Diagnostic performance of reticulocyte hemoglobin equivalent in assessing the iron status

Abstract

Background: Measurement of reticulocyte hemoglobin equivalent (RET-He) is rapid, convenient, and cost-effective. Yet, researches on its performance in diagnosing iron deficiency with concurrent inflammation are limited. Hence, this study investigated RET-He value in various states, including inflammation, and evaluated its diagnostic performance in iron status assessment.

Methods: Retrospectively, 953 clinical data and laboratory results-complete blood count, reticulocyte count, RET-He, and serum ferritin-were reviewed. Patients on iron therapy were excluded. Iron status was defined by serum ferritin as the reference method. RET-He among populations was investigated. Its diagnostic performance and optimal cutoff were determined by ROC analysis.

Results: Three population groups were classified: healthy control, iron deficiency anemia (IDA), and non-ID anemia. Significantly, RET-He value in IDA was lower than that of healthy control, anemia of inflammation, and chronic kidney disease (P < .0001). Low RET-He was also observed in IDA with concomitant inflammation despite normal-to-high serum ferritin levels. No significant difference was observed between RET-He values in pure IDA and thalassemia (P = .57). ROC curve analysis revealed AUC of 0.876 (P < .0001) at cutoff 30 pg, by which IDA was discriminated with 74.2% sensitivity and 97.4% specificity. Applying cutoff ≤30 pg, IDA can be diagnosed with 96% sensitivity, 97.4% specificity, 80% PPV, and 99.6% NPV. Hence, RET-He >30 pg signifies a non-IDA state.

Conclusion: In addition to convenience and cost-effectiveness, RET-He cutoff >30 pg can be potentially used to exclude IDA due to its excellent diagnostic sensitivity and specificity.

Keywords: diagnostic performance; exclusion; inflammation; iron deficiency anemia; reticulocyte hemoglobin equivalent (RET-He).

Figure 1

Study populations. Diagnostic criteria for each population group: (1) Healthy control: absence of clinical symptom, Hb ≥ 120 g/L (W) or ≥ 130 g/L (M), MCV 80‐100 fL, MCH 27‐31 pg, WBC count 4.0‐10.0 x 10⁹/L, platelet count 150‐450 x 10⁹/L, and serum ferritin 33.71‐674.16 pmol/L; (2) IDA: Hb < 120 g/L (W) or < 130 g/L (M), MCV < 80 fL, MCH < 27 pg, Reticulocyte Production Index (RPI) <2, and serum ferritin < 33.71 pmol/L or ferritin ≥ 33.71 pmol/L with clinical diagnosis of IDA; (3) IDA‐inf: Hb < 120 g/L (W) or < 130 g/L (M), MCV < 80 fL, MCH < 27 pg, and serum ferritin ≥ 33.71 pmol/L in presence of inflammation; (4) Anemia of inflammation: Hb < 120 g/L (W) or < 130 g/L (M), MCV 80‐100 fL, MCH 27‐31 pg, and serum ferritin ≥ 33.71 pmol/L with associated inflammatory conditions; (5) Anemia of chronic renal insufficiency: Hb < 120 g/L (W) or < 130 g/L (M), MCV 80‐100 fL, MCH 27‐31 pg, and serum ferritin ≥ 33.71 pmol/L in patients diagnosed of CKD; (6) Thalassemia: Hb < 120 g/L (W) or < 130 g/L (M), MCV < 80 fL, MCH <27 pg, and Hb typing and/or DNA analysis results demonstrating alpha and/or beta thalassemia

Figure 2

RET‐He values among the population groups. Box‐and‐Whisker plot illustrates RET‐He values among six population groups in this study. Comparison of values between groups is performed by the Kruskal‐Wallis test (P < .05)

Figure 3

Optimal RET‐He cutoff. RET‐He cutoff value in distinguishing IDA is optimally determined by ROC analysis. Cutoff ≤30 pg demonstrates AUC of 0.876 (74.2% sensitivity, 97.4% specificity; P < .001)

Figure 4

Proposed diagnostic algorithm. Evaluation of RET‐He is incorporated into the proposed diagnostic algorithm. At RET‐He cutoff >30 pg, IDA is excluded. As IDA can co‐exist with non‐ID conditions, ferritin still plays a role in the confirmation of such condition