Factors associated with decreased anal sphincter tone and the accuracy of forced anal examinations to detect individuals having receptive anal intercourse: An observational study.

OBJECTIVE AND DESIGN: Forced anal examinations are used to prosecute sexual and gender minorities (SGM) in at least seven countries under the presumption that decreased sphincter tone, estimated by a finger inserted into the anal canal, can detect persons practicing receptive anal intercourse. In a cross-sectional analysis of the baseline data from a longitudinal study, we aimed to determine factors associated with sphincter tone and the accuracy of sphincter tonality to detect persons engaging in receptive anal intercourse.

SETTING: Clinicians in Chicago, Houston, and Milwaukee, USA conducted digital anal rectal examinations (DARE) on 838 participants, 94.0% of whom were cisgendered males. Clinicians used the Digital Rectal Examination Scoring System to score sphincter resting tone (RT) and squeeze tone (ST). On a separate survey, individuals reported their preferred position for anal intercourse: i.e., either always/mostly insertive anal intercourse, always/mostly receptive anal intercourse, or both receptive and insertive anal intercourse. Multivariable regression assessed factors associated with decreased sphincter tone while area under the Receiver Operating Characteristic curves (AUC) estimated the accuracy of sphincter tonality to detect receptive anal intercourse.

RESULTS: 11.3% had decreased RT (95/838) and 6.3% had decreased ST (53/838). The accuracy of DARE to detect any receptive anal intercourse was little better than random guessing (AUC 0.53, 95% CI 0.51 to 0.55, and AUC 0.51, 95% CI 0.49 to 0.53, respectively. RT and ST decreased with age regardless of sexual behavior (p trend <0.01 for both). Compared to individuals having always/mostly insertive anal intercourse, individuals having always/mostly receptive anal intercourse was associated with decreased RT, but not ST, while those equally preferring both insertive and receptive anal intercourse were not associated with decreased RT or ST.

CONCLUSIONS: Decreased sphincter tone is uncommon among SGM who prefer receptive anal intercourse. Given virtually no accuracy, a finger inserted into the anus has no utility to detect individuals practicing receptive anal intercourse and thus should not be used as such.

TRIAL REGISTRATION: NCT04090060.

SUMMARY BOX: What is already known on this topic: To gather evidence for prosecution of sexual and gender minorities, forced anal exams are used in multiple countries. The examination includes inserting the index finger into the anal canal to detect decreased sphincter tone which is considered evidence of receptive anal intercourse. We found only two small studies (n= 58 and n=24) assessing factors associated with decreased sphincter tone and none assessing the accuracy of sphincter tone to detect sexual and gender minorities having receptive anal intercourse. What this study adds: Our study suggests that a finger inserted into the anal canal is not useful to detect a history of receptive anal intercourse. As such, the sexual practices of individuals cannot be known using a forced anal examination.