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INFECTIOUS DISEASE SURVEILLANCE
in Canadian Federal Penitentiaries 2005-2006

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Part II: Results

Chapter 3: Hepatitis C Virus (HCV)

Aggregate IDSS HCV Data
Participation in Screening

Table 3.1 shows the total number of HCV tests reported via the aggregate IDSS system for inmates between 2000 and 2006 by inmate status. There were 5,489 screening tests for HCV in 2005 and 5,509 in 2006. Prairies reported the highest number of HCV tests in 2005 (1,613) and in 2006 (1,633).

The results for 2005-2006 from IDSS by region and inmate status for HCV are shown in Appendix B, Tables B.1.i, B.1.ii and B.1.iii. Among all new admissions, HCV testing uptake was 49.1% in 2005 and 49.4% in 2006.

Testing uptake was highest in Ontario Region for 2005 (58.9%) and 2006 (64.2%), and lowest in Pacific Region for 2005 (23.0%) and 2006 (13.8%).

Participation in testing among female new admissions was reported to be greater than 100% in Ontario and Prairies (Appendix B, Table B.1.ii). This is likely reflective of reporting re-testing of parole suspension in the same line as new admissions or because a single institution handles admissions and multiple security levels for females so the distinction between ‘new admission’ and ‘general population’ is less clear (see Methods, IDSS and Discussion, Limitations).

 

Table 3.1: Total Number of HCV Tests, Inmates, 2000 - 2006
  2000 2001 2002 2003 2004 2005 2006

Source: IDSS Aggregate Surveillance Data, CSC 2010
† - includes temporary detainees

New Admissions
Population 4,302 4,288 4,159 4,238 4,413 4,819 5,079
HCV Test Requisitions 1,583 1,908 2,307 1,987 2,074 2,367 2,511
HCV Testing Uptake 36.8% 44.5% 55.5% 46.9% 47.0% 49.1% 49.4%
General Population
Population 12,363 12,479 12,295 12,179 13,107 12,222 13,280
HCV Test Requisitions 2,151 2,512 3,423 3,887 3,432 3,122 2,998
HCV Testing Uptake 17.4% 20.1% 27.8% 31.9% 26.2% 25.5% 22.6%
Total Number of HCV Tests 3,734 4,420 5,730 5,874 5,506 5,489 5,509

 

Newly Diagnosed HCV Cases

The number of newly diagnosed positive HCV cases7 in 2000-2006, where the inmates HCV status was previously negative or unknown8, is shown in Table 3.2 (also see Appendix B, Tables B.1.i – B.1.iii). The total number of newly diagnosed HCV cases was 354 in 2005 and 357 in 2006. The overall HCV positivity rate (number of positive tests divided by the number of tests), shown in Table 3.2, was 14.3% in 2000, 6.5% in 2005 and in 2006. Among new admissions the HCV test positivity rate was 15.4% in 2000, 7.5% in 2005, and 7.7% in 2006. Among the general population, the rate was 13.4% in 2000, 5.6% in 2005 and 5.5% in 2006.

Inspection of Appendix B Table B.1.i indicates marked regional differences among new admissions. HCV test positivity was highest in Quebec Region for 2005 at 14.8% and 2006 at 18.8% and lowest in Ontario Region for 2005 (3.1%) and 2006 (3.0%). Testing uptake however was highest in Ontario Region as well. Among general population inmates test positivity was highest in Atlantic Region for 2005 (9.1%) and 2006 (12.1%) and lowest in Quebec Region for 2005 (2.1%) and 2006 (3.4%).

Participation in HCV testing among females on admission (Appendix B Table B.1.ii) was high at greater than 90% and the HCV test positivity rate for females on admission was 7.6% in 2005 and 2.4% in 2006. Among female new admissions, HCV test positivity was highest in Atlantic in 2005 (26.1%) and in Quebec in 2006 (10.8%), and lowest in Ontario in 2005 (2.6%) and in Prairies and Pacific in 2006 (0%). Note that the female institution in Pacific Region only opened in April 1st 2004.

Among new male admissions, the HCV test positivity rate was 7.5% in 2005 and 8.4% in 2006 (see Appendix B, Table B.1.iii). HCV test positivity was highest in Quebec Region in 2005 at 14.9% and in 2006 at 19.5%. Participation in testing among male new admissions was 46.5% in 2005 and 46.4% in 2006. Ontario had the highest HCV testing uptake among male new admissions in 2005 at 53.0% and in 2006 at 61.1%.

