Background: for the diagnostic evaluation of microcytic or normocytic anaemia in a heterogeneous group of patients, the value of newer parameters, such as zinc protoporphyrin (ZPP), plasma transferrin receptor (PtrfR) and PtrfR/ferritin ratio is not clear. We have performed a prospective study to determine the predictive value of these parameters and ferritin, for diagnosing iron deficiency anaemia (IDA).
Methods: sixty-two patients with Hb<8.2 (men) or <7.0 (women) and mean cell volume (MCV)<96 fl were included. Exclusion criteria were: known haematological disease, pregnancy, bone marrow suppression or iron therapy within the previous 7 days. Bone marrow examination was used as a golden standard to discriminate between IDA and non-IDA.
Results: twenty-four patients had depleted iron stores. We found that the reticulocyte response on iron supplementation correlated well with the iron-status of the bone marrow. Univariate analysis showed that ferritin, PtrfR/ferritin ratio, ZPP and PtrfR have significant predictive values for differentiating IDA from non-IDA. Interestingly, multivariate analysis revealed that ferritin was the only significant, independent predictor of IDA, with a cut-off point of 32 microg/l (sensitivity 79.2%, specificity 96.9%).
Conclusions: the low sensitivity and specificity of ZPP, PtrfR and PtrfR/ferritin ratio render them insufficient to be used as a single 'best' test for the identification IDA in a non-selected group of anaemic patients and do not even add to the prediction if the value of ferritin is known.