The kinetics of haemoglobin and ferritin in longitudinal community patients with iron deficiency or hypoxia

Red cell distribution width (RDW) is well recognised as a marker of iron-deficient anaemia, as well as useful to the distinction between some anaemic states. A role in the prediction of patient mortality and for the laboratory diagnosis of organ dysfunction has been also investigated. RDW has recently been suggested as a marker of acute and chronic hypoxia. In this paper we use RDW kinetics to identify different patient groups and then investigate the relationship between RDW, ferritin and haemoglobin kinetics in a large cross-sectional community patient dataset. A novel mathematical model of this relationship is developed that captures all aspects of variation in the data. A linear regression of RDW/log(ferritin) on days is combined with a multi-level random structure including random intercepts and slopes for each patient. No evidence of an age affect was found in the data. On the other hand, significant patterns in the rises and falls of log(ferritin) and haemoglobin with RDW over time are identified.