Contact investigation outcomes of Canadian-born adults with tuberculosis in indigenous and non-indigenous populations in Alberta.

Eisenbeis, Lisa ; Gao, Zhiwei ; Heffernan, Courtney 等

In Canada, the incidence of tuberculosis (TB) is significantly higher among peoples of Indigenous ancestry, including First Nations (FN), Metis and Inuit peoples, relative to Canadian-born people of non-Indigenous ancestry. (1) In fact, in Canada, Indigenous peoples account for more than 50% of the Canadian-born cases of TB despite representing only 5% of the overall Canadian-born population, with the majority of the cases being reported in the Prairie provinces and mid to high North. (2,3)

Between the years 2005 and 2009 in Alberta, the rates of active TB among FN peoples living on-reserve were similar to those among FN peoples living off-reserve, at 14.9 and 15.4 per 100,000 respectively. (4) Almost 20% of FN TB cases in the province are identified through contact investigation, which is a significantly higher percentage compared to in other population groups. (4) Contact investigation is considered a high-priority screening activity for TB programs in high-income countries. Close contact, defined as "regular, extensive contact with the source case" whether household or non-household, carries the greatest risk of infection. (5) The traditional concentric circle approach to contact investigation identifies the closest contacts to a case; if there is evidence of transmission among them, the investigation is expanded to contacts with less intense exposure to the index case. (6) The concentric circle approach is recommended by the US Centers for Disease Control on the basis of its simplicity and intuitive appeal. (7) While newer methods have been proposed to address limitations of contact investigations in populations with different social structures, there has not yet been any empirical study of conventional contact investigations in Indigenous peoples against which those new methods might be validated.

This study compares outcomes of concentric circle contact investigation in Canadian-born Indigenous peoples living on- and off-reserve versus Canadian-born non-Indigenous persons. While tuberculosis also disproportionately affects foreign-born populations in Canada, tuberculosis in the foreign-born is more frequently due to reactivation of previous latent infection, and there is less clustering of cases. (8,9) As such, this study is focused on the performance of contact investigation in Canadian-born population groups. In most provinces, jurisdiction of communicable disease control differs for Indigenous peoples living on- and off-reserve. In Alberta, the First Nations Inuit Health Branch of Health Canada provides ancillary TB services on-reserve, which include case management, contact investigation and provision of directly observed preventive therapy to newly infected contacts. Efficacy of the traditional approach to contact investigation among these population groups is examined to determine how current program delivery is affected by population factors, such as community structure and size of contact investigations, as well as by jurisdictional differences.

METHODS

All contact investigations for Canadian-born cases of pulmonary tuberculosis in Alberta from 2001 to 2010 were evaluated. Data were abstracted from the tuberculosis registry of Alberta Health Services for all adult (>14 years) Canadian-born, culture-confirmed, pulmonary cases of TB ("eligible cases") and included population group, smear status, sex, age and HIV status. For population group, the Indigenous group is defined as persons who reported identifying with at least one Aboriginal group, that is First Nations (North American Indian), Metis or Inuit. (10) Inuit peoples are defined as Indigenous people originating from the Arctic. Metis are people of mixed First Nation and European ancestry who identify themselves as Metis, as distinct from First Nations people, Inuit or non-Aboriginal people. (10) Residence was determined by the location patients reported as being their usual place of residence at the time of diagnosis. Off-reserve people were defined as people who identified as First Nations but did not reside on-reserve most of the time at the time of diagnosis.

In addition to being a notification database, the TB Registry in Alberta systematically collects information on contacts of cases, with emphasis on contacts of pulmonary cases. National standards and provincial guidelines in circulation inform this process. Contact lists are constructed collaboratively by TB control physicians and nurses. The assessment status of contacts is reviewed by TB clinic staff and field nurses at regular intervals over the 12 months immediately following the date of diagnosis of the source case. Contacts are categorized as close if they are "household or equivalent who share same breathing space on a regular basis" with a source case, and the rest are recorded as other. (11) No specific duration of contact was outlined in the Alberta or Canadian guidelines of this era. Data for contacts of eligible cases extracted from the registry included demographics and number of contacts having completed their recommended follow-up.

