Guidance: Duplicate Review

National HIV Surveillance System (NHSS)

Attachment 4(c)
Technical Guidance for HIV Surveillance Programs: Duplicate Review

Technical Guidance for HIV
Surveillance Programs
Duplicate Review

HIV Surveillance Branch
Atlanta, Georgia

Contents
Background ................................................................................................................................... 3
Intrastate Duplicate Review .......................................................................................................... 3
Structural Requirements .............................................................................................................. 3
Process Standards ........................................................................................................................ 4
Outcome Standard ....................................................................................................................... 6
Interstate Duplicate Review .......................................................................................................... 6
National Data Processing and RIDR/CIDR Report Generation .................................................. 8
Structural Requirements .............................................................................................................. 9
Process Standards ........................................................................................................................ 9
Outcome Standard ..................................................................................................................... 11

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National HIV Surveillance System Technical Guidance – Duplicate Review, January 2022

Background
HIV surveillance systems must provide a reliable measure of the number of persons in need of
HIV prevention and care services at the local, state, and national levels. An accurate HIV
surveillance system is one that minimizes the degree to which it overcounts or undercounts
reported cases of HIV infection and maximizes the reliability with which data for a given
person are linked over time. Failing to properly link an incoming surveillance report to an
existing case leads to overcounting and incomplete case information or incorrectly linking an
incoming surveillance report to an existing case may lead to undercounting and data
contamination.
Because doctors, hospitals, laboratories, and other reporting entities may be required to report
all diagnoses of HIV infection, duplicate case reports within a state (intrastate) or between
states (interstate) may not be identified during routine case entry into the surveillance database.
To prevent overcounting and undercounting of cases, identification of potential intrastate and
interstate duplicate case reports, merging case reports that have been deemed to be duplicates at
all levels, and providing duplicate review resolution to CDC (i.e., Same as or Different than)
must be carried out on a regular basis.
Within a state, surveillance software and routine surveillance practices are used to identify and
eliminate duplicate case reports. These processes can use personally identifiable information
(PII) and other useful information maintained at a state or local level. At the national level,
CDC does not receive PII (e.g., name, Social Security Number) so duplicate case reports
cannot be identified with the same degree of accuracy. Thus, CDC requires all surveillance
areas to perform both intrastate and interstate review and de-duplication on a routine basis and
ensure that each person in the surveillance database is given one unique state-assigned case
number (stateno).

Intrastate Duplicate Review
The prerequisites (structural requirements), best practices (process standards), and outcome
standards for intrastate duplicate review are described next, followed by more in-depth
guidance on specific topics.

Structural Requirements
1. Case, laboratory, and other reports received on a person
2. HIV Surveillance System Software, eHARS

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3. eHARS User Guide1
4. eHARS Technical Reference Guide2
5. Data processing policies, procedures, and tools for record linkage (see Technical
Guidance File Record Linkage)
6. Procedures for evaluating accuracy of HIV surveillance systems (see Technical
Guidance File Evaluation and Data Quality)
7. Variables to ascertain potential intrastate duplicate case reports:
• The eHARS report “Identify Intrastate Duplicate Cases Based on CDC Matching
String” is available under Operational in the eHARS REPORT module index.
The report identifies and generates a list of potential duplicate case reports within
a jurisdiction’s eHARS using CDC matching strings. Cases are first matched
using the following Person View variables: last name soundex (last_name_sndx),
date of birth (dob), sex at birth (birth_sex) and state of residence at HIV diagnosis
(rsh_state_cd). Country of residence at HIV diagnosis (rsh_country_cd) is used if
rsh_state_cd is ‘FC – Foreign Country’. If no match is found, then cases are
matched on last name soundex, date of birth, sex at birth and state or country of
residence at stage 3 AIDS diagnosis (rsa_state_cd / rsa_country_cd). Cases that
match on the CDC string but have previously been confirmed by the jurisdiction
as different persons are excluded from the list.
• In addition to running the above eHARS report, jurisdictions are encouraged to
perform more in-depth duplicate reviews using information that are readily
available at the state level, e.g., first name (first_name), last name (last_name),
middle name (middle_name), first and last name soundex (first_name_sndx,
last_name_sndx), date of birth (dob), sex at birth (birth_sex), race/ethnicity
(race), full Social Security Number (ssn), death date (dod). When these values are
identical, other variables may be used to determine if the cases are duplicates.
Examples of such variables include: medical record number (medrecno); inmate
identification number (prisno); date of diagnosis of HIV infection (hiv_dx_dt);
and date of diagnosis of stage 3 AIDS diagnosis (aids_dx_dt).

