Our study had 2 objectives. The first objective was to describe findings from 6 US state or county health departments that have been funded by CDC to perform enhanced surveillance for HCV infection. The second objective was to discuss the limitations and challenges of conducting population-based surveillance for HCV infection in the United States.
The sites where enhanced hepatitis surveillance was conducted during 2006–2007 were Colorado, Connecticut, Minnesota, New York (excluding New York City), and Oregon; Pinellas County, Florida, a sentinel counties (8
) site, also contributed hepatitis C reports. The combined population under surveillance from the 5 states and 1 county was an estimated 29.3 million in 2007 (). In each of these jurisdictions, clinical laboratories are required to report positive results from HCV assays. For this analysis, a confirmed case of HCV infection was identified in any person who, from July 1, 2006 through June 30, 2007, had at least 1 of the following: 1) a positive result for an HCV recombinant immunoblot assay (RIBA), 2) a positive nucleic acid test (NAT) result for HCV RNA, 3) a documented HCV genotype, or 4) a positive result for a screening test for antibodies against HCV (anti-HCV) with a signal-to-cutoff (s:co) ratio predictive of a true positive result for the given assay.
Newly reported cases of past or present HCV infection in 6 US locations, July 1, 2006–June 30, 2007*†
Laboratories and providers continuously reported positive results for HCV markers (e.g., anti-HCV, RIBA, NAT, genotype) to state or local health departments. Health department staff checked patients’ names and dates of birth from each report against a surveillance database to determine whether a case had been previously reported. Newly reported cases (i.e., previously not captured in the database of this jurisdiction) were entered into this database along with hepatitis test results. Health department staff investigated cases and collected basic demographic and clinical information to confirm the case definition and to epidemiologically describe the case. We calculated rates of newly reported cases by using denominators available from the 2007 population estimates from the US Bureau of the Census (www.census.gov/compendia/statab
Two supplemental assessments were conducted. The first assessment measured the number of laboratory reports associated with each new case. Staff at each site monitored a convenience sample of laboratory reports and measured the number excluded, reasons for exclusion, and the number that eventually were classified as newly reported cases. The second assessment determined the validity of basic epidemiologic information. For this task, CDC drew a random sample of 10 cases per site from among those reported during the 12-month reporting period (n = 60) and extracted the following variables: date of birth, county of residence, sex, race, and clinical test results associated with HCV infection. Surveillance staff contacted at least 1 healthcare provider to independently collect this information. We measured agreement between the information initially reported and the information collected during the validation using a κ statistic (9
The 6 sites reported a total of 20,285 cases of confirmed HCV infection that were previously unreported in their respective jurisdictions (). Of these, 66% of case-patients were male and 56% were 40–54 years of age (men and women combined) (). More than half (52%) of the reports lacked information on race or ethnicity. Most cases (89%) were reported by clinical laboratories. The laboratory criterion most frequently reported was a positive result for HCV RNA (53%). The rate of new reports of past or present HCV infection was 69/100,000 population (range 25–108/100,000).
Sites monitored all incoming reports on average for 8 days (range 5–16 days). A total of 2,180 reports were received and, among these, 491 (23%, range 13%–52%) met the case definition and were considered newly reported cases; Oregon had the highest proportion of newly reported cases (52%) and the newest registry. The remaining reports fell into the following categories: already in the database (68%, range 30%–78%), lacking value for s:co ratio (5%, range 3%–13%), negative test results for an HCV marker (2%, range 1%–4%), or missing key demographic data (1%, range 0%–2%).
All cases were confirmed to meet the case definition. Agreement was high for age (κ = 1.0, p<0.001), sex (κ = 0.96; p<0.001), and county of residence (κ = 1.0; p<0.001); county data were missing for 6 (10%) cases.