Variable response to intracavernous prostaglandin E1 testing for erectile dysfunction

Anxiety and apprehension may negatively influence the erectile response to the first intracavernous injection with vasoactive agents. This may result in too many false-positive diagnoses of vascular insufficiency if the first injection ever made in a patient is used for color Doppler duplex sonography (CDS) evaluation.

One hundred sixty-eight consecutive patients (aged 18 to 75 years) with erectile dysfunction underwent a standardized evaluation, including the intracavernous injection test (ICIT) stimulated with 10 microg prostaglandin E1. Responses were recorded on a four-point scale: no response = 0, tumescence = 1, rigidity sufficient for intercourse = 2, full erection = 3. ICIT was repeated after 10 days and combined with CDS. The clinically assessed response to ICIT was correlated with end-diastolic flow velocity.

Of 168 patients, 114 (68%) responded equally to the first and second ICIT, but 45 (27%) had an improved response, from tumescence to full erection in the second test (P <0.0001); in 9 (5%), the response deteriorated. The overall mean response was 1.6 (95% confidence interval 1.5 to 1.7) and 1.9 (95% confidence interval 1.7 to 2.0) (P <0.0001) for the first and second test, respectively. Of 168 patients, 89 (53%) responded with erections sufficient for intercourse when tested the first time and 104 (62%) did so after the second injection.

Erectile response to diagnostic intracavernous injection of prostaglandin E1 significantly improved in the second compared with the first test. Therefore, cautious interpretation of CDS is advised when patients are injected for the first time because too many false-positive tests may result.