Nighttime penile tape test

Alternative names
Nocturnal penile tumescence (NPT) stamp test; Erection self-test

This is a test that determines the ability or inability to achieve an erection while you sleep.

How the test is performed

A strip of four to six postage stamps (any kind) is used for each test. The test needs to be done for three nights. The man needs to wear brief-type undershorts that have a fly. The penis is brought through the fly leaving most of the pubic hair against the body.

The strip of stamps is wrapped snugly around the shaft of the penis. The stamps need to overlap so the overlapped stamp can be moistened to seal the ring. When the stamp has dried, the penis is carefully replaced inside the shorts. The shorts are worn to sleep in. (They help protect the stamps from falling off).

In the morning, check to see if the stamp ring has been broken along the perforations. If the tearing of the stamps awakens the man during the night, check for an erection and how rigid the erection is.

How to prepare for the test
The stamps need to be obtained. Do not drink alcohol or take a sleep-inducing or sedative medication for at least 2 days before the test is done. Never discontinue any medications without first discussing it with your doctor.

How the test will feel
The stamps may be felt as an unusual sensation. The test should be repeated until three nights of comfortable, uninterrupted sleep is achieved.

Why the test is performed
The test is done to confirm if the man is unable to achieve an erection at night. All men with normal physiological erectile function will achieve an erection during normal sleep. The test may be helpful in determining if the cause of erectile dysfunction is psychologic or physical.

Normal Values
During at least one of the nights, the ring of stamps is broken between any two stamps.

What abnormal results mean
If the stamps are broken it may suggest that the erection problem is the result of psychological causes. If the stamps are not broken on any of the 3 nights it may indicate that the erection problem is related to physical conditions or medications (see impotence, sexual dysfunction). The health care provider should be consulted.

What the risks are
There are no risks.

Special considerations
The test is not foolproof. This test does not indicate many important factors of sexual dysfunction, such as quality, duration, or number of erections during the night. Sexual counseling may be recommended after consulting the health care provider.

Johns Hopkins patient information

Last revised: December 5, 2012
by Potos A. Aagen, M.D.

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