Epidemiology and research

Question 1

Define the term ‘sensitivity’

Answer 1

The true positive rate, or the proportion of people with disease who will test positive.

Question 2

How do you calculate ‘sensitivity’?

Answer 2

Sensitivity = true positive rate / disease present population  OR A / (A + C).
A = true positives.
C = false negatives

Question 3

Define the term ‘specificity’

Answer 3

The true negative rate, or the proportion of people without disease who will test negative.

Question 4

How do you calculate ‘specificity’?

Answer 4

Specificity = true negative rate / disease absent population OR D / (B + D).
B = false positives.
D = true negatives.

Question 5

What is positive predictive value?

Answer 5

The proportion of positive results in a test that are true positive results.

Question 6

How do you calculate positive predictive value?

Answer 6

PPV = A / (A+B).
A = true positives
B = false positives

Question 7

What is negative predictive value?

Answer 7

The proportion of negative results in a test that are true negative results.

Question 8

Is positive and negative predictive values dependent on disease prevalence?

Answer 8

Yes.

Question 9

How do you calculate negative predictive value?

Answer 9

NPV = D / (C + D).
D = true negatives.
C = false negatives.

Question 10

Define the term ‘live birth’

Answer 10

Complete expulsion or extraction from its mother of a product of conception (irrespective of gestation) which after such separation, breathes or shows any other evidence of life, such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles, whether or not the umbilical cord has been cut or the placenta is attached

Question 11

Define the term ‘stillbirth’

Answer 11

The birth of an infant of at least 20 weeks’ gestation, or if the gestation is unknown, weighing at least 400g at birth, who shows no signs of life after birth.

Question 12

Define the term ‘miscarriage’

Answer 12

Expulsion of products of conception prior to 20 weeks gestation.

Question 13

Define the term ‘preterm birth’

Answer 13

Birth prior to 37 weeks gestation.

Question 14

Define the term ‘neonatal mortality’

Answer 14

Death of a live-born child within 28 days after the birth (regardless of gestational age or birthweight).

Question 15

Define the term ‘perinatal mortality’

Answer 15

Deaths that include stillbirths and neonatal deaths.

Question 16

Define the term ‘infant mortality’

Answer 16

Death of infant before 1 year of life.

Question 17

Define the term ‘maternal morbidity’

Answer 17

All maternal Intensive Care Unit (ICU) admissions during pregnancy and up to 42 days after birth.

Question 18

Define the terms ‘maternal mortality’ and ‘direct’, ‘indirect’ and ‘incidental’ causes of

Answer 18

Maternal mortality: maternal deaths that occur during pregnancy or childbirth and up to one year post pregnancy.
○ Direct: relating to the pregnancy or birth
○ Indirect: relating to a pre-existing medical condition or newly diagnosed condition.
○ Incidental: unrelated to the pregnancy or birth

Question 19

Define the term ‘low birth weight’

Answer 19

Weighing <2500g at birth