Among male general population inmates, HCV test positivity was 5.7% in 2005 and 5.6% in 2006. Atlantic Region had the highest HCV test positivity among male new admissions in both 2005 (9.4%) and 2006 (12.4%).

 

Table 3.2: New HCV Diagnosis among New Admissions and General Population Inmates 20001 – 2006
Inmate Status 2000 2001 2002 2003 2004 2005 2006

Source: CSC IDSS Aggregate Surveillance Data, CSC 2010
1 – Total number of newly diagnosed HCV infections in CSC was 407 in 1997, 560 in 1998, and 570 in 1999
(
see surveillance report for 2002-2004 (CSC, 2008)).

New Admissions
Frequency 244 195 226 220 254 178 193
Test Positivity Rate 15.4% 10.2% 9.8% 11.1% 12.3% 7.5% 7.7%
General Population
Frequency 289 367 257 244 191 176 164
Test Positivity Rate 13.4% 14.6% 7.5% 6.3% 5.6% 5.6% 5.5%
Overall
Frequency 533 562 483 464 445 354 357
Test Positivity Rate 14.3% 12.7% 8.4% 7.9% 8.1% 6.5% 6.5%

 

HCV Diagnostic Yield among New Admissions

Dividing the number of newly diagnosed HCV cases by the number of tests conducted provides a standardized estimate of the rate of new HCV diagnoses (see Figure 3.1). The HCV diagnostic yield was 154.1 newly diagnosed HCV cases in 2000, 75.2 in 2005 and 76.9 in 2006. Combining the data for 2000 to 2006, there were 1,510 newly diagnosed HCV cases from 14,737 HCV screening tests, a diagnostic yield of 102.5 newly diagnosed cases for every 1,000 tests.

HCV Prevalence

Year-end HCV Point Prevalence

The year-end point prevalence estimate for HCV is shown in Figure 3.2 (see also Appendix B, Table B.2). The number of HCV cases reported at year-end was 3,581 in 2005 and 3,661 in 2006, an increase in prevalence of 58% since 2000. HCV prevalence was 29.3% in 2005 and 27.6% in 2006.

The year-end point prevalence also shows variance by gender (see Figure 3.3 and Appendix B, Tables B.2). The estimated HCV prevalence among women was 39.5% in 2005 and 36.0% in 2006. Among women the HCV prevalence was highest in Pacific region in 2005 (68.1%) and in 2006 (47.2%). Rates were also high among women in Atlantic region in both 2005 (57.5%) and 2006 (46.7%).

 

Figure 3.1: Diagnostic Yield among New Admissions
(Newly Diagnosed HCV Infections1 per 100,000 Tests), 2000 – 2006
Figure 3.1: Diagnostic Yield among New Admissions (Newly Diagnosed HCV Infections<sup>1</sup> per 100,000 Tests), 2000 – 2006

Source: CSC IDSS Aggregate Surveillance Data, CSC 2010
1 - Among those previously negative or of unknown status

 

Figure 3.2: Year-end Prevalence of HCV, Inmates, 1999-2006± Figure 3.2: Year-end Prevalence of HCV, Inmates, 1999-2006±

± - For data 1990-1998 see surveillance report for 2002-2004 (CSC, 2008).
Source: IDSS Aggregate Surveillance Data, CSC 2010

 

Figure 3.3: Year-end Prevalence of HCV by Gender, Inmates, 2000 – 2006 Figure 3.3: Year-end Prevalence of HCV by Gender, Inmates, 2000 – 2006

Source: IDSS Aggregate Surveillance Data, CSC 2010

 

The estimated HCV prevalence among men was 29.0% in 2005 and 27.3% in 2006. Regionally, the rates for men were highest in the Pacific region in both 2005 (44.4%) and 2006 (37.0%), and lowest in Quebec Region in 2005 (17.6%) and 2006 (19.2%).

Investigation of HCV prevalence among male inmates by security level is shown in Figure 3.4. This graph shows that HCV prevalence is lower in minimum security institutions than in medium and multi-level institutions, which includes regional hospitals and treatment centres. HCV rates in maximum security facilities were lower than the other security levels until 2003 but increased to about the same level as medium security institutions in the more recent years (2004-2006).

