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

Abstract

Introduction Forced anal examinations are used to prosecute sexual and gender minorities (SGM) in multiple countries under the presumption that decreased sphincter tone, assessed by a finger inserted into the anal canal, can detect persons practising receptive anal intercourse. Using 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. Methods Clinicians in Chicago, Houston and Milwaukee, USA conducted digital anal rectal examinations (DARE) to score sphincter resting tone (RT) and squeeze tone (ST). On a separate survey, individuals reported their preferred position for anal intercourse, that is, 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 the area under the receiver operating characteristic curves (AUC) estimated the accuracy of sphincter tonality to detect receptive anal intercourse. Results Of 838 participants, 94.0% of whom were cisgendered males, 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 behaviour (p trend <0.01 for both). Compared with individuals having always/mostly insertive anal intercourse, individuals having always/mostly receptive anal intercourse were 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. Conclusion 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 practising receptive anal intercourse and thus should not be used as such. Trial registration number NCT04090060 .