Contacts may be assessed with a baseline tuberculin skin test (TST) at the time they are identified as a contact. If it is negative, a follow-up TST is performed a minimum of 56 days (5,11) after the date of diagnosis of the source case to see if the individual acquired infection due to contact with the source case. The date of diagnosis of the source case is defined as the start date of treatment, or the date of death in the event the patient died before treatment could begin. Chest X-rays completed after the last date of contact and up to 36 months after were documented as part of follow-up. Time to TST reading and chest X-ray was calculated by determining number of calendar days from date of diagnosis of the source case to diagnostic event. Other data collected included information about risk factors for a false-positive TST result, latent TB infection or progression to disease among contacts, including a history of latent TB infection or active disease with associated treatment completion, prior documented TST, Bacille-Calmette Guerin (BCG) vaccination, and prior episodes of having been named as a TB-contact in Alberta.

Any categorical differences between eligible cases and their contacts were tested using [chi square] and t-tests. Fisher's exact test was used when the expected number of counts was less than 5. Outcomes of contact investigations were compared between population groups based on smear status (positive vs. negative). Outcomes for contacts under the age of 5 were examined separately, as they are considered high-risk, vulnerable contacts and are initially prescribed preventive therapy regardless of baseline TST (a practice referred to as window-period prophylaxis). Because these contacts are considered high priority in a contact investigation, time to assessment of contacts under age 5 was also examined separately. Multivariable analysis was used to determine factors associated with outcomes of contact investigation activities. All factors significant at a 20% level in the univariate analysis were considered for multivariate analysis. A purposeful selection method was used to determine important factors in the multivariate regression. SAS version 9.3 (SAS Institute Inc., Cary, NC, USA) was used for the statistical analysis.

Ethics approval for this study was obtained from the University of Alberta Health Ethics Review Board (Panel B) with operational and administrative approvals from Alberta Health Services. Results of this study were presented to the Co-management Health Protection Subcommittee, whose membership is from the three treaty areas of Alberta. This subcommittee reports to the Co-management Committee, constituted of representative Chiefs in the region. Presentation of these results was intended to inform leadership of First Nations communities of the efficacy of tuberculosis programming conducted on-reserve.

RESULTS

Cases

A total of 171 source cases were identified (see Table 1). Of these, 111 (65%) were Indigenous, 49 (24%) on-reserve and 62 (36%) off-reserve. Of Indigenous patients living on reserve, 48 (98%) were Registered First Nations (registered under the Indian Act as First Nations (10)) and 1 was Metis; of those living off-reserve, 30 were Registered First Nations, 24 were Metis, 3 were Inuit and 5 were non-registered First Nations. Sixty cases were identified as Canadian-born other (CBO). The majority of cases were male, and CBO cases were on average older. Significant differences in proportion of smear-positive cases and co-infection with HIV were not identified between population groups.

Contacts

The contacts are summarized in Table 2 according to the smear-status population group and place of residence of their source cases. Smear-positive cases tended to have more contacts overall, while smear-negative cases had fewer contacts. Indigenous on-reserve cases had the highest number of close contacts identified and Indigenous off-reserve cases had the highest number of contacts described as "other" (not close). More contacts from the Indigenous on-reserve group had previous contact with the TB program, having been previously prescribed medication for either latent TB or active disease.

Contact profile

Among those contacts eligible for baseline TST, completion rates differed among population groups, being highest for CBO, followed by on-reserve Indigenous cases, and lowest for those Indigenous cases who lived off-reserve (p < 0.01). When follow-up TST at 8 weeks was indicated, fewer people in the off-reserve Indigenous group completed the second one. Rates of completed assessment including a TST, chest X-ray and follow-up were lowest among non-close contacts of Indigenous cases off-reserve (Table 3). Contacts of off-reserve Indigenous cases experienced the greatest delay in assessment, with time to first chest X-ray and/or TST being significantly higher than among the other population groups (Table 3). For numbers of contacts per case and time to assessment, mean and median values differed significantly. This was due to outliers with unusually large numbers of contacts identified or lengthy follow-up assessment times. Therefore, median values were used for comparison between groups.

