Assessment of human iron status: A cross-sectional study comparing the clinical utility of different laboratory biomarkers and definitions of iron deficiency in daily practice.

OBJECTIVES

No full international consensus exists on disease markers to be used for assessing the human iron status. Therefore this study was conducted to compare performances of serum ferritin and transferrin saturation (TSAT) versus soluble transferrin receptor (sTfR)/log ferritin and reticulocyte hemoglobin content (CHr), also known as Thomas-plot, in the diagnosis of iron deficiency (ID).

DESIGN AND METHODS

A total of 445 consecutive hospitalized patients, referred for routine testing of the actual iron status, were included. Logistic regression models for the probability of functional ID (CHr<28pg) were constructed for all 445 patients, for 225 patients without (C-reactive protein [CRP]≤0.5mg/dL) and 220 patients with acute-phase reaction (CRP>0.5mg/dL).

RESULTS

Based on the Thomas-plot analyses, 153/445 (34.38%) patients were identified with ID. When ID was diagnosed by means of serum ferritin levels<30ng/mL and TSAT levels<20%, 105/445 (23.60%) and 215/445 (48.31%) patients were identified with ID, respectively. The sTfR/log ferritin ratio showed the best positive predictive values (PPV) (62.50 and 64.41%) to indicate functional ID in patients without as well as with acute-phase reaction compared to sTfR (58.14 and 61.67%), ferritin (32.50 and 32.86%) and TSAT (26.74 and 42.86%).

CONCLUSIONS

In clinical practice, the prevalence of ID and the accuracy to detect functional ID are dependent on marker selection and its definition. Regarding the results of this work, for laboratory investigation of ID, however, we suggest using Thomas-plot analyses in combination with ferritin single-marker measurements to efficiently identify patients with ID.