Process Standards
1. Frequency of Procedure
•

Monthly run eHARS canned report Identify Intrastate Duplicate Cases Based on
CDC Matching String and either merge duplicate case reports that represent the

1

All health department HIV Surveillance personnel who are United States citizens are eligible to access
the HIV Surveillance Branch (HSB) workspace on CDC SharePoint at
https://cdcpartners.sharepoint.com/sites/NCHHSTP/HICSB/default.aspx. If you have questions or
problems with access, please contact your assigned CDC epidemiologist or the HIV Surveillance
Branch main number at (404) 639-2050.
2

See footnote 1, immediately above. eHARS technical documentations available in SharePoint.
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same person or update the duplicate status in eHARS to “2-Different than” if the
case reports represent two different persons.
•

Jurisdictions should also perform more in-depth intrastate duplicate review using
exact and fuzzy (i.e., inexact) matching methods.

2 . Records that Represent the Same Person
•

Case reports that have been confirmed to be duplicates should be merged. When
merging, retain the STATENO belonging to the case that was first entered into
eHARS (the case with the earlier Person View enter_dt).

•

eHARS contains a Transfer Document feature which can be found under Document
and Case Maintenance in the ADMIN module index. Transfer Document allows the
user to merge duplicate case reports by entering the appropriate state and stateassigned case number (stateno), eHARS unique identifier (ehars_uid) or document
unique identifier (document_uid) of the source case (i.e., the case with the later
Person View enter_dt), and the appropriate state and state-assigned case number
(stateno) or eHARS unique identifier (ehars_uid) of the target case (i.e., the case
with the earlier Person View enter_dt).

•

The Adult Case Report Form (ACRF) and the Pediatric Case Report Form (PCRF)
documents in eHARS contain a Duplicate Review tab that allows the user to enter
duplicate status information regarding two reported cases of HIV infection. An
example is when a person was a pediatric “Seroreverter” and was later infected with
HIV (see Technical Guidance File Pediatric HIV Confidential Case Report Form
and Perinatal HIV Exposure Reporting Form). This person would be given two
different state (or city/county) numbers; one associated with the “Seroreverter” and
another associated with the HIV infection diagnosis.
o Jurisdictions may utilize the Duplicate Review tab to maintain a log of
cases (e.g., STATENOs) that have been merged with another case within
the jurisdiction’s eHARS. To do this, the surveillance staff will need to
enter an ACRF or PCRF document for the target case and, under the
Duplicate Review tab, select duplicate status as ‘1 – Same as’, select the
jurisdiction’s name for site and enter the STATENO of the source case as
the state ID number.

3. Records that Represent Different Persons
•

When a pair of case reports in the “Identify Intrastate Duplicate Cases Based on
CDC Matching String” report has been determined to represent two different
persons, the jurisdiction should notify CDC by entering an ACRF or PCRF
document into eHARS for at least one of the cases and updating the duplicate status
under the Duplicate Review tab to “2 – Different than” and entering the
jurisdiction’s name for site and the STATENO of the other case in the pair as the
state ID number.

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Outcome Standard
•

Of all persons with diagnosed HIV infection who were reported to the local surveillance
program through the end of the evaluation year (cumulative), less than or equal to (≤)
1% have duplicate case reports, assessed 12 months after the evaluation year.
Duplication rates should be calculated using methods shown in the Technical Guidance
File Evaluation and Data Quality.