HCV Period Prevalence

Table 3.3 (also see Appendix B, Table B.2) provides an estimate of the total known number of inmates living with HCV that were inside Canadian federal penitentiaries in a given year. The number of inmates known to be HCV positive on admission was 1,034 in 2005 and 1,165 in 2006. By combining the information on the number of HCV positive inmates at the beginning of the year with the number of new admissions known to be infected and the number of newly diagnosed HCV positive inmates, a period prevalence for HCV can be calculated. For example, a total of 3,467 HCV positive inmates were reported across CSC institutions at the start of calendar year 2006, there were 1,165 already positive on admission and another 357 newly diagnosed HCV cases. Therefore there were a total of 4,989 HCV positive inmates who were cared for in 2006 (27.2% HCV period prevalence).

 

Figure 3.4: Year-end Prevalence of HCV among Male Inmates by
Security Level, 2000 – 2006
Figure 3.4: Year-end Prevalence of HCV among Male Inmates by Security Level, 2000 – 2006

Source: CSC IDSS Aggregate Surveillance Data, CSC 2010

 

HCV Treatment

For each month, the IDSS provides the number of inmates initiated on treatment and the number of inmates currently on treatment for HCV infection (see Appendix B, Table B.3). The number of inmates initiated on HCV treatment was 91 in 2000, 267 in 2005, and 370 in 2006 (Table 3.4). The average number of inmates on HCV treatment in any given month was 40 in 2000, 136 in 2005 and 184 in 2006.

 

Table 3.3: HCV Period Prevalence1: Known Positive on Admission and
Newly Diagnosed Cases, 2000 – 2006
  2000 2001 2002 2003 2004 2005 2006

Source: CSC IDSS Aggregate Surveillance Data, CSC 2010
1 – Data vary across years due to data discrepancies, transfers in and transfers out of institutions,
and releases over the calendar year.

Number of Known HCV cases at the start of the year 2,317 2,720 2,937 3,192 3,277 3,360 3,467
Known Positive at Admission 747 858 937 989 1,074 1,034 1,165
Newly Diagnosed Positive 533 562 483 464 445 354 357
New Admissions 244 195 226 220 254 178 193
General Population 289 367 257 244 191 176 164
Annual Number of Known HCV Cases 3,597 4,140 4,357 4,645 4,796 4,748 4,989
Annual Period Prevalence 18.1% 21.6% 26.5% 28.3% 27.4% 25.9% 27.2%

 

Table 3.4: HCV Treatment: Treatment Initiation and Uptake, Inmates, 2000 - 2006
  2000 2001 2002 2003 2004 2005 2006

Source: CSC IDSS Aggregate Surveillance Data, CSC 2010

Number of Inmates Initiated on HCV Treatment 91 123 163 271 252 267 370
Average Number of HCV Positive Inmates per Month [A] 2,253 2,916 3,128 3,179 3,252 3,572 3,621
Average Number of Inmates on HCV Treatment per Month [B] 40 56 90 120 129 136 184

 

Releases to the Community - HCV

The majority of federally incarcerated inmates serve determinate sentences and are eventually released to the community. Table 3.5 (see also Appendix B, Table B.2) shows that the total number of known HCV positive inmates released to the community was 2,065 in 2005 and 2,183 in 2006.

Enhanced Surveillance: Web-IDSS HCV Data Results

HCV Medical History on Admission

Data from the enhanced surveillance for new admissions by region and gender and origin are shown in Appendix B, tables B.4.i and B.5.i. Enhanced surveillance reports for 5,840 new admissions from 2005-2006 were received at NHQ, which represents 59% of all new admissions from this period. Of these 5,840 new admissions, 49.3% reported a previous HCV test, which was higher among females compared to males (64.6% vs. 48.5%). Overall 761 or 26.4% of those tested report a previous positive result, also higher among females at 44.2% compared to 25.2% for males. Of those previous positive, 9.9% report a previous treatment for their HCV infection. While based on small numbers, the treatment uptake among females at 6.8% was lower than that for males at 10.3%.

Inspection of Appendix B Table B.5.i shows that Canadian-born inmates of Aboriginal status were more likely to report a previous HCV test at 60.3% compared to Canadian-born non-Aboriginals (46.6%) or Foreign-born (30.7%). New admissions of Aboriginal status were more likely to report a previous positive HCV result at 32.3% compared to Canadian-born non-Aboriginals (24.7%) or Foreign-born (5.9%). Among those with a previous positive result, treatment was highest among Canadian-born non-Aboriginal inmates at 9.6%, followed by Canadian-born Aboriginal inmates (8.2%).

HCV Testing on Admission

The Web-IDSS data for screening tests among new admissions are consistent with those from the aggregate IDSS. This included 4,121 HCV tests among new admissions for 2005-2006, or 84% of the 4,878 HCV test requisitions reported in Table 3.1.