More pediatric contacts (0-14 years of age) were identified among on-reserve Indigenous cases as compared to CBO and off-reserve Indigenous cases. Pediatric contacts of off-reserve Indigenous cases experienced the longest delay before first TST. Contacts under age 5 for the CBO group underwent chest X-ray sooner than their counterparts in both on- and off-reserve Indigenous groups (Table 3). More pediatric contacts were infected among the two Indigenous population groups as compared to CBO. Preventive therapy acceptance rates for children were highest among CBO, followed by on-reserve, Indigenous pediatric contacts and lowest for off-reserve, Indigenous pediatric contacts (p < 0.01, data not shown). Preventive therapy is initiated in contacts under age 5 and discontinued if the repeat TST at 8 weeks is negative (window-period prophylaxis), and very few contacts in this age category (23/201) showed evidence of infection.

Among all contacts, preventive therapy acceptance rates were significantly higher for close contacts of smear-positive CBO and on-reserve Indigenous cases as compared to off-reserve Indigenous cases (Table 4). Of those prescribed preventive therapy, completion rates were highest for close contacts of on-reserve Indigenous cases (p = 0.02). In multivariable analysis, population group was a significant predictor of outcomes of contact investigation, including completion of 8-week TST and of preventive therapy (Table 5). Other significant variables included smear status of the source case. TST completion rates were higher when the source case was female, and preventive therapy acceptance rates were higher for close contacts.

Overall, rates of preventive therapy completion were low in all groups, with only 39.8% of contacts who were offered preventive therapy completing same. No significant differences in TST conversion or development of active TB following contact with tuberculosis were observed between the population groups.

DISCUSSION

While few studies have examined population-group differences in contact investigations, especially for Indigenous peoples in Canada, larger numbers of contacts for Indigenous people with TB have previously been reported. (12,13) Higher numbers of contacts for Indigenous peoples living on-reserve may be due to poor housing quality, housing density and over-crowding. (14,15)

In Canada, health service delivery for peoples living on-reserve generally falls under federal jurisdiction. This study indicates that, in spite of difficulties that can arise in the face of multi-jurisdictional control for TB, (16) contact investigations were relatively successful on-reserve as compared to off-reserve, especially with respect to timely completion of follow-up recommendations and preventive therapy. Successful contact investigations on-reserve may be related to staff who live on-reserve assisting in program delivery and to the strong partnership between the provincial TB program and federal agency with jurisdiction over public health on-reserve. Though number of close contacts identified was often larger for Indigenous peoples living on-reserve for the reasons indicated above, it may be easier for staff on-reserve to identify household(s) of people in close proximity to a case. While travel for investigations or assessment is sometimes necessary, public health units on-reserve provide transportation to X-ray, lab facilities or clinics. These are important considerations given that social factors such as lack of transportation or resources and communal living may play a greater role in contributing to an outbreak than organism virulence or ethnicity. (17,18)

Follow-up completion and preventive therapy acceptance rates were lowest for contacts of Indigenous cases living off-reserve. In spite of both presumed and reported barriers to access of health services on-reserve, time to assessment was better on-reserve than off. This indicates that barriers to access may in fact be greater for Indigenous peoples living off-reserve, perhaps due to lack of such local public health facilities as exist on-reserve, or because people off-reserve are more likely to fall into a "service gap". (16) In 2012, Health Canada published a Strategy Against Tuberculosis for First Nations On-Reserve. (19) However, Health Canada's tuberculosis prevention and control mandate does not include First Nations people living off-reserve or the Inuit, and tuberculosis control for these populations falls under the purview of provincial and territorial programming. Furthermore, the relatively poor outcomes of contact investigation for off-reserve Indigenous cases may be related to more frequent association with inner-city populations in the major cities of the province, changes of address/mobility, or lack of prioritization of tuberculosis as a health concern. (18,20,21) As potential solutions, social network analysis, geographic information systems and genomics have been recommended for enhancing TB contact investigations in population groups with increased mobility and who are under-housed. (18) However, real-time use of genomics is costly and not widely available, and use of this approach provides retrospective insight into outbreaks rather than preventing transmission from a case. (18,22,23) With challenges faced in conducting contact investigation for population groups who have increased mobility and more casual contacts, a risk-oriented model that prioritizes contacts, or else regular enhanced surveillance for active TB may be alternative strategies to the traditional concentric circle approach.

