Hepatitis C Virus Infection: Prevalence Report, 2003

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Background
Methods
Assumptions and Limitations
Results
Conclusions
Tables and Figures

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Background

The mission of the viral hepatitis program is to provide support for hepatitis C virus (HCV) prevention and control activities by monitoring disease trends; assessing burden of disease; identifying infected persons and those contacts requiring follow-up; identifying and controlling outbreaks; and disseminating educational and referral resources to affected individuals through their healthcare providers. The HCV registry, which includes an HCV chronic carrier database and an active surveillance system to identify acute cases, has been critical to reaching these goals.

Methods

These data describe persons living with HCV in Minnesota in 2003 by person, place, and time. Data analyses excluded persons diagnosed in federal or private correctional facilities, but include state prisoners. In addition, 206 persons of whom we have knowledge of their deaths and 144 children less than 1 year of age were also excluded. Lab results in children whose only serology was conducted prior to 1 year of age represent maternal antibody and are therefore not included in the dataset.

Age is defined as the difference between date of birth and first laboratory collection date on record. If no collection date is available, age is based on date of birth and date record was created in the database. Metro consists of four categories: greater Minnesota, suburbs, Minneapolis and St. Paul. Greater Minnesota includes all counties except the 7-county metro area. Suburbs include only the 7-county metro area less Minneapolis and St. Paul residents.

Data cleaning and basic descriptive analysis was conducted using Intercooled STATA 8.2 (STATA Corp LP, College Station, TX).

Assumptions and Limitations

Some assumptions about HCV surveillance data follow:

• Data do not include HCV-infected persons who have not been tested for HCV.

• Data do not include persons whose positive test results have not been reported to MDH.

• Persons are assumed to be alive unless the MDH has knowledge of their death.

• Persons whose most recently reported state of residence was Minnesota are assumed to be currently residing in Minnesota unless MDH has knowledge of their relocation. (The ability to track changes of residence, including within the state, is limited.)

• Data include false-positive, resolved infections, and chronic cases of HCV. Since surveillance is based on positive reporting of disease, it is impossible to identify resolved infections, unless conscientious clinicians follow-up with these data. It is also difficult to identify false-positive results due to confusion in interpretation over HCV screening test results. Most clinicians fail to order confirmatory testing, removing the ability to identify false-positives. Signal-to-cutoff ratios greater than 3.8 are indicative of a confirmed result. Therefore, if labs can begin to report these data, cases can be confirmed in the absence of a confirmatory test being run.

• Risk factor data is not mutually exclusive. In addition, due to the temporal disjuncture between acquisition of disease and diagnosis of disease, it is extremely difficult to determine the exact route of transmission in chronic cases of HCV.
  

Results

As of December 31, 2003, 22,356 persons are assumed alive and living in Minnesota with HCV (Fig. 1). The median age at diagnosis is forty-three (Fig. 2). Of HCV positive individuals reported to MDH, 65% were male and 32% were female (Fig. 3). Both genders had similar median ages at time of diagnosis (Fig. 4).

Of this sample, 22% reside in the suburbs; 32% live in Greater MN; 25% live in Minneapolis; and 9% live in St. Paul (Fig. 5 and Fig. 6). Median age at time of diagnosis was 43, regardless of area of residence (Fig. 7).

Race breakdown was as follows: 5% were American Indian; 2% were Asian, 15% were Black or African American; 0.02% were Native Hawaiian or Pacific Islander; 44% were white; 1% were other, unspecified race; and 33% were had unreported race (Fig. 8). Race breakdown by age revealed similar proportions (Fig. 9).

Risk factor data was not mutually exclusive. The most commonly cited risk factor was any type of illicit drug use (Table 1).

Conclusions

The number of Minnesotans living with HCV reported to MDH is small proportion of the actual persons living with HCV infection. It is hoped that this snapshot will be useful for policy and planning related to HCV prevention and control.

In the future, the surveillance databases can be linked with death records to more accurately remove deceased individuals. Also, algorithms will be developed based on repeated laboratory testing to determine if patients are receiving follow-up care. Finally, signal-to-cutoff ratio data will be collected to obtain confirmed HCV antibody test results.

Tables and Figures

Figure 1: Newly Identified Cases of Chronic HCV Infection in Minnesota by Year, 1990-2003

Figure 2: Persons Living with HCV in Minnesota by Age, 2003

Figure 3: Persons Living with HCV in Minnesota by Gender, 2003

Figure 4: Persons Living with HCV in Minnesota by Age and Gender, 2003

Figure 5: Persons Living with HCV in Minnesota by Residence at Diagnosis, 2003

Figure 6: Persons Living with HCV in Minnesota by Residence at Diagnosis, 2003

Figure 7: Persons Living with HCV in Minnesota by Age and Residence at Diagnosis, 2003

Figure 8: Persons Living with HCV in Minnesota by Race, 2003

Figure 9: Persons Living with HCV in Minnesota by Gender and Race, 2003

Table 1: Reported Risk Factors in Persons Living with HCV in Minnesota, 2003

(non-mutually exclusive) (n=22,356)

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