Devices for pregnancy

Question 1

What do pregnancy tests measure?

Answer 1

Human chorionic gonadotropin hCG

Question 2

What is hCG?

Answer 2

Glycoprotein produced by the trophoblastic cells of the placenta after the ovum has been fertilized and implanted in the uterus

Question 3

How do the pregnancy tests chemical reaction work?

Answer 3

• hCG comes in contact with monoclonal hCG antibodies that are labeled with detection molecules
• (colloidal gold, latex beads)
• hCG-antibody complex migrates by capillary force onto specific analyte capture zones, forming a visible line

Question 4

When do hCG levels become detectable?
What rate do the levels go up by?
What days do they peak?
When do they return to baseline?

Answer 4

When do hCG levels become detectable?
- 10-12 days after fertilization

What rate do the levels go up by?
- doubles every 2-3 days

What days do they peak?
- Day 60-70

When do they return to baseline?
- 10 days after birth

Question 5

Where do the excess buffer along with reagents that are not captured at test control line move onto?

Answer 5

The absorbent wicking pad

Question 6

What is the lateral flow technology membrane made of?

Answer 6

Nitrocellulose membrane

Question 7

What is the sensitivity of a pregnancy test dependant on? (2)

Answer 7

Timing of test
Detection level of the test

Question 8

What is the detection level for most pregnancy tests?

Answer 8

25-50 IU/L

Question 9

As you get closer to menses, does accuracy of pregnancy test increase or decrease? How many days before the expected period can you test?

Answer 9

increase
- 0-4 days before

Question 10

What are causes of false positive during pregnancy tests? (5)

Answer 10

• Fertility drugs
• Ectopic production
• Conducting the test after missed or incomplete abortion
• Early pregnancy loss (miscarriage)
• low levels of hCG produced by pituitary during LH surge in menopausal women

Question 11

What are causes of false negatives during pregnancy tests? (2)

Answer 11

• Testing too early after conception
• Human error

Question 12

What are important counselling points for instructions of use? How are results read?

Answer 12

Pee for 5 seconds
place pointing down for 20 seconds, lay flat
will see results in 3 min

Not pregnant, Pregnant 1-2 weeks etc.

Question 13

What do ovulation tests measure? How long does ovulation last

Answer 13

LH surge
- occurs 24-36 hours before ovulation
- have 2 days to maximize chances

Question 14

How is clearblue advanced ovulation test different than the regular one?

Answer 14

Measures estrogen rise as well
- increases 1-5 days prior to ovulation

Question 15

How do urine drug screening tests work? I.e What happens when presence of drug

Answer 15

• Lateral flow technology
• COMPETITIVE binding
• Presence of drug leads to missing band

Question 16

Do you have to confirm drug tests? Using what?

Answer 16

Yes,
- using gas chromotraphy/mass spectrometry

Question 17

How does the drug test competitive format work?

Answer 17

The drug of interest competes with the binding of the detection molecules to the capture molecules
- Detection molecules: antibodies conjugated with latex or gold particles

Since detection molecules cannot bind to capture molecules (since it is on the drug), no line is produced

Question 18

What do the positive, negative, invalid results show?

Answer 18

Positive: 1 line on CONTROL (C)
Negative: 2 lines
Invalid: 1 line on Test line

Question 19

What are reasons for false positives? (1)

Answer 19

Possible cross-reactivity with other drugs or foods
- doxylamine causes false positive

Question 20

What are reason for false negatives (6)

Answer 20

• Urine sample collected before drug was present in urine
• urine sample after the drug is no longer in urine
• drug used is not one detected by device
• Adulteration of urine sample with bleach
• Sample was diluted with other liquids below level of detection
• Drinking large amounts of water

Question 21

What do the adulterants test for? (4)

Answer 21

1. Tests for presence of oxidants
   - bleach or peroxide
2. Specific gravity. 1.003-1.030
   - ensure sample is not diluted
3. pH normal 4-9
   - for acidic or alkaline adulterants
4. Temperature strip
   - ensure sample is fresh

Question 22

Which vaginal infections can you self-treat? Which can you not?

Answer 22

Self-treat
- yeast

Rx
- bacterial vaginosis
- trichomonal infections

Question 23

What are symptoms of vaginal infections for when to use the test? (3)

Answer 23

• itching or burning
• excessive discharge
• abnormal discharge colour or odour

Question 24

What do vaginal tests measure?

Answer 24

pH

Question 25

What are normal pH vs elevated vaginal pH?

Answer 25

Normal: 3.8-4.5
High: over 4.5

Question 26

Why is vaginal pH measured? What is it used for?

Answer 26

Used for differential diagnosis
- over 4.5 means it is likely a bacterial infection needing referral

• if test is normal (negative result) consider OTC antifungals

Question 27

When can the vaginal test NOT be used

Answer 27

 Not if +/- 1 day of period
 Not if signs of menstruation or signs of any vaginal bleeding
 Not if less than 12 hours after sexual intercourse or vaginal douching
 Not for STI (HIV, chlamydia, herpes, gonorrhea, syphilis)
 Not until 72 hours after the application of vaginal preparations (like contraceptive creams or lubricants)

Question 28

What are important instructions for the test?

Answer 28

Insert yellow tip into vagina until your fingers reach the outer skin & ROTATE
- 5cm in
Wait 10 seconds for tip colour changes

Question 29

How to interpret results for vaginal testing?

Answer 29

Positive: tip turns blue/green
- pH high
- could be bacterial

Negative: tip stays yellow
- low risk of infection
- can use OTC products