Objective To evaluate reticulocyte haemoglobin content (CHr), compared with ferritin, transferrin saturation (TS) and mean corpuscular volume (MCV), as a marker of iron deficiency (ID).

Design Retrospective analysis of clinically indicated blood samples taken between February 2010 and October 2012.

Setting Single-centre neonatal care unit.

Patients 210 very preterm (gestational age <32 weeks) or very low birthweight infants (birth weight <1500 g) at 3–4 months corrected age.

Main outcome measures Complete blood count, CHr, ferritin and TS determined as part of a standard follow-up examination. To detect the optimal CHr cut-off, ID was defined by the presence of more than two of the following three criteria: MCV <75 fL, TS <10%, ferritin <30 µg/L.

Results 210 preterm infants were included at a corrected age of (median (IQR)) 3.5 (3.0–4.0) months and with a CHr of 29.7 (28.6–30.7) pg. There were correlations between CHr and MCV (r=0.54, p <0.0001) and between CHr and TS (r=0.44, p <0.0001). There were 27 (13.4%) iron-deficient infants, and two infants (1%) fulfilled criteria of ID-anaemia. CHr was lower in infants with ID (26.4 (23.8–28.7) pg) than in those without (29.9 (29.0–30.8) pg, p <0.0001). The optimal CHr cut-off for detecting ID was 29 pg (sensitivity 85%, specificity 73%). Areas under the receiver operating characteristic curve for detection of ID tended to be higher for CHr compared with ferritin (0.92 vs 0.75), TS (0.90 vs 0.82) and MCV (0.81 vs 0.72).

Conclusions CHr seems to be a suitable marker for latent ID in preterm infants at 3–4 months corrected age and may be superior to ferritin, TS and MCV.