The study will explore the performance of the CDMS (Cryo Detector Mass Spectrometer) method in measuring SF (serum ferritin) in human serum of healthy individuals. This will be the first experience of testing SF with this method using biologic material of human origin.

A clear interpretation of hyperferritinemia is difficult in many clinical situations. Crucial for the correct treatment of patients is the differentiation between reactively elevated ferritin and effective iron overload.The measurement methods that are routinely used provide quantitative results of the measurement of total ferritin molecules independent of their actual iron content.With a modified mass spectrometric method (CDMS), this should be possible.

In this study the investigators would like to apply this measurement technique for the first time with human serum as the investigators would like to test healthy blood donors with known normal, low or elevated ferritin levels.

Inclusion Criteria:

• age 18-75 years
• SF (serum ferritin) values known from a previous determination that must not be older than twelve months and not followed by a blood donation
• fulfillment of the eligibility criteria for blood donation
• negative serology for HBV (hepatitis B virus), HCV (hepatitis C virus), HIV (human immunodeficiency virus) as assessed in the context of a blood donation

Exclusion Criteria:

• acute illness
• chronic inflammatory disease

Since pregnancy is a contraindication for blood donation, no pregnant women will be included in the study.

The study cohort will include 20-25 experienced blood donors (not first-time donors) distributed among three groups according to SF values obtained from at least two previous measurements:

• low SF levels: < 20 ng/ml
• normal SF levels: 50-200 ng/ml (women) or 50-300 ng/ml (men)
• high SF levels: > 200 ng/ml (women) or > 300 ng/ml (men)