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INFECTIOUS DISEASE SURVEILLANCE
in Canadian Federal Penitentiaries 2005-2006

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Part II: Results

Chapter 2: Human Immunodeficiency Virus (HIV)

Aggregate IDSS HIV Data

Participation in Screening

Table 2.1 shows the total number of HIV tests reported for inmates between 2000 and 2006 by inmate status. There were 6,106 HIV tests in 2005 and 6,155 in 2006.

The IDSS results for 2005-2006 by region, inmate status and gender for HIV are shown in Appendix A, Table A.1.i – A.1.iii. Overall, Prairies reported the highest number of HIV tests in 2005 (1,802), and in 2006 (1,803).

Participation in testing among female new admissions was reported to be greater than 100% in Quebec, Ontario and Prairies (Appendix A, Table A.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 2.1: Total Number of HIV Tests, Inmates, 2000 - 2006
  2000 2001 2002 2003 2004 2005 2006

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

New Admissions
Population 4,302 4,288 4,159 4,238 4,413 4,819 5,079
HIV Test Requisitions 1,596 1,768 2,317 2,059 2,112 2,418 2,645
HIV Testing Uptake 37.1% 41.2% 55.7% 48.6% 47.9% 50.2% 52.1%
General Population
Population 12,363 12,479 12,295 12,179 13,107 12,222 13,280
HIV Test Requisitions 2,573 2,770 3,505 3,771 3,567 3,688 3,510
HIV Testing Uptake 20.8% 22.2% 28.5% 31.0% 27.2% 30.2% 26.4%
Total Number of HIV Screening Tests 4,169 4,538 5,822 5,830 5,679 6,106 6,155

 

Newly Diagnosed HIV Cases

The number of newly diagnosed positive HIV cases 2000-2006, where the inmates HIV status was previously negative or unknown5, is shown in Table 2.2 (also see Appendix A, Tables A.1.i-A.1.iii). The number of newly diagnosed HIV cases was 45 in 2000, 14 in 2005 and 15 in 2006. The HIV positivity rate (number of positive tests divided by the number of tests) is also shown in Table 2.2. Among new admissions, the HIV test positivity rate for screening tests was 0.29% in 2005 and 0.26% in 2006. Among the general population, the HIV test positivity rate for screening tests was 0.19% in 2005 and 0.23% in 2006.

Inspection of Appendix A, Table A.1.i shows that although Pacific had the highest HIV test positivity rate in 2005 at 0.89%, they also had the lowest HIV testing uptake on admission (22.8%). Ontario had the second highest test positivity rate at 0.39% with 54.9% participation in HIV testing among new admission. Quebec Region had the highest HIV test positivity rate in 2006 at 0.43% with 48.3% participation.

Appendix A, Table A.1.ii shows that all newly diagnosed HIV among females in 2005 and 2006 was detected on admission. Participation in HIV testing among females on admission was high at greater than 90%. The HIV test positivity rate for females on admission was 1.20% in 2005 and 0.64% in 2006. Overall, HIV testing uptake among female general population inmates was recorded at 37.5% in 2005 and 42.2% in 2006.

In apparent contrast, HIV case detection in males was split between new admissions and general population inmates (see Appendix A, Table A.1.iii). Among new male admissions, the HIV test positivity rate was 0.18% in 2005 and 0.21% in 2006. HIV test positivity was highest in Pacific Region at 0.90% although this was based on 22.7% testing uptake; Atlantic reported 0.35% test positivity with 53.6% testing uptake (highest testing uptake in 2005). Atlantic had the highest test positivity in 2006 as well at 0.33% with 56.3% test uptake. Ontario had the highest HIV testing uptake among male new admissions in 2006  at 64.2%.

Among male general population inmates, HIV test positivity was 0.20% in 2005 and 0.24% in 2006. Pacific Region had the highest HIV test positivity among male new admissions in both 2005 (0.40%) and 2006 (0.53%), with participation rates of 28.0% and 29.2% respectively.