Of the 4,121 HCV screening tests recorded in Web-IDSS, results were available for only 2,494 (60.5%). A total of 224 newly diagnosed HCV infections were reported in the enhanced surveillance data compared to the 371 in Table 3.2, or 60%. Conversely, there were 2,199 prevalent positive HCV cases among new admissions reported in IDSS in 2005-2006, compared to 761 in Web-IDSS, representing 35%. Combined, this results in an inability to directly measure and estimate HCV prevalence using the Web-IDSS data. Of note is that the Web-IDSS data only include confirmatory tests for 441 of these 761; operationally, all self-reported HCV infections would be laboratory confirmed by repeating the EIA test or assessing HCV RNA / viral load.

 

Table 3.5: Number of Known HCV Positive Inmates Released to the Community, 2000 - 2006
  2000 2001 2002 2003 2004 2005 2006

Source: IDSS Aggregate Surveillance Data, CSC 2010

Number of HCV Positive Inmates Released to the Community 1,156 1,506 1,856 2,354 2,472 2,065 2,183

 

Using the Web-IDSS data for new admissions, an estimate of diagnostic yield (newly diagnosed cases per 1,000 tests) can be calculated (see Appendix B Tables B.4.i and B.5.i.). Considering only those records where Web-IDSS has a valid laboratory result, the number of newly diagnosed HCV infections per 1,000 screening tests was 90/1,000, higher than the IDSS estimate at 75-76 per 1,000. Diagnostic yield was higher among females at 127/1,000 compared to males at 88/1,000 and for Canadian-born Aboriginal offenders at 131/1,000 compared to Canadian-born non-Aboriginal offenders at 79/1,000.

HCV Testing while Incarcerated and Seroconversion

A total of 2,850 HCV tests were recorded in Web-IDSS among general population inmates (see Appendix B Tables B.4.ii and B.5.ii), or 47% of the 6,120 reported in Table 3.1. Overall, 60.3% report a previous HCV test, suggesting that at least for the group recorded in Web-IDSS, they tend to have been tested previously, either at reception or in the community prior to reception. A total of 334 newly diagnosed HCV infections among general population inmates are recorded in Web-IDSS, compared to the 340 in Table 3.2.

It is not clear that the test positivity for HCV among general population inmates, estimated at 5.5-5.6% from the IDSS in 2005-2006, approximates a seroconversion rate since the aggregate data do not include information on previous testing (see Table 3.2).

The Web-IDSS data does allow an estimate of HCV seroconversion. There were 424 individuals recorded in Web-IDSS with repeat HCV tests who were negative on admission. Of these, 13 subsequently tested positive for HCV on follow up. Assuming that each of the 424 inmates contributes a year of observation, a crude measure of seroconversion can be calculated by dividing the 13 by 424 and standardizing to a rate per 1,000; this results in a seroconversion estimate of 31 HCV seroconversions per 1,000 HCV negative inmates per year.

HCV Prevalence Estimation

A prevalence estimate for HCV using Web-IDSS data can be calculated by combining all laboratory confirmed HCV cases with those self-reported HCV positive inmates for whom we do not have a laboratory result (see Appendix B, Tables B.4.iii and B.5.iii). Among those tested, the overall HCV prevalence estimate is 31.6%, slightly higher than the IDSS estimate of 27.6% (see figure 3.2). Consistent with the IDSS data, HCV prevalence was higher among females at 40.7% versus males at 31.1% (Appendix B, Table B.4.iii). HCV prevalence estimate was higher among Canadian-born Aboriginals (39.4%) compared to Canadian-born non-Aboriginals (27.4%) and Foreign-born (7.7%) (Appendix B, Table B.5.iii).

In order to approximate the IDSS methodology for calculating prevalence estimates by dividing number of cases by the entire population, a second measure was constructed whereby the number of cases was divided by the number of inmates regardless of test status. This method produced an overall HCV prevalence estimate of 18.0% with similar trends for gender and origin.

 


Footnote

7 A new HCV diagnosis for the purposes of this report is a reactive antibody test result for anti-HCV. In the years 2005-2006, PCR testing for HCV was available in some provinces (Wong, 2006). Therefore confirmatory HCV testing was not done consistently across CSC or indeed across regions.

8 A new diagnosis is not synonymous with a new infection – a person may have been infected some time ago, and be unaware of their status. In order to determine a timeframe for seroconversion, previous negative test data are required.

 

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