Below is more detailed information on the methods used for HPV-IMPACT, including our case definition, populations, data collection, and laboratory testing.
Since 2008, HPV-IMPACT has monitored pre-invasive cervical lesions that could progress to invasive cancer if left untreated as early indicators of population vaccine impact. Because showing the impact of vaccine on reducing the burden of cervical cancer is of highest importance, HPV-IMPACT has revised its case definition to include invasive cervical cancer. Cervical carcinomas diagnosed in catchment area residents are being identified retrospectively (2008-present). Tissue for HPV typing is being requested for cervical carcinoma cases diagnosed in 2016 or later. Once all sites have submitted data on cancer cases, reporting of HPV-IMPACT CIN2+ case counts will include cancers.
A case is defined as a resident in one of the surveillance areas who has a histologically confirmed diagnosis of cervical intraepithelial neoplasia (CIN) grades 2 or 3, or adenocarcinoma in situ (collectively referred to as CIN2+) and is at least 18 years of age at the time of diagnosis. The date of diagnosis must be on or after January 1, 2008.
Cases are identified based on laboratory reports of CIN2+. Each laboratory in the surveillance area regularly provides laboratory reports of CIN2+ findings to the local site. Because classification for pre-invasive cervical neoplasia is not standardized in the United States, a master list of possible diagnostic codes, terminology, and search terms has been provided to all sites and reporting laboratories to standardize case identification.
The HPV-IMPACT surveillance areas include Monroe County, NY; Davidson County, TN; New Haven County, CT; Alameda County, CA; and 28-zip codes in metropolitan Portland, OR, including portions of Multnomah County and Washington County. Over 1.5 million women aged 18 and older reside in the catchment areas. The surveillance sites include racially and ethnically diverse populations similar to the United States as a whole. Enhanced surveillance is conducted among over half a million women aged 18-39 years.
For each case of CIN2+ identified among women aged 18 years or older, a case report form with basic demographic and clinical data is completed. If the patient is between the ages of 18-39 years, an enhanced case report form is completed and tissue specimen is sent to CDC for HPV type testing. Additional data include race, ethnicity, insurance, cervical cancer screening history, and vaccination history and are obtained from laboratory and medical records.
A portion of tissue that was originally used by a pathologist to diagnose the patient with CIN2+ is sent to CDC for HPV DNA typing. A pathologist at CDC examines tissue samples to make sure that a high-grade cervical lesion is present in the tissue specimen that was sent. DNA is extracted and tested for a panel of HPV types, including all vaccine types and several additional high-risk and non-high-risk HPV types. From 2008-2019, all specimens were tested for 37 HPV types (6, 11, 16, 18, 26, 31, 33, 35, 39, 40, 42, 45, 51, 52, 53, 54, 55, 56, 58, 59, 61, 62, 64, 66, 67, 68, 69, 70, 71, 72, 73, 81, 82, 83, 84, 89, IS39). During 2020, the HPV laboratory is transitioning to using a new assay that will detect 28 HPV types. The previously used assay has been discontinued by the manufacturer.