFICIENCY AMONG CKD PATIENTS?

Introduction:

Accurate diagnosis of iron deficiency (ID) in chronic kidney disease (CKD) adults is challenging at times. Though CKD anemia is normocytic, normochromic, associated iron deficiency is present in majority of patients. Early detection of iron-deficiency anemia (IDA) can significantly enhance the effectiveness of treatment of CKD. However iron overload is also a concern, which happens when iron therapy is initiated in iron replete patients or continuing unsupervised iron therapy. In order to avoid such situation of ‘over’ treatment of ID, one needs to asses iron stores, the gold standard being invasive bone marrow examination, or hepatic MRI. KDIGO recommends transferrin saturation (TSat) and serum ferritin levels for tailoring iron therapy, however their accuracy and even serum Fe as hepatic or cardiac iron overload indicators is questionable. Other markers of IDA include % of hypochromic red blood cells (CHr), soluble transferrin receptor (sTfr) and reticulocyte hemoglobin equivalent (RetHE).

Among these, RetHE is promising. The reticulocytes last only 24 to 48 h in circulation before developing into mature red blood cells. During the initial stages of iron deficiency, insufficient iron supply would cause a decline of hemoglobin production in reticulocytes in bone marrow, which can be detected through reduced RetHE. In addition to its rapid, convenient, and cost-effective measurement, RET-He >30 pg is a potential marker in ruling out IDA with an excellent diagnostic sensitivity and specificity. However, when IDA co-exists with other non-ID conditions, which is common in actual clinical practice, evaluation of serum ferritin remains necessary for making the diagnosis.

Methods:

To compare RetHE value with conventional markers of IDA, i.e., Serum Iron levels, total iron binding capacity (TIBC), transferrin saturation and ferritin levels among adult stable CKD patients. They were iron and erythropoietin naive, had not been transfused and had no concurrent illness. The samples were collected prospectively as per figure 1. SPSS version 21.0 was used for analysis. RetHE assessment is rapid, fully automated, can be measured in same sample used for complete blood count test and it does not get affected in inflammatory states.

Results:

Study population had 80 patients (CKD II 6, CKD III 18, CKD IV 32 and CKD V 24), 67.5% were above 60 years old. Mean and SD of salient values are shown in Table 1. Figure 2 shows that RetHE has sensitivity of 92.86% and specificity is 34.85%. Predictive positive test is 23.21% and predictive negativity is 95.83%.

Cut off level should be 21.9 to assess the true Iron deficiency in study population with good specificity.

Conclusions:

It is necessary to diagnose IDA accurately among CKD patients and to avoid iron overload during the treatment. If the traditional indices of IDA, viz. TSat and S. Ferritin level are unable to assist in diagnosis of IDA or FDA, one can use RetHE as a parameter. In the present study, it has been found to have good sensitivity and a negative predictive value. The specificity and positive predictive value is low. The decision of when not to initiate iron therapy in CKD can be guided by such values and one can avoid using iron supplements in a situation where the diagnosis of IDA is doubtful.

I have no potential conflict of interest to disclose.

I did not use generative AI and AI-assisted technologies in the writing process.