Concept: Human Immunodeficiency Virus (HIV) - Method of Identification

Introduction

This concept provides an overview of the Human Immunodeficiency Virus (HIV) and describes the methods used at MCHP to investigate HIV in the administrative data held in the Manitoba Population Research Data Repository. The concept describes the methods used over time to define HIV, including the list of ICD-9-CM and ICD-10-CA diagnostic codes to identify HIV in the hospital abstracts data and the medical services data, and the lists of laboratory test / laboratory result codes that are used from the different Cadham Provincial Laboratory data sets over time to investigate the presence of HIV in the population. SAS® code is also available for working with the laboratory data.

Definition of Human Immunodeficiency Virus (HIV)

Human Immunodeficiency Virus (HIV) is a retrovirus (usually HIV 1) that mainly infects mononuclear white blood cells, specifically macrophages and helper T-lymphocytes. By attacking the cells of the immune system, the viral infection causes individuals to become vulnerable to opportunistic pathogens and cancers. When the number of helper T-lymphocytes is significantly depleted and the body can no longer fight common infections, the individual has progressed to AIDS (Acquired Immunodeficiency Syndrome). Without treatment with anti-HIV therapy, the progression from initial HIV infection to AIDS varies from less than one year to 15 years (Manitoba Health - Communicable Disease Control Branch, 2010).

As an infectious disease, HIV in transmitted from one individual to another through contaminated bodily fluids such as: unprotected sexual contact, sharing of contaminated needles among injection drug users, unsterilized needles (for acupuncture, electrolysis, piercings or tattoos), contaminated blood transfusion, tissue or organ transplantation, perinatal mother-to-child transmission (in utero, intrapartum or through breastfeeding), and occupational exposure in health care settings Public Health Agency of Canada Website - What is HIV/AIDS? In Manitoba, the most common methods of transmission are unprotected sexual activity and sharing of contaminated injection drug equipment (Manitoba Health - Communicable Disease Control Branch, 2010).

Because of the significant public health implications, HIV is a notifiable disease in Canada since 2000 (Lix et al., 2012). All positive laboratory-confirmed cases of HIV are reportable to Manitoba Health Public Health Surveillance Unit. For more information on HIV, see the Public Health Agency of Canada Website - What is HIV/AIDS? and the Manitoba Health - Public Health Website - Human Immunodeficiency Virus (HIV).

MCHP HIV Algorithms

The following three methods have been used at MCHP over time to determine testing for, and identifying individuals with HIV.

1. Brownell et al. (2012)

In the deliverable How are Manitoba's Children Doing? by Brownell et al. (2012), a Manitoba Health report on the provincial count of new cases of HIV by age and sex distribution between 2000 and 2009 was examined (Manitoba Health - Public Health and Primary Health Care Division, 2010). For youths aged 15 to 19 years, 23 cases of HIV for females were identified and six for males. For youths less than 15 years of age, there were seven new cases for females and one case for males. According to this provincial report, between 2000 and 2009, the incident of new cases of HIV was four times greater for female youths. In 2010, there were two new cases of HIV for females aged 15 to 19 years of age and one for males. For those less than 15, only one new case was identified in females and none for males.

Because the percent of youths with a reported case of HIV in Manitoba is relatively low, it precludes presentation by region or income quintile. For more information read the section HIV in Brownell et al. (2012) .

2. Lix et al. (2012)

In the deliverable A Systematic Investigation of Manitoba's Provincial Laboratory Data by Lix et al. (2012), the Cadham Provincial Laboratory (CPL) data from 1992/93 to 2008/09 was used to identify the frequency of records for HIV tests with a linkable PHIN; that is, a PHIN that can link the CPL data to the administrative records at the MCHP Population Health Repository. Prior to 2006/07, the PHINs in the CPL data were not linkable to the administrative data. In 2006/07, only a small amount of tests were linkable and this number increased significantly in 2007/08 and in 2008/09. Thus, record linkage is not possible prior to 2007/08 in Manitoba.

Data from the CPL Serology Section was used to identify the CPL number of tests and the frequency of positive laboratory-confirmed cases in Manitoba. As an initial screening test, CPL uses an ELISA (enzyme-linked immunosorbent assay) on serum to detect antibodies for HIV and all positive ELISA test results are confirmed by a western blot (Manitoba Health - Communicable Disease Control Branch, 2010). In Manitoba, CPL is responsible for all confirmatory HIV antibody testing.

Table 1 reports the AUXCD5 codes used to identify HIV in the Serology Section of CPL. For more information on CPL, see the CADHAM Provincial Laboratory (CPL) - Overview of Services and Data concept.

NOTE: Individuals infected with HIV usually develop detectable antibodies within two weeks to three months after initial infection (antibodies detected by ELISA and western blot). However for some, this detection window might be more prolonged (Manitoba Health - Communicable Disease Control Branch, 2010).

