Pregnancy test false positives and false negatives

Whether the pregnancy is planned or not, or whether the test is marked by feelings of hope or fear, an accurate response is crucial. So do drugstore pregnancy tests ever get it wrong?

The answer is yes. Results reporting a condition that is not actually present are called false positives. When a negative test result fails to detect pregnancy, this is called a false negative (it’s the opposite).

A false positive pregnancy test, which incorrectly indicates a pregnancy that is not there, is more frequent and likely to occur than a false negative (the inverse).

Drugstore pregnancy tests detect hormone levels, in particular human chorionic gonadotropin (HCG) in women. A positive test indicates a physiological change in hormones and therefore it’s strongly recommended to consult a doctor after a positive pregnancy test result, even if you believe that you are not pregnant.

Among the causes, a false positive test may be explained by the following:

• Hormonal imbalance
• Kidney or bladder disease
• An ovarian cyst
• A miscarriage
• Recent fertility treatment
• A molar pregnancy or extra-uterine pregnancy
• Test malfunction (98% rate of reliability)

Frequently, a false negative test fails to indicate pregnancy despite the presence of one.

False negative results are often due to a handling error, and it is suggested to re-test with another one if in doubt. It is important to follow the instructions as indicated on the box, and to check the expiration date.

Another frequent cause of a false negative is when the test is done too early. The average pregnancy test requires a delay of approximately 12 days in order to test properly.

Other possible causes of a false negative result:

• Testing at a different time of day other than first thing in the morning
• Excessive water consumption during the day
• Kidney or bladder disease
• Test malfunction (98% rate of reliability)

In all cases, it is recommended to consult a doctor, gynecologist or pharmacist. In the instance of a false positive, you need to rule out any of the possible complications indicated above.