Interstate Duplicate Review
The same HIV-infected person may be reported multiple times to public health departments in
different states. Interstate duplicate case reports can result from persons moving or receiving
care in different states over time and being reported to multiple state health departments in
accordance with local reporting requirements. Through routine duplicate review, health
departments may determine that a potential case may have been previously diagnosed in
another jurisdiction rather than a new or late diagnosis reported to their surveillance systems.
Further, interstate duplicate review is a critical component of Data-to-Care and other routine
surveillance activities (e.g., updating current address, HIV medical care status, viral
suppression, and vital status) to ensure persons with HIV infection are tested, diagnosed, linked
and retained in care, and virally suppressed.
Interstate duplicate review is also designed to ensure that a case of HIV infection is counted
only once in the National HIV Surveillance System (NHSS). The potential for duplicate
reporting in the NHSS may increase as persons with HIV infection remain healthier longer due
to advances in the clinical treatment of HIV infection and increased laboratory-driven
surveillance. Therefore, routine interstate case de-duplication activities are critical to ensure
accurate case counts at the national level. In 1986 and 2001, respectively, the Council of State
and Territorial Epidemiologists (CSTE) passed resolutions for state-to-state reciprocal
notification processes for AIDS and HIV case reporting to encourage resolution of duplicate
case counting (See https://cdn.ymaws.com/www.cste.org/resource/resmgr/PS1/2001-ID04.pdf). HIV surveillance program staff should communicate with other states to resolve
potential duplicates using guidance outlined below in accordance with CSTE position
statements and detailed procedural guidance disseminated by CDC.
Potential interstate duplicate case reports may be identified in three ways. Before entering a
new case into eHARS, surveillance staff may use the Secure Online Soundex Match
application [accessible 24/7 through CDC’s Secure Access Management Services (SAMS)
Secure Data eXchange (SDX)] to determine if the case has been reported by another
jurisdiction. For access to the Secure Online Soundex Match application, state and local health
departments should contact the CDC epidemiologist assigned to your jurisdiction or the CDC
Division of HIV Prevention (DHP) Helpdesk at 1-877-659-7725 to complete the Soundex
Match application form.
If a potential match is identified by the Secure Online Soundex Match application, the
jurisdiction should contact the other reporting jurisdiction to determine if the case report
represents the same person or different persons. There are three potential outcomes:

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National HIV Surveillance System Technical Guidance – Duplicate Review, January 2022

1. The case has been reported by another jurisdiction. In this situation, surveillance staff
should still enter the case into eHARS and ensure that the data elements in the
Duplicate Review tab are appropriately populated (i.e., if the same person, select ‘1 –
Same as’ for ‘duplicate status’, the name of the other jurisdiction for ‘site’, and the
other jurisdiction’s STATENO for the case for ‘state ID number’)
2. The case has not been reported by another jurisdiction, but the person’s last name
soundex, date of birth, and sex at birth match those of a case reported by another
jurisdiction. In this situation, when entering the case into eHARS, surveillance staff
should also ensure that data elements in the Duplicate Review tab are populated (i.e., if
different persons, select ‘2 – Different than’ for ‘duplicate status’, the name of the other
jurisdiction for ‘site’, and the other jurisdiction’s STATENO for the case for ‘state ID
number’)
3. The case has not been reported by another jurisdiction and no match on the last name
soundex, date of birth, and sex at birth are found by the Secure Online Soundex Match
application, then data elements in the Duplicate Review tab should be left blank when
entering the case into eHARS.
The second way that potential interstate duplicate case reports are identified is through
duplicate review reports that CDC distributes to local and state health departments; the semiannual Routine Interstate Duplicate Review (RIDR) reports and the Cumulative Interstate
Duplicate Review (CIDR) report that was distributed in January 2018. RIDR/CIDR reports are
generated after data transmitted to CDC by local and state health departments have been
consolidated. It is highly encouraged that jurisdictions proactively use the Secure Online
Soundex Match application for more timely identification of potential duplicates to help reduce
the number of potential interstate duplicate pairs in their semi-annual RIDR reports. When a
jurisdiction contacts the other reporting jurisdiction(s) to determine if a case report represents
the same person or different persons, the jurisdictions should share any relevant information
(e.g., STATENO) to update their case records so that the reports are properly merged later for
de-duplication.
The third way that potential interstate duplicate case reports can be identified is using a secure
data sharing tool. Through the grant PS18-1805, Georgetown University is funded to provide a
secure data sharing tool with matching algorithm to all 59-funded state and local health
departments. The secure data sharing tool will assess case pairs using information available at
the local level that is not available at the national level (e.g., Social Security Number, last
name, etc.), and will generate a report indicating the matching level for each potential duplicate
(e.g., exact, extremely high, etc.). Therefore, the tool can more efficiently identify “exact”
matches compared to standard RIDR/CIDR methods and may also find matches not detected
through RIDR/CIDR. However, accuracy of the matches should be determined before entering
the information into eHARS. Accuracy can be determined by selecting a subset of matches at
various matching levels and discussing them further with the other jurisdictions to determine if
they are true matches. This will establish a threshold where matches can be assumed to be true
matches. For details on Georgetown’s secure data sharing tool and requirements for
participation, please contact Georgetown University at [email protected].