Table 1 - HIV: Serology Section

STARTDT 1	STOPDT 2	AUXCD5	DESCR40
11/25/1993	01/01/2099	HIV	ANTI-HIV1/HIV2
01/01/1990	05/01/2006	HIV1C	HIV1 CONFIRM
01/01/1990	05/01/2006	HIV2C	HIV2 CONFIRM
10/23/2007	01/01/2099	HIVA	ANTI-HIV1/HIV2
01/01/1990	01/01/2099	HIVAG	HIV1 ANTIGEN DETECTION
04/02/1998	01/01/2099	HIVDN	HIV-DNA
04/30/2003	01/01/2099	HIVGT	HIV-1 DRUG RESISTANCE
01/01/1990	05/01/2006	HIVIF	HIV1 IFA
12/21/2006	01/01/2099	HIVN	ANTI-HIV1/HIV2
09/24/1996	01/01/2099	HIVQR	HIV QUANTITATIVE RNA - PCR
02/01/2008	01/01/2099	HIVRT	ANTIBODY TO HIV (RAPID TEST)
05/01/2006	01/01/2099	HIVVL	HIV VIRAL LOAD
01/01/1990	01/01/2099	HVCC	HIV1/HIV2 CROSSREACT/CONFIRM
05/07/2009	01/01/2099	HVCOM	COMBO ANTI-HIV-1/O/2 AND HIV-1 P24
01/01/1990	12/03/1993	HVCS	HIV1/HIV2 SCREEN
05/03/1993	05/01/2006	HVCS2	HIV1-HIV2 SUPPLEMENTARY SCREEN TEST
03/20/1997	05/01/2006	HVRNA	HIV QUANTITATIVE RNA-PCR
12/21/2006	01/01/2099	ROHIV	ANTI-HIV1/HIV2


¹ - The date that the code was created in the file.
² - The date that the code became inactive.

Comparison of Lab Data to Hospital Discharge Abstracts and Medical Services Data

Incident HIV cases identified from the hospital abstracts data and medical services data were compared to the CPL data for the fiscal years 2007/08 and 2008/09. ICD-9-CM codes 042 and ICD-10-CA codes B20-B24 were used to identify the diagnoses of HIV. In the two-year period, a total of 203 new cases of HIV were identified in the hospital abstracts and medical services/physician claims data. Of these cases, 33.0% had a positive HIV test result in the CPL data 30 days before or after the diagnosis date. When a 180-day period was used, 45.8% had a positive test in the CPL data, indicating a moderate agreement between positive test results and diagnoses for HIV in hospital abstracts and medical services/physician claims data. For more information on how HIV was investigated in the CPL data, read the section titled Case Study #1: Record Linkage for HIV Tests in Lix et al. (2012).

3. Fransoo et al. (2019)

In the deliverable The 2019 RHA Indicators Atlas by Fransoo et al. (2019), they investigated the prevalence of HIV in the population.

DATA SOURCE: - The Cadham Provincial Laboratory (CPL) - Laboratory Management Information System (LIMS) data from August 31, 2009 to December 31, 2017 was used to identify records with a positive HIV laboratory test results. The lab data is considered the "gold standard" for identifying cases of HIV.

METHOD: - The method for determining a positive HIV laboratory test in the RESULTS file of the CPL - LIMS data was established in partnership with the CPL. This involved analyzing the values from two variables in the RESULTS file: ANALYSIS and FORMATTED_ENTRY. The following algorithm was applied to identify positive HIV test results:

Specific Inclusion Criteria:

if analysis = 'HIV_DRUGRES_REF' then hiv_positive = '1';
if analysis = 'HIV_VL' and formatted_entry ^in: ( 'Invalid', 'Ottawa result', 'nlhrs', 'Specimen inhibitory' ) then hiv_positive = '1';
if analysis = 'HIV' and formatted_entry = 'Positive' then hiv_positive = '1';
if analysis = 'HIV_COMBO' and formatted_entry in ( 'Positive', 'Screen Test Positive' ) then hiv_positive = '1';
if analysis = 'HIV_PRO_REF' and formatted_entry = 'Detected' then hiv_positive = '1';

Specific Exclusion Criteria:

- remove "Target Not Detected" HIV_VL tests performed before 18 months
- keep only those records that were reported to Manitoba Health (e.g. records with an invalid scrambled PHIN are removed) to reduce duplicate tests and remove 'child' tests.

Findings in this Research

For more information on the HIV prevalence findings from this research, please see section 4.12 Human Immunodeficiency Virus (HIV) Prevalence

SAS Code

SAS code for identifying HIV tests in the original Cadham Provincial Laboratory (CPL) data is available in the SAS code and formats section below (internal access only).

Limitations / Cautions

• CPL performs all clinical serologic confirmatory testing for HIV in Manitoba, but laboratory data may not capture all cases in a jurisdiction.
  
  
• The number of incident cases and general trends of HIV within the population should be construed with caution due to an under-diagnosis of cases, underreporting, incomplete reporting of anonymous testing, and the possibility of dual reporting (under nominal and non-nominal testing) (Manitoba Health - Communicable Disease Control Branch, 2010).
  
  
• A value of P [Positive] to identify a positive test result in the POSNEG field [Positive-Negative] for specific AUXCD5 codes in the original CPL data was used to determine a positive test result.
  
  
• The AUXCD5 codes used to identify HIV in the Serology Section should be verified at the beginning of each new study to ensure they are up-to-date.