Accounting for failures may improve precision: evidence supporting improved validity of self-reported condom use.

OBJECTIVES

To determine whether a measure of unprotected vaginal sex that is adjusted for condom failures would produce improved accuracy in predicting biologically confirmed STDs (chlamydia and gonorrhea) among female teens.

METHODS

Self-reported measures were collected using audio-computer-assisted self-interviewing. DNA amplification for the presence of Chlamydia trachomatis and Neisseria gonorrhoeae was conducted.

RESULTS

The unadjusted measure of unprotected vaginal sex was not significantly associated with biologically confirmed prevalence of STDs (prevalence ratio [PR] = 1.51; 95% CI = 0.71-3.21; P = 0.28). Alternatively, the adjusted measure achieved significance (PR = 3.59; 95% CI = 1.13-11.38; P = 0.014). More than one quarter (25.6%) of teens using condoms inconsistently and/or incorrectly tested positive for an STD compared to 7.1% among those reporting the consistent and correct use of condoms.

CONCLUSION

Findings demonstrate that studies of condom effectiveness should use an adjusted measure of condom use to achieve precision and rigor.