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National Data Processing and RIDR/CIDR Report Generation
To prevent overcounting of cases at the national level, on a quarterly basis, CDC de-duplicates
the national HIV surveillance database as part of National Data Processing. The de-duplication
process involves 1) identifying duplicate case reports and 2) combining duplicate case reports
as appropriate for the case (Figure 1). Duplicate case reports are identified using the CDC
match strings as well as the eHARS duplicate review data. Cases are first linked by last name
soundex (last_name_sndx), date of birth (dob), sex at birth (birth_sex), and state of residence at
HIV diagnosis (rsh_state_cd). Country of residence at HIV diagnosis (rsh_country_cd) is used
if rsh_state_cd is ‘FC – Foreign Country’. If no match is found, the process substitutes state
and country of residence at stage 3 AIDS diagnosis (rsa_state_cd / rsa_country_cd) for state
and country of residence at HIV diagnosis. Moreover, case reports are regarded as duplicates if
they do not agree on the CDC match strings but one or more jurisdiction’s duplicate review
data indicate that the cases are the “1 – Same as”; case reports are regarded as for different
persons if they match on the CDC match string, but one or more jurisdiction’s duplicate review
data indicate that the cases are “2 – Different than”.
Figure 1: National Duplicate Processing

RIDR reports are generated using data from the eHARS consolidated database on a semiannual
basis. The list is generated by identifying cases reported by different jurisdictions but match on
last name soundex (last_name_sndx), date of birth (dob), and sex at birth (birth_sex) but have
not been confirmed as the same or different persons by the local and state health departments.
These potential interstate duplicate case reports are distributed to local and state health
departments for resolution. In RIDR reports, at least one case in the potential interstate
duplicate pair had to be reported during the six months prior to the generation of the report. To
identify and resolve older potential interstate duplicates in the national dataset, CDC generated

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and distributed the CIDR report in January 2018. CIDR reports contain all unresolved potential
interstate duplicates regardless of when they were reported to CDC through December 2017.
The prerequisites (structural requirements), best practices (process standards), and outcome
standard for interstate duplicate review are described next.

Structural Requirements
1. Link to CSTE 2001-ID-04 Reciprocal (Interstate) Notification of HIV Cases
(https://cdn.ymaws.com/www.cste.org/resource/resmgr/PS1/2001-ID-04.pdf).
2. HIV Surveillance System Software, eHARS.
3. Variables used for CDC matching string last name soundex (last_name_sndx), date of
birth (dob), sex at birth (birth_sex), and state of residence at diagnosis (rsh_state_cd or
rsa_state_cd) or, if a non-US resident at time of diagnosis, country of residence at
diagnosis (rsh_country_cd / rsa_country_cd).
4. Standard procedure for processing of CDC’s Cumulative and Routine Interstate
Duplicate Review reports (see file Instructions for Processing CDC’s Duplicate Review
Report_YYYYMM labeled RIDR under Case Surveillance in SharePoint).
5. Case Residency Assignment Policies and Procedures (see Technical Guidance File Date
and Place of Residence).
6. Procedures for evaluating accuracy of integrated HIV surveillance systems (see
Technical Guidance File Evaluation and Data Quality).
7. Access to Secure Access Management Services; Current Digital Certificate.
8. Access to encryption software that meets federal Advanced Encryption Standard.