Limitations

The discrepancy in contact investigation outcomes for Indigenous people living on- and off-reserve may not be generalizable to other provinces and territories. Geographic isolation is associated with higher tuberculosis rates and may play a greater role in limiting access to services in other regions. (2,10) Furthermore, tuberculosis programming and services in reserve communities vary between provinces. Finally, there is a great deal of heterogeneity between First Nations communities, and not all communities suffer from disproportionate rates of tuberculosis. (3,4)

BCG status was not consistently entered in the database, and BCG history may impact on interpretation of the TST. Vaccination would occur mainly in patients from the on-reserve Indigenous group, though currently only four reserve communities in Alberta still administer BCG vaccination. In general, close contacts of tuberculosis with a positive skin test would be offered preventive therapy regardless of BCG history, as interferon gamma release assays were not widely available in the province during most of the study period.

This study had several other limitations, including its retrospective design. During the study period, policy regarding contact investigation as well as program management changed, which led to heterogeneity in the observed contact investigations over the course of the study period. Data collection limitations included differences in the quality of entered data depending on the health care worker who managed a case, as well as a lack of consistent collection of health history and ethnicity of contacts. Definitions of "close" vs. "other" contacts were imprecise and may have varied. Finally, contact lists may be abbreviated depending on logistics and workload of the health care workers conducting the contact investigation and by how forthcoming an index case is in identifying their contacts. Furthermore, expanding the initial contact list to more remote contacts because an index case is thought to have been particularly infectious and assessment of risk of transmission in various settings are largely discretionary.

CONCLUSIONS

The devastating history of tuberculosis in Indigenous peoples in Canada impacts the acceptance of TB program recommendations and participation in contact investigation. Stigma and the association of tuberculosis with colonization history, sanatoria and residential schools are important considerations in provision of programming that is minimally intrusive and culturally sensitive. (24-26) Other challenges to program delivery may include language and literacy barriers, and increased population mobility between communities, and sometimes between provinces. (17) In Alberta, some of the observed "success" of contact investigation on-reserve may reflect delivery of services on-reserve, improving access and engaging Indigenous health care workers in program delivery. These factors along with community engagement are important in helping to identify TB as an important health issue and go a long way toward building trust. (17,19) The strength of programming and higher preventive therapy completion rates for close contacts on-reserve may contribute to declining tuberculosis rates on-reserve in Alberta. (27) Disproportionate rates of TB among Indigenous people living on-reserve as compared to CBO persist in Alberta in spite of findings that outcomes of contact investigation in the former group compare favourably with the other population groups. Low transmission rates were observed during the study period, indicating that contact investigation is not the only activity required to reduce rates of TB in this population. Other screening programs, such as screening of patients with high-risk medical conditions, may be important in TB control for Indigenous populations, though further research on this may be required.

REFERENCES

(1.) Public Health Agency of Canada. Tuberculosis in Canada, 2012. Ottawa, ON: Minister of Public Works and Government Services Canada, 2015. Available at: http://phac-aspc.gc.ca/tbpc-latb/pubs/tbcan12/index-eng.php (Accessed May 15, 2015).

(2.) Long R, Hoeppner V, Orr P, Ainslie M, King M, Abonyi S, et al. Marked disparity in the epidemiology of tuberculosis among Aboriginal peoples on the Canadian prairies: The challenges and opportunities. Can Respir J 2013; 20(4):223-30. PMID: 23717818.

(3.) Statistics Canada. 2006 Census of Population, 2006. Available at: http:// www12.statcan.gc.ca/census-recensement/2006/index-eng.cfm (Accessed January 6, 2015).

(4.) Tuberculosis Surveillance Report Alberta 2005 to 2009 With Preliminary Summary 2010. Edmonton, AB: Alberta Health and Wellness, 2012.

(5.) Canadian Tuberculosis Standards, 7th ed. Ottawa, ON: Canadian Thoracic Society and Public Health Agency of Canada, 2014.

(6.) Veen J. Microepidemics of tuberculosis: The stone in the pond principle. Tuber LungDis 1992; 73:73-76. PMID: 1643300. doi: 10.1016/0962-8479(92)90058-R.