 

Table 2.2: New HIV Diagnosis among New Admissions and General Population Inmates, 2000 – 2006
Inmate Status 2000 2001 2002 2003 2004 2005 2006

Source: IDSS Aggregate Surveillance Data, CSC 2010

New Admissions
Frequency 24 11 15 13 3 7 7
Test Positivity Rate 1.50% 0.60% 0.65% 0.63% 0.14% 0.29% 0.26%
General Population
Frequency 21 5 12 20 2 7 8
Test Positivity Rate 0.90% 0.20% 0.34% 0.53% 0.06% 0.19% 0.23%
Overall
Frequency 45 16 27 33 5 14 15
Test Positivity Rate 1.12% 0.36% 0.46% 0.57% 0.09% 0.23% 0.24%

 

HIV Diagnostic Yield among New Admissions

Dividing the number of newly diagnosed HIV cases by the number of tests conducted provides a standardized estimate of the rate of new HIV diagnoses (see Figure 2.1). The HIV diagnostic yield was 15.0 newly diagnosed HIV cases in 2000, 2.9 in 2005 and 2.6 in 2006. Combining the data for 2000 to 2006, there were 80 newly diagnosed HIV cases from 14,888 HIV screening tests, a diagnostic yield of 5.4 newly diagnosed cases for every 1,000 tests.

 

Figure 2.1: Diagnostic Yield among New Admissions
(Newly Diagnosed HIV Infections1 per 100,000 Tests), 2000 – 2006
Figure 2.1: Diagnostic Yield among New Admissions 
(Newly Diagnosed HIV Infections per 100,000 Tests), 2000 – 2006

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

 

HIV Prevalence

Year-end HIV Point Prevalence

The year-end point prevalence estimate for HIV among inmates in Canadian federal penitentiaries 1999 – 2006 is shown in Figure 2.2 (also see Appendix A, Table A.2). The HIV prevalence was 1.67% in 2005 (n=204) and 1.64% in 2006 (n=218). Overall HIV prevalence was highest in Pacific Region in both 2005 (2.79%) and 2006 (2.28%), followed by Quebec (1.75% and 1.71%, respectively) (Appendix A, Table A.2).

The year-end point prevalence also shows variance by gender (see Figure 2.3 and Appendix A, Table A.2). The estimated HIV prevalence among women was 2.84% in 2005 and 4.49% in 2006. Women continue to have higher rates of HIV infection compared to men. The estimated HIV prevalence among men was 1.63% in 2005 and 1.54% in 2006. Regionally, the rates for women were highest in the Prairie Region in 2005 (5.56%) and 2006 (6.85%). For men, the highest rates were seen in Pacific Region in both 2005 (2.79%) and 2006 (2.28%).

Investigation of HIV prevalence among male inmates by security level is shown in Figure 2.4. This graph shows that HIV prevalence is lowest in minimum security institutions. HIV tends to be higher in multi-level institutions, which includes regional hospitals and psychiatric treatment centres. With some variability across the years, HIV prevalence in maximum and medium institutions tend to be quite similar.

 

Figure 2.2: Year-end Prevalence of HIV, Inmates, 1999 – 2006± Figure 2.2: Year-end Prevalence of HIV, Inmates, 1999 – 2006±

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

 

Figure 2.3: Year-end Prevalence of HIV by Gender, Inmates, 2000 – 2006 Figure 2.3: Year-end Prevalence of HIV by Gender, Inmates, 2000 – 2006

Source: IDSS Aggregate Surveillance Data, CSC 2010

 

HIV Period Prevalence

Table 2.3 provides an estimate of the total known number of inmates living with HIV that were inside Canadian federal penitentiaries in a given year. The number of inmates known to be HIV positive on admission rose from 126 in 2005 to 155 in 2006. By combining the information on the number of HIV positive inmates at the beginning of each year with the number of new admissions known to be infected and the number of newly diagnosed HIV positive inmates, a period prevalence for HIV can be calculated. For example, a total of 205 HIV positive inmates were reported across CSC institutions at the start of calendar year 2006, there were 155 already positive on admission and another 15 newly diagnosed HIV cases. Therefore there were a total of 375 HIV positive inmates who were cared for in 2006 (2.04% HIV period prevalence).

