Indirect maternal biomarkers

Carbohydrate-deficient transferrin (CDT) is synthesized and secreted in the liver and it acts as a carrier for iron in the blood (Joya et al., 2012). It is elevated 1-3 weeks after heavy alcohol consumption and maesurements of CDT are made from serum samples. CDT is a group of minor isoforms of human transferrin with a lower degree of glycosylation than major

isoforms of this glycoprotein (Allen & Litten, 2003). The mean half-time of CDT is approximately 14-17 days (Maenhout, Baten, De Buyzere, &

Delanghe, 2012).

The most common CDT measurement technique is microcolumn anion-exchange chromatography followed by immunoassay for transferrin quantification. Additionally, high-performance liquid chromatography, capillary electrophoresis and isoelectric focusing methods are used to analyse CDT (Helander, Vabo, Levin, & Borg, 1998). The hormonal status of women influenced CDT levels: CDT was 9.9% higher in pregnant women and 7.5% lower among those who used oral contraceptives wheareas postmenopausal women had 10.3% lower levels of CDT. Women using oral contraceptives and hormone intrauterine device for contraception had lower CDT (Sillanaukee et al., 2000b).

There are some studies analysing CDT and alcohol use during pregnancy (Azurmendi-Funes et al., 2019; Bakhireva, Ludmila N. et al., 2012; Bianchi, Ivaldi, Raspagni, Arfini, & Vidali, 2011; Comasco, Hallberg, Helander, Oreland, & Sundelin-Wahlsten, 2012; Howlett, Abernethy, Brown, Rankin, & Gray, 2017; Kenan, Larsson, Axelsson, & Helander, 2011;

Magnusson, Göransson, & Heilig, 2005; Niemela et al., 2016; Sarkola, Eriksson, Niemela, Sillanaukee, & Halmesmaki, 2000). The clinical utility of CDT in alcohol use identification, especially in pregnancy, seems to be substantial. Niemelä et al. (Niemela et al., 2016) showed 39.5% sensitivity

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for FAS outcome and 54% sensitivity for the combination of GGT-CDT for FAS outcome with a %CDT cut-off 1.7%. Sarkola and collegues found low sensitivity and specificity for CDT during pregnancy (Sarkola et al., 2000).

However, based on interpretation of the previous studies, it seems that accuracy to detect alcohol use increases when analysing CDT together with other biomarkers and questionnaires (Azurmendi-Funes et al., 2019;

Howlett et al., 2017).

2.6.3.1.2 Gamma-glutamyl transferase, alanine aminotransferase and aspartate aminotransferase

Liver enzymes, including gamma-glutamyl transferase (GGT), alanine

aminotransferase (ALT) and aspartate aminotransferase (AST), are elevated 1-3 weeks after the last exposure (Bakhireva, L. N. & Savage, 2011). ALT is aggregated primarily in the cytosol of hepatocytes and consists of 496 amino acids and has a half-life of approximately 47 hours. ALT is normally detectable in serum at low concentrations (typically <30 IU/L). However, any process that leads to loss of hepatocyte membrane integrity or necrosis results in the release of ALT in high concentrations into the plasma (Moriles & Azer, 2021). These markers can measure recent

changes in alcohol consumption from blood, but they are not increased by binge drinking. Only 30-50% of excessive drinkers in the general

community have elevated levels of GTT (Poikolainen & Vartiainen, 1997;

Sillanaukee, P. et al., 2000a). Liver enzymes are elevated by other forms of liver damage (Bakhireva & Savage, 2011). A systematic review of Howlett et al. (2017) and the review of Cook (2003) concluded that none of the blood biomarkers GGT, ALT and AST had both high specificity and sensitivity.

2.6.3.1.3 Mean corpuscular volume

Mean corpuscular volume (MCV) is an index of red blood cell size. Alcohol and its metabolites have toxic effects on the production of hematologic precursor cells and on red cell morphology. MCV is naturally elevated in mid-to late stage pregnancy. Macrocytosis, enlarged erythrocytes, is a common finding in chronic alcoholics.