(7.) Centers for Disease Control and Prevention, Guidelines for the Investigation of Contacts of Persons With Infectious Tuberculosis-Recommendations from the National Tuberculosis Controllers Association and CDC-Guidelines for Using the QuantiFERON-TB Gold Test for Detecting Mycobacterium Tuberculosis Infection. Atlanta, GA: MMWR, 2005; 54 (No. RR-15).

(8.) Kunimoto D, Sutherland K, Wooldrage K, Fanning A, Chui L, Manfreda J, Long R. Transmission characteristics of tuberculosis in the foreign-born and the Canadian-born populations of Alberta, Canada. Int J Tuberc Lung Dis 2004; 8(10):1213-20. PMID: 15527153.

(9.) Sandgren A, Schepisi MS, Sotgiu G, Huitric E, Migliori GB, Manissero D, et al., Tuberculosis transmission between foreign- and native-born populations in the EU/EEA: A systematic review. Eur Respir J 2014; 43(4):1159-71. PMID: 24114966. doi: 10.1183/09031936.00117213.

(10.) Aboriginal Affairs and Northern Development Canada. Government of Canada. Available at: http://www.aadnc-aandc.gc.ca/eng/1100100014642/ 1100100014643 (Accessed October 22, 2015).

(11.) Tuberculosis Prevention and Control Guidelines for Alberta. Edmonton, AB: Government of Alberta, Alberta Health and Wellness, 2007.

(12.) Grzybowski S, Barnett G, Styblo K. Contacts of cases of active pulmonary tuberculosis. Bull Int Tuberc 1975; 50(1):90-106. PMID: 1218291.

(13.) Cook V, Shah L, Gardy J. Modern contact investigation methods for enhancing tuberculosis control in Aboriginal communities. Int J Circumpolar Health 2012; 71. PMID: 22663943. doi: 10.3402/ijch.v71i0.18643.

(14.) Clark M, Riben P, Nowgesic E. The association of housing density, isolation and tuberculosis in Canadian First Nations communities. Int J Epidemiol 2002; 31(5):940-45. PMID: 12435764. doi: 10.1093/ije/31.5.940.

(15.) Housing as a Social Determinant of First Nations, Inuit and Metis Health. National Collaborating Centre for Aboriginal Health, 2010. Available at: http:// www.nccah-ccnsa.ca/docs/fact%20sheets/social%20determinates/NCCAH_fs_ housing_EN.pdf (Accessed October 5, 2014).

(16.) Roscelli M. Political advocacy and research both needed to address federal-provincial gaps in service: Manitoba First Nations personal care homes.Can J Public Health 2005; 96(Suppl 1):S55-59. PMID: 15686155.

(17.) Orr P. Adherence to tuberculosis care in Canadian Aboriginal populations, Part 1: Definition, measurement, responsibility, barriers. Int J Circumpolar Health 2011; 70(2):113-27. PMID: 21524359.

(18.) Gardy J, Johnston J, Ho Sui S, Cook V, Shah L, Brodkin E, et al. Whole-genome sequencing and social network analysis of a tuberculosis outbreak. NEngl J Med 2011; 364(8):730-39. doi: 10.1056/NEJMoa1003176.

(19.) Health Canada's Strategy Against Tuberculosis for First Nations On-Reserve. Ottawa, ON: Health Canada, Minister of Health, 2012.

(20.) Malejczyk K, Gratrix J, Beckon A, Moreau D, Williams G, Kunimoto D, Ahmed R. Factors associated with non-completion of latent tuberculosis infection treatment in an inner-city population in Edmonton, Alberta. Can J Infect Dis MedMicrobiol 2014; 25(5):281-84. PMID: 25371692.

(21.) Hirsch-Moverman Y, Shrestha-Kuwahara R, Bethel J, Blumberg HM, Venkatappa TK, Horsburgh CR, et al. Latent tuberculous infection in the United States and Canada: Who completes treatment and why? Int J Tuberc LungDis 2015; 19:31-38. PMID: 25519787. doi: 10.5588/ijtld.14.0373.

(22.) Rothenberg RB, McElroy PD, Wilce MA, Muth SQ. Contact tracing: Comparing the approaches for sexually transmitted diseases and tuberculosis. Int J Tuberc Lung Dis 2003; 7(12 Suppl 3):S342-48. PMID: 14677820.

