The laboratory assessment of haemoglobin, Ret-He, plasma ferritin, serum vitamin B12 and folate deficiency in anaemic and non-anaemic women during pregnancy: Can laboratory screening predict outcomes?

Abstract

Anaemia in pregnancy is a worldwide health issue affecting both developing and developed countries, with epidemiological studies showing a variation in prevalence of between 25% to 92%, often attributed with socioeconomic background (Bencaiova, et al., 2012). Recently it has been reported that there is a high incidence of iron deficiency in both anaemic and non-anaemic women during pregnancy (Mahdy, et al., 2017). A high frequency of iron deficiency in pregnancy has also been reported in the UK (Daru, et al., 2016). Iron deficiency is thought to be the main contributor of anaemia during pregnancy, although haemodilution due to plasma expansion exacerbates this in the latter stages of gestation. The majority of studies have centred on providing trials of iron to assess improvement in haemoglobin levels. It is not disputed that iron supplementation in pregnancy can improve anaemia. However, despite this there have been no significant improvements in outcomes such as pre-term delivery and low birth weight with the literature being contradictory (Bencaiova, et al., 2012, Nair, et al., 2017, Haider, et al., 2013, Dewey & Oaks 2017). Routine screening using assessment of haematinic parameters is not recommended as it is considered that a trial of iron with improved haemoglobin will inform the diagnosis (Pavord, et al., 2012). There are few studies reporting the effect of iron deficiency in the absence of anaemia. Reticulocyte haemoglobin equivalent (Ret-He) is a newer extended red cell parameter available on some automated full blood count (FBC) analysers. This measurement assesses the haemoglobin concentration of reticulocytes thereby providing an estimation of the supply of iron for erythropoiesis. This could be a useful measurement during pregnancy not only to identify possible iron deficiency but also to monitor response to iron supplementation (Schoorl, et al., 2012). Although studied and used in assessment of other conditions, such as chronic kidney disease, only one study, at the end of pregnancy, could be found demonstrating its potential usefulness (Schoorl, et al., 2012). Similarly there is conflicting evidence around other haematinic parameters such as Vitamin B12 (VB12) and folate. Again it is well known that folate supplementation is important before and during pregnancy in reducing fetal abnormalities, although there is little in the literature regarding birth outcomes. Very few studies have considered mixed haematinic deficiency or the effect of infection and inflammation on ferritin, the traditional marker of iron stores, which rises in response to an inflammatory response. This may have led to misclassification of the anaemia. These gaps in knowledge have been acknowledged in a number of recent reviews (Pavord, et al., 2012, Rukuni, et al., 2015, Moin & Lassi, 2015, Daru, et al., 2017, O’Brien & Ru, 2017, Roy & Pavord, 2018). Aims and purpose of the research Full blood counts are routinely used in the assessment of anaemia during pregnancy at several stages. However, given the limited data, there is little in relation to laboratory assessment of haematinic parameters in relation to pregnancy outcomes, the aims and purpose of this study are to: 1. Assess haemoglobin (Hb), reticulocytes, including the extended red cell parameter Ret-He, plasma ferritin, C-reactive protein (CRP), serum VB12 and serum folate during early pregnancy (8 to 14 weeks); then iron stores and Ret-He again at 28 weeks. With the aim of predicting haematinic and Hb levels at delivery including potential outcomes i.e. transfusion requirements, low birth weight or pre-term delivery. 2. Assess iron stores, using ferritin, during early pregnancy and at 28 weeks for subjects with iron deficiency in the absence of anaemia to evaluate prevalence and outcomes. 3. Compare socio-economic variance of haematinic deficiency during pregnancy. 4. Suggest an optimum testing pathway/protocol for screening of haematinic deficiency in early pregnancy. Expected value and impact Literature suggests that low iron stores, VB12 and folate can have significant impact on the morbidity of patients both during, at delivery and post-partum from premature birth, low birth weights, increased risk of post-partum haemorrhage or significant blood loss as well as other physiological and psychological effects. However, despite being well researched there are still significant gaps in the literature and outcomes generally have not improved. There are few studies using the assessment of laboratory parameters to screen for haematinic deficiencies, with the majority of studies focusing on assessment of trials of iron to improve anaemia status. Additionally haematinic deficiency (iron, VB12 and/or folate) in the absence of anaemia is an under researched area. Equally only one study can be found in respect of Ret-He in pregnancy. This haematologic parameter may be more informative than Hb levels alone in assessing early onset anaemia as well as responses to iron supplementation. The potential to assess haematinic levels earlier in pregnancy may inform optimum intervention preventing some of these patients becoming severely anaemic. The significance and prevalence of iron deficiency in the absence of anaemia is unknown and will be of significant interest in the study. The potential impact would be more appropriate prescribing of iron therapy, less wastage, reduced transfusion requirements by optimising Hb levels before delivery, potentially less premature births and improved physiological and psychological effects.