Chempath 5: Metabolic disorders and screening 1

Question 1

List the 9 diseases that are tested for in newborns with the Guthrie heel prick test ?

Answer 1

Congenital hypothyroidism
Sickle cell disease
Cystic fibrosis 
Maple syrup urine disease (MSUD)
Phenylketonuria (PKU)
Homocystinuria (HCU)
Medium chain acyl-CoA dehydrogenase disease (MCADD)
Isovalaeric acidaemia (IVA)
Glutaric aciduria type 1  (GA1)

Question 2

How is MCADD managed ?

Answer 2

with MCAD enzyme deficient you can’t break down fats into ketones for metabolism meaning you rely solely on glucose.

• Never let the child become hypoglycaemic or they die.
• NG tube feeds at night

Question 3

Define specificity ?

Answer 3

The probability that someone without the disease will also test negative.

TN/(FP+TN)

Question 4

Define sensitivity ?

Answer 4

The probability that someone with the disease will correctly test positive

TP/(TP+FN)

Question 5

Define positive predictive value ?

Answer 5

The probability that someone who tests positive actually has the disease.

TP/(TP+FP)

Question 6

Define negative predictive value ?

Answer 6

The probability that someone who tests negative actually does not have the disease.

TN/(TN+FN)