(23.) Andre M, Ijaz K, Tillinghast M, Krebs V, Diem L, Metchock B, et al. Transmission network analysis to complement routine tuberculosis contact investigations. Am J Public Health 2007; 97(3):470-77. PMID: 17018825. doi: 10.2105/AJPH.2005.071936.

(24.) Adelson N. The embodiment of inequity: Health disparities in Aboriginal Canada. Can J Public Health 2005; 96:S45-61. PMID: 16078555.

(25.) Hackett P. From past to present: Understanding First Nations health patterns in a historical context. Can J Public Health 2005; 96(1):S17-21. PMID: 15686148.

(26.) Gibson N, Cave A, Doering D, Ortiz L, Harms P. Socio-cultural factors influencing prevention and treatment of tuberculosis in immigrant and Aboriginal communities in Canada. Soc Sci Med 2005; 61(5):931-42. PMID: 15896894. doi: 10.1016/j.socscimed.2004.10.026.

(27.) Jensen M, Lau A, Langlois-Klassen D, Boffa J, Manfreda J, Long R. A population-based study of tuberculosis epidemiology and innovative service delivery in Canada. Int J Tuberc Lung Dis 2012; 16:43-49. PMID: 22236844. doi: 10.5588/ijtld.11.0374.

Received: August 6, 2015

Accepted: December 20, 2015

Lisa Eisenbeis, MSc, [1] Zhiwei Gao, PhD, [2] Courtney Heffernan, MA, [1] Wadieh Yacoub, MD, [3] Richard Long, MD, [1] Geetika Verma, MD [1]

Author Affiliations

[1.] Department of Medicine, University of Alberta, Edmonton, AB

[2.] Department of Medicine, Memorial University of Newfoundland, St. John's, NL

[3.] First Nations Inuit Health Branch, Health Canada, Alberta Region

Correspondence: Dr. Geetika Verma, Department of Medicine, University of Alberta, 1584 Firwood Cres, Peterborough, ON K9K 1S8, Tel: 705-875-6827, E-mail: gverma@ualberta.ca

Acknowledgements: The authors thank the staff of the Provincial Tuberculosis Clinic, Alberta Health Services and the First Nations Inuit Health Branch, Alberta region, for their assistance with the data.

Source of funding: University of Alberta Hospital Foundation.

