Non-Invasive Zinc Protoporphyrin Screening Offers Opportunities for Secondary Prevention of Iron Deficiency in Blood Donors

Abstract

Background: Frequent blood donors are at high risk of developing iron deficiency. Currently, there is no potent screening during blood donation to detect iron deficient erythropoiesis (IDE) before anemia develops and deferral from donation is inevitable.

Study design and methods: In addition to capillary and venous hemoglobin, the iron status of 99 frequent blood donors was assessed by various venous blood parameters and zinc protoporphyrin IX (ZnPP). ZnPP was determined by high-performance liquid chromatography (HPLC) and a new prototype fiber-optic device was employed for non-invasive measurements of ZnPP through the blood collection tubing (NI-tubing) and on lip tissue (NI-lip). We aimed to evaluate the feasibility and diagnostic value of the NI-tubing measurement for early detection of severe iron deficiency in blood donors.

Results: NI-tubing and HPLC reference measurements of ZnPP showed narrow limits of agreement of 12.2 μmol ZnPP/mol heme and very high correlation (Spearman's Rho = 0.938). Using a cutoff of 65 μmol ZnPP/mol heme, NI-tubing measurements (n = 93) identified 100% of donors with iron deficiency anemia (IDA) and an additional 38% of donors with IDE. Accordingly, NI-tubing measurements would allow detection and selective protection of particularly vulnerable donors.

Conclusion: NI-tubing measurements are an accurate and simple method to implement ZnPP determination into the routine blood donation process. ZnPP was able to identify the majority of subjects with IDE and IDA and might therefore be a valuable tool to provide qualified information to donors about dietary measures and adjustments of the donation interval and thereby help to prevent IDA and hemoglobin deferral in the future.

Keywords: Anemia; Blood donation; Erythropoiesis; Iron deficiency; Zinc protoporphyrin.

Fig. 1

Applicator for measurement of ZnPP fluorescence through the blood collection tubing. The inserted picture shows how the tubing is clicked into a groove in one part of the applicator, where the measurement fiber then is in contact with the tubing. The two halves of the applicator are fixed to each other by small magnets and shield the tubing from ambient light during measurement.

Fig. 2

Flowchart of study. From 100 recruited subjects, 1 dropped out prior to venous blood collection voluntarily. Venous blood parameters as well as capillary Hb and ZnPP measurements on the lip and by HPLC were determined from the remaining 99 subjects. 6 of the remaining 99 subjects were deferred from blood donation due to low capillary Hb and no NI-tubing measurement of ZnPP could be performed. The right side of the chart shows the assignment of the subjects to the applied iron deficiency stages.

Fig. 3

Comparison of ZnPP measured in venous blood samples by high-performance liquid chromatography (HPLC measurement) and non-invasively through the blood collection tubing during blood donation (NI-tubing measurement). a Correlation between the two measurements. The red diagonal line represents the balance line. b Bland-Altman plot. The blue horizontal lines indicate the robust limits of agreement of 12.2 μmol ZnPP/mol heme.

Fig. 4

Bar charts showing the assignment of potential donors to the applied iron deficiency stages. a Number of subjects accepted for donation (blue) and number of deferred subjects due to low capillary Hb (red) in each group. b Number of accepted donors (without deferred subjects) with NI-tubing measurement of ZnPP below (blue) and above (orange) the cutoff value of 65 μmol ZnPP/mol heme. c Number of accepted donors (without deferred subjects) with NI-tubing measurement of ZnPP below (blue) and above (green) the cutoff value of 40 μmol ZnPP/mol heme.