Background and aims Iron deficiency anaemia (IDA) and thalassemia are the most common microcytic anaemia in children. Sometimes, expensive or invasive investigations are necessary for their distinction. A number of haematological indices are useful, but some of them assume difficult calculation. In practice, most paediatricians use Mentzer index, maybe out of convenience. The aim of the study is to demonstrate the specificity and sensitivity of the haematological indices.

Methods Retrospective study conducted on a total of 144 patients with IDA diagnosis at hospital discharge. Criteria for study group selection were: age bigger than 1 month, haemoglobin below the minimum age reference, serum iron determination, negative history of other hematologic disorders or chronic diseases. Depends on IDA/thalassemia severity, the aforesaid indices accuracy is the following: Shine and Lal (S and L) > Green and King (G and K) > England and Fraser (E and F) > Red Blood Count (RBC), Red Distribution Width Indice (RDWI) > Mentzer (MI) > Srivastava (S) > Ricerca (R) > RDW-CV (RDW), for mild and moderate forms and S and L > G and K > E and F, RDWI > RBC > R > MI > S > RDW, for severe forms.

Results 106 patients had low levels of serum iron; 121 had mild, 13 moderate and 10 severe anaemia. There were not any statistical difference among the anaemia severity forms. The highest sensitivity presented E and F (99,1%), followed by RBC (95,3%), S (94,3%), RDWI (86,8%) and G and K (85,8%), and the highest specificity presented R (92,1%), followed far away by S and L (57,9%). MI had a (predictive) positive value at 88 from 106 low level iron patients but a negative value at only 3 from 38 normal level iron patients (p 0,12). The IDA diagnosis supposed a different number of positive indices (2 to 8), almost always others.

Conclusions The haematological indices are useful in differentiating microcytic anaemia, but the selection of one of the best is difficult. The choice requires haematological assessment.