Process Standards
1. Frequency of Procedure
Routine Interstate Duplicate Review must be performed semi-annually. Cumulative
Interstate Duplicate Review must be completed over the course of the PS18-1802
funding cycle (2018-2022).
2. Duplicate Review of Out-of-Jurisdiction Cases
States should maintain information on out-of-jurisdiction cases in eHARS. To
determine if a pair in the RIDR/CIDR report represents the same person or different
persons, contact the other state’s surveillance coordinator (or his or her designees) to
compare and collect additional information. Questions to ask to determine if pairs are the
same or different persons might include:
•

Do the cases share the same name, including considerations of other available name
types (e.g., alias)?

•

Does the Social Security Number prefix come from the other state?
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National HIV Surveillance System Technical Guidance – Duplicate Review, January 2022

•

Are there any comments that reference the other state?

•

Is there a death date match?

•

Is there a current residence match?

•

Is there an unusual mode of exposure?

3. Records that Represent the Same Person
If, after discussion with the other state’s surveillance coordinator (or his or her
designees), the cases are deemed to represent the same person, case residency at
diagnosis must be established for the pair. Use policies and procedures for state of
residence at diagnosis to ensure that cases are counted appropriately (see Technical
Guidance File Date and Place of Residence). Once state of residence is established,
jurisdictions should inform CDC of the duplicate review resolution by updating the data
elements in the Duplicate Review tab of the ACRF or PCRF document (i.e., select “1same as” for duplicate status, etc.) as well as the residency at diagnosis information (i.e.,
rsh_state_cd / rsh_country_cd and rsa_state_cd / rsa_country_cd [if the person has a
diagnosis of stage 3 AIDS Diagnosis]).
In addition to updating the residence at diagnosis and information on the Duplicate
Review tab, jurisdictions are encouraged to share with each other additional
information about the case in accordance with their respective reporting and data
sharing laws and regulations. Such information may include risk factors, AIDS-defining
conditions, vital status, date of death, last negative test result, if nucleotide sequences
are available, care status etc. In particular, surveillance staff from each jurisdiction
should help each other determine in which jurisdiction does the patient currently reside
and enter the address information into the Identification tab of the ACRF or PCRF
document in eHARS.
4. Records that Represent Different Persons
If, after discussion with the other state’s surveillance coordinator (or his or her
designees), the cases are deemed to represent different persons, jurisdictions should
inform CDC of the duplicate review resolution by updating the data elements in the
Duplicate Review tab of the ACRF or PCRF document (i.e., select “2 – Different than”
for duplicate status, etc.).
5. Resolution of Potential Duplicates
100% of potential interstate duplicate pairs in the RIDR/CIDR reports should be
resolved and duplicate status updated in eHARS in the following timeframes:
•

RIDR report released in January should be completed by June of the same year.

•

RIDR report released in July should be completed by December of the same year.

•

CIDR report released in January 2018 should be completed by December 2022,
with at least 20% of duplicates resolved each year.

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Staff approved to release information about HIV cases to other jurisdictions can be found on
the CSTE HIV/AIDS Contact Board Web site. Please contact the HIV surveillance support
staff at CSTE for information on obtaining sign-on identifications and passwords to access the
web site (https://www.cste.org/page/HIVContact); the CSTE point of contact can be reached at
770-458-3811.
Contact the CDC’s designated subject matter expert (SME) for RIDR/CIDR for any questions
related to the RIDR/CIDR process. The RIDR/CIDR SME may be reached through the CDC
HIV Surveillance Branch’s main number (404-639-2050) or through the CDC epidemiologist
assigned to your jurisdiction for technical assistance support.

Outcome Standard
•

Of all pairs on the Routine Interstate Duplicate Review (RIDR) list, at least (≥) 98%
were resolved, assessed at the end of each RIDR cycle.

•

Of all pairs on the Cumulative Interstate Duplicate Review (CIDR) list, at least (≥) 20%
are resolved annually by December of each of the 5 years of the funding cycle and the
duplicate status updated in eHARS at the end of December each year of the funding
cycle (2018-2022). At the end of PS18-1802 (December 2022), 100% of all CIDR pairs
are completed, assessed at the end of 2022.

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National HIV Surveillance System Technical Guidance – Duplicate Review, January 2022