Combined use of zinc protoporphyrin (ZPP), mean corpuscular volume and haemoglobin measurements for classifying microcytic RBC disorders in children and young adults

Summary The diagnostic potential of the combined use of zinc-protoporphyrin (ZPP), mean corpuscular volume (MCV) and haemoglobin measurements for discriminating between iron deficiency anaemia, beta-thalassaemia minor and lead poisoning has been studied. Lead poisoning could be identified by ZPP > 50 μg/dl in the presence of normal MCV or ZPP > 150 μg/dl in the presence of microcytosis (MCV < 80 fl) with a sensitivity of 97% and specificity 94%. Beta-thalassaemia minor was identified by the coexistence of microcytosis and ZPP <50 μg/dl with a sensitivity of 91% and specificity 79%. Iron deficiency anaemia defined by the combination of microcytosis and ZPP ranging from 50 to 150 μg/dl was identified with a sensitivity of 95%, but the specificity was only 51%, with many of the patients overlapping with thalassaemia minor. This problem did not exist in iron-deficiency anaemia with haemoglobin < 10 g/dl as at that range no patients with uncomplicated thalassaemia minor have been encountered. A great advantage of the combined use of ZPP, MCV and haemoglobin for the initial screening of microcytic anaemia is its ease of performance and low cost. However, this information should only be regarded as presumptive evidence of disease, requiring subsequent confirmation by appropriate direct measurements such as transferrin saturation, serum ferritin, haemoglobin electrophoresis, or blood lead determinations.