HIV Treatment

For each month, the IDSS provides the number of inmates initiated on treatment and the number of inmates currently on treatment for HIV infection (see Appendix A, Table A.3). Table 2.4 shows that the number of inmates initiated on treatment was 68 in 2000, 50 in 2005 and 70 in 2006. Overall the proportion of HIV positive inmates on therapy was 54.2% in 2005 and 52.9% in 2006.

The proportion on therapy shows regional variation, with the Quebec Region having the highest treatment uptake at 64.9% and 65.5% in 2005 and 2006 respectively. HIV treatment uptake was lowest in Pacific Region in 2005 at 33.3% and in Atlantic Region in 2006 at 32.0%. By gender, HIV treatment uptake was lower for women than men in both 2005 (40.3% vs 55.3%) and 2006 (41.3% vs 53.8%).

 

Figure 2.4: Year-end Prevalence of HIV among
Male Inmates by Security Level, 2000 – 2006
Figure 2.4: Year-end Prevalence of HIV among Male Inmates by Security Level, 2000 – 2006

Source: CSC IDSS Aggregate Surveillance Data, CSC 2010

 

Table 2.3: HIV 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 out of institutions,
and releases over the calendar year.

Number of Known HIV Cases at the Start of the Year 149 210 225 235 211 190 205
Known HIV Positive at Admission 104 123 139 118 128 126 155
Newly Diagnosed HIV Positive 45 16 27 33 5 14 15
New Admissions 24 11 15 13 3 7 7
General Population 21 5 12 20 2 7 8
Annual Number of Known HIV Cases 298 349 391 386 344 330 375
Annual Period Prevalence 1.51% 1.75% 2.38% 2.35% 1.96% 1.80% 2.04%

 

Table 2.4: HIV Treatment Initiation and Uptake, Inmates, 2000 – 2006
  2000 2001 2002 2003 2004 2005 2006

Source: IDSS Aggregate Surveillance Data, CSC 2010

Number of Inmates Initiated on HIV Treatment 68 41 46 40 55 50 70
Average Number of HIV Positive Inmates per Month [A] 197 215 233 232 198 203 215
Average Number on HIV Treatment per Month [B] 119 122 128 121 116 110 114
Treatment Uptake (percent) [B/A*100] 60.3% 56.9% 55.0% 52.1% 58.7% 54.2% 52.9%
Males 61.2% 60.2% 56.0% 52.4% 58.5% 55.3% 53.8%
Females 43.5% 13.2% 35.6% 48.4% 60.5% 40.3% 41.3%

 

Table 2.5: Number of Known HIV Positive Inmates Released to the Community, 2000 – 2006
  2000 2001 2002 2003 2004 2005 2006

Source: IDSS Aggregate Surveillance Data, CSC 2010

Number of Known HIV Positive Inmates Released to the Community 162 173 183 205 214 175 193

 

While intuitively, a treatment uptake of 100% may seem optimal6, there may be a number of clinical (e.g., being taken off medication due to side-effects or drug resistance) and logistical (e.g., specific drug was temporarily unavailable) reasons for an inmate NOT being on treatment in any given month.

Releases to the Community - HIV

The majority of federal inmates serve determinate sentences and are eventually released to the community. Table 2.5 (see also Appendix A, Table A.2) shows that the total number of inmates known to be living with HIV released to the community was 175 in 2005 and 193 in 2006.

Enhanced Surveillance: Web-IDSS HIV Data Results

HIV Medical History on Admission

Data from the enhanced surveillance for new admissions by region and gender and origin are shown in Appendix A, Tables A.4.i and A.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, 3,167 (54.2%) reported a previous HIV test, which was higher among females compared to males (74.4% vs. 53.1%). Of those tested 50 or 1.6% reported a previous positive result, which was also higher among females (4.4%) compared to males (1.4%). Of those positive, only 26.0% report previous treatment for their HIV infection.

