Inputs to a case-based HIV surveillance system

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

WHO Surveillance Case Definitions

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

WHO Clinical and Immunological Classification for HIV

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%

HIV Case-Based Surveillance

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

Data Flow for Case Surveillance

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:

Thank You

Working Together to Plan, Implement, and Use

HIV Surveillance Systems