Diagnostic significance of penile erections during sleep

The evidence for the validity of nocturnal penile tumescence as a means of differentiating between psychogenic and organic impotence is reviewed. Five necessary stages in the validation process are described, and the relevance of the research literature to each stage is examined. Problems and issues in the clinical application of NPT recording are discussed, including (1) the need to validate NPT against independent diagnostic criteria; (2) the high probability of misdiagnosis when the absolute magnitude of NPT is used to determine cause; and (3) the need for follow-up studies to establish that NPT can be of value in the diagnoses of those patients who do not clearly belong to either the psychogenic or organic categories. We conclude that further validation studies are required before the clinical utility of NPT can be determined.