Inspection of Appendix A Table A.5.i shows that Canadian-born inmates of Aboriginal status were more likely to report a previous HIV test at 66.6% compared to Canadian-born non-Aboriginals (51.3%) or Foreign-born (36.4%). New Admissions of Aboriginal status and Foreign-born were more likely to report a previous positive HIV result at 1.9% and 1.8%, respectively, compared to Canadian-born non-Aboriginals (1.5%).

HIV Testing on Admission

The Web-IDSS data for screening tests among new admissions are consistent with those from the aggregate IDSS. This included 4,770 HIV tests among new admissions for 2005-2006, or 94% of the 5,063 HIV test requisitions reported in Table 2.1.

Of the 4,770 HIV screening tests recorded in Web-IDSS, results were available for only 3,177 (66.6%). A total of 10 newly diagnosed HIV infections were reported in the enhanced surveillance data, compared to the 14 in Table 2.2 (71%). In addition, there were 281 prevalent positive HIV cases among new admissions reported in IDSS in 2005-2006, compared to only 50 in Web-IDSS, representing 18%. Combined, this results in a differential bias that will underestimate HIV prevalence among inmates using the Web-IDSS data. Of note is that the Web-IDSS data only include confirmatory tests for 29 of these 50; operationally, all self-reported HIV infections would be laboratory confirmed by repeating the EIA test or assessing viral load and CD4+ count.

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 A, Tables A.4.i and A.5.i.). Considering only those records where Web-IDSS has a valid laboratory result, the number of newly diagnosed HIV infections per 1,000 screening tests was 3.1/1,000, higher than the IDSS estimate at 2.6 (see Figure 2.1). Diagnostic yield was higher among females at 5.1/1,000 compared to males at 3.0/1,000 and for Canadian-born Aboriginals at 6.2/1,000 compared to Canadian-born non-Aboriginals at 2.2/1,000.

HIV Testing while Incarcerated and Seroconversion

A total of 3,773 HIV tests were recorded in Web-IDSS among general population inmates (see Appendix A, Tables A.4.ii and A.5.ii), or 52% of the 7,198 reported in Table 2.1. Overall, 64.2% report a previous HIV test, suggesting that at least for the group recorded in Web-IDSS for 2005-2006 they tend to have been tested previously, either at reception or in the community prior to reception. A total of 7 newly diagnosed HIV infections among general population inmates are recorded in Web-IDSS, compared to the 15 in Table 2.2.

It is not clear that the test positivity among general population inmates approximates a seroconversion rate since the aggregate data do not include information on previous testing (see Table 2.2). The Web-IDSS data does allow an estimate of HIV seroconversion. However, none of the 7 newly diagnosed HIV cases had a recorded baseline negative test. Although there were 651 individuals recorded in Web-IDSS with repeat HIV tests who were negative on admission, all of these inmates subsequently tested negative for HIV on follow up. Therefore there were no HIV seroconversions reported via the Web-IDSS in 2005-2006.

HIV Prevalence Estimation

A prevalence estimate for HIV using Web-IDSS data can be calculated by combining all laboratory confirmed HIV cases with those self-reported HIV positive inmates for whom we do not have a laboratory result (see Appendix A, Tables A.4.iii and A.5.iii). Among those tested, the overall HIV prevalence estimate is 0.95%. As expected this result is lower than the IDSS estimate of 1.64% (see Figure 2.2). Consistent with the IDSS data, HIV prevalence was higher among females at 2.14% versus males at 0.88% (Appendix A, Table A.4.iii). HIV prevalence estimate was higher among Aboriginals at 1.27% compared to Canadian-born non-Aboriginals (0.83%) and Foreign-born (0.75%) (Appendix A, Table A.5.iii).

In order to approximate the IDSS methodology for calculating prevalence estimates by dividing the 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 HIV prevalence estimate of 0.64% with similar trends for gender and origin.

 


Footnote

5 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.

6 ”Please note that outside the prison settings in Canada and the US, the use of antiretroviral therapy for HIV is only recommended for certain stages of HIV, but not for all.”

 

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