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Also known as
Postage stamp test, Nocturnal penile tumescence (NPT) test, Erection self-test.
Definition
The postage stamp test is a simple method used to evaluate nocturnal erections in the workup of male impotence. A length of connected postage stamps are secured loosely around the male’s flaccid penis just prior to sleeping. If the perforated connections between the individual stamps are torn upon awakening, this is taken as evidence of nocturnal tumescence. However, there is also a chance that the male may shift his position in bed in such a way as to unknowingly tear the perforated connections between the stamps without having achieved a nocturnal erection, thus causing a false positive [1, 2].
Clinical Context
The Nocturnal Penile Tumescence (NPT) test, including the stamp test, is primarily used in the clinical evaluation of erectile dysfunction (ED) to differentiate between physiological (organic) and psychological causes [1, 6]. Men typically experience 3 to 5 full erections during sleep. The presence of normal nocturnal erections, as indicated by a positive NPT test, suggests that the erectile dysfunction is likely due to psychological factors rather than a physical impairment [1]. Conversely, the absence of nocturnal erections may indicate an underlying physiological issue [4].
Patient Selection Criteria: The NPT test is often recommended for men presenting with ED to help determine the etiology. It is a non-invasive, at-home test that can provide valuable diagnostic information [4].
Expected Outcomes: A positive NPT test (indicating nocturnal erections) suggests that the patient’s ED may be psychogenic, guiding treatment towards counseling or psychological interventions. A negative NPT test (indicating absence of nocturnal erections) points towards an organic cause, necessitating further medical investigation and potentially different treatment approaches, such as medication or surgical options [1, 6].