Inputs to a case-based HIV surveillance system
Dec 25, 2015
Objectives
Review HIV case definitions
Understand clinical and immunologic staging
Identify the sentinel events in a case reporting system
Identify existing data sources to report sentinel events
Background 2004 – 2005
WHO regional meetings to revise guidelines
April 2006 WHO global consensus meeting to finalize the
revision of clinical stage and case definitions
Case Definition: HIV Infection Adults and children 18 months or older:
Positive HIV antibody testing (rapid or laboratory-based enzyme immunoassay) confirmed by a second HIV antibody test (rapid or laboratory-based enzyme immunoassay) relying on different antigens or of different operating characteristics.
and /or; Positive virological test for HIV or its components (HIV-RNA
or HIV-DNA or ultrasensitive HIV p24 antigen) confirmed by a second virological test obtained from a separate determination.
Children younger than 18 months: Positive virological test for HIV or its components (HIV-RNA
or HIV-DNA or ultrasensitive HIV p24 antigen) confirmed by a second virological test obtained from a separate determination taken more than four weeks after birth. Note: Positive antibody testing is not recommended for definitive or
confirmatory diagnosis of HIV infection in children until 18 months of age.
Case Definition:Advanced HIV Infection (including
AIDS)
Adults and children with confirmed HIV infection: Clinical criteria:
Presumptive or definitive diagnosis of any stage 3 or stage 4 condition
Immunological criteria: CD4 count less than 350/mm of blood
Children younger than five years of age with confirmed HIV infection:
%CD4+ <30 among those younger than 12 months %CD4+ <25 among those aged 12–35 months %CD4+ <20 among those aged 36–59 months
Primary HIV Infection Definition: The time of HIV infection. Some
clinical symptoms, but no (or few) antibodies present in blood There is no standard case definition This can be identified by recent appearance of HIV
or by identifying viral products (HIV-RNA or HIV-DNA and/or ultrasensitive HIV p24 antigen) with negative (or weakly reactive) HIV antibody
If identified, this should be reported
Primary HIV Infection should not be confused with clinical staging conditions developed with established HIV infection
Purpose of Classification System
Classification is used to assess patients before they are put on treatment (presumptive and definitive diagnosis)
Proposed to use clinical staging events and immunologic classification to assess individuals once they are receiving ART
WHO Clinical Classification of Established HIV Infection
HIV associated symptoms
WHO clinical stage
Asymptomatic 1
Mild symptoms 2
Advanced symptoms 3
Severe symptoms 4
WHO Immunological Classification of Established HIV Infection
HIV associated immunodeficiency
<= 11mos(%CD4+)
12-35 mos(%CD4+)
36-59 mos(%CD4+)
>= 5 yrs (absolute no/mm or %CD4+)
None or not significant
>35 >30 >25 >500
Mild 30-35 25-30 20-25 350-499
Advanced 25-29 20-24 15-19 200-349
Severe <25 <20 <15 <200 or <15%
WHO classificationsWHO
ClinicalStage
HIV-associatedsymptomatology
HIV-associatedImmuno-deficiency
E.g. CD4 countFor persons ≥ 5
Yrs (mm/3)
1 Asymptomatic None/not significant
> 500
2 Mild symptoms Mild 350−499
3 Advancedsymptoms
Advanced 200−349
4 Severesymptoms
Severe <200 or <15%
Review: WHO Surveillance System Recommendations WHO now recommends that reporting be
expanded to cover the entire spectrum of HIV disease. Previous case definitions focused only on AIDS cases
WHO recommends that countries standardise their reporting practices.
Countries may: Report all HIV cases (clinical stages1through 4) Report advanced HIV disease (clinical stages 3 and 4) Report AIDS cases (clinical stage 4)
Pro and Cons of WHO Options Report all HIV cases (clinical stages1through
4) Pros:
Full picture of epidemic Allows tracking of disease progression Follow disease trends for both new infections and later
stages Identifies priority populations that may need additional
surveillance activities and prevention services Can be generalized to entire population
Cons: Can be difficult to implement Can be expensive
Pro and Cons of WHO Options Report advanced HIV disease (clinical
stages 3 and 4) Pros:
Measure of clinical burden Those how are diagnosed with HIV and who need ART
Some disease trends
Cons: Under-reporting May increase even as prevention decreases new cases
Report AIDS cases (clinical stage 4) Pros:
Clinical burden Easier to manage
Cons: Under estimation of epidemic Trends for AIDS cases may differ from new HIV infection
Pro and Cons of WHO Options
Monitor HIV Disease
HIV exposure(exposed infants or
sexual transmission)
HIV infection1st positive HIV test
1st CD4 count
1st CD4count <350
1st viral load 1st CD4 <200AIDS-related Opportunistic Infection
Death
Monitor HIV Disease
HIV exposure(exposed infants or
sexual transmission)
HIV infection1st positive HIV test
1st CD4 count
1st CD4count <350
1st viral load 1st CD4 <200AIDS-related Opportunistic Infection
Death
AIDS reporting
Monitor HIV Disease
HIV exposure(exposed infants or
sexual transmission)
HIV infection1st positive HIV test
1st CD4 count
1st CD4count <350
1st viral load 1st CD4 <200AIDS-related Opportunistic Infection
Death
HIV case reporting
Where Will the Data Come From? HIV antibody test (positives only) – probably
already exists in most countries Laboratories, rapid testing from facilities
Clinical stages? Which ones? HIV facility identifies clinical stage at first visit
and reports it All CD4 tests?
Labs All Viral load tests?
Labs
How Will Cases be Identified?
All laboratories Health centres ART treatment
clinics TB clinics VCT sites Private physicians
Hospitals PMTCT programme Blood banks Hospice Vital statistics
registries
Potential sources of HIV case reports: