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BIOM3009 – Studies in Clinical Biochemistry
Dr Evans
Clinical Biochemistry in Pregnancy and Neonates
Learning Outcomes
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Describe the common types of clinical biochemistry tests used in pregnancy - with suitable
examples
Describe neonatal screening for genetic and non-genetic conditions - with suitable examples
Explain what is meant by a sequential approach to diagnosis

Terminology of Age
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Embryo – from fertilisation
Foetus – gestation week 11 to birth
Neonate – birth to 4 weeks
Child – 4 weeks to 18 years
Adult – above 18 years
Geriatric – elderly
Trimester = 3 months

The metabolism of drugs is an essential step in both drug activity and clearance
...

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Phase 1 metabolism: simple changes to a molecule
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Process of phase 1 and 2 metabolism is to increase the excretion of foreign compounds like
drugs
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Most of these reactions occur in the liver, with phase 1 reactions using enzymes in the
cytochrome P450 (CYP) family
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Therefore, the rate of metabolism is often dependent on age, with dose adjustments being
necessary to deliver the same therapeutic outcome as metabolic systems develop
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Appropriate reference ranges need to
be used
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o Can't use the same reference ranges
to see what’s normal/abnormal
between neonates and adults
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o Foetus even harder to sample because it’s in the womb
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Neonatal Reference Range
Blood levels of selected analytes in neonatal and adult blood (generalised)

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Kidney function not as developed in neonates as in adults
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Calcium and phosphorus higher in neonates
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Urea cycle occurs in liver
predominantly
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The hCG levels in the body quickly rise
during the first few weeks of pregnancy and decline after this
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Can cause morning sickness
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The hCG blood test can:
o confirm pregnancy - hCG levels increase 7-9 days after conception
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g
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A
laparoscopy may be carried out
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o Tumour marker - Abnormally high levels can be present in GTD - group of rare
tumours that arise form placental cells and develop elsewhere in the reproductive
tract
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o Used to diagnose Gestational diabetes - mother with BMI >30 screened more, South
Asian mothers more susceptible
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Some evidence for pathology from maternal blood, urine, amniotic fluid

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Ultrasounds have superseded some biochemical tests due to being less invasive
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Performing and evaluating
them together, increases the sensitivity and specificity of the screening results
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Reduced levels suggest Edwards
syndrome
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- Blood is tested for Alpha-fetoprotein (AFP), hCG and unconjugated oestriol (uE3)
- Low AFP, high hCG, low uE3 -> Down’s syndrome
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Cell-free foetal DNA analysis (cffDNA) – analyses foetal DNA circulating in mother’s blood
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Prenatal diagnosis:
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Amniocentesis – amniotic fluid analysis

Bilirubin; Haemolytic Disease of the Newborn
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Rhesus disease/Haemolytic disease of the foetus and newborn (HDFN) – production of
maternal antibodies in response to antigens on foetal RBCs
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 Intrauterine transfusions IUT can be used for treatment
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• Hydrops foetalis – large volumes of amniotic fluid; thickened placenta; enlargement
of foetal liver, spleen, heart
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Neonatal Screening
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Physical examination – APGAR
Blood spot sampling (heel prick test); Guthrie test

APGAR
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Invented by Virginia Apgar in 1952
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Repeated if required

BIOM3009 – Studies in Clinical Biochemistry
Dr Evans
●

Score of 7 or above normal
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3 or below critically low
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APGAR Score

Heel prick (Guthrie test)
Newborn heel prick (Guthrie) test  Screens for various, rare conditions – developmental (nongenetic), inherited (genetic)
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Baby's heel pricked with needle; blood spots are placed on a blood spot card for analysis
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o A single gene defect in most cases - monogenetic disorders – rare
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o These amino build up in baby’s blood and urine
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o Treatment: special low protein diet to reduce the build-up of leucine, isoleucine and
valine which can cause metabolic crisis and learning difficulties
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Associated with iodine deficiency
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Causes:
• Anatomical defect
• Failure of thyroid glands to fully develop at birth
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1 in 3000
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Diagnosis - Low levels of T4 and high levels of thyroid-stimulating hormone (TSH),
thyroxine-binding globulin
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Cystic Fibrosis
A hereditary disease that affects the lungs and digestive system
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Autosomal recessive inheritance
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Mutations in chloride channel
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Affects lungs, pancreas, kidneys, liver, intestine
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Mucus on lungs makes sufferers susceptible to infections as well as having difficulty
breathing
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1/2500 births
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IRT is normally found in small levels in the body
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Genetic analysis of CTFR mutation:
o 29mM, CF unlikely
o 30-59 mM, CF possible
o ≥ 60 mM, CF likely
Sweat test – high chloride concentration in sweat
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o Odourless chemical pilocarpine and electrical stimulation encourages sweat glands
to produce sweat  collected on filter paper  chloride analysis
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PKU is caused by a
defect in the gene that helps create the enzyme needed to break down phenylalanine
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Deficiency in phenylalanine hydroxylase
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Causes progressive mental retardation
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Treatment – diet lacking Phe
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