Assessment of De-Duplication Methods for Gonorrhea and Chlamydia Case Reports

BACKGROUND: Chlamydia and gonorrhea, the two most commonly reported notifiable conditions, can be diagnosed with highly sensitive nucleic acid amplification tests (NAATs). A positive NAAT in the weeks following successful treatment may indicate residual genetic material rather than a new or persistent infection and should not be reported as a second infection. However, there is no national guidance on the minimum amount of time between positive laboratory test results to trigger a report of a new infection. To inform guidance development, we reviewed current surveillance practices in local and state jurisdictions.

METHODS: In 2015, sexually transmitted disease surveillance programs in CDC funded project areas completed an assessment of current surveillance practices. We reviewed reporting practices for de-duplication of cases of chlamydia and gonorrhea separately, including time period used to decide when a second positive test should be reported as a case and the method of de-duplication (e.g., automatic or manual).

RESULTS: In total, 58 project areas completed the survey and 54 (93%) provided valid responses for the de-duplication questions. Reported time period for de-duplication of case data varied by jurisdiction and by pathogen. Sites reported using a range of 7 to 90 days for de-duplication of gonorrhea and chlamydia case report data. The majority of jurisdictions used 30 days; 31 of 54 (57%) jurisdictions for chlamydia and 29 of 54 (54%) jurisdictions for gonorrhea. A few jurisdictions (n=2) had additional de-duplication rules for certain populations (e.g., different time periods for pregnant women). Several jurisdictions (n=6) reported different time periods for gonorrhea and chlamydia with 5 jurisdictions using a shorter time period for de-duplication of gonorrhea cases. In jurisdictions that provided enough details, de-duplication methods also varied across jurisdictions with 28% using automated de-duplication within their surveillance information system, 20% using manual methods (e.g., data clerk deciding whether to enter the laboratory report as a new case) and 22% using a combination of methods.

CONCLUSIONS: Methods and time periods for de-duplicating chlamydia and gonorrhea case report data vary and may lead to non-comparability across jurisdictions. National guidance is needed to standardize surveillance practices. Guidance may need to be specific to each pathogen and should consider available evidence on when NAATs become negative following treatment.