The sensitivity and specificity of MCV are low as a marker for recent excessive alcohol intake during the pregnancy, but its sensitivity and specificity are superior to CDT (Sarkola et al., 2000).Sillanaukee et al.

(Sillanaukee, P., Aalto, & Seppä, 1998) found that in detecting excessive drinking in the early phase, MCV in women was more sensitive (40%) than CDT (29%) or GGT (34%) in a primary care sample. However, the best sensitivity was reached in using combination of three biomarkers (MCV, CDT and GGT). Other reports support the poor usefulness of MCV in women to detect heavy drinking, even though it seems to be a slighltly better indicator of alcohol use among women than among men (Allen, Litten, Fertig, & Sillanaukee, 2000; Mundle, Munkes, Ackermann, & Mann, 2000; Sillanaukee et al., 1998; Wetterling, Kanitz, Rumpf, Hapke, & Fischer, 1998). While elevated MCV is found after sustained and regular excessive drinking, the clinical utility of MCV in alcohol use identification, especially in pregnancy, is limited (Allen et al., 2000; Bearer, 2001; Mundle et al., 2000;

Sillanaukee et al., 1998; Wetterling et al., 1998).

2.6.3.1.4 Acetaldehyde protein adducts

Acetaldehyde is the main product of oxidation in ethanol metabolism.

Acetaldehyde is rapidly converted to acetate by acetaldehyde

dehydrogenase. Due to its high reactivity, it is not suitable as an alcohol biomarker (Cederbaum, 2012). Acetaldehyde forms both stable and unstable adducts with various proteins (Conduah Birt, Shuker, & Farmer, 1998). Stable acetaldehyde-protein adducts (APAs) have been proposed as a biomarker of alcohol use, because they have a longer half-life than free acetaldehyde and remain measurable in blood for approximately a month after alcohol intake (Conduah Birt et al., 1998; Howlett et al., 2017;

Magnusson et al., 2005). So far, the use of APAs as a biomarker of alcohol use remains unclear. Future studies to determine whether APAs are uselful tools to detect alcohol consumption are warranted.

2.6.3.1.5 Phosphatidylethanol

Phosphatidylethanol (PEth) is a group of compunds derived from

phospholipids, formed in the presence of ethanol. PEth can be detected

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3 weeks after ethanol ingestion with a mean half-time of approximately 3 days. LC-MS/MS method for maternal and neonatal blood samples are used to analyse PEth. It is considered a sensitive indicator of heavy alcohol use (area under the receiver operating characteristic (AUROC) 0.69 for abstainers versus any alcohol consumption during pregnancy, sensitivity 40.7%, specificity 95.4%; AUROC 0.99 differentiating heavy drinkers from light, moderate and non-drinkers) (Kwak et al., 2014; Yang, J. et al., 2015).

However, low-to-moderate drinkers are not detected, and PEth has been found to be unstable for storage (Faller et al., 2013; Gnann, Weinmann, & Thierauf, 2012; Howlett et al., 2017; Schröck, Thierauf-Emberger, Schürch, & Weinmann, 2017).

2.6.3.1.6 First trimester trisomy screening paramaters:

pregnancyassociated plasma protein A, free β-human chorionic gonadotropin and nuchal translucency thickness

Pregnancy-associated plasma protein A (PAPP-A) and free β-human chorionic gonadotropin (free β-hCG) are influenced by maternal and pregnancy variables such as smoking, gestational age and ethnic background (Kagan, Wright, Spencer, Molina, & Nicolaides, 2008).

Additionally, PAPP-A is influenced by maternal weight, height, diabetes mellitus, method of conception, previous pregnancy with or without pre-eclampsia and birth weight Z-score of the neonate in the previous pregnancy (Wright, Silva, Papadopoulos, Wright, & Nicolaides, 2015).

Previous experiments with human placental cell lines and extraction analyses using human placental samples demonstrated that ethanol exposure increased hCG production in a dose-dependent matter (Joya et al., 2015). Little is known about the effects of alcohol use on these first trimester screening parameters.