Conflict of Interest: None to declare. Table 1. Canadian-born adult pulmonary TB source case characteristics by population group, 2001-2010 INON n (%) INOFF n (%) CBO n (%) p-value # assessed 49 (29) 62 (36) 60 (35) Average age 45 (19) 49 (16) 55 (18) 0.01# (years [+ or -] SD) Age group (years) 15-44 26 (53) 25 (40) 16 (27) 0.02# 45-64 15 (31) 26 (42) 28 (47) 0.22 65+ 8 (16) 11 (18) 16 (27) 0.33 Sex Male 32 (65) 33 (53) 47 (78) 0.01# Female 17 (35) 29 (47) 13 (22) Smear Positive 28 (57) 40 (65) 31 (52) 0.35 Negative 21 (43) 22 (35) 29 (48) HIV status Positive 4 (8) 8 (13) 1 (2) 0.18 Negative 38 (78) 48 (77) 51 (85) Unknown 7 (14) 6 (10) 8 (13) INON = Indigenous on-reserve; INOFF = Indigenous off-reserve; CBO = Canadian-born other. Bold in table indicates p < 0.05. Note: p < 0.05 are indicated with #. Table 2. Characteristics of contacts of Canadian-born pulmonary TB cases, 2001-2010, by population group and smear status of source case Smear positive INON n INOFF n CBO n p-value Total number of 1766 3952 1600 contacts Contact type Close 898 690 474 Other 868 3262 1126 Average number of Close 32.1 17.3 15.3 0.01# contacts per case by Other 31 82 36 0.048# contact type Median number of Close 28 11.5 7 <0.01# contacts per case by Other 23.5 28 10 0.26 contact type Median number with Close 3 1 0 <0.01# history of TB Other 2.5 1 0 0.002# infection/disease per case by contact type Smear negative INON n INOFF n CBO n p-value Total number of 281 125 234 contacts Contact type Close 226 113 163 Other 55 12 71 Average number of Close 10.8 5.1 5.6 0.04 *# contacts per case by Other 2.6 0.5 2.4 0.09 contact type ([dagger]) Median number of Close 10 3 3 0.02# contacts per case by Other 1 0 1 0.03# contact type Median number with Close 1 0 0 0.017# history of TB Other 0 0 0 0.03# infection/disease per case by contact type INON = Indigenous on-reserve; INOFF = Indigenous off-reserve; CBO = Canadian-born other. * Differences in means were obtained through t-tests. ([dagger]) Differences in medians were obtained through non- parametric methods. Bold in table indicates p < 0.05. Note: p < 0.05 are indicated with #. Table 3. Timeliness of assessment of close contacts (ages [greater than or equal to] 5 and <5 years) of Canadian-born smear-positive pulmonary TB cases, 2001-2010 Age [greater than or equal to] 5 years INON n INOFF n CBO n p-value Number identified 797 646 418 Number of first 365 320 264 TSTs done Time to first TST 9 17 8 <0.01# (median) Number of initial 361 205 61 CXRs done Time to first CXR 12 25.5 14 <0.01# (median) Age < 5 years INON n INOFF n CBO n p-value Number identified 101 44 56 Number of first 79 32 50 TSTs done Time to first TST 7 10 3 <0.01# (median) Number of initial 87 31 52 CXRs done Time to first CXR 8 20 1 <0.01# (median) INON = Indigenous on-reserve; INOFF = Indigenous off-reserve; CBO = Canadian-born other; TST = tuberculin skin test; CXR = chest X-ray. Bold in table indicates p < 0.05. Note: p < 0.05 are indicated with #. Table 4. Preventive therapy recommendation, acceptance and completion rates for contacts [greater than or equal to] 5 years of age * by proximity of contact and population group, 2001-2010 INON INOFF CBO p-value # recommended Close 209 120 68 latent Other 125 189 115 TB infection treatment # accepted Close 152 71 (59.2%) 46 (67.6%) 0.04# (72.7%) Other 56 109 (57.7%) 72 (62.6%) 0.01# (44.8%) # completed Close 112 387 25 0.045# Other 37 64 42 0.60# % complete/ Close 53.6 40.8 36.8 0.02# recommended Other 29.6 33.9 36.5 0.51# * Excludes contacts <5 years of age because of the practice of offering window-period prophylaxis and discontinuing treatment if repeat testing is negative. INON = Indigenous on-reserve; INOFF = Indigenous off-reserve; CBO = Canadian-born other. Bold in table indicates p < 0.05. Note: p < 0.05 are indicated with #. Table 5. Multivariable analysis of contact investigation outcomes preventive therapy acceptance including 8-week TST completion, and preventive therapy completion, 2001-2010 8-week TST Preventive Preventive Predictor completion treatment treatment estimate/ accepted completed p-value estimate/ estimate/ p-value p-value Reserve CBO 15.0/0.0123# -2.0/0.7933 -13.2/0.0566 status 0.0 0 0.0 INON 17.7/0.0031# 9.5/0.1979 8.9/0.1826 2.6/0.6337 11.5/1.1377 20.8/0.0064# INOFF 0 0.0 0.0 -15/0.0123# 2.01/0.7933 10.7/0.166 Sex of Female 11.0/0.0358# -0.9/0.8914 7.5/0.2101 source Male 0 0 0 case Source Negative 0.7/0.8841 -16.6/0.0129# -24.8/0.0001# case Positive 0 0 0 smear status Source 15-44 -4.2/0.479 2.0/0.8153 -3.7/0.6494 case age 45-64 -11.3/0.0681 -2.9/0.7381 -4.1/0.6126 category 65+ 0 0 0 (years) Contact Close 0.0/0.7997 0.0/0.0289# 0.0/0.6287 type Other 0 0 0 Sex of Female 0 0 0 contact Male 0.0/0.4055 0.0/0.157 0.0/0.0958 INON = Indigenous on-reserve; INOFF = Indigenous off-reserve; CBO = Canadian-born other. Bold in table indicates p < 0.05. Note: p < 0.05 are indicated with #.